The Experts below are selected from a list of 3081 Experts worldwide ranked by ideXlab platform
F. Ghadami - One of the best experts on this subject based on the ideXlab platform.
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Comparative tribological study of air plasma sprayed WC–12%Co coating versus conventional Hard Chromium electrodeposit
Tribology International, 2010Co-Authors: M. Heydarzadeh Sohi, F. GhadamiAbstract:Abstract In this work, the properties of air plasma sprayed WC–12%Co coating before and after heat treatment were compared with the properties of the Hard Chromium electrodeposit. WC–12%Co coatings were heat treated at 650, 900 and 1150 °C for 1 h in an argon atmosphere. XRD patterns confirmed the formation of an amorphous phase in the as-sprayed coating. This amorphous phase gradually transformed to η -carbides in the course of heat treatment of the coating. This transformation was confirmed by the XRD analysis of the coatings heat treated above 900 °C. Pin-on-disc wear test results showed that WC–12%Co coatings had a significantly better tribological performance as compared with that of the Hard Chromium electrodeposits. The results also indicated that heat treatment of the WC–12%Co coatings at 900 °C gave the highest wear resistance among the coatings, which was due to the formation of Hard η -carbides at this temperature.
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comparative tribological study of air plasma sprayed wc 12 co coating versus conventional Hard Chromium electrodeposit
Tribology International, 2010Co-Authors: Heydarzadeh M Sohi, F. GhadamiAbstract:Abstract In this work, the properties of air plasma sprayed WC–12%Co coating before and after heat treatment were compared with the properties of the Hard Chromium electrodeposit. WC–12%Co coatings were heat treated at 650, 900 and 1150 °C for 1 h in an argon atmosphere. XRD patterns confirmed the formation of an amorphous phase in the as-sprayed coating. This amorphous phase gradually transformed to η -carbides in the course of heat treatment of the coating. This transformation was confirmed by the XRD analysis of the coatings heat treated above 900 °C. Pin-on-disc wear test results showed that WC–12%Co coatings had a significantly better tribological performance as compared with that of the Hard Chromium electrodeposits. The results also indicated that heat treatment of the WC–12%Co coatings at 900 °C gave the highest wear resistance among the coatings, which was due to the formation of Hard η -carbides at this temperature.
Heydarzadeh M Sohi - One of the best experts on this subject based on the ideXlab platform.
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comparative tribological study of air plasma sprayed wc 12 co coating versus conventional Hard Chromium electrodeposit
Tribology International, 2010Co-Authors: Heydarzadeh M Sohi, F. GhadamiAbstract:Abstract In this work, the properties of air plasma sprayed WC–12%Co coating before and after heat treatment were compared with the properties of the Hard Chromium electrodeposit. WC–12%Co coatings were heat treated at 650, 900 and 1150 °C for 1 h in an argon atmosphere. XRD patterns confirmed the formation of an amorphous phase in the as-sprayed coating. This amorphous phase gradually transformed to η -carbides in the course of heat treatment of the coating. This transformation was confirmed by the XRD analysis of the coatings heat treated above 900 °C. Pin-on-disc wear test results showed that WC–12%Co coatings had a significantly better tribological performance as compared with that of the Hard Chromium electrodeposits. The results also indicated that heat treatment of the WC–12%Co coatings at 900 °C gave the highest wear resistance among the coatings, which was due to the formation of Hard η -carbides at this temperature.
Herman Jacobus Cornelis Voorwald - One of the best experts on this subject based on the ideXlab platform.
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effects of tungsten carbide thermal spray coating by hp hvof and Hard Chromium electroplating on aisi 4340 high strength steel
Surface & Coatings Technology, 2001Co-Authors: Marcelino P Nascimento, Ivancy M Miguel, R C Souza, W L Pigatin, Herman Jacobus Cornelis VoorwaldAbstract:Abstract In cases of decorative and functional applications, Chromium results in protection against wear and corrosion combined with chemical resistance and good lubricity. However, pressure to identify alternatives or to improve conventional Chromium electroplating mechanical characteristics has increased in recent years, related to the reduction in the fatigue strength of the base material and to environmental requirements. The high efficiency and fluoride-free Hard Chromium electroplating is an improvement to the conventional process, considering chemical and physical final properties. One of the most interesting, environmentally safer and cleaner alternatives for the replacement of Hard chrome plating is tungsten carbide thermal spray coating, applied by the high velocity oxy-fuel (HVOF) process. The aim of this study was to analyse the effects of the tungsten carbide thermal spray coating applied by the HP/HVOF process and of the high efficiency and fluoride-free Hard Chromium electroplating (in the present paper called ‘accelerated’), in comparison to the conventional Hard Chromium electroplating on the AISI 4340 high strength steel behaviour in fatigue, corrosion, and abrasive wear tests. The results showed that the coatings were damaging to the AISI 4340 steel behaviour when submitted to fatigue testing, with the tungsten carbide thermal spray coatings showing the better performance. Experimental data from abrasive wear tests were conclusive, indicating better results from the WC coating. Regarding corrosion by salt spray test, both coatings were completely corroded after 72 h exposure. Scanning electron microscopy technique (SEM) and optical microscopy were used to observe crack origin sites, thickness and adhesion in all the coatings and microcrack density in Hard Chromium electroplatings, to aid in the results analysis.
L Fedrizzi - One of the best experts on this subject based on the ideXlab platform.
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corrosion and wear behaviour of hvof cermet coatings used to replace Hard Chromium
Electrochimica Acta, 2004Co-Authors: L Fedrizzi, S Rossi, R Cristel, P L OnoraAbstract:Abstract The high velocity oxygen fuel (HVOF) powder spray process represents the state-of-the-art for thermal spray metallic coatings and can result in very dense, tightly adherent coatings with little or no oxidation during the application and low residual stresses. In particular this technology is applied in the automotive industry as well as in the textile and paper machinery and can be an interesting alternative to the use of galvanic processes with high environmental impact. Substitution of Hard Chromium coatings with new HVOF cermet coatings has been studied in this paper. Coatings obtained from conventional and nano-powders with the chemical composition 75Cr 3 C 2 –25NiCr were applied on AISI 1045 steel used for cylinders in earth moving machines. A special apparatus was used to perform tribo-corrosion tests. The applied load ranged between 5 and 80N using a rotation speed of the sample of about 200 rpm. The counterface was an alumina block working in a block on ring configuration. Electrochemical methods were used to modify and control the degradation mechanisms and then tribo-corrosion tests were carried out under different working conditions: (a) free corrosion (no applied polarisation); (b) only lubricated wear (by applying a cathodic polarisation); (c) forced corrosion (by applying an anodic current). The behaviour of the cermet coatings was compared to that of conventional Hard Chromium coatings. It was very interesting to observe that nano-powder coatings displayed a markedly smaller weight loss value with respect to Hard Chromium and conventional HVOF coatings under all the selected working conditions. This better behaviour can be related to the lower surface roughness and to the better distribution of carbides in the metal matrix and also to the lower porosity of the coating.
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wear corrosion mechanism of Hard Chromium coatings
Wear, 2002Co-Authors: L Fedrizzi, S Rossi, F Ellei, F DefloriaAbstract:Abstract Hard Chromium coatings are frequently used for application where corrosion and wear degradation are combined, as an example in earthmovers, in mining transport systems or in moulds for plastics. The aim of this work is to study the mechanisms of tribocorrosion of Hard Chromium coated steel bars in a sodium chlorides solution under sliding wear. Using a self-made wear–corrosion apparatus, many parameters were monitored to analyse both kinds of damage: the mechanical and the electrochemical one. Different test conditions were considered by changing imposed load on the counterface and rotation speed. It was observed that the change of testing parameters was insignificant on the degradation mechanism: mainly adhesive wear was observed and secondary abrasive wear (at test beginning) and localised corrosion were present. Degradation synergy was also observed both by electrochemical tests and weight loss measurements.
Marcelino P Nascimento - One of the best experts on this subject based on the ideXlab platform.
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The Significance and Determination by Image Analysis of Microcrack Density in Hard Chromium Plating
Plating and Surface Finishing, 2008Co-Authors: Marcelino P Nascimento, Herman Jacobus Cornells VoorwaldAbstract:It is well known that the microcrack density is a fundamental parameter in Hard Chromium electroplating. The chemical and mechanical properties of this coating are widely dependent on its microcrack density. In this paper a simple image analysis procedure to determine microcrack density is presented in order to demonstrate it as a fundamental tool to estimate the fatigue, corrosion and wear behavior, as well as the residual stress field of a coated component. For this purpose, the image analysis procedure was carried out on two kinds of Hard Chromium plating - one called “accelerated” (high velocity of deposition and fluoride-free) and the other conventional (with fluoride). The coatings were applied on samples of AISI 4340 aeronautical steel, which is widely used in aircraft landing gear components. To characterize the practical significance of this study, the microcrack density results were related to the fatigue, wear and corrosion behavior from previous study and to the residual stress field in the coatings.
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effects of tungsten carbide thermal spray coating by hp hvof and Hard Chromium electroplating on aisi 4340 high strength steel
Surface & Coatings Technology, 2001Co-Authors: Marcelino P Nascimento, Ivancy M Miguel, R C Souza, W L Pigatin, Herman Jacobus Cornelis VoorwaldAbstract:Abstract In cases of decorative and functional applications, Chromium results in protection against wear and corrosion combined with chemical resistance and good lubricity. However, pressure to identify alternatives or to improve conventional Chromium electroplating mechanical characteristics has increased in recent years, related to the reduction in the fatigue strength of the base material and to environmental requirements. The high efficiency and fluoride-free Hard Chromium electroplating is an improvement to the conventional process, considering chemical and physical final properties. One of the most interesting, environmentally safer and cleaner alternatives for the replacement of Hard chrome plating is tungsten carbide thermal spray coating, applied by the high velocity oxy-fuel (HVOF) process. The aim of this study was to analyse the effects of the tungsten carbide thermal spray coating applied by the HP/HVOF process and of the high efficiency and fluoride-free Hard Chromium electroplating (in the present paper called ‘accelerated’), in comparison to the conventional Hard Chromium electroplating on the AISI 4340 high strength steel behaviour in fatigue, corrosion, and abrasive wear tests. The results showed that the coatings were damaging to the AISI 4340 steel behaviour when submitted to fatigue testing, with the tungsten carbide thermal spray coatings showing the better performance. Experimental data from abrasive wear tests were conclusive, indicating better results from the WC coating. Regarding corrosion by salt spray test, both coatings were completely corroded after 72 h exposure. Scanning electron microscopy technique (SEM) and optical microscopy were used to observe crack origin sites, thickness and adhesion in all the coatings and microcrack density in Hard Chromium electroplatings, to aid in the results analysis.
