Study on mechanical properties of CoCrFeNiNx high entropy alloy films based on nanoindentation

CoCrFeNiNx films were prepared by magnetron sputtering under different nitrogen flow ratios (R-N). The mechanical properties were measured by nanoindentation. The results show that with the increase of R-N, the content of N in the films increases, and the contents of Cr, Co, Fe and Ni decrease with basically unchanged composition ratio. The films have very dense structure with uniformly distributed elements. With increasing R-N the film changes from metal solid solution phase with weak FCC (111) preference to nitrogenous solid solution phase with FCC (200) strong preference, then to FCC (200) weak preference, finally to near amorphous. The hardness and elastic modulus increase with R-N, but are almost independent of the strain rate. The CoCrFeNiNx films with R-N = 20% and R-N = 60% have lower creep deformations and demonstrate better creep properties, probably related to their composition, structure (oriented growth, crystallinity, defects, etc.) and residual stress.