Strategy for achieving high-performance PVD nano-multilayered AlTiN/TiN coated milling tool: Fine platelet-grained WC–Co substrate and interface regulation

Abstract

For a coating and substrate system, the ability to jointly resist external force damage determines the tool-life. To enhance such a mutual synergy, one-dimensional ultrafine platelet-grained WC–10Co–0.4TiC–0.6Cr3C2 alloy (PG alloy) was designed and prepared, based on Ti-induced enlargement of the interfacial energy difference. Submicron-grained WC–10Co–0.6Cr3C2 alloy was used as the reference. On the two kinds of substrates, nano-multilayered Al0.55Ti0.45N/TiN coating was deposited. The results show that compared with the reference, PG alloy with a texture coefficient TCWC(0001) of 3.27 and free of apparent micro-pore defect within the WC grains is characterized by higher hardness (1632 vs. 1567HV30), higher toughness (14.7 vs. 13.4 MPa∙m0.5), high strength (3737 vs. 4434 MPa), and stronger dislocation-forming ability. By using PG alloy as the substrate, high film adhesion strength (>100 N) is achieved, and readily formed coherent and semi-coherent interfaces between TiN (film) and WC are revealed by high-resolution transmission electron microscopy observation. As a result of interface strengthening and excellent combination of the substrate and the coating couple, compared with the reference tool, 1.4–1.5 times higher average tool-life under a wet or dry milling condition of 316L stainless steel is achieved.