Structure, hardness, and tribological properties of reactive magnetron sputtered chromium nitride films

Abstract

Chromium nitride (CrN) films with Cr/N atomic ratios of 0.73–1.46 were prepared by reactive dc- magnetron sputtering with Ar as the sputtering gas and N2 as the reactive gas. The application of a negative bias voltage to the substrates and the decrement of the gas flow ratio of N2 to Ar (or FN2/FAr) promoted the growth of CrN films with preferred orientations of (200)+(220), high Cr/N ratios, and high densities. The functional hardness and compressive stress were highly dependent on the magnitude of the bias voltage and the Cr/N ratio that was adjusted by the FN2/FAr ratio during film deposition. The optimal energy conditions for ion impingement on growing CrN films with compact columnar crystal structure, high hardness, and enhanced tribological properties were studied with respect to the modulations of the bias voltages and the Cr/N ratios. The CrN films with high hardness and high wear resistance were synthesized in this study at low bias voltages of −(100–300) V and FN2/FAr ratios of 1–3.