Friction plates are often described as ‘glazed’ when they become smoother, or take on a darkened or shiny appearance. Several mechanisms may lead to this type of appearance; hence, within the industry, the term ‘glazed’ is not universally defined. The term has been used to describe damage of the friction material due to excessive heat, deposition of fluid degradation products, the contamination of the friction material by fine particles or even the inclusion of used oil. We promote the use of the term ‘glazed’ to describe damage to friction plates resulting only from the deposition of fluid degradation products on the friction material surface.
In this paper, we offer a methodology to evaluate friction material plates such that the nature of the damage is well understood. Some of the techniques described use advanced analytical equipment to provide direct information regarding the chemical nature of the glaze. However, the overall condition of the plates can be evaluated with inexpensive equipment or that found in most laboratories.