Investigation on microstructure, surface properties and anti-wear performance of HVOF sprayed WC-CrC-Ni coatings modified by laser heat treatment

Laser heat (LH) treatment was found to be an effective method to alter the microstructure and mechanical properties of conventional coatings. In this investigation, the effects of laser scanning velocity on microstructure, microhardness and wear performance of high velocity oxygen fuel sprayed (HVOF) WC-CrC-Ni coatings during laser heating treatment were investigated. The results showed that the microstructure of the HVOF coatings changed greatly after the LH treatment. X-ray diffraction (XRD) patterns indicated that WC and Cr3C2, as primary phases, were present in both the HVOF- and LH-treated coatings, while only a small amount of Ni phase existed in the LH-treated coatings. With the post-treatment process of laser heating, a compact interface was found between the coating and substrate. When the laser scanning velocity decreased, the porosity and thickness of the LH-treated coatings decreased, leading to a gradual increase of microhardness. In the wear test, the friction and wear resistance of the coating were improved significantly with an optimal laser heating process (600 W power, 300 nm/min scanning velocity). The improvement can be attributed to the improved porosity and hardness, as well as the formation of oxide tribofilms. (C) 2009 Elsevier B.V. All rights reserved.