ABSTRACT
A key feature of solid lubricants is their performance at high temperatures. Twenty-ve years ago, DellaCorte (1987) could not nd liquid lubricants to operate above 400°C, and, for space applications, the range of interest was up to 1000°C. He characterized the solid lubricant as a solid that shears easily, providing low friction, yet separating sliding surfaces. Many solid lubricants are laminar, such as MoS2 or graphite. One sheet sticks to the substrate, and the others slide, having low shear strength (Johnson, Godfrey, and Bisson, 1948). Sliney (1987) believed that a good solid lubricant should be thermodynamically stable, possess a high degree of plasticity, adhere to substrate and have a compatible thermal expansion with it. Hironaka (1984) discussed reaction-generated coating, which is formed by chemical reactions in advance, or during the sliding by frictional heat (‘in-situ lms’).
