thesis/report.org

#+LaTeX_CLASS: elsarticle
#+EXPORT_FILE_NAME: ./src/report.tex
#+latex_compiler: pdflatex
#+cite_export:
#+TITLE: Influence of manufacturing process on Cavitation Erosion in CoCrWMoCFeNiSiMn (Stellite 1) alloys
#+OPTIONS: author:nil date:nil title:nil toc:nil

# Submerged Sonic Sledhammers Sharply Shape Synthesized Stellite Specimens, Showcasing Superior Strength

# %% Do not edit this top bit unless you really know what you are doing.
# \documentclass[3p,11pt]{elsarticle}


#+BEGIN_SRC emacs-lisp :exports none :results none :eval always
(with-eval-after-load 'ox-latex
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               ("\\paragraph{%s}" . "\\paragraph*{%s}")
               ("\\subparagraph{%s}" . "\\subparagraph*{%s}"))))
;;
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* Preamble :ignore_heading:

# What the hackety heck is going on?

** Fundamental Setup (Encoding, Fonts, Language) :ignore_heading:
#+LaTeX_HEADER: \usepackage[utf8]{inputenc} % Set input encoding to UTF-8
#+LaTeX_HEADER: \usepackage[T1]{fontenc}    % Use modern 8-bit font encoding
#+LaTeX_HEADER: \usepackage{textcomp}       % Provides extra symbols
#+LaTeX_HEADER: \usepackage{mathptmx}       % Use Times-like fonts for text and math
#+LaTeX_HEADER: \usepackage{slantsc}        % Provides slanted small caps font shape
#+LaTeX_HEADER: \usepackage[english]{babel} % Language-specific settings and hyphenation
#+LaTeX_HEADER: \usepackage{csquotes}       % Context-sensitive quotation marks (works well with babel)

# What the heck is going on
** Page Layout & Geometry :ignore_heading:
#+LaTeX_HEADER: % \usepackage[left=4cm, right=2cm, top=2cm, bottom=2cm]{geometry} % Example geometry settings
#+LaTeX_HEADER: \usepackage{fancyhdr}       % For custom headers and footers
#+LaTeX_HEADER: \pagestyle{fancy}           % Apply the fancy page style
#+LaTeX_HEADER: \usepackage{setspace}       % For adjusting line spacing (e.g., \onehalfspacing)
#+LaTeX_HEADER: \usepackage{titlesec}       % For customizing section and chapter titles
#+LaTeX_HEADER: \usepackage{pdflscape}      % For creating landscape pages
#+LaTeX_HEADER: \usepackage{afterpage}      % Execute commands after the current page is shipped out

# What the heck is going on
** Mathematics :ignore_heading:
#+LaTeX_HEADER: \usepackage{amsmath}        % Core package for math environments and commands
#+LaTeX_HEADER: \usepackage{amssymb}        % Provides additional math symbols
#+LaTeX_HEADER: \usepackage{mathtools}      % Extends amsmath with fixes and more tools
#+LaTeX_HEADER: \usepackage{calc}           % Allows for arithmetic in LaTeX commands

# What the heck is going on
** Graphics, Figures, and Floats :ignore_heading:
#+LaTeX_HEADER: \usepackage{graphicx}       % For including images
# #+LaTeX_HEADER: \graphicspath{{expt/}}      % Set path for graphics files
#+LaTeX_HEADER: \usepackage{subcaption}     % For subfigures within a figure environment
#+LaTeX_HEADER: \usepackage{wrapfig}        % To wrap text around figures
#+LaTeX_HEADER: \usepackage{rotating}       % To rotate elements, like figures and tables
#+LaTeX_HEADER: \usepackage{float}          % Improves float control (e.g., [H] placement)

# What the heck is going on
** Tables :ignore_heading:
#+LaTeX_HEADER: \usepackage{booktabs}       % For professional-quality table rules
#+LaTeX_HEADER: \usepackage{longtable}      % For tables that span multiple pages
#+LaTeX_HEADER: \usepackage{multirow}       % Create table cells that span multiple rows
#+LaTeX_HEADER: \usepackage{makecell}       % For line breaks and advanced formatting within table cells
#+LaTeX_HEADER: \usepackage[flushleft]{threeparttablex} % For tables with notes

# What the heck is going on
** Captions & Typography :ignore_heading:

#+LaTeX_HEADER: \usepackage{subcaption}     % Advanced control over subcaptions
#+LaTeX_HEADER: \usepackage{caption}        % Advanced control over caption appearance
#+LaTeX_HEADER: \usepackage{capt-of}        % To use \captionof for captions outside floats
#+LaTeX_HEADER:                             % (often not needed if `caption` package is used)
#+LaTeX_HEADER:                             % required by Org
#+LaTeX_HEADER: \usepackage[normalem]{ulem} % For underlining, striking out text, etc.
#+LaTeX_HEADER: \usepackage{mfirstuc}       % For capitalizing the first letter of a word

# What the heck is going on
** References :ignore_heading:

# # Elsevier insists on using natbib for somereason.
# #+LaTeX_HEADER: \usepackage{natbib}

# natbib.sty is loaded by default. However, natbib options can be
# provided with \biboptions{...} command. Following options are
# valid:
#   round  -  round parentheses are used (default)
#   square -  square brackets are used   [option]
#   curly  -  curly braces are used      {option}
#   angle  -  angle brackets are used    <option>
#   semicolon  -  multiple citations separated by semi-colon (default)
#   colon  - same as semicolon, an earlier confusion
#   comma  -  separated by comma
#   authoryear - selects author-year citations (default)
#   numbers-  selects numerical citations
#   super  -  numerical citations as superscripts
#   sort   -  sorts multiple citations according to order in ref. list
#   sort&compress   -  like sort, but also compresses numerical citations
#   compress - compresses without sorting
#   longnamesfirst  -  makes first citation full author list
# \biboptions{longnamesfirst,comma}

#+LaTeX_HEADER_EXTRA: \biboptions{square,comma,sort&compress}

** Document Structure :ignore_heading:

#+LaTeX_HEADER: \usepackage[acronym, nonumberlist]{glossaries} % For creating glossaries and lists of acronyms
#+LaTeX_HEADER: \usepackage{minitoc}        % To create mini tables of contents for each chapter/section
#+LaTeX_HEADER: \usepackage{pdfpages}       % To include external PDF documents


# What the heck is going on
** Hyperlinks (LOAD LAST) :ignore_heading:
#+LaTeX_HEADER: % For clickable links, bookmarks, and document metadata
# #+LaTeX_HEADER: \usepackage[colorlinks=true,linkcolor=black, citecolor=blue, urlcolor=blue]{hyperref}

# What the hackety heck is going on?





#
# What the heck is going on

** COMMENT General Style Guide

The ‘dissertation’ is in the form of a journal paper:
 Do not need detailed literature review (already done in B81EZ or include in work report).
 Work Report allows more detail to be included (there is an analogy of this for journals BTW).
 More contemporary for engineering disciplines and the workplace.

| Section                            |   Word count | Figures | Tables |
|------------------------------------+--------------+---------+--------|
| Introduction and Literature Review |         1500 |       2 |      0 |
| Apparatus and Methods              |         1500 |       3 |      2 |
| Results                            | 1000 -- 1500 |       5 |      0 |
| Discussion and Conclusions         |  1000 - 1500 |       0 |      1 |
| Conclusions and Future work        |          500 |       0 |      1 |
|------------------------------------+--------------+---------+--------|
| Total                              |         6000 |      10 |      4 |

References 25 - 35.
HAHAHAHAHHAHAHAHHAHAH

* Frontmatter :ignore_heading:

#+LaTeX: \lhead{Vishakh Pradeep Kumar}
#+LaTeX: \rhead{\thepage}
#+LaTeX: \lfoot{MSc Adv. Mechanical Engineering}
#+LaTeX: \journal{MSc Advanced Mechanical Engineering}

#+LaTeX: \begin{frontmatter}
# %% Title, authors and addresses
#+LaTeX: \title{Dissertation title}
#+LaTeX: \author{Vishakh Pradeep Kumar\fnref{label2}}
#+LaTeX: \ead{vp2039@hw.ac.uk}
#+LaTeX: \fntext[label2]{Student ID : H00428384 }
#+LaTeX: \author{\\ Supervisor: Dr Rehan Ahmed}
#+LaTeX: \address{Heriot-Watt University, School of Engineering and Physical Sciences, Mechanical Engineering, Dubai}

#+LaTeX: \begin{abstract}
# 48 words
The lifespan and reliability of components subjected to severe cavitation and corrosion erosion depend critically on material properties and failure mechanisms. The microstructure, and hence performance, of wear-resistant alloys used in such aggressive conditions is not dictated by chemical composition alone but is critically shaped by manufacturing process.
Cobalt-based Stellite alloys are a primary choice for these applications, deriving their exceptional wear resistance from hard carbide phases embedded within a tough cobalt-alloy matrix. Traditionally, these alloys are produced by casting, which often produces a coarse and brittle carbide network. In contrast, powder metallurgy routes, such as Hot Isostatic Pressing (HIP), yield a significantly more refined and homogeneous microstructure, offering a pathway to superior durability.
However it remains a critical question whether the microstructural refinement achieved through HIPing enhances toughness and fatigue resistance in high carbon alloys like Stellite 1, particularly in the context of cavitation erosion.
Here we show, by directly comparing a cast and a HIPed cobalt alloy (Co-30Cr-12W-2.5C by wt%), that the HIPing route produces a material with superior cavitation erosion and order of magnitude greater corrosion resistance to its cast counterpart.
#+LaTeX: \end{abstract}

#+LaTeX: \begin{keyword}
#+LaTeX: 3 to 5 keywords here, in the form: keyword \sep keyword
#+LaTeX: \end{keyword}

#+LaTeX: \end{frontmatter}

** COMMENT How to write a Keyword list

- Abrasive wear
- Cobalt based alloys
- Fatigue;
- HIPing;
- Stellite 1

** COMMENT How to write an Abstract :ignore:ignore_heading:

# Mostly cribbed from Dr Mutassim
Readers use an abstract to rapidly assess a paper's relevance, particularly when reviewing numerous search results. A successful abstract persuades its target audience to read the full paper, and the gold standard is one so clear that its message can be grasped even by a sleep-deprived, over-caffeinated brain. This level of informative clarity is achieved through a highly structured, concise, and perhaps unapologetically formulaic composition, reserving any literary flair for the paper itself.

Abstracts are quite limited in word length (submition guidelines limit it to 200 words) and the below checklist/structure is suggested as a template.
- [ ] One or two sentences providing a basic introduction to the field, comprehensible to a scientist in any discipline
- [ ] Two or three sentences of more detailed background, comprehensible to scientists in related disciplines
- [ ] One sentence clearly stating the general problem being addressed by the particular study.
- [ ] One sentence summarizing the main results (with the words "here we show" or their equivalent).
- [ ] Two or three sentences explaining what the main results reveals in direct comparison to what was thought to be the case previously, or how the main result adds to previous knowledge
- [ ] One of more sentences to put the results into a more general context


*** One or two sentences providing a basic introduction to the field, comprehensible to a scientist in any discipline :ignore:ignore_heading:

# ahmedInfluenceReHIPingStructure2013
Developing materials that can withstand extreme wear and degradation is a central challenge in materials science, with profound implications for the longevity and reliability of critical industrial components. High-performance alloys are essential for manufacturing parts that operate under such aggressive conditions.

# yuComparisonTriboMechanicalProperties2007
The performance and reliability of components in demanding industrial environments depend critically on the materials from which they are made. A material's ultimate properties are not solely determined by its chemical composition but are profoundly influenced by its manufacturing process.

# yuinfluencemanufacturingprocess2008
The operational lifespan of critical components in industries from aerospace to energy is often limited by material wear and failure.

Consequently, the development of robust, wear-resistant materials is paramount, where the manufacturing process itself plays a decisive role in defining final performance.

# yuTriboMechanicalEvaluationsCobaltBased2007
The development of materials capable of withstanding severe mechanical wear and stress is fundamental to advancing technology in critical sectors like energy and manufacturing.
# Eww
A material's resilience is not dictated by its composition alone but is critically shaped by its microstructural architecture, which is controlled by the manufacturing process.

*** Two or three sentences of more detailed background, comprehensible to scientists in related disciplines :ignore:ignore_heading:


# Cobalt-based Stellite alloys, are a primary choice for these applications, deriving their exceptional wear resistance from hard carbide phases embedded within a tough cobalt-alloy matrix. Traditionally, these alloys are produced by casting, which while cost-effective, often produces a coarse & brittle carbide network as well as being susceptible to preferential corrosive attack. In contrast, powder metallurgy routes, such as Hot Isostatic Pressing (HIP) can produce a significantly more refined and homogeneous microstructure, offering a pathway to superior durability.

# ahmedInfluenceReHIPingStructure2013
Cobalt-based Stellite alloys, renowned for their exceptional hardness and corrosion resistance, are a cornerstone material for these applications. These alloys are often produced via powder metallurgy consolidated by Hot Isostatic Pressing (HIP), a process that subjects the material to high temperature and isostatic pressure to reduce porosity and enhance mechanical properties.

# yuComparisonTriboMechanicalProperties2007
Cobalt-based alloys, such as the Stellite family, are widely used for their exceptional resistance to wear and corrosion due to a hard carbide phase embedded within a tough cobalt matrix. Traditionally, these alloys are produced by casting, a process that is cost-effective but often results in a coarse, brittle microstructure. An alternative route is powder consolidation via Hot Isostatic Pressing (HIPing), which can produce finer, more homogeneous structures.


# yuinfluencemanufacturingprocess2008
Cobalt-based Stellite alloys are a primary choice for these applications, deriving their properties from a microstructure of hard carbide particles in a ductile cobalt-chromium matrix. Stellite 6 (Co–28Cr–4.5W–1C), a widely used variant, is typically produced by casting, which yields a coarse and brittle carbide network. Powder metallurgy combined with Hot Isostatic Pressing (HIPing) offers an alternative route to produce a more refined and homogeneous microstructure.


# yuTriboMechanicalEvaluationsCobaltBased2007
Cobalt-based alloys, particularly the Stellite family, are benchmark materials for such applications, prized for the high hardness imparted by a network of chromium and tungsten carbides. Conventionally produced by casting, these alloys often suffer from brittleness due to a coarse carbide structure. An alternative route, Hot Isostatic Pressing (HIPing) of pre-alloyed powder, can produce a more refined microstructure.

*** One sentence clearly stating the general problem being addressed by the particular study. :ignore:ignore_heading:

However it remains a critical question whether the microstructural refinement achieved through HIPing enhances toughness and fatigue resistance in high-carbon alloys like Stellite 1, particularly in the context of cavitation erosion.

# ahmedInfluenceReHIPingStructure2013
However, while the benefits of a single HIP cycle are well-established, the potential for further microstructural and mechanical property enhancement through a subsequent 're-HIPing' treatment has remained largely unexplored.

# yuComparisonTriboMechanicalProperties2007
However, for high-carbon alloys designed for severe wear, it has been unclear whether the microstructural refinement from HIPing could enhance toughness without compromising the wear performance endowed by the coarse carbide structure of cast products.


# yuinfluencemanufacturingprocess2008
However, it remains poorly understood how the microstructural refinement from HIPing affects the intricate balance between hardness, impact toughness, and contact fatigue resistance in medium-carbon alloys like Stellite 6.


# yuTriboMechanicalEvaluationsCobaltBased2007
However, it has remained a critical question whether the microstructural refinement achieved through HIPing can enhance toughness without significantly compromising the excellent wear resistance conferred by the coarse carbides in their cast counterparts.

*** One sentence summarizing the main results (with the words "here we show" or their equivalent). :ignore:ignore_heading:

Here we show, by directly comparing a cast and a HIPed cobalt alloy (Co–30Cr–12W–2.5C by wt %), that the HIPing route produces a material with superior cavitation erosion and order of magnitude greater corrosion resistance to its cast counterpart.

# ahmedInfluenceReHIPingStructure2013
Here we show that subjecting HIP-consolidated Stellite 4, 6, and 20 alloys to a second re-HIPing cycle induces significant carbide coarsening and matrix strengthening, leading to concurrent improvements in hardness, indentation modulus, and wear resistance.

# yuComparisonTriboMechanicalProperties2007
Here we show, by directly comparing a cast and a HIPed cobalt alloy (Co–33Cr–17.5W–2.5C by wt %), that the HIPing route produces a material with an order-of-magnitude greater impact resistance and superior contact fatigue performance, all while maintaining equivalent hardness and wear resistance to its cast counterpart.


# yuinfluencemanufacturingprocess2008
Here we show that while HIPing significantly enhances the impact toughness and contact fatigue of Stellite 6 compared to its cast counterpart, the fatigue resistance does not scale with toughness and is instead dominated by the alloy's intrinsically lower hardness and carbide volume fraction.

# yuTriboMechanicalEvaluationsCobaltBased2007
Here we show that for a Co−30Cr−14W−1C alloy, the HIPing process yields a material with substantially improved impact toughness and contact fatigue performance while largely preserving the high hardness and suffering only a slight reduction in abrasive wear resistance compared to the cast version.

*** TODO Two or three sentences explaining what the main results reveals in direct comparison to what was thought to be the case previously, or how the main result adds to previous knowledge :ignore:ignore_heading:

#+NAME: findings_add_knowledge
#+BEGIN_SRC latex
This research reveals that the refined microstructure of alloys processed via Hot Isostatic Pressing (HIP) successfully mitigates the classic trade-off between wear resistance and toughness. The fine, discrete carbides in the HIPed structure resist the catastrophic brittle fracture that plagues the coarse carbide networks found in conventionally cast materials. This fundamentally alters the dominant failure mechanism from carbide fracture to more ductile modes like matrix ploughing and carbide pull-out, enhancing energy absorption and dramatically improving impact properties.
#+END_SRC

# ahmedInfluenceReHIPingStructure2013
These findings demonstrate that re-HIPing is not merely a densification process but acts as an effective thermal treatment for tuning the alloy's microstructure. The observed solid solution strengthening of the cobalt matrix, coupled with the coarsening of the strengthening carbide phases, provides a clear microstructural basis for the enhanced tribomechanical performance.


# yuComparisonTriboMechanicalProperties2007
This result directly challenges the assumption that achieving maximum wear resistance in this class of alloy necessitates a trade-off with toughness. We reveal that the refined carbide morphology in the HIPed alloy fundamentally alters the dominant failure mechanism from brittle carbide fracture to matrix ploughing and carbide pull-out, which explains the dramatic improvement in impact properties.

# yuinfluencemanufacturingprocess2008
This finding reveals a complex and non-linear interdependency of tribological properties, challenging the common design principle that a substantial increase in toughness should directly translate to superior fatigue performance. In contrast to high-carbide alloys like Stellite 20, our results demonstrate that in medium-carbide systems, bulk hardness can be the limiting factor for contact fatigue, even in a microstructure optimized for impact resistance.


# yuTriboMechanicalEvaluationsCobaltBased2007
This outcome demonstrates a successful mitigation of the classic wear-resistance-versus-toughness trade-off. The fine, discrete carbides in the HIPed microstructure resist the catastrophic fracture that plagues the coarse carbide networks in the cast alloy, thereby providing a mechanism for enhanced energy absorption and fatigue life.

*** TODO One of more sentences to put the results into a more general context :ignore:ignore_heading:


These findings show that HIPing is a viable processing strategy for creating components that are simultaneously hard and tough, moving beyond the classic trade-off between wear resistance and toughness,

s a key design parameter for engineering superior materials. This approach allows for creating components that are simultaneously hard and tough, optimizing service life in applications requiring both wear and impact resistance.

# ahmedInfluenceReHIPingStructure2013
Our results establish re-HIPing as a viable and straightforward post-processing strategy to further optimize the service life and performance of cobalt-based components, offering a pathway to creating more durable materials for demanding engineering applications.

# yuComparisonTriboMechanicalProperties2007
These findings establish that the choice of processing route is a critical tool for engineering superior material properties, enabling the design of next-generation components that are simultaneously ultra-hard and exceptionally tough for high-stress applications.


# yuinfluencemanufacturingprocess2008
These results provide critical insight for tailoring material processing routes for specific engineering applications, highlighting that a holistic approach—considering the complex interplay between multiple mechanical properties—is necessary to design the next generation of high-performance materials.

# yuTriboMechanicalEvaluationsCobaltBased2007
Our results provide a clear processing strategy for engineering cobalt-based alloys with a more versatile combination of properties, enabling their use in higher-stress applications where resistance to both steady wear and mechanical shock is required.


** COMMENT Style guide
*** Page and text formatting
If you use the provided templates, the style requirements are already the default settings --- so don't tinker with them!  This LaTeX template is based on the Elsevier class but using 11pt (instead of the standard 10pt).  We use the single-column format for practical reasons.

The document has to be prepared for the UK standard paper of A4 size with a text area of 16.45~cm by 21.9~cm using single columns at a `normal' serif font (e.g., Times New Roman or Cambria) with font size 11pt.

*** Word count
#+LaTeX: \label{S:Wordcount}
The expected word count is between 5000 and 7000 words. The word count includes everything from the start of the Introduction to the end of the Conclusions,  including text in figure captions and tables.   Excluded from the word count is the front matter (from the title to the end of the abstracts and key words) and the end matter (acknowledgements, references, appendices).

If you try to cheat the word count by having a lot of important information in appendices:   remember that appendices only provide supplementary material, not essential material for the assessment.  The markers are not required to read any appendix during the marking of the dissertation.

**** Section and item numbering
Paragraphs are justified on both sides and start with an indent.  Section numbering is numeric, with `section' headings in bold but sub-section and subsub-section headings in italics.  Each heading is preceded and followed by some space (about 6pt or half a line).

Figures, tables, and equations are numbered consecutively:  Figure 1, Figure 2,  Table 1, Table 2, (1), (2), and so on.  That means that they are not sub-numbered for each section, so no Figure 1.2.  However, a figure might have two or more graphs.  In that case, each graph is labelled a), b) and so on.  Similarly, equations can be single equations such as
\begin{equation}\label{eq1}
 e = m c^2
\end{equation}
or they could be a set of equations, using the environment `subequation' from the subcaption package,
\begin{subequations} \label{eq2}
	\begin{gather}
	C_p  = \frac{p}{\frac{1}{2} \rho U^2} \label{eq2a} \\
	C_P  =  \frac{P}{\frac{1}{2} \rho A U^3} \label{eq2b}
	\end{gather}
\end{subequations}

When referring to these objects in the text, you can use either `figure~\ref{exFigure}', `Figure~\ref{exFigure}', or `Fig~\ref{exFigure}', as long as you do it consistently.  A specific graph in a multi-graph figure would be referred to as, for example Fig.~2b.  Likewise, for referring to a table, you would use table, Table, or Tab.~\ref{Tab:method}, and equations are referred to as Eq.~(\ref{eq1}), Equations~(\ref{eq2}) or equation~(\ref{eq2b}).

*** References

These must follow the style of the journal used in the `References' at the end of this template, with an example for citing a journal article given by \cite{article}, for a contribution to conference proceedings by \cite{proc1}, and for a book by \cite{book1} or a chapter \citep{bookchapter}. If you do need to refer to websites, for example for data sources, an example is given by \cite{MIDAS} or \citep{web1}.

You can create your own *.bib file using EndNote or Mendeley and then extract and format the cited references using BibTeX.


* Introduction

# - Background on Cobalt-Based Superalloys (2-3 paragraphs)
# - Industrial relevance
# - Stellite 1 (2 paragraphs)
# - Casting of Stellite Alloys
# - Hot Isostatic Pressing (HIP)
# - Problem Statement (2-3 paragraphs)
#   This new section will explicitly detail the specific performance limitations or failure modes of as-cast Stellite 1 components (e.g., premature failure due to subsurface porosity, unpredictable corrosion) that provide the industrial motivation for this research.
# - Aims and Objectives
#   1 paragraph, followed by a bulleted list.
# - Thesis outline (Optional)

# Cavitation erosion is an issue, aaa
# Stellites are great at combating this, in addition to other stuff.
# Provide historical context: development by Elwood Haynes and establishment of Stellite family.


# Cavitation erosion
# Principal alloying philosophy
# Type of carbides and how solid solution
Cavitation erosion, the mechanical degradation of surfaces due to collapse of bubbles and the resulting high-frequency high-pressure shock waves, is a common failure mechanism that limits the durability and service life of hydraulic components operating in aggressive service environment \cite{houCavitationErosionMechanisms2020, ashworthMicrostructurePropertyRelationships1999}. Bubbles filled with vapor or dissolved gases form in low pressure regions and implode violently in areas of higher pressure.


# \cite{ashworthMicrostructurePropertyRelationships1999}
# The incidence of erosino has increased in recent years due to higher operational pressures and speeds.



Stellites, a family of cobalt-based superallys, are widely used in industry to resist cavitation, in addition to their strength, wear resistance, and corrosion/oxidation resistance at high temperatures.


The main alloying elements of stellite are cobalt (Co), chromium (Cr, 25-33 wt.%), tungsten (W) and/or molybdenum (Mo) (up to 18 wt.%), and carbon (C, 0.1-3.3 wt.%) \cite{davisNickelCobaltTheir2000, ferozhkhanMetallurgicalStudyStellite2017}, which form a composite-like microstrucuture consisting of a ductile cobalt-rich solid solution, that absorbs energy through a sluggish FCC to HCP phase transformation, with embedded hard carbide phases \cite{ahmedSlidingWearBlended2021a, crookCobaltbaseAlloysResist1994, nevilleAqueousCorrosionCobalt2010, zhangFrictionWearCharacterization2002}.
The proportion and type of carbides depend on carbon content and the relative amounts of chromium (of carbide type $\textrm{M}_{7}\textrm{C}_{3}$, $\textrm{M}_{23}\textrm{C}_{6}$) and tungsten and molybdenum (of carbide type $\textrm{M}_{6}\textrm{C}$, $\textrm{M}_{12}\textrm{C}$), with the solid solution strengthened by incorporating the elements not consumed in carbides.

Several investigations have sought to develop mathematical models that link the weight percentages of key elements,

to the hardness of the alloy,

Chen et al \cite{chenCharacterisationsElectrosparkDeposition2010} find that electro-spark deposition of Stellite 6 on 316L steel creates a uniform coating with fine microstructure and has greater corrosion resistance than a plasma cladding layer of Stellite 6, and attribute it to the rapid solidification process.

Hoffard et al found that electro-spark deposition of Stellite 6 performs worse than as-welded Stellite 6,
\cite{hoffardCavitationErosionElectro}




Collier et al find that increased carbide content due to increased molybdenum content has beneficial properties to increasing hardness and reducing wear rates \cite{collierTribologicalPerformanceMolybdenum2020}

Ahmed et al find that Vicker's microhardness and yield strength are approximately linearly proportional to the wt% of carbon and tungsten, $H = 242.26 \left( \frac{W wt%}{16.30} + \frac{C wt%}{3.21} \right) + 256.33$, where the constants are related to the maximum tungsten and carbon content in the blended alloys studied \cite{ahmedMappingMechanicalProperties2024}.



Yu et al \cite{yuInfluenceManufacturingProcess2008} find that HIPed Stellite 6 and 20 alloys have significantly high contact fatigue resistance and impact toughness.

Heathcock et al note find that as-cast Stellite 20 had lower cavitation erosion resistance compared to as-cast Stellite 3, despite Stellite 20 having higher tungsten and chromium content, and attribute the difference to microstructure morphology; Stellite 3 had a fine inderdendritic network of carbides in a tough cobalt-rich solid solution while Stellite 20 had needle-like Cr7C3 and islands of cobalt-rich solid solution embedded in a brittle complex carbide eutectic which was more prone to cracking and erosion \cite{heathcockCavitationErosionCobaltbased1981}.


# Too preachy
# However, the total volume fraction of carbides is not the only microstructural parameter of importance. The morphology—that is, the size, shape, and distribution of the phases—also plays a critical role. The fine, well-dispersed dendritic and eutectic structures produced by the rapid solidification inherent in additive manufacturing processes often lead to higher hardness and improved mechanical properties compared to the coarse, networked carbides found in conventional castings, even at similar overall compositions. Conversely, detrimental phase morphologies, such as the continuous oxide networks that can form along splat boundaries in HVOF coatings, can act as preferential sites for crack initiation and lead to delamination during wear, a failure mechanism governed by phase distribution rather than just bulk fraction.

The size and distribution of the carbides, and the resulting microstructure, is heavily dependent on its manufacturing process, especially the rate of solidification. For instance, the slow freezing rates inherent to traditional casting lead to a microstructure of large, dendritic carbides characterized by elemental segregation. Conversely, powder metallurgy creates a highly homogeneous microstructure with small, spherical carbides by largely retaining the properties of the initial powder \cite{yuInfluenceManufacturingProcess2008, wong-kianComparisonErosioncorrosionBehaviour}.

# Is great info, but maybe best suited for the WORK REPORT
# Perhaps this is there that Table will come in handy too.
# as seen in Table \ref{tab:stelliteComposition}
# \cite{ahmedMappingMechanicalProperties2023, alimardaniEffectLocalizedDynamic2010, ashworthMicrostructurePropertyRelationships1999, bunchCorrosionGallingResistant1989, davisNickelCobaltTheir2000, desaiEffectCarbideSize1984, ferozhkhanMetallurgicalStudyStellite2017, pacquentinTemperatureInfluenceRepair2025, ratiaComparisonSlidingWear2019, zhangFrictionWearCharacterization2002},
# High-carbon alloys (>1.2 wt%) have greater wear resistance, while low-carbon alloys (0.5 wt%) are used for enhanced corrosion resistance, with medium carbon alloys used in applications requiring a combination of wear and corrosion resistance \cite{davisNickelCobaltTheir2000}.


# Essentially, this is pretty close to being good
Wong-Kian et al \cite{wong-kianComparisonErosioncorrosionBehaviour} found that HIPed Stellite 1, 6, and 21 had superior erosion-corrosion characteristics to welded coatings when subjected to nitric acid in slurry pot, as well as found that increasing contents of chromium, carbonm and tungsten resulted in better performance.


Ashworth et al investigated the effect of
found that high carbon Stellite alloys benefitted from higher hipping temperatures (1200 C) while low carbon Stellite alloys reached optimum properties at a HIPing temperature of 1120 C \cite{ashworthMicrostructurePropertyRelationships1999}.

Yu et al \cite{yuInfluenceManufacturingProcess2008} found that HIPed stellite 6 had lower fatigue performance to HIPed stellite 20.


Laser-cladded Stellite alloys exhibit a more refined microstructure when compared to their cast counterparts, as found by Bozzi et al. \cite{bozziMicroabrasiveWearBehavior2023}.


frenkMicrostructuralEffectsSliding1994 has good notes on effects of manufacturing

# Heathcock and Ball, 79 compared the cavitation erosion resistance of a number of Stellite alloys, (3, 4, 6, 8, 20, and 2006), cemented carbides and surface-treated alloy steels. They showed that among the Stellite alloys, Stellite 3 has the highest resistance to cavitation erosion. Stellite 4, 6, 8, and 20 have similar resistance and Stellite 2006 is a little less resistant than all the Stellite alloys. They considered this difference to be a consequence of the microstructure. \cite{heathcockCavitationErosionCobaltbased1981}





# corrosion resistance
As well as the corrosion behaviour being of interest, Malayoglu and Neville [16] conducted a  comparative study on the erosion-corrosion performance of both HIPed and investment cast  Stellite 6® in 3.5% NaCl solution as a function of temperature and the level of erosive particle  loading. They found that in all cases, the HIPed Stellite 6® exhibited the higher erosioncorrosion resistance, which they attributed to the fact that the carbides are not interconnected  in the HIPed material whereas eutectic and dendritic carbides in the cast structure form a  network of interconnected material. Furthermore, the mean free path between carbides is  much smaller in the HIPed material and as such the material responded homogenously to 4  erosion-corrosion. Another study comparing the erosion-corrosion behaviour of a range of  HIPed and weld-deposited Stellite alloys in a nitric acid environment demonstrated that the  HIPed alloys generally exhibited a lower mass loss which was again attributed to the finer  microstructure [17].
A similar conclusion was also reached by Neville and Malayoglu [18] who  attributed the superior corrosion resistance of HIPed Stellite 6 to its microstructure with  equiaxed carbides and an absence of areas of chromium-depleted matrix material, due to  reduced segregation.













krellComprehensiveInvestigationMicrostructureproperty2020

# Wong-Kian et al.16 showed that under erosioncorrosion conditions HIPed Stellite alloys 1, 6, and 21 had lower mass loss than the welded specimens of the same Stellites. They related their finding to the finer and homogeneous microstructure, which was obtained after HIPing. They also showed that wear resistance of the cobalt-based alloys is promoted by the harder complex carbides of chromium and tungsten, while corrosion resistance is enhanced by the presence of cobalt in the matrix.	nevilleAqueousCorrosionCobalt2010

# Let's go to the actual topic
Although cobalt-based alloys are extensively studied <?>, a knowledge gap exists in understanding how different processing routes affect their cavitation erosion resistance. To address this, our work provides a direct comparison of the structure-property relationships in alloys produced by casting and powder-consolidated Hot Isostatic Pressing (HIP). We characterized the alloys through microstructural analysis (SEM) and evaluated their relative tribo-mechanical performance based on hardness, impact toughness, resistance to abrasive and sliding wear, and contact fatigue.



# carbides provide higher strength and but may reduce corrosion resistance due to localized corrosion at carbide boundaries.

# In addition to the solid solution toughness and carbide hardness, the stress-induced FCC \textrightarrow{} HCP phase transformation of the Co-based solid solution further increases wear resistance through work hardening.


# Cr has a dominant role in the formation of carbide type $\textrm{M}_23\textrm{C}_6$

# The strength of most cobalt base superalloys is derived from the carbide phases present in the matrix and distributed around the grain boundaries. The carbides that form depend on the composition and thermal history of the material. The carbide former elements are from group IV (Ti, Zr, Hf), group V (Cb, Ta), and group VI (Cr, Mo, W). The types of carbides that are formed are as follows (M and C represents metal and carbon atoms respectively):

# Understanding the cobalt phase is crucial for studying structural changes in Co-based alloys widely used in industry. The fcc cobalt phase, especially its delayed transition to hcp at ambient and moderate temperatures \cite{DUBOS2020128812}, is of particular interest due to its impact on material properties in Co-based alloys \cite{Rajan19821161}. As the cobalt phase in stellite alloys is observed to consist of the fcc phase \cite{Rajan19821161}, the potential for strain-induced fcc to hcp transformation is of interest under the mechanical loading of cavitation erosion.


** COMMENT Draft

The microstructure of Stellite alloys varies considerably with composition. They may either be in the form of hypoeutectic structure consisting of primary dendrites of a cobalt-rich solid solution surrounded by eutectic carbides, or of hypereutectic type containing large idiomorphic primary chromium rich carbides and eutectic.	nevilleAqueousCorrosionCobalt2010
Among the alloying elements, carbon is found to have a large influence on the microstructure, causing a change from a hypoeutectic to hypereutectic alloy. Figure 2 shows the phase diagram for the carbon–cobalt alloy system. As can be seen in the hypoeutectic side of the system (<1.6at% of C) the liquidus temperature of the alloy decreases by 14 C for each 1% increase in carbon content. Carbon is clearly critical to those casting alloys formulated for the highest creep rupture strength levels, since carbide strengthening is the primary precipitation hardening mechanism utilized in the cobalt alloy system. The control of carbon is critical for tensile and rupture strength and ductility since it has been shown that a nonlinear increase in strength occurs over a range of 0.3–0.6% carbon. The strength of most cobalt base superalloys is derived from the carbide phases present in the matrix and distributed around the grain boundaries. The carbides that form depend on the composition and thermal history of the material. The carbide former elements are from group IV (Ti, Zr, Hf), group V (Cb, Ta), and group VI (Cr, Mo, W). The types of carbides that are formed are as follows (M and C represents metal and carbon atoms respectively):	nevilleAqueousCorrosionCobalt2010

M3C2: rhombic, a high chromium content carbide which forms at low Cr/C ratio; 	nevilleAqueousCorrosionCobalt2010
M7C3: trigonal, a high chromium content carbide which forms at a slightly higher Cr/C ratio; 	nevilleAqueousCorrosionCobalt2010
M23C6: cubic, a high chromium content carbide which forms at an higher Cr/C ratio, when the Cr is greater than 5 wt% of the alloy;	nevilleAqueousCorrosionCobalt2010
M6C: complex cubic, a carbide phase whose volume fraction increases as refractory metals are introduced;	nevilleAqueousCorrosionCobalt2010
MC: fcc NaCl structure, a carbide comprising metal groups IV and VI.	nevilleAqueousCorrosionCobalt2010


These carbides are listed above in the order of increasing stability, or free energy of formation. The stronger the carbide formers used, the greater is the tendency to form M6C and MC carbides. The type of carbides that form is dependent upon both thermal history and composition.	nevilleAqueousCorrosionCobalt2010


The microstructure of cobalt base superalloys is thus a combination of MC, M7C3, M23C6, and M6C carbides. In the cast structures, both composition and shape help to distinguish one carbide from another. The MC carbides have two characteristic shapes, a Chinese script and a block-like angular particles. The differences are believed to be the result of formation at various times during solidification. Block-like angular MC carbides may form initially before the bulk of the melt has started to solidify, whereas in the Chinese script, MC carbide is formed within the eutectic composition.	nevilleAqueousCorrosionCobalt2010

M23C6 carbides are found mostly as fine plates interlayered with the cobalt matrix. This eutectic structure has a block-like shape. Subsequent heating of the cast structure can dissolve the M23C6 carbides. Upon aging, the carbides are precipitated as fine particles, usually near the eutectic M23C6 islands. In contrast to other carbides, the M6C carbides do not have a characteristic morphology. Other important microstructural features of cobalt base superalloys are stacking faults, which have been reported to be present on all {111} planes.8 Stacking faults appear to be related to the tendency to form hcp. Since stacking faults in fcc materials have an hcp structure, this is not surprising.	nevilleAqueousCorrosionCobalt2010





What is HIPing?
Hot isostatic pressing (HIP) is a much newer technique, and its use to provide a wear-resistant surface is even more novel. In normal use, the technique can be employed to promotepowder consolidation, diffusion bonding, and the healing of casting defects. As used to produce a diffusionbonded coating, it has none of the deleterious effects of welding, which include unhomogeneity (segregation), dilution effects, and the risk of distortion. The diffusion bonding in HIP occurs at elevated temperatures and pressures, but is a solid-state process. The absence of solidification from a liquid phase during processing precludes segregation, cracking, and distortion, all of which are inherently associated with the as-cast structure of a welded coating. Brittle materials can be joined without fracturing, and dissimilar combinations, which are often difficult to weld, can be joined.	nevilleAqueousCorrosionCobalt2010
Hot Isostatic Pressing (HIPing) is a thermo-mechanical process [9] in which components or a contained powder are subjected to simultaneous applications of heat and high pressure in inert medium. HIPing removes internal void cavities thus consolidating the structure to be homogenous, segregation free, dense, near-net shape and requiring little or no machining.	malayogluAssessingKineticsMechanisms2005




Influence of HIPing on Stellite

Wong-Kian et al.16 showed that under erosioncorrosion conditions HIPed Stellite alloys 1, 6, and 21 had lower mass loss than the welded specimens of the same Stellites. They related their finding to the finer and homogeneous microstructure, which was obtained after HIPing. They also showed that wear resistance of the cobalt-based alloys is promoted by the harder complex carbides of chromium and tungsten, while corrosion resistance is enhanced by the presence of cobalt in the matrix.	nevilleAqueousCorrosionCobalt2010


The HIPped samples also had a different carbide morphology. Optical microscopy revealed the eutectic nature of the welded carbides, and SEM studies showed that the HIPped carbides were more angular. The globular structure in the welded sample (Figure 19) may be the result of coarsening, as well as of the original eutectic morphology.	wong-kianComparisonErosioncorrosionBehaviour

In previous work, the corrosion performance of the High Velocity Oxyfuel (HVOF) Stellite 6 coatings in as-sprayed and sprayed and HIPed conditions were compared. The corrosion resistance of HIPed coating was higher than the as-sprayed one [12] and this was found to be primarily due to the finer microstructure obtained after HIPing.




Influence of carbide size
The welded samples experienced greater mass loss because they had larger matrix areas that were unprotected by the harder carbides, and wear occurred on these areas at higher rates. The coarser carbide size meant that, when carbide removal did occur, larger pieces were removed, which also accelerated the wear rates. The microstructural coarseness was a direct result of solidification from the liquid state. The high temperature differences experienced during welding encourage steep temperature gradients, which in turn favour the growth of dendrites and, in extreme cases, an irregular eutectic morphology.	wong-kianComparisonErosioncorrosionBehaviour
More usually, the carbide particles seemed to have been fractured, and then directly removed. This would be expected in the erosion-corrosion environment that the test pieces experienced. Once broken, the free particle fragments would have been swept away by the relative motion of the slurry. The effect of the larger carbide particles is shown in Figure 22: they were broken more easily and protected the matrix less effectively. The carbide particles were observed to be in relief after the surrounding softer matrix had been eroded, and could be more easily broken and removed. The larger areas of unprotected matrix then exacerbated this process.	wong-kianComparisonErosioncorrosionBehaviour
he welded samples experienced greater mass loss because they had larger matrix areas that were unprotected by the harder carbides, and wear occurred on these areas at higher rates. The coarser carbide size meant that, when carbide removal did occur, larger pieces were removed, which also accelerated the wear rates. The microstructural coarseness was a direct result of solidification from the liquid state. The high temperature differences experienced during welding encourage steep temperature gradients, which in turn favour the growth of dendrites and, in extreme cases, an irregular eutectic morphology.	wong-kianComparisonErosioncorrosionBehaviour


** COMMENT Literature Review

% CHAPTER 2: LITERATURE REVIEW
\chapter{Literature Review}
% Total: ~10,000–15,000 words
% Reviewer's Note: The focus will be on a *critical synthesis* of the literature to build a clear argument that identifies the research gaps, rather than a purely encyclopedic summary.

*** Metallurgy of Cobalt-Based Alloys
% 5–7 paragraphs.
\lipsum[6-7]

*** Microstructure of As-Cast Stellite Alloys
% 4–6 paragraphs.
\lipsum[8-9]

*** The Hot Isostatic Pressing Process
% 4–6 paragraphs.
\lipsum[10]

*** Mechanical Properties of Stellite Alloys
% 5–7 paragraphs.
\lipsum[11]

*** Corrosion Behavior of Stellite Alloys
% 5–7 paragraphs.
\lipsum[12-13]

*** Advanced Characterization Techniques for Cobalt Superalloys
% 3-4 paragraphs.
% A new section providing a critical overview of state-of-the-art techniques, justifying the methods selected for this study.
\lipsum[14]

*** Gaps in Current Knowledge
% 2–3 paragraphs.
\lipsum[15]



** COMMENT Instructions regarding Introduction


Suggested word count 1500 (and perhaps 2 figures)

*Figures in the introduction? No*
I'd be careful about the use of figures in the introduction. I made that mistake in my preliminary report and I'm still cringing about it, haha. Generally, they feel a bit out of place (unless the figure is a conceptual diagram, and even then, it's a high bar to not feel uneeded). Save the figures for later.

Core Components of the Introduction
- [ ] Present the general context and background immediately.
- [ ] Structure the chronological-ish literature review within this subsection.
- [ ] Start with a brief description of your project.
- [ ] Provide the rationale and background for your work.
- [ ] Justify and clearly state your Aims and Objectives.
- [ ] Include a concluding paragraph that describes the structure of the remaining dissertation.

Final Review and Constraints
- [ ] Check that the Introduction has a word length of 1500.
- [ ] Ensure all material presented is relevant to your research question.

The main body of the dissertation starts with an introduction, which in turn starts with a brief description of your project.

Depending on the scope of this chapter and the structure of the overall dissertation, the initial section could be followed by a statement and explanation of the Aims and Objectives. In many cases, however, this section comes after the section describing the Background

Introduction giving the rationale and background to your work. This also should justify and clearly state your aims and objectives.

There are two typical ways of structuring the introduction.  The more compact form is to combine the `context' and `literature review' in a single main section, where the context is presented immediately after the section heading (ie, no subsection), and then structure the literature review as subsection within the first section, finishing off with a final subsection which states the aims and objectives as well as a paragraph describing the structure of the remaining paper.

The more extended form is to separate the context and aims from the literature review.  In this case, the first 'Introduction' section presents the context and concludes with the aims and objective plus the paragraph outlining the structure of the remaining paper.  The literature review itself will then be the main Section 2, with suitable subsections to structure the material.

The introduction and literature review usually makes up about 20 to 30\% of the overall paper.  Make sure that all the material is relevant to your research question and your research.   An example of a typical balance of the different sections expected in a standard paper is given in Tab.~\ref{Tab:method}.  However, each dissertation is different, and might end up with a different balance, as long as the overall length is not exceeded.  In particular, the number of figures, tables and reference can vary widely (and wildly), very much depending on the type of work carried out.


\begin{table}
\protect\caption{Illustration of relative length of different sections, taken from a representative paper from a previous student.\label{Tab:method}}
\begin{tabular}{|l|c|c|}
\hline
Section & Word count & Number of figures and tables\\
\hline  \hline
Introduction and Literature Review & 1500 & 2 Figures \\
\hline
Apparatus and Methods & 1500 & 3 Figures and 2 Tables \\
\hline
Results & 1000 -- 1500 & 5 Figures \\
\hline
Discussion and Conclusions & 1000 -- 1500 & 1 Table \\
\hline
Conclusions and Future work & 500 & 1 Table \\
\hline
References &  & 25 -- 35 references; 60\% journal articles, 10\% books, 30\% websites \\
\hline \hline
Total & 6000 & 10 Figures and 3 Tables\tabularnewline
\hline
\end{tabular}
\end{table}



** Hardness

The cavitation erosion resistance depends on material properties, with the highest cavitation erosion resistance exhibited by materials with

homogeneous and fine-grained structure

Hardness is the most mentioned property, along with Young's modulus.

Heyman noted the existence of an exponential correlation between hardness

* Methodology and Apparatus

# Clear description of how you approached the problem and what you did (NOT, what somebody else should do...).

# This might start with an introductory paragraph providing a high-level description of your overall approach, then some specific subsections on your data sources, the methods to obtain your primary research data, sections on the instrumentation (including their accuracy and precision) or simulation software used, followed by a section how you used those tools, and complemented by an introduction to any more advanced analysis method you might have applied for the secondary analysis.

# Especially in the description of your experiments or other activities, tables can be useful to summarise the key information, such as Table \ref{Tab:method}. Make sure it is complete but not too complex.  Consider putting large tables in an appendix, but keep in mind the role of appendices mentioned in Section~\ref{S:Wordcount}.

** Cavitation erosion test

Cavitation erosion was evaluated in accordance with the ASTM G32-06 standard using a 500 W ultrasonic vibratory apparatus (Fig. 1) operating at a frequency of 20 kHz and a peak-to-peak amplitude of 100 µm. As-cast specimens were fabricated as discs (31 mm diameter×8 mm height), whereas hot isostatically pressed (HIPed) specimens were cuboids (25×25×13 mm). Prior to testing, all surfaces were ground to a 1000-grit finish and subsequently polished with a 0.25 µm diamond suspension. Tests were conducted by immersing specimens in a seawater bath maintained at 25±1 °C. To quantify erosion, specimens were removed from testing apparatus after test duration of 1 hr, rinsed with distilled water, and ultrasonically cleaned in acetone. Mass loss was measured using an electronic balance with a precision of 0.01 mg; each reported value is the average of three consecutive measurements.

* Results

# Describe the results and the results of their analysis


The resistance of as-cast and HIPed Stellite 1 to cavitation erosion is presented by the curves of mass/volume loss in exposure time.

** Carbide volume analysis

# Stellite 1 is a CoCrW alloy with find Cr-rich and W-rich carbides

As-cast Stellite 1 shows a hyper-eutectic microstructure, with rod-like primary Cr-rich carbides (dark phase in BSE), lamellar W-rich carbides (light phase in BSE), and CoCrW matrix (gray region) as seen in Fig. <?>.

HIPed Stellite 1 shows a homogeneous microstructure in which fine carbides (Cr-rich and W-rich) are uniformly distributed in the matrix, as seen in Fig. <>.

Table 2 lists the image analysis results.

# yuComparisonTriboMechanicalProperties2007

** COMMENT Results and primary analysis

Present the primary results in sufficient detail that the reader can get a good insight into what you obtained from your experiments or field work (or whatever you did), but avoid showing many similar graphs. Only show key samples, for example a typical case and a few unusual cases. Here, you will need to make good use of figures, such as that in Fig.~\ref{exFigure}

# \begin{figure}
# \begin{centering}
# \includegraphics[width=0.7\textwidth]{CP_vs_U_Turb_Farm}
# \par\end{centering}
# \protect\caption{Range of observed power output from a single turbine (blue shaded and cross-hatched region) and from an entire wind farm at the same site (red shaded region) against wind speed. Both are normalised by the rated power and number of turbines contributing to the power output (Data source: Vattenfall).}
# \label{exFigure}
# \end{figure}



** COMMENT Secondary analysis

Try to build up your many results into a systematic analysis which distills the main results and presents them in a clear way in well-designed figures.


* Discussion

# The microstructure of cobalt-based Stellite alloys has been the topic of research for almost a century and a number of investigations have discussed their microstructure on the basis of alloy composition and processing route 4,5,10–17 . However, comparative analysis of the microstructure of these alloys is scarce in the published literature. The aim of the discussion here is therefore to highlight the differences in the microstructure of the two alloys, with a view to underpin the understanding of structure–property and tribo-mechanical behavior.

The as-cast Stellite 1 alloy had a hypereutectic microstructure, with the Cr-rich (dark) carbides having a composition of $(Cr_{0.75}Co_{0.20}W_{0.05})_7C_3)} and identified as ${M}_{7}{C}_{3}$, and W-rich (dark) regions having a composition of $(Co_{0.6}W_{0.6})_{12}C$ and identified as ${M}_{12}C$. Cr-rich carbides



# Generally, the cavitation erosion resistance of materials is known to be less dependent on the hard precipitates than the matrix phase.

Stellite's cavitation erosion resistance depends more on its matrix phase than on its hard precipitates <?>
# Cite all the papers after this sentence over here as well


Ion implantation is a surface modification technique that deposits ions like nitrogen, manganese, and titanium to improve tribological properties, and causes microstructural effects and phase transformation effects in cobalt-based alloys.

\cite{dillichStructuralChangesCobaltbased1987, szalaEffectManganeseIon2022, szalaEffectNitrogenIon2021, szalaPhenomenologicalModelCavitation2023, yamanakaDevelopingHighStrength2016, poshtahaniPlasmaNitridingEffect2023}.


# Unimplanted stellite ε-rich matrix is less prone to plastic deformation than γ and consequently, increase of γ phase effectively holds carbides in cobalt matrix and prevents Cr7C3 debonding. This phenomenon elongates three times the CE incubation stage, slows erosion rate and mitigates the material loss.

Manganese ion implantation appears to have minimal effect on the cavitation erosion and microstructue of Stellite 6 \cite{szalaEffectManganeseIon2022}

Dillich et al find that titanium ion implantation inhibits debonding at carbide-matrix interfaces and contributes additional toughness to the matrix of cobalt-based alloys
\cite{dillichStructuralChangesCobaltbased1987}.

Szala et al find that nitrogen ion implantation promotes $\epsilon(hcp) \rightarrow \gamma(fcc)$ phase transformation, and argue that as the fcc structure bonds Cr7C3 carbides in matrix and mitigates matrix ductile fracture, promoting the fcc phase and delaying the $\gamma \rightarrow \epsilon$ martensitic phase transformation is responsible for the superior performace of nitrogen-implanted Stellite 6.
\cite{szalaEffectNitrogenIon2021, szalaPhenomenologicalModelCavitation2023}

Yamanaka et al note that carbon implantation increases stacking fault energy (SFE), ie the stability of the gamma phase, and ductility of the matrix, although excess carbon implantation beyond 0.1 wt% leads to carbide precipitation and reduction in ductility
\cite{yamanakaDevelopingHighStrength2016}.


Poshtahani et al find that plasma nitriding results in hard nitrided phases (CrN, CoN, W_2N) that increase hardness and wear properties of Stellite 6 and 12, and that the depleted chromium in the matrix due to nitriding was an obstacle to forming protective chromium oxide layers, resulting in decreased corrosion resistance
\cite{poshtahaniPlasmaNitridingEffect2023}.

Despite the

The relationship between erosion resistance and the chemical composition of Stellite alloys has not yet been systematized or published in a broader publication.


** Carbide volume fraction

As hard phases (carbides and intermetallics) contribute to hardness and wear resistance, it is beneficial to estimate the volume fraction of different phases, through thresholding BSE images

In the present work, BSE images were taken on the polished samples, and thresholded using histogram analysis, with ten readings taken and averages to calculate the volume fraction of hardness phases.

Stellite 1 includes two kinds of carbides, chromium rich carbides and tungsten-rich carbides.

ratiaComparisonSlidingWear2019
The total volume fraction of carbides

** Cavitation erosion mechanism

Eroded surfaces of as-cast and HIPed Stellite 1 were observed by scanning electron microscopy to clarify the erosion mechanism. In the center of the cavitation crater, material removal is observed in both as-cast and HIPed samples

The original surface was exposed to the high-frequency collapses of cavitation bubbles resulting in plastic deformation of the material surface, especially at the boundary with the neighbouring carbide. The plastic deformation produces a step relative to the adjacent grain, resulting in crack initiation. The crack initiation near the boundary results in erosion of the matrix near the carbide, which may be seen as preferential erosion at matrix-carbide boundaries. With the loss of support of the nearby matrix, carbides are removed, revealing the matrix underneath.




* COMMENT Conclusions

A fairly concise section which summarises your main findings from your results and discussion sections, identifies your contribution to the field, and suggests some further work.


* Bibliography :ignore_heading:

#+LaTeX: \bibliographystyle{elsarticle-num}
#+LaTeX: \bibliography{references}

\appendix

* Essential appendices

Essential appendices; ie, detail without which the main paper is difficult to understand should be included here.

* List of further material in the Work Progress Report

All working material and non-essential appendices must be submitted separately as the `Work Progress Report'.  There is no need to refer to that material.  However, if you feel that certain sections or files in that report would be useful to the reader, you can list here that material and how to find it in the Work Progress Report submission.

* Local Variables :ignore_heading:

# Local Variables:
# after-save-hook: (lambda nil (org-export-to-file 'latex (format "src/%s.tex" (file-name-nondirectory (file-name-sans-extension (buffer-file-name))))))
# End: