The influence of TiC, CaF2 and MnS additives on friction and lubrication of sintered high speed steels at elevated temperature

Friction behaviours of sintered high speed steels containing TiC, CaF2 and MnS additives and lubrication mechanisms of these additives have been investigated at sliding conditions at 600 degrees C. Results shown that these additives strongly affected friction behaviours of the sintered high speed steels. Ceramic carbide TiC, as a bonding agent and enhancement phase, bonded the solid lubricant CaF2 and MnS surrounding it and supported these solid lubricant particles so that friction process become stable. Fluoride calcium CaF2 has a better high temperature lubrication properties than MnS, and that the addition of TiC + CaF2 in the sintered high speed steels achieved excellent friction performances both a stable and a low friction coefficient value. Analysis results by X-ray indicated that the surface film appearing on worn path consists of some molten metal matters and very fine carbide particles. During sliding, the surface film separated contacts and resulted in a lower friction coefficient. Because of the sintered high speed steels usually to be used to manufacture high temperature components, these results are helpful for their engineering use.