Ir-based multi-component coating on tungsten carbide by RF magnetron sputtering process

Ir-based noble metal hard coatings were deposited onto the tungsten carbide substrate by RF magnetron sputtering. Films were prepared by multi-target sputtering with iridium, rhenium and chromium as the sources. Argon and nitrogen were inlet into the chamber to be the plasma and reactive gases. The correlations between contents of each component in the noble metal alloy films and the control parameters in the input power of the sputtering gun was investigated. The contents of Cr and N ranged from 3.2 to 33.5 at.% and 7.3 to 21.0 at.%, respectively, as the power applied to the Cr source was varied from 50 to 250 W. The atomic ratio of Ir/Re remained constant at 2.0, regardless of the amount of Cr and N co-deposited. The coating microstructure and morphology were also studied by X-ray diffraction and atomic force microscopy, respectively. It was shown that the surface roughness (Ra) values of uncoated substrate and Ir–Re–Cr–N protective thin film were in the same order of approximately 2–4 nm. Microhardness test indicated that the Ir–Re–Cr–N multi-component coating exhibited compatible hardness with the Ir–Re binary hard films, and the surface hardness was better than that of the Ir–Pt film.