Microstructure and oxidation-resistance of Ti1 − x − y −zAlxCryYzN layers grown by combined steered-arc/unbalanced-magnetron-sputter deposition

Abstract Cation-substituted Ti 1 − x − y −z Al x Cr y Y z N alloys, with y = 0.03 and z = 0.02, have been shown to offer greatly enhanced high-temperature oxidation resistance compared to presently used TiN and Ti 1 − x Al x N films. Layers (3 μm thickness) were deposited by unbalanced magnetron sputter deposition onto austenitic stainless steel and M2 high-speed steel substrates which had been ion etched in situ using a steered Cr-metal-ion cathudic arc discharge at an Ar pressure of 6 × 10 −4 mbar (0.45 mTorr). The metal ion-etching promoted initial local epitaxy on individual substrate grains while the overall film texture evolved through competitive growth to (111) in Ti 0.44 Al 0.53 Cr 0.03 N alloys and (200) in Ti 0.43 Al 0.52 Cr 0.03 Y 0.02 N. Although Ti 0.44 Al 0.53 Cr 0.03 N layers exhibited a columnar microstructure similar to that previously observed in Ti 1 − x Al x N alloys, the addition of 2 mol% YN resulted in significant grain refinement giving rise to a more equiaxed structure. The Knoop microhardness of Ti 0.43 Al 0.52 Cr 0.03 Y 0.02 N alloys was HK 0.025 = 2700 kg mm −2 compared to 2400 kg mm −2 for Ti 0.44 Al 0.53 Cr 0.03 N. The onset of rapid oxidation, as determined from thermo-gravimetric measurements, ranged from ≈ 600 °C for TiN to 870 °C for Ti 0.46 Al 0.54 N to 920 °C for Ti 0.44 Al 0.53 Cr 0.03 N to 950 °C for Ti 0.43 Al 0.52 Cr 0.03 Y 0.02 N.