ICMCTF2000 Session B2: Chemical Vapor Deposition Techniques

The ternary phase Cr₃(C_0.8N_0.2)₂ is known to be stabilized both at high temperature and under a high pressure of nitrogen. Therefore it is unstable in the typical conditions of the vapor deposition processes, i.e. moderate temperature and normal or low total pressure, and so far, the potentiality of this ternary phase to be used as metallurgical coatings has not been investigated. We report in this contribution a novel deposition process of this ternary phase on various substrates including steel.

Single-phased coatings of Cr₃(C_0.8N_0.2)₂ have been deposited by combining an MOCVD process and an annealing post-treatment. The films were grown in the temperature range 683-793 K by low pressure MOCVD using Cr(NEt₂)₄) as single-source precursor. As-deposited films are very smooth and x-ray amorphous. A relatively low amount of nitrogen is uniformly incorporated into the film. The nitrogen content is nearly independent on the growth conditions and it amounts the value of the ternary phase (about 7 at. %). The as-deposited films crystallize upon annealing at 873 K under vacuum to form the orthorhombic Cr₃(C_0.8N_0.2)₂ phase. No evidence for additional phases has been found. Both as-deposited and annealed coatings exhibit a high hardness and a good adhesion on stainless steel substrates. The hardness slightly increases upon crystallization to reach typically 17 GPa. Preliminary properties of this metastable carbonitride phase are reported and its potentialities as hard metallurgical coating are discussed.

In contrast to the effect of nitrogen ion implantation, where changes in properties are related [1] to the chemical and tribological character of the implanted zone (i.e. the near-surface zone where the implanted ions reside), metal ion implantation hardens the substrate and enhances wear resistance to depths well beyond that zone -- this is known as the 'long range effect'. As shown recently, the extent of this hardening depends on the conditions generated in the implanted zone during the implantation process [2].

In the present study, the surface topography and residual stress in TiN deposited by CVD and subjected to a metal ion implantation post-treatment are presented covering the range from Al to W ions. Coatings made by CVD were chosen because of their low residual stress (0 - 0.5 GPa tensile). The surface topography is discussed in terms of Ra values determined by profilometry and by AFM and studied by fractal analysis. It is found that the residual stress increases with ion beam energy but that there is no concomitant change in the coefficient of friction, the surface roughness nor in the surface topography caused by the associated sputter loss. The stress in the implanted zone is shown to correlate directly with the stress generated in the material affected by the long range effect, in accordance with the mechanism proposed recently [2]. ¹ R.R. Manory et al., Surf. Coat. Technol., 114 (1999) 137. ² Y.P. Sharkeev et al., Vacuum, 52 (1999) 247.