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 ) B 2 and Ti(C,N) crystallites distributed in an amorphous boron nitride (BN) phase including some of carbon, CN x , B 2 O 3 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 ( ∼ 35 GPa ) . The Ti–B–C–N(10 at .%) film also showed the highest H 3 ∕ E * 2 value ( ∼ 1.7 GPa ) 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.