Deposition and Properties of Amorphous TiBN/AlCrYN Multilayer Coatings with Various Modulation Periods

In this paper, multilayer coatings consisted of amorphous AlCrYN layers and TiBN layers were deposited by the cosputtering technique. The influence of the modulation period of the multilayer coatings on the structure, mechanical properties, and oxidation behavior of the coatings was studied carefully by using scanning electron microscope, X-ray diffraction, nanoindentation, scratch tester, and thermogravimetric analyzer. The results show that the TiBN/AlCrYN multilayer coatings exhibit an amorphous structure without any feature. Decreasing the modulation period could significantly improve the coating hardness and elastic modulus. In addition, the adhesion of the multilayer coatings could be enhanced as the modulation period decreases. At relative low oxidation temperature (≤900°C), a dense aluminum oxide layer formed on the coating surface can effectively hinder the inward diffusion of O and the outward diffusion of metal elements. The oxidation behaviors of the TiBN/AlCrYN multilayer coatings obeyed the diffusion control law. The oxidation resistance of the coatings was increasing with decreasing the modulation period since the interfaces of multilayer structures would block the diffusion of elements. At relative high oxidation temperature (1000°C), however, the coating surface was rapidly oxidized into the porous TiO₂ whiskers rather than the dense Al₂O₃ layer, resulting in the inward diffusion of O and thus causing the serious oxidation of the coatings.