LPCVD and PACVD (Ti,Al)N films: morphology and mechanical properties

Coatings of (Ti, Al)N with different Ti/Al ratios have been deposited on silicon and different steel substrates by both low pressure CVD (LPCVD) and low frequency plasma-assisted CVD (PACVD) processes starting from metal chlorides generated by in situ chlorination of a TiAl alloy and the resulting gaseous products were mixed with NH3 or N-2, H-2 and Ar. The morphology and the microstructure of the as-deposited (Ti, Al)N films were investigated using XRD, SEM, EDS as well as glow discharge optical spectroscopy (GDOS). Microhardness and scratch tests and have also been performed in order to evaluate mechanical performance. For both techniques, dense and quite homogeneous layers with composition ranging from Ti/Al = 99/1 to 30/70 have been synthesized depending on the experimental parameters. It seems that PACVD coatings have slightly higher hardness levels and a better adhesion than LPCVD coatings. Some preliminary correlations between the layer morphologies and mechanical properties were established. (C) 1999 Elsevier Science S.A. All rights reserved.