MICROSTRUCTURE AND OXIDATION-RESISTANCE OF TIL-X-Y-ZALXCRYYZN LAYERS GROWN BY COMBINED STEERED-ARC UNBALANCED-MAGNETRON-SPUTTER DEPOSITION/

Cation-substituted Til-x-y-zAlxCryYzN alloys, with y = 0.03 and z = 0. 02, have been shown to offer greatly enhanced high-temperature oxidati on resistance compared to presently used TiN and Til-xAlxN films. Laye rs (3 mu m thickness) were deposited by unbalanced magnetron sputter d eposition onto austenitic stainless steel and M2 high-speed steel subs trates which had been ion etched in situ using a steered Cr-metal-ion cathodic are discharge at an Ar pressure of 6 x 10(-4) mbar (0.45 mTor r). The metal ion-etching promoted initial local epitaxy on individual substrate grains while the overall film texture evolved through compe titive growth to (111) in Ti0.44Al0.53Cr0.03N alloys and (200) in Ti0. 43Al0.52Cr0.03Y0.02N. Although Ti0.44Al0.53Cr0.03N layers exhibited a columnar microstructure similar to that previously observed in Til-xAl xN alloys, the addition of 2 mol% YN resulted in significant grain ref inement giving rise to a more equiaxed structure. The Knoop microhardn ess of Ti0.43Al0.52Cr0.03Y0.02N alloys was HK0.025 = 2700 kg mm(-2) co mpared to 2400 kg mm(-2) for Ti0.44Al0.53Cr0.03N. The onset of rapid o xidation, as determined from thermo-gravimetric measurements, ranged f rom approximate to 600 degrees C for TiN to 870 degrees C for Ti0.46Al 0.54N to 920 degrees C for Ti0.44Al0.53Cr0.03N to 950 degrees C for Ti 0.43Al0.52Cr0.03Y0.02N. (C) 1997 Elsevier Science S.A.