Surface Modification of Ti600 Alloy with Laser Cladded Ti/TiB₂ Coatings for Internal Combustion Engine

The surfaces of Ti600 alloy,an internal combustion engine material,were modified with Ti/TiB₂ composite coatings synthesized by laser cladding of Ti and TiB₂ powders.The influence of the specific energy of laser on the microstructures,tribological behavior of the Ti/TiB₂ coatings was investigated with X-ray diffraction,scanning electron microscopy and conventional mechanical probes.The results show that the specific energy of laser had a major impact.For instance,the Ti/TiB₂ coatings with strong interfacial adhesion comprised cellular TiB₂ grains/whiskers on the top,dispersed TiC/TiN nuclei and dendritic structures in the middle,and TiB₂ grains and lamellar biphasic clusters at the bottom.As the specific energy increased,the micro-hardness changed in an increase-decrease mode,peaking to 990 HV at 15 kJ/cm²,and the wear-rate and average friction coefficient monotonically decreased.Shallow wear-tracks and some scraps existed on worn surface of the coatings.