The effect of Cu and Ni on the nanostructure and properties of arc-PVD coatings based on titanium nitride

Metal-ceramic TiN-Cu (TiN-Ni) coatings with metal contents from 0 to 20-26 at.% can be synthesised by filtered vacuum arc deposition of carbide cutting tools. Adding metals into the coating reduces the nitride phase crystalline grain size from 100 to 20 nm. Additionally, the enhancement of metal content in the coating of up to 3-5 at.% results in an increase of the coating hardness from 20-22 GPa (typical for TiN) to 45-50 GPa and a decrease of the friction coefficient from 0.65 (typical for a hard alloy) to 0.45 (sliding wear tests against 100Cr6 balls under dry condition using a ball-on-disc method at high speed). Further enhancement of metal content up to 20 at.%, which is accompanied by a reduction in the nitride phase crystalline grain size, results in a decrease in hardness by 15-19 GPa due to additional introduction of soft ductile metal and emerging coating porosity. Adhesive/cohesive properties of coatings were investigated. It was established that the coatings were destroyed according to the cohesion mechanism. The critical loads characterising the emergence of the first cracks in the coatings and complete abrasion of the coating to the substrate (Lc1 and Lc3) were determined to be 14 N and 80 N, respectively. The formed coatings display stability of structure and composition for up to 800 °C. Coated carbide tools with developed coatings have increased the lifetime 5 times for continuous cutting steels (35HGSA) and more than 3 times for interrupted cutting steels (Cf53).