Microstructure and wear behavior of laser-textured and micro-alloyed Co-based WC and TiC composite sintered-carbide coating

A new laser-texturing method, laser coating texturing, combining surface-laser alloying and texturing was proposed. A thin film of alloy powder was sprayed on the surface before it was textured and alloy elements were introduced into the coating with this method. Experiments of laser texturing and micro-alloying of composite Co-based WC-TiC sintered-carbide coating were performed by pulse laser. Microstructures, roughness and phase compositions of the processed coating were analyzed while its hardness distribution and wear resisting property were also investigated The results show that the processed coating is metallurgical bonded with the substrate without crack and porosity and mainly composed of Ti, Co,TiC, WC, W(2)C, Co(2)C, CoC(x). New phases alpha-W(2)C, Co(3)W(3)C, Co(6)W(6)C, CCo(2)W(4) are formed with W decomposed from WC. Structure in the laser-melted zone is mainly cellular and dendritic. The coating is of high micro-hardness, 1000 HV(0.2), and has excellent wear resistance, about 1/4 of the wear rate of the substrate. Fatigue wear and grain abrasion of hard particle are the main abrasion mechanisms of the coating through the friction and wear tests. The depth and height of textured craters can be increased and the wear resisting property of textured surface can be improved with the proposed method. (c) 2008 Elsevier B.V. All rights reserved.