Microstructure and mechanical properties of superhard Ti–B–C–N films deposited by dc unbalanced magnetron sputtering

Abstract

Superhard quarternary Ti–B–C–N films were successfully deposited on AISI 304 stainless steel substrates by a dc unbalanced magnetron sputtering technique from a Ti–B–C composite target. The relationship between microstructures and mechanical properties was investigated in terms of the nanosized crystallites∕amorphous system. The synthesized Ti–B–C–N films were characterized using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). These analyses revealed that our Ti–B–C–N films are composites of solid-solution (Ti,C,N)B2 and Ti(C,N) crystallites distributed in an amorphous boron nitride (BN) phase including some of carbon, CNx, B2O3 components. The hardness of the Ti–B–C–N films increased with the increase of N content up to a maximum value of approximately 45 GPa at 10 at. % N, with a subsequent decrease in hardness at higher N content. This value is considerably higher than the hardness measured in our Ti–B–C films (∼35GPa). The Ti–B–C–N(10 at .%) film also showed the highest H3∕E*2 value (∼1.7GPa) among the coatings produced. A systematic investigation of the microstructures and mechanical properties of Ti–B–C–N films prepared with various N contents is reported in this paper.