Effect of N2 partial pressure on the microstructure and mechanical properties of magnetron sputtered CrNx films

In this paper, Chromium nitride (CrNx) thin films were deposited with reactive magnetron sputtering method. EDX, X-ray diffraction and transmission electronic microscopy were employed to characterize their chemical compositions, phases and microstructures. Microhardness and elastic modulus were evaluated using a microhardness tester and the effect of N2 partial pressure on the composition, phases, microstructure and mechanical properties of CrNx thin films was investigated. The results show that the phase formation of CrNx thin films varies from Cr+Cr2N to single-phase Cr2N, and then Cr2N+CrN to nearly single-phase CrN with increasing N2 partial pressure. The microhardness values of these films make a distribution ranging from HV 21.4 to 27.1 GPa, and when the atom ratio of Cr:N is 1:2 and 1:1, thin film reaches peak hardness values (HV 27.1 and HV 26.8 GPa, respectively), while the elastic modulus is maximal (350 GPa) when single-phase Cr2N films is formed.