The Research Of Laser Cladding Composite Coating And Wear-resistance On Tc4 Alloy

In this article research of laser cladding process optimization and wear-resistance property wewe carried out, which mainly aims at solving the problems of low hardness, poor wear- resistance of TC4 titanium alloy and “crescent” defects existing in the surface morphology in our early research. Laser cladding experiments were carried out with the mixed powder of Ti C/Ti B2 and Ti C/Ti B2/Ni on TC4 titanium alloy surface respectively. SEM, EDS, XRD, microhardness tester and friction and wear tester were used to detect and analysis the surface morphology, microstructure, phase, microhardness and friction and wear properties. Main work and conclusions are as follows:(1) The pore-free and cracks-free cladding coating was in-situ synthesized. And the coating was dense, smooth and well metallurgically bonded with substrate. A moderate amount of Ni is helpful to improve the “crescent” surface morphology; surface roughness of laser cladding layer improves with the increasing of scanning speed.(2) Ti, Ti C, Ti B, Ti B2 phases were found when Ti C/Ti B2 were used as cladding materials and Ti, Ti C, Ti B, Ti B2, Ti Ni, Ti2 Ni phases were found when Ti C/Ti B2/Ni were used as cladding materials.The cladding layer is mainly composed of particles, dendrites, acicular, rod and bluk structure. From the surface layer to the bonding zone, the number of particles structure decreases while dendrites, acicular structure increases. The microstructure refines and becomes denser when laser power density increases.(3) The microhardness decreases from the surface to the substrate, and the highest value reaches 1257.35 HV0.2 which is 2.5 times higher than substrate.(4) The average friction coefficient of Ti-C-B and Ti-C-B-Ni composite coating were 0.46 and 0.35 which reduce 0.13 and 0.24 respectively compared with substrate which was 0.59. And the mass loss were 5.1% and3.5% that of the substrate respectively. The wear mechanism of substrate was adhesion wear, while Ti-C-B and Ti-C-B-Ni was abrasive wear. The wear resistance of Ti-C-B and Ti-C-B-Ni composite coating has improved significantly, and wear resistance of Ti-C-B-Ni is better than Ti-C-B.