INFLUENCE OF DEPOSITION CONDITIONS ON MICROSTRUCTURE AND TEXTURE OF Ti1-XAlXN PVD COATINGS

This study is focused on how the application of pulsed substrate bias during cathodic arc deposition affects the microstructure, texture, grain size and phase composition of (Ti,Al)N coatings. A series of Tix-1AlxN, 0.25≤x≤0.55 coatings were deposited on WC-Co cemented carbide substrates with -30 V, -60 V and -300 V pulsing bias (duty cycle 10 % and a frequence of 1 kHz) under controlled chamber conditions at 4.5 Pa N2-gas and a substrate temperature about 400 °C. The pulsing parameters for the bias (voltage, duty cycle and frequency) were deliberately selected to influence structure, microstructure and composition of the deposited coatings. All Tix-1AlxN coatings had a consistent columnar cubic B1 structure regardless of their chemical composition. Coatings grown at -30 V and -60 V pulsed bias exhibited a pronounced <111> texture attributed to a kinetically driven mechanism influenced by the relative flux of ion species, affecting the surface migration of adatoms during growth. In contrast, the coatings grown with a pulsed bias of -300 V exhibited a reduced <111> texture and the onset of grains with <100> preferred orientation. The transition to the <100> orientation with increased ion energy agrees with the fact that the <111> directions expose the densest array of atoms to the ion beam during growth while the <100> are the most open channeling directions in a B1 structure. The correlation to the preferred with respect to pulsing conditions during growth, correlated to microstructure, grain size and phase composition be further discussed. Surface roughness was highest (Sa≈0.17-0.22 µm) for coating deposited at pulsed bias -30 V.