Cutting performances and the related characteristics of CVD coated hardmetal inserts changed by post-treatments

A TiN/MT-TiCN/alpha-Al2O3/TiN coating is deposited on a WC-6Co hardmetal substrate by chemical vapor deposition (CVD). The influence of the post-treatments after the CVD process on the performances of the inserts in the tuning of grey cast iron EN-GJL-250 and the related characteristics are investigated. Conventional brushing, polishing and wet-blasting are employed for the comparison. The results demonstrate that the coated inserts post-treated by wet-blasting followed by polishing exhibit in a cost effective way the lowest surface roughness, the best combination of cooling micro-crack healing effect and surface finish state, a moderate compressive stress state, and > 100 N adhesion strength. As a result, in the wet cutting condition, the lowest roughness and the smallest work hardening value of the workpieces compared at a fixed time parameter in their middle-later cutting lifetime and the longest tool life are attained. Crater wear developed from adhesive wear is the main reason for the tool failure. The same tool life conclusion is reached in the dry cutting condition.