Hard nanocomposite Ti–Si–N films prepared by DC reactive magnetron sputtering using Ti–Si mosaic target

Hard nanocomposite Ti–Si–N films were deposited on 321 stainless steel substrates by direct current (DC) reactive magnetron sputtering using a Ti–Si mosaic target consisting of a Ti plate and Si chips. The composition, microstructure, and mechanical properties were investigated using EDX, XRD, XPS, nano-indentation, and scratch tests. The results indicate that the hardness of the Ti–Si–N film gradually rises with increasing Si contents in the layer until the peak value of 42 GPa appears corresponding to a Si content of 11.2 at.%. The hardness then decreases with further increase in the Si content. XRD and XPS reveal that the hardest Ti–Si–N film consists of fine TiN crystallites (approximately 8 nm in size) in an amorphous Si3N4 matrix. Preferential growth of TiN is indicated by the XRD patterns. All the Ti–Si–N films show high adhesive strength as indicated by the scratch tests. The strengthening mechanism of the nanocomposite films is also discussed.