Growth and Properties of TiN/Al2O3/Ti(C, N)/TiN Multilayer CVD Coatings on Ti (C, N)-Based Cermet Substrates with Ni, Co and Fe Binders

Abstract

In this article, Ti (C, N)-based cermets with Ni, Co and Fe binder phase were manufactured by traditional powder metallurgical techniques. The multilayer TiN/Al2O3/Ti (C, N)/TiN CVD (chemical vapor deposition) coatings were deposited on the three kind of cermets, and the growth and properties of the coatings were studied. The results show that massive cores-incomplete rims are found in the cermet-Ni (cermets with Ni binder) and cermet-Fe (cermets with Fe binder), while in the cermet-Co (cermets with Co binder), the small black cores are surrounded by a complete and well-developed rim phase. When the TiN coating is deposited on the cermets with cores-incomplete rims, the Ti and N atoms stack on the face-centered cubic structure of Ti (C, N) first, and epitaxial growth of the TiN crystals takes place. The epitaxial growth is attributed to the same preferred orientation (2 0 0) of the TiN layers to the Ti (C, N) of the substrate. While on the cermets with cores-complete rims, (Mo, Ti) (C, N) solid solution and binder phase (Ni/Co/Fe), which has a distinct crystal structure or lattice parameters, TiN grains nucleate first and then grow. In this case, the TiN coatings show a (1 1 1)-oriented structure. Dense and thin coatings grow on the cermets-Co. The adhesion of the multilayer coatings to the substrate increases in the order cermets-Fe, cermets-Ni and cermets-Co. In addition, the coating on the cermets-Co has the lowest COF (coefficient of friction) as the thin TiN layer (0.7 μm) is propitious to diffusion of Al and O, and a protective transfer layer is formed by AlOx.