The microstructure, phase and chemical composition of a bonding-template layered structure used in order to nucleate α-Al2O3 on TiN/Ti(C,N) coated cemented carbide have been investigated using scanning electron microscopy, X-ray diffraction and Auger electron spectroscopy. Further, the adhesive strength of the coating multilayer interfaces was investigated using scratch adhesion testing.
The results show that the bonding-template layered structure, deposited on an inner TiN/Ti(C,N)/TiN structure, consists of a Ti(C,N,O) phase (bonding layer) and a Ti4O7 phase (template). The Al2O3 layer nucleated on the Ti4O7 template consists of 100% α-Al2O3. During the deposition of Al2O3 the Ti4O7 template transforms to a Ti(C,N,O) phase. Scratch adhesion testing shows that the interfacial strength within the bonding-template-α-Al2O3 multilayer structure is high and exceeds the interfacial strength displayed by the cemented carbide-TiN layer interface. AES depth profiling of the multilayer coating structure illustrates that diffusion of C, N, and O takes place during the deposition of the Ti(C,N,O) , Ti4O7 and Al2O3 layer.