Solid lubricant materials for high temperature application: A review

Understanding the nature of the frictional behaviour of sliding contacts at high temperatures is of fundamental importance, which ultimately leads to material loss. Modern applications require proper lubrication to improve the life of the components used in extreme environment. Liquid lubricants in contacting surfaces are still in wide use, but the same has a constraint to work in extreme conditions i.e. in high temperature environment. So, currently, worldwide research is going on towards development of innovative solid lubricants for use in various such conditions. In current context, the review article provides a brief overview of current research in this area. This article concentrates on four different types of solid lubricants mostly used in high temperature tribological application on the basis of their crystal structures and compositions viz. Layered Structure Solid Lubricants, Soft Metals Solid Lubricants, Oxides Solid Lubricants and Fluorides Solid Lubricants. The review highlights the operating range of these solid lubricants and limitations of their usage. The application of those solid lubricants as coating (such as, monolithic, multiphase and self-adaptive coating) or composite (such as metallic, intermetallic and ceramic matrix) has also been discussed. This review will make a path way for researchers towards further application specific development of the solid-lubricating materials and their future evolution.