Solid Lubricants: Overview and Recent Developments

Abstract

A renaissance in research and development of solid lubricants has taken place during the past 10 years. This renaissance has been driven by the needs of advanced technological applications, for which liquid lubricants alone have become either ineffective or undesirable. Increasing the efficiency of jet and automobile engines, which entails engine operation at significantly higher temperatures, and increasing the longevity of space vehicles have been central technology drivers.In the past 10 years, many new solid lubricants have been developed to address these needs for higher temperature operation and longer life. Their development, for the most part, has taken advantage of what is known concerning their mechanism of action. Although this mechanistic knowledge is incomplete, particularly at high temperatures, significant advances in material performance have been made. In addition, new methods of applying solid lubricant coatings, namely plasma and ion-beam-assisted vacuum deposition methods, have recently come into their own and produced improved materials.This article will highlight developments in the 1980s which produced new solid lubricants and the advanced technologies which these materials will enable.Several reviews of solid lubricants survey the area in more detail than is possible here. For overview purposes, this article will briefly describe the classes of materials used as solid lubricants, their mechanism of action, and areas of application.

Solid lubrication in fluid film lubrication

“…Several inorganic lamellar materials such as molybdenum and tungsten disulfide (MoS 2 ‐WS 2 ), graphite (C), hexagonal boron nitride (hBN), boric acid (H 3 BO 3 ), etc. can provide excellent lubrication …”

“…can provide excellent lubrication. [2][3][4][5][6][7] A combination of solid and liquid lubrication is also feasible and may have a beneficial synergistic effect on the friction and wear performance of sliding surfaces, in particular, in the boundary and mixed regimes of lubrication. 8 In various mechanical systems, for example, in piston compressors and internal combustion engines, movement occurs in a reciprocating way and induces hydrodynamic, mixed, and boundary lubrication regimes.…”

The Low-Pressure Gas and Vacuum Processing Environment

“…[127]- [131] Burnishing is another way of applying solid lubricants. These include the sulfides (MoS 2 and WS 2 -lubricants, usable to 10 -9 Torr), silicides (WSi 2 -anti-stick) and the selenides (WSe 2 -electrical conductors,).…”

Interface Design for Oxidation‐Resistant Ceramic Composites

“…233 Other refractory solid lubricants, such as MoS 2 , Cs 2 MoOS 3 , and ZnMoO 2 S 2 , are known, but there is no evidence that any function in air above 700°C. 249 The fluorides CaF 2 , BaF 2 , and LaF 3 are also known to be solid lubricants. 249 Evidence for debonding and stability with Al 2 O 3 has been found, but the intrinsic stability of these materials with water is of concern.…”

“…249 The fluorides CaF 2 , BaF 2 , and LaF 3 are also known to be solid lubricants. 249 Evidence for debonding and stability with Al 2 O 3 has been found, but the intrinsic stability of these materials with water is of concern. 233 There are proprietary solid lubricants that are reported to function at up to 1000°C.…”