Morphology, structure and constitution of metastable single-phase Ti1-xAlxN films grown by reactive MSIP

Metastable, single phase, polycrystalline Ti1-xAlxN hard layers were deposited on HSS-substrates with reactive magnetron sputtering ion plating (MSIP). The substrate temperature was 400 degrees C, the bias -60 V, the argon pressure 1.2 Pa and the sputter power 6 W cm(-2). Compound targets with a Ti:Al ratio of 75/25, 50/50 and 25/75, expressed in at-%, were sputtered. The nitrogen reactive gas pressure during sputtering was 8.4 x 10(-2) Pa for the 75:25 target and 1.08 x 10(-1) Pa for the 50:50 and 25:75 targets. The Ti1-xAlxN layers grew with x = 0.26, 0.54 and 0.75, as determined with EPMA. Thin film XRD and HEED structure analysis showed that the Ti0.74Al0.26N layer had grown as B1 structure (a(0):0.4214 nm) with [211] texture, the Ti0.46Al0.54N layer likewise as B1 structure (a(0):0.4154) with [111] texture, but the Ti0.25Al0.75N as B4 structure (a(0):0.317 nm and c(0):0.5014 nm) with [110] texture. Pronounced columnar growth was observed with HR-SEM in the fractured surface of the cubic layers. The mean grain size, and consequently the surface roughness, diminished with increasing Al-content of the layer.