Tribological properties of NiAl matrix composite coatings synthesized by plasma spraying method

The NiAl matrix composite coatings containing silver and molybdenum were prepared by atmospheric plasma spraying and their tribological properties were investigated in details from 25 to 900 degrees C. The X-ray diffraction (XRD), micro-Raman, scanning election microscopy (SEM) and transmission election microscopy (TEM) were used to analyze the composition and microstructure of composite coatings. The X-ray diffraction (XRD) results shown that molybdenum and silver were exist in single-phase, but not alloyed in composite coatings. The addition of silver could effectively improve the tribological properties of composite coatings at the wide range of temperature. The silver, nickel and molybdenum could occur the tribo-chemical reaction and form silver molybdates and nickel molybdates lubricating films inside the wear track of composite coatings at high temperature. The friction process promoted the formation of the silver molybdates. The silver molybdates, nickel molybdates and NiO were the main components in composite coatings at high temperature, which could effectively improve tribological properties of composite coatings.