The main objective of this research is to investigate the effect of wide peening and cleaning (WPC) also known as fine particle peening on the surface properties and cutting performance of cemented carbide inserts. In WPC, the surface of the material is bombarded with millions of high-velocity fine shot generating a uniform layer of plastic deformation near the surface. The plastically deformed layer will have higher compressive residual stress levels, higher surface hardness, experience changes in surface morphology and changes in microstructure. Selecting suitable peening parameters is crucial for achieving proper results. In this study, tools are treated under different pressures varying between 0.2 to 0.4 MPa, and for different peening durations of 2.5 to 10 s. The cutting performance of uncoated tools treated with WPC was examined while turning ductile cast iron and AISI 4140. To have a better understanding, the surface morphology, microstructure, surface roughness, cutting edge radius, residual stresses, and surface hardness were measured and discussed. The results are also compared with untreated tools. The compressive residual stresses were significantly higher after WPC. In addition, uncoated tools treated with WPC resulted in a 12-30% higher tool life over untreated tools. Based on the findings outlined in this thesis, WPC can be recommended as a surface treatment on uncoated cemented carbide inserts for increasing tool life. Also, this study shows significant potential for using WPC as a pre-coating treatment for improving coating adhesion on cemented carbide cutting inserts. / Thesis / Master of Applied Science (MASc)

<p>WC/Co cemented carbide is a composite material for highly demanding wear applications. The unique combination of hardness (from the WC-phase) and toughness (from the binder Co) gives a material especially suitable for rock drilling. This thesis, investigates the deterioration and wear of these cemented carbide buttons and the correlation to different rock types.</p><p>To better understand the nature of the wear of the cemented carbide buttons, the counter surface –the rock- has also been studied. A range of important rock types has been investigated with respect to hardness distribution and scratch response in a micro scale and friction properties when slid against cemented carbides. </p><p>The cemented carbide may deteriorate due to a number of mechanisms. The effect of fatigue in the structure was studied in TEM and particle erosion response was used to probe the corresponding mechanical degradation. </p><p>Further, homing cross sectioning has been developed and used as a new technique to investigate the presence of weak zones in the surface layer of a drill button. It was found that rock penetration into this layer is a very common mechanism, with profound implications for the nature of the wear. </p><p>High resolution scanning electron microscopy has been extensively used to map the deterioration and wear of numerous drill buttons, worn against different rock types in different kinds of drilling applications. Finally, the collected data on the surface damage, the reptile skin formation, the rock intrusion and the properties of the rock are assembled into a new view of the deterioration and wear of cemented carbide in rock drilling. </p>

WC/Co cemented carbide is a composite material for highly demanding wear applications. The unique combination of hardness (from the WC-phase) and toughness (from the binder Co) gives a material especially suitable for rock drilling. This thesis, investigates the deterioration and wear of these cemented carbide buttons and the correlation to different rock types. To better understand the nature of the wear of the cemented carbide buttons, the counter surface –the rock- has also been studied. A range of important rock types has been investigated with respect to hardness distribution and scratch response in a micro scale and friction properties when slid against cemented carbides. The cemented carbide may deteriorate due to a number of mechanisms. The effect of fatigue in the structure was studied in TEM and particle erosion response was used to probe the corresponding mechanical degradation. Further, homing cross sectioning has been developed and used as a new technique to investigate the presence of weak zones in the surface layer of a drill button. It was found that rock penetration into this layer is a very common mechanism, with profound implications for the nature of the wear. High resolution scanning electron microscopy has been extensively used to map the deterioration and wear of numerous drill buttons, worn against different rock types in different kinds of drilling applications. Finally, the collected data on the surface damage, the reptile skin formation, the rock intrusion and the properties of the rock are assembled into a new view of the deterioration and wear of cemented carbide in rock drilling.

In this study, the possibilities to produce metallic glass as binder phase in hard metal by means of powder metallurgical methods have been investigated. The aim of the study was to do an initial investigation about metallic glass as alternative binder phase to cobalt in hard metal. Production of samples with metallic glass forming alloys and an amorphous powder as binder phase in hard metal by means of quenching and hot pressing have been performed. Moreover, mechanical alloying of metallic glass forming powder to achieve amorphicity has been performed. The samples and powders were analyzed by means of XRD, LOM, STA, SEM and EDS. The results showed that no glass formation of the binder phase was achieved by quenching, hot pressing or mechanical alloying. However, interesting information about glass formation by means of metallurgical methods was obtained. The main conclusion was that production of metallic glass by means of metallurgical methods is complicated due to changes in the binder phase composition throughout the production process as well as requirements of high cooling rates when quenching and high pressures when hot pressing.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Sliding wear is a complicated form of wear involving different factors. The factors affecting the process are the mechanical properties of the materials, sliding distance, sliding speed, and normal force applied to the contact. An experimental study was conducted to assess the performance of Ti6Al4V in self-mated and various counterface material contact couples subjected to linear reciprocating dry sliding motion. The normal force was varied for all the experiments to understand the effect it had on specific couples. Sliding wear experiments were also conducted on cemented carbides coupled with Ti6Al4V. In certain applications carbide coatings are used and could possibly come into contact with Ti6Al4V. Cemented carbides used in the study were manufactured through spark plasma sintering and liquid phase sintering. An in depth study was conducted to assess the spark plasma sintered materials and compare these to those manufactured through liquid phase sintering. The experimental study revealed that an increase in normal force, in sliding experiments, led to an increase in friction and wear volume loss of the Ti6Al4V pin. In addition the experiments found that Ti6Al4V was prone to adhesion and surface oxidation. / AFRIKAANSE OPSOMMING: Glyslytasie is 'n gekompliseerde slytasievorm wat verskillende faktore behels.Die faktore wat die proses beïnvloed is die meganiese eienskappe van die materiale,gly-afstand,glyspoed en normale druk(krag) wat op die kontakoppervlakte toegepas word. 'n Eksperimentele studie om die werksverrigting van Ti6Al4V in verenigde en verskeie teenwerkende materiaal kontakpare wat onderwerp is aan lineêre omgekeerde droë gly-aksie te assesseer is uitgevoer.Die normale krag vir al die eksperimente om die effek wat dit op die spesifieke pare gehad het te verstaan is gevarieer. Glyslytasie-eksperimente is ook op gesementeerde karbiedes wat met Ti6Al4V gekoppel is,uitgevoer. In sekere toepassings is karbiedlae gebruik en kon moontlik met Ti6Al4V in kontak gekom het. Gesementeerde karbiedes wat in die studie gebruik is, is deur vonkplasmasinter en vloeibare fase-sinter vervaardig. 'n Indieptestudie is ook uitgevoer om die vonkplasmasintermateriale en dié materiale wat deur vloeibare fasesinter vervaardig is te vergelyk. Die eksperimentele studie het getoon dat 'n toename in normale krag in glyeksperimente gelei het tot 'n toename in wrywing en slytasievolumeverlies van die Ti6Al4V pin. Bykomend tot die eksperimente is gevind dat Ti6Al4V geneig was tot adhesie en oppervlakteoksidasie.

Cemented carbide containing sub carbide phases, M6C and M12C, known as eta-phase, increases the lifetime milling cutters due to increased resistance to comb cracks. When milling, the inserts much sustain high temperatures, meaning edgeline toughness and thermal fatigue resistance are needed. To obtain this, finer grains and higher binder content are needed. In this study, WC-Co cemented carbides with eta-phase and Cr as well as a higher binder content are investigated. The microstructure is the focus, with parameters such as eta-phase particle size and volume fraction, WC grain size being evaluated. Another part of the study is the investigate the effect of Cr on heat treatment. The addition of Cr in a WC-Co cemented carbide with eta-phase has shown to give rise to smaller eta-phase particle sizes and WC grain size as compared to without Cr. Also, increasing the volume fraction of eta-phase has less influence on WC and eta-phase particle size. Heat treated samples without Cr is shown to increase the coercivity of the samples at 700 degrees Celsius, without change in WC grain size. The effect is also leading to an increase in hardness. But with addition of Cr, the effect seems to diminish.

Cutting tool inserts are often coated with thin layers either through chemical vapor deposition (CVD) or physical vapor deposition (PVD) processes. In order to have a better wear resistance cutting tools are mostly subjected to post-coating treatment processes. Shot peening is one of the processes that is used to improve the fatigue life of metallic components. In this study, the finite element (FE) method is employed to model the elastic-plastic deformation and development of residual stress distributions in a cutting tool after the impact of a shot medium. To carry out the work, CVD coated cemented carbide has been chosen to be the workpiece (insert), and the coatings of the chosen insert are Titanium Carbo Nitride (TiCN)  and Aluminum Oxide (Al2O3). Aim of the study is to model a single impact in the shot peening process on a surface of a coated cemented carbide insert while simulating the plastic deformation of the materials. In addition, the objective of the study is also to understand and explain the mechanics of shot peening process and find applicable mechanical properties of the materials for FE modeling. Conjugately, the influence of shot peening process parameters (e.g. velocity, diameter or shape of the peening media) on residual stress distribution has been investigated and the results obtained were compared to the one observed from experiment. The modeling in the study is carried out both with and without initial residual stresses in the materials. The initial residual stresses are estimated by applying a thermal load to the model. The results show that the compressive residual stresses achieved while shot peening by an edge-shaped medium are significantly higher at the surface (i.e. in a coated layer) than compared to a globular medium. In contrast, it is observed that the compressive residual stresses in the cemented carbide are significantly higher and deeper when shot peened with globular medium than the edge-shaped medium. Furthermore, the results of parameteric study demonstrate that the smaller medium induces higher residual stresses at the surface (i.e. in a coated layer) than in the cemented carbide. In contrast, it is observed that the bigger medium induces less residual stresses at the surface (i.e. in a coated layer) and higher residual stresses deeper in the cemented carbide. Whereas, it is observed that the higher residual stresses at the surface (i.e. in a coated layer) and in the cemeneted carbide can be achieved simultaneously by shot peens having a  higher velocity. Residual stress profiles modelled in this report correlate with data from previous studies.   This study has been carried out at Sandvik Coromant, Edge and Surfaces department in Stockholm, Sweden.

This work has been performed at the Applied Materials ScienceDivision at The Ångström Laboratory in collaboration with SandvikMining AB. The project is part of the joint research programmeCoFree.In this work, the problem of finding an impact test method forcemented carbide rock drill inserts is considered. A suitable testmethod is required to benchmark alternative binder cemented carbidesagainst today’s cobalt based grades. The developed test method isbased on a Charpy pendulum arrangement and utilizes, as in rockdrilling, impact of cylindrical bars to achieve the high impact forcesufficient to fracture the rock drill inserts. The impact issymmetrical with two inserts facing each other, which proves to be anefficient way of damaging the inserts. To gain more informationregarding the force and pulse duration, the history of the impact isrecorded with the use of strain gauges. The measured force curvesfrom repeated tests are typically very similar, a strong indicationthat the test loads the buttons in a well-defined, repeatable way.Also, quasi-static loading of the insert is present in the impactwhich agrees to the results from a static compression test. Thisindicates that the inserts are subjected to quasi-static loading,rather than dynamic loading.A single impact test procedure was developed in this work. Thismethodology proved capable of differentiating the impact performanceof two different button cemented carbide grades. Hence, the test canbe used in the future as a benchmark test. It is however necessary toobtain statistical evidence. The impact performance was measured byobserving cracks produced in the impact contact zone with the aid ofan optical microscope with 85x objective. Radial cracks are veryoften found, often forming a cross around the contact zone. Whenlarge button chippings occur due to the impact loading, a very clearsudden drop in the measured force pulse is seen. This is however notseen for impacts that only produces cracks.

A necessidade de se usinar materiais de alta dureza e garantir bom acabamento superficial é um desafio para as atuais indústrias metal/mecânica. Além disso, coloca-se também a necessidade de fazê-lo de forma técnica e economicamente viável. Diante desse desafio o torneamento duro surge como uma opção. Com o uso dos parâmetros (velocidade de corte, avanço e profundidade de corte) e ferramentas adequadas o torneamento duro possibilita uma adequada rugosidade superficial e pode substituir a necessidade de retificação, simplificando e reduzindo custos no processo de fabricação. Para que seja possível alcançar tais resultados, é necessária a pesquisa e validação de parâmetros que permitam a execução do torneamento de materiais de alta dureza. Por meio de ensaios, de desbaste interno, realizados com peças de metal duro H11N e com ferramentas de diamante, foram feitos testes preliminares com o uso da ferramenta de projeto de experimentos (DOE), para selecionar os melhores conjuntos de parâmetros (velocidade de corte e avanço). Foi realizado um segundo grupo de testes, finais, para garantir estatisticamente os melhores resultados, as informações obtidas foram rugosidade, desgaste e número de passes. Com a análise dos resultados preliminares obtidos utilizando a ferramenta estatística de projeto de experimentos (DOE), foi identificado alta quebra de ferramentas (54%). Com a realização de micrografias, a possibilidade do problema estar relacionado com a estrutura do material e ou com o tamanho do grão foi descartada. Foram detectadas ainda, marcas na superfície usinada dos corpos de prova que são indicadores da existência de vibrações durante o processo, o que justifica o número elevado de quebras das arestas de corte de forma prematura. Os testes finais não apresentaram quebra prematura de ferramentas, e sim uma vida maior que o esperado. Foi estabelecido parâmetros viáveis para o processo, velocidade de corte de 22,1 m/min e avanço de 0,09 mm/rev. Através da análise do desgaste foi possível estabelecer um critério para troca de ferramenta, que foi o desgaste de flanco (Vb) de 0,2mm. / The necessity of machining materials with high hardness to ensure a good surface finish is a challenge for metal mechanic industries these days. Furthermore, it has the necessity to achieve this goal in a technical way and be economically viable. An option to tackle this challenge is hard turning. Through the use of parameters (speed cutting, feed rate and cut depth) and adequate tools, the hard turning enables a good surface roughness and can replace the need for grinding, making the fabrication process simpler and reducing the cost. In order for these results to be achieved, research is required and validation of parameters, which allow the realization of turning materials with high hardness. Through trials of internal thinning, with pieces made of H11N material and diamonds tools, Design of experiments (DOE) preliminary tests were carried out to select the best parameters group (cutting speed and feed rate). Secondary tests were done to ensure statically the best results in this case, the data obtained was of roughness, wear and tool life. When analyzing the preliminary results obtained using the statistic tool, design of experiments (DOE), it was identified that a high breakage of tools was occurring (54%). Through micrograph tests, the possibility of the problem being with the material structure and grain size was discarded. Traces were detected in the machining surface on the machined piece, these are indicators of the chance of vibration during the process, which can justify the high premature tool breakage. The final tests didnt show premature tool breakage, they showed the life span of the tool was longer than what was expected. Viable parameters were established for this process, cutting speed of 22.1 m/min and feed rate of 0.09 mm/rev. Through the wear analysis it was possible to establish a criterion of tool change, it was flank wear (Vb) of 0.02mm.

In the thesis is solved manufacturing technology of step drill from material of cemented carbide. At first is made review of existing shank cutting tool types, after that follows an analysis of cemented carbide tool material. In the next part of thesis is manufacturing technology of this tool, including review of grinding wheels, designed. Output of this work is procedure of program designing for manufacturing this tool in software Numroto. Next output is techno-economic evaluation of step hole manufacture with combined tool and comparison to conventional type of manufacture.