Microstructure and high temperature wear behavior of in-situ synthesized carbides reinforced Mo-based coating by laser cladding

Abstract

To broaden the application fields of Mo coating as wear resistant coatings for hot-end components in jet engines, the in-situ synthesized carbides reinforced Mo-based coatings were prepared by laser cladding. The effect of nickel-coated graphite (carbon source) on the microstructure, hardness and elevated-temperature wear behavior of coatings was studied. The wear behavior of coatings was evaluated by using a tribotester with a ball-on-disc configuration from room temperature to 1000 °C against Si3N4 ball in air. The results showed that the carbides played a role of dispersion-strengthening. The coatings were composed of Mo, Cr1.12Ni2.88, Cr9Mo21Ni20, Mo2C, Cr7C3 and Mo6Ni6C. The wear resistance of the laser clad coatings was significantly enhanced by the addition of nickel-coated graphite, and the wear rates firstly decreased and then increased with increasing graphite content. The friction coefficients of laser clad coatings increased with an increase in nickel-coated graphite content. There existed a critical content of nickel-coated graphite that best strengthened the tribological behavior from room temperature to 1000 °C. The coating with 6.0 wt% nickel-coated graphite exhibited favorable tribological properties due to the moderate ductility, carbides, lubricating layer and in-situ synthesized solid lubricants.