Thermal decomposition routes of CrN hard coatings synthesized by reactive arc evaporation and magnetron sputtering

This study presents a comparison of the thermal decomposition of CrN hard coatings synthesized by reactive arc evaporation and magnetron sputtering. Structural changes in the coating material were determined by in-situ high-temperature X-ray diffraction and correlated to the results of simultaneous thermal analysis. Annealing temperatures up to 1440 deg. C in Ar and a variation in heating rates gave insights to the different decomposition kinetics for the material deposited by reactive arc evaporation and magnetron sputtering. Both single-phase CrN coatings start to decompose above 925 deg. C under release of nitrogen in two major reaction steps to pure Cr via the intermediate step of Cr2N. While the kinetics for the first decomposition reaction from CrN to Cr2N is different for both samples, the second step from Cr2N into Cr is similar. This behavior can be understood considering the differences in structure, composition, and morphology of both as-deposited coatings and their evolution during thermal analysis