This diploma work is performed at Sandvik Mining and Rock Technology, Rock Tools division, a world-leading mining equipment manufacturer. The aim is to study the wear of cemented carbide rock drill inserts worn against granite and sandstone countersurfaces, with focus on the impact of binder phase composition and flushing agent chemistry. A brief introduction to rock drilling, cemented carbides and the wear and degradation mechanisms of cemented carbides in rock drilling is given. Wear is induced in a lab test by sliding cemented carbide inserts against granite and sandstone countersurfaces while flushing with deionized water or synthetic mine water. The wear is quantified by measuring material weight loss, and worn inserts are studied by SEM. All wear marks feature crushed, fragmented and heavily deformed WC grains and cavities left after individually removed WC grains. Rock adhere strongly on inserts worn against both granite and sandstone, and adhered material from both rock types sometimes endure the mechanical contact between insert and rock without significant spalling. Inserts tested with deionized water against sandstone wear 2.2 - 5.1 times more relative to against granite, and the only distinct difference observed is the distribution of adhered rock. The use of synthetic mine water relative to deionized water impacts the wear of all inserts, though corrosion products are only found on some of them. Further, the tribological contact greatly impacts the corrosive attack. The relative wear difference using different water chemistries is larger for inserts with a smaller relative amount of binder. In most cases, increased wear is measured for inserts tested with synthetic mine water. For reasons yet unknown, this trend is reversed for inserts with a high relative amount of binder tested against sandstone, where a decrease in wear is measured instead. / Detta examensarbete har utförts åt Sandvik Mining and Rock Technology, Rock Tools avdelningen, som är en världsledande utrustningstillverkare inom gruvindustrin. I arbetet undersöks nötningen av så kallade bergborrstift av hårdmetall. Berg är generellt ett mycket hårt och sprött material, och borrning i berg går därför i huvudsak ut på att krossa och spola bort krossad sten. Längst fram på bergborrar sitter borrkronor som till största del är gjorda i stål. Då stål är för mjukt för att effektivt kunna avverka berg monterar man in stift av hårdmetall längst fram på borrkronan. Hårdmetall är ett kompositmaterial av mycket hårda men spröda wolframkarbidkorn (WC) som hålls ihop av en, jämfört med WC, mjuk och formbar metall som kallas bindefas. Resultatet är ett mycket hårt men fortfarande relativt segt material som dessutom klarar de mycket höga temperaturer som uppstår vid bergborrning. Traditionellt används kobolt som bindefas, men nu tros det finnas hälsorisker med kobolt och dessutom sker en stor del av världens koboltutvinning under oetiska förhållanden i konfliktländer i Afrika. Detta i kombination med att koboltpriserna ökat dramatiskt de senaste åren leder till att man nu söker efter alternativa bindefaser. Bland annat undersöker man olika legeringar av nickel och järn. I detta arbete jämförs nötningen av stift med nickel-, järn- och olika koboltbindefaser. I ett labtest fås nötning genom att stiften trycks mot en roterande stencylinder av antingen granit eller sandsten. I verkliga förhållanden används ofta så kallat gruvvatten som sipprar in i gruvan som spolvatten för att ta bort stenkrosset och kyla borrkronan. För att se hur kemin i spolvattnet påverkar nötningen spolas kontaktytan mellan stift och stencylinder med antingen avjoniserat vatten eller syntetiskt gruvvatten under testerna. Stiftens materialförlust under provningen beräknas genom att mäta deras vikt innan och efter. För att se om skillnader i nötningshastighet mellan olika stifttyper eller testvillkor avspeglas i olika utseenden på slitytorna undersöks stiften med hjälp av ett svepelektronmikroskop (SEM). Från SEM-bilderna ser man att alla stift från alla testvillkor har krossade och fragmenterade WC-korn på ytan och att stora delar av slitytorna täckts av påkletat berg. Bergpåsmetningarna är ibland mycket tunna (< 1 μm) och delvis inblandade i bindefasen, och ibland betydligt tjockare (flertal μm). De tjockare påsmetningarna är bundna så pass hårt till ytan att de kan upprätthålla delar av kontakten mellan stiftet och berget under testningen utan att lossna. Huruvida detta skyddar hårdmetallen från att nötas eller om det påkletade berget reagerar med, och därmed ökar den kemiska nedbrytningen av stiftet är inte utrett. Berget skyddar dock den underliggande hårdmetallen mot den korrosion som uppstår i kontakt med spolvattnet. Resultaten visar att stiften nöts betydligt mer mot sandsten än mot granit. Förutom att bergpåsmetningarna har en annan fördelning över ytan så syns inga tydliga skillnader mellan stiften testade mot de båda bergarterna. De flesta stiften nöts mer när de testas med gruvvatten än med avjoniserat vatten. Detta gäller alla stift utom de som har hög relativ mängd bindefas och som testats mot sandsten. Dessa stift nöts tvärt om mindre när de testas med gruvvatten än med avjoniserat vatten. Hittills har ingen anledning till denna konsekventa avvikelse hittats.

Dans l'industrie du forage pétrolier, les conditions de travail de plus en plus sévères requièrent sans cesse de nouveaux outils plus résistants à l'usure abrasive et à l'impact. Afin de répondre à ce défi, les travaux présentés ici, ont pour but l'élaboration de matériaux en carbure cémenté à gradient de composition par le procédé d'imbibition réactive. Ce procédé peut être décomposé en deux procédés de gradation, à savoir : l'imbibition et le revêtement réactif. L'imbibition a pour rôle d'enrichir graduellement, en phase liante, le coeur d'une pièce en carbure cémenté dense et repose sur le principe de migration de phase liquide dans un corps solide-liquide. Le revêtement réactif est un procédé qui s'applique également sur un carbure cémenté dense sur lequel est déposé un revêtement de nitrure de bore. Après avoir atteint le liquidus de la phase liante du carbure cémenté, une précipitation de borures ternaires prend place à la surface du matériau et s'étend graduellement sur des distances millimétriques. Dans le cas de pièces industrielles (inserts tricône et supports de taillants PDC (Polycrystalline Diamond Compact)), le traitement d'imbibition réactive permet de générer des gradients de dureté pouvant atteindre 450 HV sur 25 mm. L'élaboration de tels gradients a nécessité une meilleure compréhension des cinétiques ainsi que des phénomènes mis en jeu durant l'imbibition et le revêtement réactif. Dans le cas des taillants PDC, l'influence des paramètres du procédé HPHT de synthèse de la plaquette diamantée, sur le gradient de composition présent dans le support WC-Co après imbibition réactive, a été étudiée. Ces travaux se sont également intéressés à l'effet de ces gradients de composition sur les propriétés des plaquettes diamantées ainsi obtenues. A la suite d'essais mécaniques, les inserts WC-Co et taillants PDC gradués montrent une augmentation significative de leur résistance à l'abrasion (de 30 à 100%) et de leur tenue à l'impact (de 20 à 40%). / In oil drilling industry, harsher working conditions require ever new and more abrasive wear and impact resistant tools. To meet this challenge, the work presented here, is to develop graded cemented carbide materials by reactive imbibition process. This method can be divided into two gradation processes, namely, reactive coating and imbibition. Imbibition gradually enriches the core of dense cemented carbide with binder phase and is based on the principle of liquid phase migration in a solid-liquid body. Reactive coating also takes place in dense cemented carbide on which a boron nitride coating is deposited. After reaction with the WC-Co liquid binder, some ternary boride precipitations take place from surface to several millimeters deep. For industrial parts (inserts for roller cone bits and PDC (Polycrystalline Diamond Compact) cutters substrates), hardness gradients obtained can reach 450 HV on 25 mm. Such gradients development is passed through a better understanding of kinetics and phenomena occurring during imbibition and reactive coating. In case of PDC cutters, influence of HPHT process parameters, allowing diamond table synthesis, on the WC-Co substrate gradient, generated by reactive imbibition, was studied. This work was also interested in gradient effect on the obtained diamond tables properties. After mechanical tests, graded WC-Co inserts and graded PDC cutters show a significant increase of both wear resistance (from 30 to 100%) and impact resistance (from 20 to 40%).

The development of alternative binder systems for tungsten carbide (WC) based cemented carbides has again become of relevance due to possible changes in EU regulations regarding the use of Cobalt (Co). A framework for the ICME (Integrated Computational Materials Engineering) based Materials Design is presented to accelerate the development of alternative binder systems. Part one of this work deals with the design of the cemented carbide composite hardness. It has been shown that the intrinsic binder hardness is comparable to a bulk metal alloy and that based on the binder solubilities a solid solution strengthening model developed in this work can be employed. Using a method presented in this work the non-equilibrium, frozen-in binder solubilities can be obtained. Both the design of the binder phase and composite hardness is presented based on a general Materials Design approach. Part two deals with a multiscale approach to model the surface gradient formation. The experimentally missing data on liquid binder diffusion has been calculated using AIMD (Ab initio Molecular Dynamics). The diffusion through the liquid cemented carbide binder has to be reduced to an effective diffusion value due to the solid carbides acting as obstacles that increase the diffusion path. The geometrical reduction of the diffusion has been investigated experimentally using the SIMS (secondary ion mass spectroscopy) technique in WC-Nickel-58Nickel diffusion couples. The geometrical contribution of the so-called labyrinth factor has been proven by the combination of the experiments and in conjunction with DICTRA simulations using the precise liquid AIMD diffusivities. Unfortunately, despite the improved kinetic database and the geometrical diffusion reduction, the surface gradient formation cannot be explained satisfactory in complex cemented carbide grades. Additional, but so far unidentified, contributions have to be considered to predict the surface gradient thickness. / <p>QC 20170919</p>

This diploma thesis deals with increasing the service life of parts intended for soil cultivation. The work evaluates the current possibilities of increasing the utility value of spare parts. Practical tests will provide recommendations for the most appropriate method to increase durability. The work examines uncharted methods of testing soldered joint. The results are evaluated in terms of quality and economic profitability. All results from this work are based on the basis of practical tests of plowing machine in rocky soil.

This eleborate study is aimed at analysis of complete methods machining. There are characterized particular methods and their effect on the surface´s quality of machined area in this study. Concluding part of the study includes practical demonstration of machining by using cemented carbide-tipped tool and polycrystalline diamond and evaluation of this demonstration.

This diploma thesis is aimed on methods of the coating cutting material (cemented carbide, cermets, cutting ceramic, super hard materials) and evalutation individual method regarding technological posibilities of deposition of hard coatings a their mechanical, thermal and che-mical properties. The task of the work is full elaboration obtained technical knowledges and mainly evalutation a comparison of the work conditions (kind of the cutting materials, cutting conditions) that selected producers recomended for effective turning aplications of the coa-tings cutting materials.

Thema dieser Arbeit ist eine experimentelle Untersuchung zur Verbesserung der tribologischen Eigenschaften von Hartmetallen auf der Basis von Wolframkarbid– Kobalt unter Benutzung von Ionen–Implantation in Kombination mit den hierbei auftretenden Struktur– und Phasen–Änderungen. Die vorliegende Arbeit unterscheidet sich von allen anderen bisherigen Arbeiten besonders durch (1.) die detaillierte Analyse der mikroskopischen Veränderungen und durch (2.) deren Verknüpfung mit der Änderung der tribologischen Eigenschaften des Materials.

In this master thesis, performed at Sandvik Coromant Västberga (Stockholm), a comprehensive study has been made to investigate the wear on textured alumina (Inveio™) coated cutting tools when turning low-alloy steels. Specifically, wear studies have been made on tools’ rake faces when turning two separate batches of SS2541, after an initial turning time of 4 min. A particular focus has been given to elucidate what particular role the inclusions might have for the wear of the alumina coating onthe tools. Evaluation of tool wear has been made by employing several different analytical techniques, such as LOM, SEM, Wyko, Auger-spectrometry (AES), EPMA and XRD. The results shows that the arisen wear marks on both tested tool types may be divided into three separate and highly distinguishable wear zones, denoted here in thiswork as “wear bands”. Largest amount of wear tended to occur initially at the topmost part of the 3rd wear band. This was true for both tested tool types. This area demonstrated a characteristic 'lamellar' wear pattern, composed of narrow andstructured ridges. All the tools tested demonstrated the adhesion of workpiece materials of various composition that formed into smeared layers in these formed ridges. Depth-profiling Auger-spectrometry revealed that a significant amount of calcium was present in the machined alumina coating layers. This suggests that a reaction between the calcium-containing inclusions found in the steel and the aluminacoating layer had occurred during the performed turning tests.These results arecontradictory to the general belief that alumina is chemical inert during machiningand has previously, to the authors knowledge, not yet been published. Based on the results from this thesis and from a literature review concerning thebehavior of α-alumina during deformation, a new theoretical wear model has been developed. In this model, it is emphasised that the sliding of hard inclusions from the steel may activate pyramidal slip systems in the textured alumina coating. This causes a nano-crystallisation and/or amorphisation in the topmost part of the coating, which facilitates the further wear of these coated tools. / I detta examensarbete, som har utförts vid Sandvik Coromant i Västberga (Stockholm), har en omfattande studie gjorts i syfte att undersöka slitaget på texturerad aluminiumoxid-belagda skärverktyg (Inveio™) vid svarvningen av låglegerade stålsorter. Förslitningsstudier har framförallt gjorts på verktygens spånsidor vid svarvningen av två separata batcher av stålsorten SS2541 efter en inledande ingreppstid på 4 min. Ett särskilt fokus har även ägnats åt att belysa vilken roll stålets inneslutningar kan ha för slitaget av aluminiumoxidbeläggningen. Utvärderingen av verktygsslitaget har gjorts med hjälp av flera olika analytiska tekniker, däribland LOM, SEM, Wyko, Auger-spektrometri (AES), EPMA samt XRD. Resultaten från detta examensarbete visar på att det uppkomna slitaget på de verktyg som har testats kan uppdelas till tre separata och mycket distinkta ”slitagezoner”. Dessa zoner har för detta arbete benämnts som ”nötningsband”. Störst förslitning framträdde initialt i den översta delen av det 3:e nötningsbandet på de testade skärverktygen. Detta område uppvisade ett karaktäristiskt ”lamell”-liknande utseende, bestående av smala och strukturerade åsar och skåror. Vidare uppvisade samtliga undersökta verktyg på förekomsten av påsmetat arbetsmaterial av varierande sammansättning i dessa bildade åsar. När de slitna verktygen undersöktes med djuprofilerande Auger-spektrometri påvisades det att en signifikant mängd kalcium fanns inuti aluminiumoxidbeläggningen. Detta tyder på att en reaktion mellan de kalciuminnehållande inneslutningarna (som finns inuti stålet) och aluminiumoxidbeläggningen har reagerat med varandra under bearbetningsförloppet. Dessa resultat är motsägande till den allmänna uppfattningen om att aluminiumoxid är kemiskt inert vid bearbetningen av stål. Därutöver har dessa resultat även, till författarens kännedom, aldrig tidigare publicerats. Baserat på de resultat som har erhållits från detta examensarbete, och från en omfattande litteraturstudie gällande deformationen av α-aluminiumoxid, har en ny teoretisk förslitningsmodell utarbetats. I denna modell betonas det särskilt att glidningen av hårda inneslutningar från stålet kan aktivera s.k. pyramidala glidsystem i den texturerade aluminiumoxidbeläggningen. Detta orsaker en nano-kristallisering och/eller amorfisering av den översta delen av aluminiumoxidbeläggningen.  Denna omvandling tros kunna underlätta den fortsatta förslitningen av dessa belagda skärverktyg.

The object of this work is to obtain a fundamentalunderstanding of the principal issues concerning the handlingof an aqueous WC-Co powder suspension. The WO3 surface layer on the oxidised tungsten carbidepowder dissolves at pH&gt;3 with the tungsten concentrationincreasing linearly with time. Adding cobalt powder to thetungsten carbide suspension resulted in a significant reductionof the dissolution rate at pH&lt;10. Electrokinetic studiesindicated that the reduced dissolution rate may be related tothe formation of surface complexes; the experiments showed thatCo species in solution adsorb on the oxidised tungsten carbidepowder. The surface forces of oxidised tungsten and cobalt surfaceswere investigated using the atomic force microscope (AFM)colloidal probe technique. The interactions at various ionicstrengths and pH values are well described by DLVO theory. Theadsorption of cobalt ions to tungsten oxide surfaces resultedin an additional non-DLVO force and a reduced absolute value ofthe surface potential. It was shown that the adsorption ofpoly(ethylene imine) (PEI) to the WO3 surfaces induces anelectrosteric repulsion. The properties of spray-dried WC-Co granules were related tothe WC primary particle size, and the poly(ethylene glycol)(PEG) binder and PEI dispersant content in aqueous WC-Cosuspensions. The granule characterisation includes a new methodfor measuring the density of single granules. The increase inthe fracture strength of granules produced from suspensionsthat were stabilised with PEI was related to a more densepacking of the WC-Co particles. The AFM was used to study the friction and adhesion ofsingle spray-dried WC-Co granules containing various amounts ofPEG binder. The adhesion and friction force between two singlegranules (intergranular friction) and between a granule and ahard metal substrate (die-wall friction) have been determinedas a function of relative humidity. The granule-wall frictionincreases with binder content and relative humidity, whereasthe granule-granule friction is essentially independent of therelative humidity and substantially lower than the granule-wallfriction at all PEG contents. Key words:Hard Metal, Cemented Carbide, WC-Co, TungstenCarbide, Cobalt, Oxidation, Dissolution, Surface Complexation,XPS, AFM, Colloidal Probe, Hamaker Constant, Cauchy, WO3,CoOOH, ESCA, Zeta-Potential, Surface Potential, Poly(ethyleneimine), PEI, Suspension, van der Waals, Steric, Spray-Dried,Poly(ethylene glycol), Strength, Density, Friction, Adhesion,Granule, PEG, Pressing, FFM. / <p>QC 20161027</p>

<p>The object of this work is to obtain a fundamentalunderstanding of the principal issues concerning the handlingof an aqueous WC-Co powder suspension.</p><p>The WO3 surface layer on the oxidised tungsten carbidepowder dissolves at pH>3 with the tungsten concentrationincreasing linearly with time. Adding cobalt powder to thetungsten carbide suspension resulted in a significant reductionof the dissolution rate at pH<10. Electrokinetic studiesindicated that the reduced dissolution rate may be related tothe formation of surface complexes; the experiments showed thatCo species in solution adsorb on the oxidised tungsten carbidepowder.</p><p>The surface forces of oxidised tungsten and cobalt surfaceswere investigated using the atomic force microscope (AFM)colloidal probe technique. The interactions at various ionicstrengths and pH values are well described by DLVO theory. Theadsorption of cobalt ions to tungsten oxide surfaces resultedin an additional non-DLVO force and a reduced absolute value ofthe surface potential. It was shown that the adsorption ofpoly(ethylene imine) (PEI) to the WO3 surfaces induces anelectrosteric repulsion.</p><p>The properties of spray-dried WC-Co granules were related tothe WC primary particle size, and the poly(ethylene glycol)(PEG) binder and PEI dispersant content in aqueous WC-Cosuspensions. The granule characterisation includes a new methodfor measuring the density of single granules. The increase inthe fracture strength of granules produced from suspensionsthat were stabilised with PEI was related to a more densepacking of the WC-Co particles.</p><p>The AFM was used to study the friction and adhesion ofsingle spray-dried WC-Co granules containing various amounts ofPEG binder. The adhesion and friction force between two singlegranules (intergranular friction) and between a granule and ahard metal substrate (die-wall friction) have been determinedas a function of relative humidity. The granule-wall frictionincreases with binder content and relative humidity, whereasthe granule-granule friction is essentially independent of therelative humidity and substantially lower than the granule-wallfriction at all PEG contents.</p><p><b>Key words:</b>Hard Metal, Cemented Carbide, WC-Co, TungstenCarbide, Cobalt, Oxidation, Dissolution, Surface Complexation,XPS, AFM, Colloidal Probe, Hamaker Constant, Cauchy, WO3,CoOOH, ESCA, Zeta-Potential, Surface Potential, Poly(ethyleneimine), PEI, Suspension, van der Waals, Steric, Spray-Dried,Poly(ethylene glycol), Strength, Density, Friction, Adhesion,Granule, PEG, Pressing, FFM.</p>