Structure and fracture toughness of TiAlN thin films deposited by deep oscillation magnetron sputtering

TiAlN thin films were deposited on Si(100) and AISI 304 austenitic stainless steel substrates at the low deposition temperature below 250℃ by the deep oscillation magnetron sputtering (DOMS), respectively. The peak sputtering power changed from 58.7 kW to 129.9 kW by adjusting the oscillation voltage on-time (τon) / off-time (τoff) ratio with 6–12 μs to 30 μs. All TiAlN thin films have a face centered cubic structure with a composition of Ti0.22Al0.28N0.50. With increasing the peak powers, a transit of the columnar morphology in Zone I with the preferred orientation of c-TiAlN(111) to a compact morphology in Zone T with c-TiAlN(200) was characterized. The hardness, residual stress, and H/E and H3/E2 ratios of TiAlN thin films increased with the maximal values obtained at the peak power of 90.2 kW, and then slightly decreased. Correspondently, the fracture toughness (KIC) of TiAlN thin films on Si(100) and AISI 304 stainless steel increased firstly from 0.56 MPa∙m1/2 to 1.10 MPa∙m1/2 and from 0.58 MPa∙m1/2 to 1.08 MPa∙m1/2 as the structure from Zone I with c-TiAlN(111) to Zone T with c-TiAlN(200), and then decreased to 0.94 MPa∙m1/2 and 0.71 MPa∙m1/2 at the structure of Zone T with c-TiAlN(200), respectively. The higher KIC values of Ti0.22Al0.28N0.50 thin films in Zone T were achieved on Si(100) and AISI 304 stainless steel at 90.2 kW. The excellent mechanical properties of TiAlN thin films on Si(100) and AISI 304 stainless steel substrates were carried out by using DOMS at the low deposition temperature.