The tribological characteristics of hot-pressed self-lubricating composites, consisting of molybdenum disulfide, refractory metal oxides and refractory metals, were evaluated at temperatures up to 450-degrees-C in vacuum. Sliding bearings made from the composites were run against 304 stainless steel shafts at a rotational speed of 120 rev min-1 under an applied load of 1.7 N for (6-10) X 10(6) revolutions. Wear was negligible at temperatures under 100-degrees-C. However, wear of the composite bearings, at a specific wear rate of (2-5) X 10(-8) mm3 N-1 mm-1, occurred at 300-degrees-C. At 450-degrees-C, a weight loss of about 10-30 mg of the shaft and a weight gain of almost the same amount of the bearings were observed. X-ray photoelectron spectroscopy analysis revealed iron and traces of iron sulfide on the bearing surface, indicating that a chemical reaction had occurred between the composite bearing and the steel shaft. To examine the effect of counterpart material, pin-on-disk friction tests using a composite pin and an Si3N4 disk were performed at temperatures up to 450-degrees-C. In contrast to the 304 steel counterpart, an excellent tribological response was found with the Si3N4 disk. The specific wear rate of the composite pin at 450-degrees-C was 2.2 X 10(-10) mm3 N-1 mm-1 and the wear of the Si3N4 disk was negligible. An attempt was made to improve the strength of the composite. By adding 304 stainless steel in a fraction of 5% to the composition, an improvement in strength of the composite of about 30% was obtained. Furthermore, this bad a good effect on the tribological performance of the composite at high temperature.
