Etude des mecanismes d'oxydation de couches minces ultra-dures par thermodiffractometrie X et ATG

Hard coatings elaborated by PVD (physical vapor deposition) technology are often metastable. They are used in conditions where high temperature is encountered like in metal machining applications where heat is generated by friction. These applications induce non-reversible microstructural modifications and oxidation of the coating. The transformation mechanism had to be understand in order to prevent their damage effect. The aim of this work is the investigation of the temperature effects on structural changes and oxidation evolution of Cr2Nx, CrNx, TiN and TiNx(B)y coatings. The structural changes were studied by high temperature X-ray diffraction (XRD-TIR) and grazing incidence X-ray diffractometry (GIXRD). Correlation with thermal gravimetric analysis (ATG) in purr oxygen had been realized. The mechanisms of coating transformation as a function of temperature have been developed for each type of coating. The highest thermal stability was observed for TiNx(B)y coatings, according to microstructure, oxidation resistance and mechanical properties.