Mechanical and tribological properties of CrTiCu(B,N) glassy-metal coatings deposited by reactive magnetron sputtering

Abstract

Copper-based bulk nanocrystalline and amorphous alloys offer attractive mechanical properties such as high hardness and fracture toughness—as well as good corrosion resistance. Such materials can potentially be used as thin film tribological coatings to improve the wear resistance of low strength steels and the light alloys. In this paper novel CrTiCu(B,N) glassy-metal coatings have been successfully deposited on Si-wafer, AISI 316 stainless and AISI M2 tool steel substrates, over a wide range of compositions, by hot-filament enhanced reactive magnetron sputtering. The majority of the coatings produced are X-ray amorphous and exhibit Knoop microhardness values above Hk25g=2000 Kgf/mm2 (i.e. ≥20 GPa). The coatings provide a significant improvement, by more than two orders of magnitude, in reciprocating sliding wear rate (compared to the stainless steel substrate) when tested against a 10 mm diameter SAE 52100 hardened steel ball counterface at 10 N normal load. In impact tests for 105 cycles against a 10 mm diameter WC–6% Co ball, at a maximum load of 1 kN, the coatings exhibit excellent resilience and ductility—with small impact cavities and little or no peripheral or radial cracking around the impact craters.