A study of TiN coatings on a low alloy high speed steel

This paper deals with the TiN coating of a new low alloy high speed steel W3Mo2Cr4VSi. According to transmission electron microscopy and X-ray diffraction investigations, the TiN coating can be divided into two layers: the main-body layer and the transition layer. The main-body layer consists of columnar TiN which is vertical to the substrate surface, with fine-grained TiN and small amounts of ε-Ti2N between some columns. The transition layer is composed of equiaxed grains of TiN, ε-Ti2N and α-Fe. The orientation relationship between the columnar TiN and the ε-Ti2N grains in the main-body layer was found to be (101)Ti2N parallel (200)TiN and [111]Ti2N parallel [011]TiN. It was shown that the amount of α-Fe in the transition layer decreased with increasing silicon content to this steel. A compressive residual stress between 180 and 200 N mm-2 exists in the coating. (orig.)