Effect of substrate rotation on structure, hardness and adhesion of magnetron sputtered TiB 2 coating on high speed steel

Abstract

Titanium diboride (TiB 2) coatings have been deposited on stationary and rotating high speed steel substrates by magnetron sputtering of a TiB 2 target. The structure and hardness of the coatings and the coating–substrate adhesion have been investigated by X-ray diffraction, field emission scanning electron microscopy, nanoindentation and microscratch tests. The results show that substrate rotation has a significant effect on these structural and properties features. It was found that, with substrate rotation, the TiB 2 coating exhibits a columnar structure with random orientation and relatively low hardness and coating–substrate adhesion. On the other hand, without substrate rotation, the TiB 2 coating shows a strong (001) texture with dense, equiaxed grain structure. The hardness and coating–substrate adhesion of the coatings deposited on stationary substrates are much higher than those deposited on rotating substrates. The observed phenomena are discussed in terms of the energy of the sputtered flux, which varies with the substrate–target distance during deposition.