Low Friction and Wear Surface for Application over a Wide Range of Temperature

Abstract : HERE IS A STRONG DEMAND FOR SOLID LUBRICANT COATINGS THAT CAN FUNCTION OVER A WIDE RANGE OF TEMPERATURES. Since none material can provide adequate lubricating properties over a wide temperature range, an approach of a composite coating was evaluated in Phase I. Composite coatings of ZnO and MoS2 were deposited by sputtering on M5O steel and Si3N4 substrates. Coatings were characterized by Rutherford back scattering (RBS), Auger electron spectroscopy (ABS) and Transmission electron microscopy (TEM), both before and after exposure to high temperatures (up to 700 deg C) in air. Friction measurements were performed at temperatures in the range of room temperature to 700 deg C in air. Results indicate that layered ZnO+MoS2/ZnO coating performed better at high temperature than the mixed composite coatings. Friction coefficients were in the range 0.2 to 0.3 at temperatures below 400 deg C for coated M50 substrate against uncoated M5O ball. At higher temperatures, the friction coefficient increased to greater or equal to 0.4 for coated Si3N4 substrate against uncoated Si3N4 ball.