The Influence of Etching in a Glow Discharge Plasma on the Properties of Wear-Resistant Coatings for Metal-Cutting Tools

Abstract

The properties of three Ti-TiN-(Ti,Cr,Al)N coatings, which have identical thickness and elemental composition, but a different scheme of ion etching by glow discharge plasma during the deposition process, were compared. Various etching times of the substrate before coating deposition were considered, as well as the use of additional etching during the deposition process and after coating deposition. It was found that additional etching in a glow discharge plasma during the deposition process and after completion of coating deposition increased the hardness by 100-300 HV units. Increasing the time of preliminary etching of the substrate surface before coating deposition from 5 to 10 minutes allows significant increase of the resistance to destruction during the scratch test (from 22 N to 38-40 N). Additional etching by glow discharge plasma during the deposition process and after coating deposition can increase the tool life by 30%. The coating deposited after pre-etching the substrate for 5 minutes, without additional etching operations, exhibits a brittle nature of failure combined with partial delamination from the substrate, while coatings pre-etched for 10 minutes maintain a strong adhesive bond to the substrate. Additional etching during the coating deposition process creates an interface that slows down the overall degradation of the coating during the cutting process, thus increasing the overall wear resistance of the tool.