Superhard nanocomposite Ti1−Al N films prepared by magnetron sputtering

Abstract Ti 1− x Al x N 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 N 2 ranging from 0 to 0.2 Pa, different substrate temperatures T s ranging from room temperature RT to 400°C and two substrate biases U s = U fl , i.e. floating potential, and U s =−200 V. It was found that: (i) the continuous change in p N 2 induces a dramatic change in the film structure and (ii) different values of microhardness of Ti 1− x Al x N films produced at different p N 2 , correlate well with changes in the film structure. Superhard (≥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 (∼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 Ti 1− x Al x N films can be prepared are given.