Sputtered Coatings Based on the Al₂AU Phase

Abstract

Transition metal nitride-based, wear-resistant hard coatings on cutting tools and other substrates often lack distinct colorations allowing product differentiation and self-lubricating properties. In the present work, the possibility of achieving these objectives for sputtered coatings based on the purple-red Al₂Au phase within the Al-Au system was investigated. Coatings were characterized with respect to morphology, chemical and phase composition, hardness, optical, oxidation and tribological properties. Al₂Au-containing coatings were deposited with dense, fine-grained structures yielding a hardness of 4 GPa and pink coloration. The coatings were stable up to about 850°C, where the onset of oxidation occurs. Low friction coefficients against alumina were achieved between 500 and 700°C. The concept of applying Al₂Au-containing coatings as a colored self-lubricating layer on top of a hard coated cemented carbide tool warrants further investigations.