Surface modification of HVOF thermal sprayed WC–CoCr coatings by laser treatment

In this work the affects of laser characteristics on microstructure and microhardness of high velocity oxygen fuel sprayed (HVOF) WC–CoCr coatings were investigated. The coating was deposited with a Sulzer Metco WokaJet™-400 kerosene fuel and the laser surface treatments were applied using CO2 laser with 10.6 μm wavelength. Large variations in surface properties were produced from variation in the laser processing parameters. In total, four levels of peak power (100, 200, 300 and 350 W), four levels of spot diameter (0.2, 0.4, 0.6 and 1 mm) and three levels of pulse repetition frequency (PRF) were investigated. An initial set of tests were followed by a more detailed 33 factorial design of experiments. Pulse repetition frequency and duty cycle were set in order to maintain the same overlap in the x and y directions for the raster scanned sample spot impact dimensions. Overlaps of 30% were used in the initial tests and 10% in the more detailed trials. The results have shown that care must be taken to keep the irradiance at a relatively low level compared to uncoated surfaces. High irradiance can in this case result in rough and porous surfaces. Lower levels of irradiance are shown to provide more uniform microstructures, reduced porosity and increased microhardness

Corrosion and wear behaviour of alumina coatings obtained by various methods

Alumina coatings are widely used in a range of industrial applications to improve corrosion protection, wear and erosion resistance and thermal insulation of metallic surfaces. From various efficient and adjustable processes refined alumina surfaces with long-term use are obtained. It can be seen that cost-efficient arc-sprayed Al coatings post-treated by plasma-electrolytic oxidation (PEO) form Al₂O₃-layers with remarkable corrosion protection, hardness, bonding strength and abrasion resistance as well as extended service time. The properties of these coatings are compared to alumina coatings obtained by flame spraying and atmospheric plasma spraying.Покриви на основі оксиду алюмінію широко використовують у промисловості для поліпшення корозійного захисту, зносо- та ерозійної тривкості, а також теплоізлояції металевих поверхонь. Різними методами отримано удосконалені покриви. Показано, що економічно ефективні алюмінієві покриви, сформовані методом електродугового розпилення, а потім оброблені плазмово-електролітичним оксидуванням, утворюють шари Al₂O₃ з високими антикорозійними характеристиками, твердістю, силою зчеплення та абразивною тривкістю і продовженим ресурсом роботи. Порівняно їх властивості з покривами на основі оксиду алюмінію, одержаними методами полуменевого та атмосферного плазмового розпилення.Покрытия на основе оксида алюминия часто применяют в промышленности для улучшения коррозионной защиты, износо- и эрозионной стойкости, а также теплоизлояции металлических поверхностей. Различнымы методами получены усовершенствованные покрытия. Показано, что экономически эффективные алюминиевые покрытия, сформированные методом электродугового распыления, а потом обработаные плазменно-электролитическим оксидированием, образуют слои Al₂O₃ с высокими антикоррозионными характеристиками, твердостью, силой сцепления, абразивной стойкостью и длительным ресурсом работы. Сравнены их свойства с покрытиями на основе оксида алюминия, полученными методами пламенного и атмосферного плазменного распыления

Cellulosic films obtained from the treatment of sugarcane bagasse fibers with N -methylmorpholine- N -oxide (NMMO)

Ethanol/water organosolv pulping was used to obtain sugarcane bagasse pulp that was bleached with sodium chlorite. This bleached pulp was used to obtain cellulosic films that were further evaluated by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). A good film formation was observed when temperature of 74 °C and baths of distilled water were used, which after FTIR, TGA, and SEM analysis indicated no significant difference between the reaction times. The results showed this to be an interesting and promising process, combining the prerequisites for a more efficient utilization of agro-industrial residues.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), (CNPq), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil; Fundação para a Ciência e a Tecnologia (FCT) and CEMU

Improving tribological properties of cast Al-Si alloys through application of wear-resistant thermal spray coatings

Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 103-104, which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity

Moeglichkeiten zur Qualitaetsoptimierung von Hochtemperaturloetverbindungen mittels geeigneter Fertigungs- und Pruefverfahren

Available from TIB Hannover: FR 6223 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Schriftenreihe Werkstoffe und werkstofftechnische Anwendungen

Die Schriftenreihe „Werkstoffe und werkstofftechnische Anwendungen“ behandelt Themengebiete der Werkstoffwissenschaft und -technik, der Oberflächentechnik sowie deren industriellen Anwendungen. Es werden vorrangig aktuelle Forschungsergebnisse der Professuren Verbundwerkstoffe und Oberflächentechnik/Funktionswerkstoffe des Instituts für Werkstoffwissenschaft und Werkstofftechnik der TU Chemnitz vorgestellt. Weiterhin sind in der Schriftenreihe die Tagungsbände des jährlich am Institut stattfindenden „Werkstofftechnischen Kolloquium“ enthalten. Die einzelnen Bände beschäftigen sich mit den Forschungsgebieten Galvanische Metallabscheidung, Anodisieren, Thermisches und Kaltgas-Spritzen, Löten, Verbundwerkstoffe, Werkstoffverbunde, Wärmebehandlung, CVD-Beschichtungen/PVD-Beschichtungen, Simulation in der Beschichtungstechnik, Organisches Beschichten (Pulverbeschichten, Lackieren, Sol-Gel-Verfahren), Elektrochemisches Strukturieren, Thermomechanische Behandlung und Mechanische Werkstoffeigenschaften.The book series „Werkstoffe und werkstofftechnische Anwendungen“ outlines up-to-date topics of material science and engineering, surface engineering as well as resulting industrial applications. Mainly, recent research results of the departments Composite Materials and Surface Engineering/Functional Materials of the Institute of Material Science and Engineering of Chemnitz University of Technology are presented. In addition, the book series includes the proceedings of the annual in-house conference “Werkstofftechnisches Kolloquium”. The separate volumes concentrate on the following fields of scientific research: Galvanised Coating, Anodising, Thermal and Cold Spraying, Soldering and Brazing, Composite Materials, Composite Structures, Thermal and Thermomechanical Treatment, CVD and PVD Coating, Simulation of Coating Processes, Organic coating (Powder Coating, Varnishing, Sol-Gel Processes), Electrochemical Structuring and Mechanical Material Properties

Moeglichkeiten zur Qualitaetsoptimierung von Hochtemperaturloetverbindungen mittels geeigneter Fertigungs- und Pruefverfahren

Available from TIB Hannover: FR 6223 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman