Effects of blending elements on wear resistance of plasma-sprayed molybdenum blend coatings used for automotive synchronizer rings

In this study, a pure Mo coating and six Mo blend coatings in which bronze and Al–Si alloy powders were blended with Mo powders were fabricated by atmospheric plasma spraying (APS), and effects of blending elements on wear resistance were investigated. Three kinds of spray powders, one of which was pure molybdenum powders and the others were blend powders of bronze and aluminum–silicon alloy powders mixed with molybdenum powders, were sprayed on a low-carbon steel substrate. Microstructural analysis of the coatings showed that blend phases formed during spraying were homogeneously distributed in the molybdenum matrix. The wear test results revealed that wear rate of all the coatings increased with increasing load and that the blend coatings showed better wear resistance than the pure molybdenum coating, although the hardness was lower. In particular, the molybdenum blend coating where bronze and Al–Si powders were blended with Mo powders showed the best wear resistance because it contained a large amount of hard Cu–Al phases. Because it also had the highest friction coefficient, it would be desirably applicable to automotive parts such as synchronizer rings.