Metal-Ceramic Nanocomposite Coatings Produced by HVOF Thermal Spray and in-situ Precipitation of Ceramic Components for Tribological Applications

Protective coatings with high wear, erosion and corrosion resistance are of great importance in many fields of application and in particular, in the electric power generation sector. In this paper, the HP-HVOF (high-pressure high velocity oxy-fuel) technique is used to produce dense rapidly quenched metal-ceramic nanocomposite protective coatings. The powders for the thermal spray process are produced by high energy ball milling using mechanochemical displacement reactions to synthesize the ceramic components in-situ at the nanometric scale. Solid lubricants like graphite and boron nitride are used as a source of carbon, nitrogen and boron to form and precipitate carbides, nitrides or borides in a corrosion resistant metal matrix. The mechanisms of precipitation during the milling and/or thermal spray processes are investigated using various analytical methods. The tribological properties of the coatings such as wear, cavitation erosion and corrosion are investigated using pin-on-disc, ultrasounds and various electrochemical techniques.