TiN COATINGS FOR PROTECTION AGAINST COMBINED WEAR AND OXIDATION

Abstract

A method has been developed to study the behaviour of materials under conditions of simultaneous high temperature oxidation and mechanical wear by the action of abrasive particles in a jluidised bed. The possibility of using TiN coatings to provide a barrier to such an environment has been explored. The behaviour of steels coated with TiN by PVD was compared with that of the unprotected substrate materials. It wasfound that the TiN coating survived for a longer period at lower impact velocities of the bed particles. An increase in coating wastage rate with temperature between 200 and 400°C was suggested to be primarily due to a decrease in the coating hardness. A large reduction in the survival time of the coating above 400° C was believed to be due to the increase in the oxidation rate of TiN at these temperatures. Mechanisms of material removal were identified by SEM examination of worn specimen surfaces.