Detta arbete undersöker huruvida reparation genom påläggsvetsning kan användas på tågrälsar i Stockholms tunnelbana istället för tillverkning av nya. Olika metallpulver och slitageprofiler analyseras genom en livscykelanalys ur vilken energiförbrukning och CO2-utsläpp jämförs med konventionell tillverkning av tågrälsar. Utifrån olika rekommendationer gällande maximalt sido- och höjdslitage av en rälprofil, skapades en CAD-modell i Solid Edge ur vilken volymen av beläggningen togs fram. Beräkningen av livscykel gjordes sedan med hjälp av programmet CES EduPack och dess inbyggda verktyg Eco Audit tool. Resultatet som togs fram var att laserpåsvetsning minskar både CO2-utsläppen och energiåtgången markant under både transport, tillverkning och materialframtagning för alla material och slitagefall som testades. Som mest sänktes CO2-utsläppen med 95 % och som minst med 85 %. Energiåtgången minskade som mest med 95 % och som minst med 67 %. Materialet som ansågs vara mest lämplig för påläggssvetsning var Rockit 401, då denna bidrog till största minskningen av energiåtgång och koldioxidutsläpp samt hade bäst egenskaper gällande sprickbildning samt hårdhet. / This report investigates the method of laser cladding and its possibility to repair worn down subway tracks as an alternative to manufacturing new ones. Different types of metal powders and wear profiles were studied through a life cycle analysis from which the energy consumption and carbon dioxide emissions were compared to the conventional method of manufacturing rails. Based on data and recommendations for maximum wear a CAD-model in Solid Edge was constructed, from which the volume of the coating was calculated. The life cycle analysis were calculated using the program CES EduPack and its built-in application Eco Audit tool. The result is that laser cladding will lower both the carbon dioxide emission and the energy consumption significantly during both transport, manufacturing and production for every material and wear profiles that were tested. The biggest reduction for carbon dioxide emissions was 95 % and the lowest was 85 %. The biggest reduction of energy consumption was 95 % and the lowest was 67 %. The material that was considered the most suitable for our purpose was Rockit 401 since it contributed to the biggest reduction of both energy consumption and carbon dioxide emission. Rockit 401 also showed good properties regarding cracking and hardness.

This thesis reveals the tribological mechanisms behind the intrinsic low friction potential of the Co-based family of alloys called Stellites. Although being an established and important group of materials, a satisfactory explanation to why they exhibit low-friction properties under severe sliding conditions has not previously been found in the literature. The main part of this thesis is dedicated to the clarification of the tribological performance of Stellites in highly loaded sliding contact. The results should assist the development of Co-free alternatives, suitable for replacing Stellites in nuclear applications. Owing to their beneficial properties they are today the most commonly used material in the sealing surfaces on gate valves in the primary circuits of boiling water reactors (BWR). The underlying reason for the replacement in the nuclear applications is an undesired contribution to the background radiation level, originating from the Co in the Stellite surfaces. The Stellites mainly consist of Cr-rich carbides in a solid solution dominated by Co. The commonly used Stellite 6 and Stellite 21 were chosen as primary test materials and applied by laser cladding, providing a metallically bonded clad layer with a fine dendritic microstructure. By combining information from a series of dedicated tribological tests and modern high-resolution analysis instruments (e.g. SEM, XRD and TEM) available at the Ångström Laboratory at Uppsala University, the following conclusions can be made regarding the tribological performance of Stellites under high load sliding. Mechanisms. The (tested) Stellites form a thick deformation hardened layer, topped with a superficial easily sheared layer of hcp basal planes aligned parallel to the worn surface. The easy-shear layer is continually regenerated, replacing worn off material. Technical benefits. The Stellites offer low-friction properties thanks to their easily sheared surface layers. The risk of severe galling is also avoided by restricting shear and adhesive transfer to very thin superficial layers. In closed sliding contacts, self-generated protective layers formed by re-deposition of wear fragments are also offered.

Mechanical components operating at elevated temperatures can be identified in the aerospace industry as well as in metal forming. Hot stamping is a metal forming technique utilized for manufacturing high strength lightweight components for the automotive industry. Three types of Ni-based hardfacings doped with solid lubricants were manufactured using laser cladding. An additional hardfacing was also manufactured using the Ni-based alloy only as a reference. Solid lubricants added were Ag+WS2, WS2 and Cu+MoS2. These hardfacings were manufactured and tribologically evaluated for potential application in hot stamping tooling. Direct diode laser was used for the cladding process. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for characterization of the microstructure after deposition. Tribological testing was done using a reciprocating pin-on-disk tribometer under dry sliding conditions at temperatures in the range between RT and 600°C. Bearing steel ball and a flat pin made of the same material were used as counterbodies. Wear volume loss was measured using a 3D optical interferometer. For identification of the wear mechanisms SEM/EDS techniqueswere used. Formation of a lubricious CrxSy phase was detected after deposition, additionally encapsulation of silver particles by CrxSy was also observed. Reduction of friction coefficient was observed for every self-lubricating hardfacing compared to the reference. Lowest friction coefficient (0.23-0.3) was observed when the testing temperature was set to 400°C using a pin-on-flat configuration. Lowest wear rate was observed at 400°C, with the coating containing Ag and WS2 having a specific wear rate of 3.04 · 10−5mm3/Nm. The lubricity of the self-lubricating hardfacings was attributed to the CrxSy phase observed on the worn surface. At low to moderate temperatures abrasive wear is the main wear mechanism. At the highest testing temperature, oxidative wear was dominant.

Diploma thesis studies the layers created by laser cladding and method of testing abrasion resistance of these layers using the method of dynamic shock impactor. In the theoretical part describes laser technologies and their applications, hardness testing and methods of testing of coatings. Proposed by the mechanical testing of the selected materials were carried out and evaluated in the experimental part. The conclusion summarizes final results of the experiment.

The aim of my thesis is the analysis of properties of laser cladding. The theoretical part is focus on conventional methods of laser cladding, types and properties of lasers and its applications in industry. Then there is the description of preparing metallographic samples and its assessment, also there are types of wear enclosed. In the experimental part the nickel laser cladding were made by using semiconductor laser, in which the structure, the dilution, the EDS analysis and the hardness with respect to input parameters are assessed.

Ground engaging tools are very important components of machinery for agricultural applications, such as soil tillage. Ploughshare points serve as the first point of contact between ploughs and the hard minerals in the soil. One of the biggest problems that these tools encounter is abrasive wear, which decreases tillage quality, causes frequent tillage stops, increases fuel consumption of the tractor, and results in soil erosion. During this investigation, wear measurement, surface profiling and microscopic analysis were performed on three share point samples running in silica and granite sand – two points were commercial ones made of steel EN 22MnB5 and hardened. They served as commercial references. A third share point was also a commercial EN 22MnB5 one, but not hardened and laser cladded by a Ni-base + 50% carbide powder mix (Höganäs 1559–40 + 50% 4590). The abrasive wear testing was performed in an especially designed carousel tribometer. The laser cladded sample suffered only 30% of the wear shown in the EN 22MnB5 reference sample running under the same conditions. / Jordbearbetningsverktyg är väldigt viktiga komponenter i maskiner för jordbruksapplikationer, såsom jordbearbetning. Det är skärbladet på plogen, den så kallade plogbillen, som står för kontakten mellan plogen och de hårda mineralerna i jorden. Ett av de största problemen som dessa verktyg möter är abrasivnötning, som gör att verktygen efter en tid blir ineffektiva och bland annat orsakar frekventa stopp, erosion av marken och låg jordkvalité på grund av den försämrade jordbearbetningen samt ökar traktorns bränsleförbrukning. I denna undersökning testades provbitar av två olika slags stål runt i kvarts- respektive granitsand, och därefter utfördes mätningar på den nötning som skett samt även ytprofilering och mikroskopi gjordes. Testerna utfördes i kvartsand och i granitsand. Provbitar var två kommerciellt tillverkad härdade skärblad gjorda i stål EN 22MnB5. Ett tredje skärblad var också en komerciellt gjord i EN 22MnB5 stål men ohärdad och laserpåsvetsad med Ni-bas + 50% karbid pulverblandning (Höganäs 1559-40 +50% 4590). Provkörningarna utfördes i en speciellt utvecklad karusell-tribometer. Resultatet från provningarna visade att i fallet med laserpåsvetsade bitarna så var nötningen endast 30% relativt nötningen som EN 22MnB5-provet uppvisade under samma förutsättningar.

Orientador: Juno Gallego / Resumo: O desgaste abrasivo é uma das causas de falhas em equipamentos e responsável por prejuízos nos processos industriais. Uma técnica capaz de minimizar os efeitos deste fenômeno é a aplicação de revestimentos duros nas superfícies críticas. Recentemente foram desenvolvidos revestimentos contendo carbonetos de titânio formados pela fusão de misturas contendo cavacos das ligas ASTM F67 e ASTM F136 sobre peças de aço-carbono ASTM A-36. Após a aplicação do processo de soldagem GTAW obteve-se significativa fração volumétrica de TiC grosseiro com elevada dureza. No presente trabalho foi investigada a refusão dessas soldas pelo processo de soldagem a Laser Nd:YAG pulsado. A microestrutura das amostras foi analisada por difração de raios-X (DRX), microscopia eletrônica de varredura (MEV) e microdureza Vickers. A caracterização microestrutural mostrou que houve refinamento dos carbonetos de titânio (TiC) na matriz ferrítica refundida com o Laser, cujo principal efeito foi um endurecimento do metal de solda. A caracterização mecânica demonstrou um aumento na microdureza da superfície do material. Este comportamento favorece o uso da refusão a Laser para a melhoria da qualidade das superfícies que demandam maior resistência ao desgaste abrasivo. / Mestre

Le remplacement des alliages durs à base cobalt par des alliages à base fer suscite un intérêt croissant pour la protection anti-usure des pièces métalliques fonctionnant dans le circuit primaire d’une centrale nucléaire. Dans le cadre de cette thèse, une étude métallurgique détaillée a été effectuée sur des dépôts épais en Norem 02™ élaborés par le procédé de projection laser.Un affinement significatif de la microstructure du Norem 02™ a été obtenu après optimisation des paramètres du procédé (puissance laser, vitesse de balayage et débit de poudre), par rapport à un procédé concurrent par Plasma à Arc Transféré. Les essais tribologiques montrent que l’amélioration de la microstructure n’empêche cependant pas l’apparition du grippage à 300°C.La deuxième partie de cette étude a été consacrée à l’amélioration du Norem 02™ avec ajout de différents éléments chimiques. Le choix de ces ajouts adéquats a été validé grâce aux tests de frottement réalisés sur des échantillons en Norem 02™ modifié, sous haute contrainte mécanique (1 GPa) et à haute température (300°C). Parmi une dizaine d’éléments d’ajouts testés, l’ajout de titane a permis une transformation complète de la microstructure du Norem 02™. Cette transformation métallurgique a amélioré son comportement tribologique avec un faible coefficient de frottement (<0.3) à 300°C.L’origine de cette amélioration du comportement mécanique du Norem 02-Ti a été étudiée et expliquée par différentes analyses microstructurales (MO, MEB, EDS, EBSD) ainsi que des essais de traction sur des éprouvettes extraites des revêtements épais. / This study aims to substitute the cobalt-based hardfacing alloys with iron-based hardfacing alloys to protect mechanical parts operating in the primary circuit of a pressurized water reactor (PWR)Firstly, a detailed metallurgical study was carried out to characterize a thick deposit on Norem 02™ produced by the laser process (Direct Metal Deposition - DMD). Compared with a classical PTA process, a microstructure refinement was achieved after an optimization of process parameters (laser power, scanning speed and powder flow-rate). However, wear tests show that the improvement of the microstructure does not prevent the occurrence of galling at 300 ° C.The second part of this study is dedicated to Norem 02™ improvement with the addition of various chemical elements. The appropriate additions to this application have been validated by wear tests under high mechanical stress (1 GPa) and at high temperature (300°C). Among a dozen samples of modified Norem 02 ™, the addition of titanium was shown to provide a complete transformation of the initial Norem 02™’s microstructure. This metallurgical transformation improved its tribological behavior with a low friction coefficient (<0.3) obtained at 300 °C.Last, the origin of the mechanical behavior improvement of Norem 02-Ti was studied and explained by microstructural analysis (MO, MEB, EDS, EBSD) and tensile tests on specimens extracted from thick coatings.

Submitted by GABRIEL INÁCIO PONTIN null (gabrielguaira@hotmail.com) on 2017-08-15T18:00:10Z No. of bitstreams: 1 Dissertação Final - Gabriel Inacio Pontin.pdf: 2725651 bytes, checksum: f1433687bb33e3c16dd042c87cb686db (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-08-22T17:44:39Z (GMT) No. of bitstreams: 1 pontin_gi_me_ilha.pdf: 2725651 bytes, checksum: f1433687bb33e3c16dd042c87cb686db (MD5) / Made available in DSpace on 2017-08-22T17:44:39Z (GMT). No. of bitstreams: 1 pontin_gi_me_ilha.pdf: 2725651 bytes, checksum: f1433687bb33e3c16dd042c87cb686db (MD5) Previous issue date: 2017-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O desgaste abrasivo é uma das causas de falhas em equipamentos e responsável por prejuízos nos processos industriais. Uma técnica capaz de minimizar os efeitos deste fenômeno é a aplicação de revestimentos duros nas superfícies críticas. Recentemente foram desenvolvidos revestimentos contendo carbonetos de titânio formados pela fusão de misturas contendo cavacos das ligas ASTM F67 e ASTM F136 sobre peças de aço-carbono ASTM A-36. Após a aplicação do processo de soldagem GTAW obteve-se significativa fração volumétrica de TiC grosseiro com elevada dureza. No presente trabalho foi investigada a refusão dessas soldas pelo processo de soldagem a Laser Nd:YAG pulsado. A microestrutura das amostras foi analisada por difração de raios-X (DRX), microscopia eletrônica de varredura (MEV) e microdureza Vickers. A caracterização microestrutural mostrou que houve refinamento dos carbonetos de titânio (TiC) na matriz ferrítica refundida com o Laser, cujo principal efeito foi um endurecimento do metal de solda. A caracterização mecânica demonstrou um aumento na microdureza da superfície do material. Este comportamento favorece o uso da refusão a Laser para a melhoria da qualidade das superfícies que demandam maior resistência ao desgaste abrasivo. / The abrasive wear is one of the causes of failures in equipment and responsible for damages in industrial processes. A technique capable of minimizing the effects of this phenomenon is the application of hard coatings on critical surfaces. Recently, coatings containing titanium carbides produced by melting mixtures containing ASTM F67 and ASTM F136 chip blends on ASTM A-36 carbon steel parts have been developed. After an application of the GTAW get process, an important volumetric fraction of coarse TiC with high hardness was obtained. In the present work the remelts is investigated for welds by the pulsed Nd: YAG Laser process. A microstructure of the samples was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers microhardness. The microstructural characterization showed that there was a refinement of the titanium carbides (TiC) in the ferritic matrix remelt with the Laser, whose main effect was a hardening of the weld metal. The mechanical characterization showed an increase in the microhardness of the material surface. This behavior favors the use of laser cladding to improve the quality of surfaces that require high abrasive wear resistance.

The purpose of the project work was to build knowledge of the tribological behaviour of self-lubricating laser cladding, with and without external solid lubricant during conditions relevant for hot metal forming of aluminium. The materials used during the project were plates coated with a Ni-based self-lubricating clad and a reference sample of work tool steel. The self-lubricating laser clad was applied using a high power direct diode laser. The external solid lubricant used was a graphite dispersion. The external solid lubricant was applied on the samples using a spraying technique, leaving a dry layer of solid graphite on the plates. To test the tribological behaviour of the plates, linear reciprocating friction and wear tests were performed both under lubricated and dry conditions. During the dry tests, different surface roughness of the plates where investigated. The pins for the tribological test were made of AA7075. Parameters chosen for the tribological tests were based on conditions during hot forming of aluminium. After having taken images of the plates using scanning electron microscopy, and using a 3D optical profiler, the wear volume and material transfer was evaluated, and wear mechanism analysis was performed.   The tribological behaviour of polished Ni-based laser clad under dry conditions is comparable to that of the reference sample at its best performance. Using a mirror polished Ni-based laser clad under dry condition can be an option to not using external solid lubricant during hot forming of aluminium. Also, the surface roughness of the self-lubricating clad under dry conditions does not affect the coefficient of friction.