AB SOMAS Ventiler manufactures valves for different applications. A valve of type DN VSSL 400, PN 100, used in high-temperature and high-pressure applications was investigated in this thesis. This type of valve is coated with high cobalt alloys to achieve the tribological properties needed for this severe condition. However there is a request from AB Somas Ventiler to find another solution. This request is based on the fact that demands on higher temperatures, from customers, yields higher requirements on the material. It is also a price issue since cobalt is quite expensive. Materials investigated were high-nitrogen steel, Vanax 75, nickel-based superalloy Inconel 718 and hardened steels, EN 1.4903 and EN 1.4923 presently used as base material in the valve. Calculation of contact pressure that arises when the valve is closed was first approached by using finite element method (FEM). Several models were constructed to show the behavior of the valve during closing in terms of deformation. Hot wear tests, in which a specimen was pressed against a rotating cylinder, were performed to be able to compare the materials to the solution of today and among each other. Data extracted from the tests were compiled in the form of coefficients of friction. Profilometer examinations were used to reveal the volumes of worn and adhered material and together with scanning electron microscopy (SEM) the wear situation for each material couple could be assessed. Wear mechanisms detected in SEM were adhesive and abrasive and the results clearly showed that the steels were not a good solution because of severe adhesive wear due to the similarity of mating materials creating a more efficient bonding between the asperities. Vanax 75 showed much better performance but there was still an obvious difference between the steels and the superalloy in terms of both coefficient of friction and amount of wear. On this basis, Inconel 718 was selected as the most suitable material to replace the high cobalt alloys used in the valves today. / AB Somas ventiler är ett företag som tillverkar ventiler för ett brett spann av applikationer. I det här examensarbetet har undersökningar genomförts på en ventil av modell DN VSSL 400, PN 100, som normalt används i applikationer för höga tryck och höga temperaturer. Ventilen beläggs i dagsläget med höghaltiga koboltlegeringar för att uppnå de tribologiska egenskaper som krävs i de påfrestande arbetsförhållanden som råder. AB Somas Ventiler har dock framfört en förfrågan om att hitta en alternativ lösning, en förfrågan som grundar sig i att kundernas ständiga önskemål på att ventilerna ska klara högre arbetstemperaturer också medför högre krav på ventilmaterialen. Det är även en prisfråga, då kobolt är en dyr legering att använda sig av. De material som inkluderades i undersökningen var det kvävelegerade stålet Vanax 75, nickelbaserade superlegeringen Inconel 718 samt de två stålen EN 1.4903 och EN 1.4923 i härdat tillstånd. De två sistnämnda används idag som basmaterial i ventilen. Genom att använda den finita element metoden (FEM) kunde en första beräkning göras av det kontakttryck som uppstår då ventilen stängs. Flera modeller konstruerades för att simulera ventilens deformation vid stängning. Där efter utfördes nötningstester i hög temperatur på de alternativa materialen, genom att låta en provbit pressas mot en roterande cylinder, för att sedan kunna göra en jämförelse mellan materialen och även med den nuvarande lösningen. Från nötningstesterna erhölls data som kunde användas för att ta fram friktionskoefficienter för de olika materialparen. Med hjälp av undersökningar med profilometer och svepelektronmikroskop (SEM) kunde värden på nötta och vidhäfta volymer erhållas tillsammans med information om nötningssituationer för ytorna mellan de olika materialparen. De nötningsmekanismer som påvisades med hjälp av SEM-undersökningen var adhesiv och abrasiv nötning, och resultaten visade tydligt att nötningen av stålen var omfattande, på grund av att lika material i kontakt med varandra skapar starkare band mellan ytorna, och att de därför inte var en intressant lösning. Det kvävelegerade Vanax 75 uppförde sig visserligen bättre men en tydlig skillnad mot superlegeringarna kunde dock fortfarande konstateras, sett till både friktionskoefficient och mängden slitage. Baserat på dessa resultat valdes Inconel 718 som det bäst lämpade materialet att ersätta de höghaltiga koboltlegeringarna som idag används i ventilen.

The application of the thermally sprayed WC-Co and Cr 3C2-NiCr coatings have been widely used in industry for its superior sliding, abrasive and erosive wear properties. The Al2O3 coating possessing high hardness can be utilized to improve the wear resistance of the metallic surface. Replacing the stamping tool material from steel to lightweight aluminium with protective coatings offers significant gains such as reduction in power costs and increasing operational efficiency during manufacturing of sheet automobile parts. In this study, the WC-CoCr and Cr3C2-NiCr coatings were sprayed with High Velocity Air-Fuel (HVAF) process and Al2O3 coating was deposited using Atmosphere Plasma Spraying (APS) process. The coatings were evaluated and compared based on the results of roughness tests, hardness tests, adhesion tests, quantitative imaging analysis and microstructure analysis. The experimental results revealed that the roughness value varied in a lower range which implies of a high density of the coatings. It was found that coatings have an extremely high hardness value as tested by the Vickers hardness test. The WC-Co coating was found to be the hardest (1215.2HV). The adhesion test was implemented according to the ASTM C633-79 standard. The result showed that WC-Co and Cr3C2-NiCr coatings without a bond coat had high tensile strength, higher than the respective glue strength (63.54MPa, 75.89MPa). Whereas, the Al2O3 coating has a much lower tensile strength (15.2MPa, 25.68MPa, with and without bond) than others and using a bond coat layer does not contribute to an increase in adhesion strength of the cermet coatings. The coating thickness was evaluated using Light Optical Microscopy (LOM) and microstructure analysis was carried out using Scanning Electron Microscopy (SEM). From the microstructure analysis, it was observed that all the coatings have a dense microstructure, very low porosity and low oxide inclusions in top coat. The WC and Cr3C2 grains retain a large volume fraction of finely dispersed in matrix. The alumina coating was found to have low levels of un-melted or the re-solidified particles in the coating. All of the aforementioned analysis and results reveal that WC/CoCr and Cr3C2-NiCr coating show promising potential for press tool applications. However, abrasive resistance test still remained to be done and will be performed in the future. The result of it can reveal the actual wear resistance between two coatings in reality and will be helpful in determining the better protective coating for aluminium press tools

The current study focuses on improving the wear resistance of femoral head component and enhancing the osseo-integration properties of femoral stem component of a hip implant made of a new generation low modulus alloy, Ti-35Nb-7Zr-5Ta or TNZT. Different techniques that were adopted to improve the wear resistance of low-modulus TNZT alloy included; (a) fabrication of graded TNZT-xB (x= 0, 1, 2 wt%) samples using LENS, (b) oxidation, and (c) LASER nitriding of TNZT. TNZT-1B and TNZT-O samples have shown improved wear resistance when tested against UHMWPE ball in SBF medium. A new class of bio-ceramic coatings based on calcium phosphate (CaP), was applied on the TNZT sample surface and was further laser processed with the objective of enhancing their osseo-integration properties. With optimized LASER parameters, TNZT-CaP samples have shown improved corrosion resistance, surface wettability and cellular response when compared to the base TNZT sample.

The effects of octadecylamine-functionalized reduced graphene oxide (FRGO) on the frictional and wear properties of diglycidylether of bisphenol-A (DGEBA) epoxy are studied using a pin-on-disk tribometer. It was observed that the addition of FRGO significantly improves the tribological, mechanical, and thermal properties of epoxy matrix. Graphene oxide (GO) was functionalized with octadecylamine (ODA), and then reduction of oxygen-containing functional groups was carried out using hydrazine monohydrate. The Raman and x-ray photoelectron spectroscopy studies confirm significant reduction in oxygen-containing functional groups and formation of ODA functionalized reduced GO. The nanocomposites are prepared by adding 0.1, 0.2, 0.5 and 1.0 wt % of FRGO to the epoxy. The addition of FRGO increases by more than an order of magnitude the sliding distance during which the dynamic friction is ≤ 0.1. After this distance, the friction sharply increases to the range of 0.4 - 0.5. We explain the increase in sliding distance during which the friction is low by formation of a transfer film from the nanocomposite to the counterface. The wear rates in the low and high friction regimes are approximately 1.5 x 10-4 mm3/N·m and 5.5 x 10-4 mm3/N·m, respectively. The nanocomposites exhibit a 74 % increase in Young’s modulus with 0.5 wt. % of FRGO, and an increase in glass transition and thermal degradation temperatures.

The influence of the horizontal magnetic field has not been sufficiently studied in contrast to study activity on the influence of the vertical magnetic field by researchers. The reason was that the influence of horizontal magnetic field to change the wear mass loss of ferromagnetic materials is smaller compared to the vertical magnetic field. However, the influence of horizontal magnetic field on rolling contact changes the subsurface crack initiation point toward surface is postulated by a researcher. Therefore, it is significance finding out how the horizontal magnetic field influences the tribological characteristics. This thesis presents a study on the influence of the horizontal magnetic field on wear in sliding contacts contributes for ascertainment the effect and mechanism of horizontal magnetic field on tribological characteristics of sliding contacts, through the experimental approach.The static magnetic field with densities of 0 and 1.1 Tesla and different orientations was applied to different contact conditions, different surface modifications and two sliding frequencies, using a ball-on-plate contact configuration. In conclusion, the presence of magnetic field enhances the chemical adsorption between iron or oxide iron and oxygen, and causes the transition of adhesive wear to oxidative wear. Besides, the presence of magnetic field combined with low sliding frequency forms the bulging on the wear surface and weakens the prevailing wear mechanism due to the low frictional temperature. On the other hand, the presence of magnetic field combined with high sliding frequency induces the transition to the oxidative wear mechanism and reduces the wear. Also, distinctly different appearances of wear surface are created by different magnetic field orientations. In the lubricated sliding contact, the magnetic field causes the reduction of wear and induction of oxide. It is postulated that the presence of magnetic field enhances the oxygen adsorption on the wear track by iron wear particles and hence varies the tribological behaviour. The influence of magnetic field on carbon steel coating consists in changes of oxide iron layer and steel layer, alterations of mechanical properties of the coating, and decrease in the mass loss and the surface roughness on the dry sliding contact. All these could be suggested the influence of adhesive strength of the interface between the base material and coating.

OBJECTIVE: The purpose of this in vitro study was to evaluate the cutting performance and accuracy of CAD/CAM diamond burs in different chemo-mechanical conditions when machining yttria-stabilized zirconia (YTZ), lithium-disilicate, feldspathic porcelain, and double network hybrid ceramic material. The study also examined bur wear mechanisms. MATERIALS AND METHODS: Two experiments were performed. Experiment 1: 45 samples of each material were milled, and four criteria were tested: milling time; surface roughness; change in bur weight after machining, and total cement space. Experiment 2: Four different coolant liquids were used while machining 15 samples of lithium-disilicate, feldspathic porcelain, and double network hybrid ceramic material. The four criteria in Experiment 1, plus marginal adaptation, were measured. Burs and ceramic materials used were examined with SEM before and after machining. RESULTS: Experiment 1: All burs milled 15 crowns of each material successfully, with a general increase in milling time and decrease in weight. Four wear patterns were identified: grit cracks, micro-fractures, dislodgement, and matrix abrasion. Sequential milling time increased for all of the ceramic materials. Surface roughness (Ra) decreased in general for all materials used in the study except YTZ, which showed an increase in Ra by the end of the machining series. Experiment 2: Additives used in this study had no significant effect on IPS e.max CAD milling efficiency or Ra. Boric acid reduced Vita MarkII machining time significantly and Ra. CONCLUSIONS: The cutting rate of diamond burs differed when machining different ceramic materials. In sequential machining, every consecutive milling demonstrated lower cutting efficacy. The surface roughness of consecutive machined samples differed. Some cooling liquids affected the quality of the machined surface. The bur wear mechanism was the same when different ceramic materials were machined, and their microstructure affected their machinability. / 2019-09-26T00:00:00Z

This thesis project was carried out at Sandvik Coromant in Västberga, Sweden with the purpose of developing a new laboratory test method for volumetric assessment of crater wear on inserts for steel turning. The test method was developed with the Sandvik Coromant´s existing crater wear measurement method as a starting point. Crater wear is currently measured as the projected area of exposed substrate, meaning where all coating layers have been removed. Based on earlier research on volume wear assessment, a focus variation microscope was selected to carry out 3D scans. To accurately measure the removed volume, an initial reference scan is required to capture individual variations existing on samples. The insert is then scanned after turning and compared with its reference. Factors affecting accuracy as well as possible improvements were identified as: Sample preparation, scan settings (resolution, quality) and data processing (alignment of scans, volume calculation etc.). Guiding alignment markers were created by laser ablation to help with alignment.  CloudCompare software was used to process the scanned 3D point clouds. A step by step routine was developed to ensure consistent results. The repeatability was assessed showing 8% standard deviation in volume for a shallow crater within the coating to 2% for a large crater worn into the substrate. The new method provides the possibility to measure wear while still inside the coating, which has been previously unavailable data. This enables measurement of the contribution of each specific coating layer on the wear resistance such as wear rate of a single layer instead of a combined wear rate for all layers. Detailed coating wear analysis is a valuable tool for development of optimized coatings. The developed wear measurement method was implemented on a case study which demonstrated the capabilities regarding its ability to resolve performance differences in experimental coatings. Additional wear parameters were used beside crater volume to support wear rate analysis and novel ways of representing volume wear parameters were presented.

Descreve-se os principais tipos de desgaste atuantes em rodas ferroviárias tais como desgaste abrasivo e desgaste por deslizamento. No desgaste por deslizamento os principais mecanismos são deformação plástica, fadiga de contato, fadiga termomecânica, oxidação e escorregamento. Avalia-se o efeito de variáveis como dureza, microestrutura, composição química da liga e escorregamento no desgaste e em seus mecanismos. Compara-se os tipos e mecanismos de desgaste verificados em rodas ferroviárias utilizadas em trens para transporte de minérios, com os obtidos em laboratório através de ensaio de desgaste disco-contra-disco de materiais de roda e trilho. No ensaio, o desgaste foi medido por pesagem dos corpos-de-prova verificando após distâncias predeterminadas a perda de massa. Avaliou-se a influência da carga, dureza, composição química e escorregamento no desgaste. Verificou-se que o desgaste aumenta com a carga e diminui com o aumento da dureza. Aços de rodas com adição de Cromo e Vanádio apresentam um melhor desempenho em desgaste se comparados com aços AAR M 107/208 Classe B ou C. Análise microscópica dos corpos-de-prova após ensaio, mostrou que tal como nas rodas em serviço, os tipos de desgaste atuantes foram desgaste abrasivo e por deslizamento com mecanismos diversos como deformação plástica, delaminação e oxidação. Mecanismo semelhante a delaminação é a formação de escamas ou shelling em rodas. Verificou-se também a formação de camada branca na superfície desgastada, característico de transformação martensítica em aço. Mecanismo similar a este é o de formação de \"spalling\" em rodas. Apresenta-se uma metodologia para desenvolvimento de materiais de rodas, compreendendo ensaios de desgaste em laboratório, produção de rodas e acompanhamento de desempenho em campo, onde se confirma o melhor desempenho de materiais AAR M 107/208 classe C com adição de Cromo e Vanádio se comparado com aços convencionais conforme ) conforme normas AAR M 107/208. / The main types of railroad wheels wear, such as abrasive wear and sliding wear are describe. The main mechanisms of sliding wear are the plastic deformation, the contact fatigue, termomechanical fatigue, oxidation and ship wear. The variables such as hardness, microstructure, chemical composition of alloy and effects of the sliding on wear mechanisms are evaluated. The wear types and mechanisms detected on wheels and rail materials from the real railroad cars tracks, from mining company, are compared with those observed at laboratory testing on disc-against-disc wear testing. The wear rate was measured by mass loss after predefined testing distances. The influence of the load, the hardness and the sliding on the wear rate were also evaluated. It was observed that the wear of the Wheel materials increases with the load increasing and decreases with the material hardness increasing. A better performance was observed for steels AAR M 107/208 class C with Chromium and Vanadium additions when compared to AAR M 107/2088 grade B or C steels. The microscopic examination of the test specimens, as well as on the wheels removed from service, showed occurrence of the abrasive wear and sliding wear with various mechanisms such as plastic deformation, delamination and oxidation wear. A similar mechanism to the delamination is the shelling on wheels. It was observed the formation of White layer on worn surface typical to the martensitic transformation of steel. A similar mechanism is the spalling of wheels material, It is also proposed a methodology for Wheel materials development, including laboratory wear tests, the manufacturing of wheels and the use and attendance of the wheels in service. AAR M 208 grade C steels with Chromium and Vanadium additions presented a better performance when compared the standard AAR M 107/208 steels.

Optimisation du positionnement des implants lors d’arthroplastie totale de hanche primaire La prothèse totale de hanche est considérée comme l’une des plus importantes avancées médicales du XXème siècle. L’objectif de ce travail était d’étudier l’orientation anatomique des structures constituant l’articulation de la hanche et d’ensuite analyser la position des implants des prothèses totales de hanche afin d’améliorer l’implantation des composants prothétiques dans le but de réduire les phénomènes de luxation, usure, fracture et douleurs inhérents à cette chirurgie. Une étude de l’orientation anatomique du ligament transverse de l’acetabulum, du labrum et des cornes a été réalisée. Ensuite nous nous sommes intéressés au composant fémoral avec des études radiographique et tomodensitométriques de l’antéversion fémorale. Nous avons essayé de mesurer l’antéversion fémorale prothétique à partir d’une radiographie de face. Ensuite, nous avons démontré que le scanner était un moyen fiable pour localiser le centre de la tête du fémur en comparaison avec un système Motion Analysis et un bras Faro. Enfin, nous avons mesuré l’antéversion fémorale avant et après PTH ainsi que la situation du centre de tête fémorale avant et après arthroplastie. Le but était d’analyser la possibilité de reproduire, avec une tige prothétique droite, l’antéversion fémorale native. Des applications pratiques de mesure de l’amplitude de mouvement prothétique ont permis de connaître, dans des cas de luxation prothétique, si le positionnement des implants était le facteur causal. Une application clinique a montré qu’en cas de positionnement non optimal de l’implant acétabulaire, l’incidence des fractures d’insert céramique était augmentée / Optimization of components’ positioning in primary total hip arthroplasty Total hip arthroplasty is one of the most important innovations of the 20th century. The aim of this study was to evaluate the anatomical orientation of articular structures of the hip and then to analyze component’s positioning in order to improve the implantation of prosthetic components to minimize dislocation, wear, fracture and pain. The anatomical orientation of transverse acetabular ligament, labrum and horns was studied. Femoral component orientation was assessed with the help of X-rays and CT-scan. We measured femoral anteversion with AP X-rays. Then, we demonstrated that CT-scan was an accurate method to localize femoral head center in comparison with Motion Analysis and Faro. Femoral anteversion and femoral head center were assessed before and after surgery. The goal was to analyze the restoration of femoral anteversion after THA with a straight cementless stem. Some cases of THA dislocations were evaluated with measurement of prosthetic ROM. It allowed us to know whether implant positioning was the risk factor of dislocation. A clinical observation showed that in case of cup malpositioning, the rate of ceramic liner fractures increased

O objetivo neste trabalho foi avaliar a influência da variação do tempo de fotopolimerização para diferentes cores (I, B1, B3 e C4) de uma resina composta (FiltekTM Z250, da 3M ESPE), sobre a taxa de desgaste abrasivo através do método do disco retificado. Cada espécime de resina composta fotopolimerizada estava contido numa cavidade semicircular localizada na periferia de um disco constituído por polimetilmetacrilato (PMMA), denominado disco estático, sendo que a superfície curva da resina no disco sofria desgaste por um rebolo de porcelana, denominado tecnicamente de disco dinâmico, sob carga padronizada e velocidade controlada, criando no espécime uma cavidade de aspecto semicircular. O deslocamento vertical do disco estático, ao ser desgastado, era detectado por um palpador, o qual transferia estes dados a um computador e criava os arquivos de desgaste, em função do tempo. Os dados obtidos foram tratados estatisticamente. Pôde-se concluir que 1) a resistência à abrasão do PMMA foi a maior de todas e 2) a resina de cor C4, a mais resistente de todas. / The aim at this study was estimate the influence of light-curing time variation of different colors (I, B1, B3 and C4) of composite resin (FiltekTM Z250, 3M ESPE), upon abrasive wear through the retified disc method. The porcelain existent in the named dynamic disc promoted a wear of each resin specimen located in the polimethylmetacrylate (PMMA) static disc, under a standardized charge and with controlled velocity. Vertical displacement of static disc was detected by a sensor that send data to a computer where wear arquives were plotted in function of time. After data statistical analysis, it could be concluded that: 1) PMMA resistance was greater than anyone of resins and 2) C4 was more resistant than all the other colors.