Microstructure and wear performance of laser cladding Co-based alloy coatings of wheel/rail specimens

For improving the wear resistance of wheel / rail materials and decreasing the wheel / rail wear,the laser cladding Co-based alloy coating was obtained on the surface of wheel / rail specimens by CO2 multimode laser device. The microstructure and micro-hardness of the coatings were tested and analyzed,and the wear resistance of substrate and the coatings were studied using a MMS-2A rolling wear test apparatus. The results indicate that the cladding coating with thickness of 1mm on the surface of wheel / rail specimens is obtained after laser cladding,which has an excellent metallurgical bonding with the substrate. The coating consists of dendrite( γ-Co) and eutectic( Cr23C6+γ-Co). The prime phase with rich-chromium is dendritic solid γ-Co,while eutectic structure is rich in cobalt. The thick columnar dendrites are observed in the bond zone and there are some other crystallization morphologies such as cellar,columnar from the center to the top surface. The microstructures far from the interface are thinner and grow in disorder. There exist element diffusion in bond zone and the percentage of Fe,Cr,Co change significantly. The hardness of wheel / rail specimens with laser cladding Co-based alloy increases by 52. 98% and 43. 44%. The wear resistance of wheel / rail is improved about 5 times than that of substrate and it would significantly reduce the wear rate of other friction pair without laser cladding.