The study of wear characteristics of sintered high speed steels containing CaF2, MnS and TiC additives at elevated temperature

The wear characteristics of five kinds of sintered high speed steels, which contain MnS, TiC and CaF2 additives, have been investigated at 600 °C. The results show that the MnS, TiC and CaF2 additives greatly affect the wear of the steels, and that TiC can improve the wear resistance of the steels. There is also evidence that, at elevated temperature, a thin molten layer or soft metallic film covers the worn surface and affects the wear process. The mechanism and critical temperature for forming the film are studied based on experiments and microanalysis. The results show that the temperature range to form the surface film is about 500–600 °C, and that the film’s load capacity depends on its features and the hot properties of the counterface materials. For example, at 600 °C, when load is increased from 5 to 30 N, wear volume of the steel containing MnS+TiC sliding on Al2O3 increases about eight times, the wear volume of M50 on M50 increases sharply with loading from 10 to 40 N, and wear volume of the steel containing MnS+TiC sliding on Si3N4 is about twice that sliding on Al2O3 and about six times that on M50.