Superhard nanocomposite Ti1-xAlxN films prepared by magnetron sputtering

Ti1-xAlxN films were sputtered from an alloyed TiAl (60/40 at.%) target in Ar and Ar + N-2 mixture at a constant total pressure of 0.5 Pa by a planar round unbalanced magnetron of 100 mm in diameter. Films were sputtered at different partial pressures of nitrogen p(N2) ranging from 0 to 0.2 Pa, different substrate temperatures T-s ranging from room temperature RT to 400 degrees C and two substrate biases U-% = U-fl, i.e. floating potential, and U-s = -200 V. It was found that: (i) the continuous change in p(N2) induces a dramatic change in the film structure and (ii) different values of microhardness of Ti1-xAlxN films produced at different p(N2), correlate: well with changes in the film structure. Superhard (greater than or equal to 40 GPa) films with hardness of up to 47 GPa were prepared. The superhard films are nc-TiAlN/AlN nanocomposite films composed of relatively large (similar to 30 nm) TiAlN grains, oriented in one direction and surrounded by an amorphous and/or nc-AlN phase. These films exhibit a high elastic recovery up to 74% and contain about 20 at.% Ti, 25 at.% Al and 55 at.% N. The conditions under which superhard Ti1-xAlxN films can be prepared are given. (C) 2000 Elsevier science S.A. All rights reserved.