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

The effects of acid or radio-frequency (RF) CF4 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 CF4 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 CF4 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 CF4 and aqua regia treatments. [ABSTRACT FROM AUTHOR]