Single-phased hard coatings of the metastable Cr-3(C0.8N0.2)(2) ternary phase grown by low pressure MOCVD

Single-phased coatings of Cr-3(C0.8N0.2)(2) have been deposited by combinin g a metal-organic chemical vapor deposition (MOCVD) process and an annealin g post-treatment. The films were grown in the temperature range 683-793 K b y low pressure MOCVD using Cr(NEt2)(4) as the single-source precursor. As-d eposited 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 of the growth conditions and it amounts to exactly th e value required to form the title ternary phase (similar to7 at.%). The as -deposited films crystallize upon annealing at 873 K under vacuum to form t he orthorhombic Cr3(C0.8N0.2)2 phase. No evidence for additional phases has been found. Both as-deposited and annealed coatings exhibit a high hardnes s and a good adhesion on stainless steel substrates. The hardness increases slightly upon crystallization to typically reach 17 GPa. Preliminary prope rties of this metastable carbonitride phase are reported and its potential as a hard metallurgical coating is discussed. (C) 2000 Elsevier Science B.V . All rights reserved.