Microstructure, Oxidation Resistance and Mechanical Properties of Nb–Y–N Films by Reactive Magnetron Sputtering

Composite Nb–Y–N films with different yttrium content (Y/(Nb + Y), at %) were prepared by reactive magnetron sputtering and the microstructure, oxidation resistance and mechanical properties were investigated. A combination of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analyses showed that the face-centered cubic (fcc) Nb–Y–N and hexagonal close-packed (hcp) Nb–Y–N coexisted in Nb–Y–N films. The adjunction of Y into NbN matrix led to a first increase in the hardness and then a subsequent decrease after reaching a summit with the value of ~31 GPa at 9.4 at % Y. The first increase of the hardness may be caused by the solid solution hardening and the increase of grain coarsening and tensile residual stress result in the succedent decrease of hardness. The oxidation resistance temperature of Nb-Y-N films increased gradually from about 500°C to about 760°C as the Y content in the film increases from 0 to 12.1 at %.