Wear-Resistant Ceramic Films and Coatings

Abstract

Optimizing the bearing surfaces of joint replacements is an urgent socioeconomic need because of the increasing life expectancy and increased performance demands from the growing number of younger patients to whom the surgery is indicated. Ceramic surface films have a great potential to improve the tribological performance and longevity of artificial joints as they provide the metallic components with a hard, wear-resistant surface while preserving their toughness and fracture resistance. Although simple in concept, providing a clinically and commercially successful coating–substrate combination has proven challenging. A critical feature for alternative technology is the adhesion of the coating to the substrate. Not only would adhesive failure of the ceramic film negate its potential wear advantages, but also it would liberate hard third-body particles that could increase abrasive wear of the bearing surfaces. Superficial films formed by physical vapor deposition or chemical vapor deposition of titanium nitride (TiN) and diamond-like carbon, as well as zirconium oxide (ZrO2) produced by controlled oxidation of a zirconium alloy substrate, are the most extensively studied hard coatings for orthopedic applications. In this article, the structure, durability, tribological behavior, and clinical performance of these and alternative hard ceramic coatings are discussed.