Evaluation of titanium carbide thin film coatings on WC‐Co following surface microstructure treatments

The effects of acid or radio‐frequency (RF) CF 4 plasma pre‐treatments before a sputtered titanium carbide (TiC) hard coating thin film were investigated to increase the adhesion strength of TiC on WC‐16wt%Co substrate. The arithmetic average roughness (Ra) was 182.5 nm after a 5‐min aqua regia treatment at 60 °C and 247.8 nm after 30 min of RF CF 4 plasma at a substrate temperature of 500 °C. Chemically bonded cobalt disappeared from the WC‐Co substrate surface on treatment with aqua regia for 5 min based on X‐ray photoelectron spectroscopy (XPS). The TiC thin film on substrate with Ra = 150.3 nm after CF 4 plasma treatment at 300 °C for 30 min did not delaminate at up to 30 N, in contrast, the substrate with Ra = 182.5 nm after aqua regia treatment at 60 °C for 5 min underwent delamination at below 30 N. The adhesion strength was maximal, with a surface roughness of Ra ≈ 150 nm, with CF 4 and aqua regia treatments.