Cathodic arc evaporation of (Ti,Al)N coatings and (Ti,Al)N/TiN multilayer-coatings—correlation between lifetime of coated cutting tools, structural and mechanical film properties

Abstract

(Ti,Al)N and (Ti,Al)N/TiN multi-layer coatings were deposited by cathodic arc evaporation with a large area TiAl and/or Ti cathode. The ratio of Ti/Al varied between 50/50, 40/60 and 33/67. The goal was to determine the influence of the bias voltage, which varied between −30 and −125 V, on the lifetime of coated cutting tools under drilling conditions. Film orientation and compressive stress were determined by X-ray diffraction. The chemical composition of the coatings was investigated by secondary-neutral-mass spectrometry (SNMS). It was found, that in the multi-layer coatings, there is a transition in the texture from 〈2 0 0〉 to 〈1 0 0〉 with increasing negative bias voltage, beginning at approximately −75 V, while the monolayer retained 〈2 0 0〉 orientation. The stress in the monolayers reached a maximum at a bias voltage approximately −100 V. Rockwell and Scratch tests show excellent adhesion on carbide and steel materials. Multilayer tool lifetime reached a maximum at −100 V, while the monolayer coated tool life increased monotonically with negative bias.