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

• TiAlN thin films were deposited by deep oscillation magnetron sputtering. • Low deposition temperature was adjusted in oscillation voltage on-time and off-time. • Microstructure of TiAlN thin films changed from Zone I to Zone T with peak power. • Fracture toughness of TiAlN thin films in Zone T was optimized at a peak power. • Bombarding energy E bi and mobility D of species were discussed in deposition process. 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 (τ on) / off-time (τ off) ratio with 6–12 μs to 30 μs. All TiAlN thin films have a face centered cubic structure with a composition of Ti 0.22 Al 0.28 N 0.50. 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 (K IC) 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 K IC values of Ti 0.22 Al 0.28 N 0.50 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. [ABSTRACT FROM AUTHOR]