Tribological performance of TiN supported molybdenum and tantalum carbide coatings in abrasion and sliding contact

Transition metal carbides are used in industry as protective hard coatings as they combine high hardness and wear resistance with a lower friction coefficient than nitrides. Tantalum and molybdenum carbides are examples of coatings that are widely used industrially in some specific applications. For example, they are often employed as protective materials against wear and adhesion in die-casting moulds. Although these metal carbides do not present an extremely high hardness, they possess excellent low friction and wear resistant properties. These interesting properties make these coatings excellent candidates for use in applications that involve sliding contact situations. In this paper, we present a tribological characterization of tantalum and molybdenum carbide coatings, each in two variants with different chemical composition, in abrasive and sliding wear conditions against alumina and hardened steel. The results were compared to those of a titanium nitride reference coating. It was found that the tantalum and molybdenum carbide coatings were not as resistant to abrasion as the titanium nitride. However, due to their extremely low friction coefficient values they were considered superior in sliding applications against both steel and alumina. (C) 2002 Elsevier Science B.V. All rights reserved.