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1524 |
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Wear resistance of heat treated HVOF cermet coatings deposited by HVOF
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María Rodriguez / Central University of Venezuela, Venezuela Linda Gil/ Metallurgical Engineering Department, National Polytechnic University (UNEXPO), Venezuela Mariana Staia/ School of Metallurgy and Materials Science, Central University of Venezuela, Carolina Bilbao/ School of Mechanical Engineering, Central University of Venezuela, Venezuela Ivan Moreno/ School of Mechanical Engineering, Central University of Venezuela, Venezuela |
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The aim of the present work was to study the influence of both chemical composition and post heat treatment on the wear resistance of cermet (ceramic - metal) coatings deposited by the HVOF thermal spray process. For such purpose, a NiCrBSiWFe alloy was mixed mechanically with WC-12%Co powders in order to obtain two coatings with the following composition: the first coating with 50(wt%) NiCrBSi + 50 (wt%) (WC-12%Co) and the second one with 70 (wt%) (WC-12%Co) + 30 (wt%) NiCrBSi.. The mixtures were deposited by using a JP-5000 gun on an AISI 1020 steel substrate. An oxyacetylene flame was employed to carry out the post heat treatment, which was applied during 300 seconds. The evaluation of the wear resistance for these coatings was achieved by means of both the abrasion test and sliding wear test (ball on disc) according to the ASTM G65-C and ASTM G99-95ª, respectively. The hardness of the coating was obtained by means of Vickers indentation using a constant load of 300 g during 30 seconds dwell time. Average roughnes measurements were conducted before and after the thermal treatment in order to study its effect on the wear performance. A detailed study of the wear track is carried out by Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-ray microanalysis (EDX), which provides information of the wear mechanisms. The investigations showed that the wear resistance increased with the amount of the WC-Co particles in the initial powder mixture. Nevertheless, the increase in the wear resistance was more significant as consequence of the post heat treatment and this increase was attributed to factors such as the precipitation hardening of the nickel´s matrix, lower porosity, better distributions and effective cohesion between hard phases. |