Effect of AlTiN and AlTiN / AlCrN Coatings on the Properties of Ti(C, N)-based Cermets

Ti(C, N)-based cermets are important materials for cutting tools because of their excellent hardness, wear resistance, and high-temperature deformation resistance. However, the metal binder phase in Ti(C, N) cermets easily induces adhesive wear, elemental diffusion, and softening at high temperatures during high-speed machining. These problems can deteriorate the tool performance, thus limiting the further promotion and industrial application of Ti(C, N)-based cermet cutting tools. Physical vapor deposition (PVD) is an effective method for enhancing the properties of Ti(C, N)-based cermets. In this study, AlTiN and AlTiN / AlCrN coatings are deposited on Ti(C, N)-based cermet tools via cathodic arc evaporation. The effects of the surface coatings on the mechanical, friction, oxidation, and cutting properties of Ti(C, N)-based cermets are systematically investigated using X-ray diffraction, scanning electron microscopy, Rockwell hardness tests, nanoindentation tests, wear tests, oxidation experiments, and turning tests. Experimental results show that both the AlTiN and AlTiN / AlCrN coatings exhibit a single-phase face-centered cubic structure, with hardness values of 33.9 +/- 0.8 and 36.1 +/- 1.6 GPa, respectively, which are significantly higher than that (27.4 +/- 1.7 GPa) of uncoated Ti(C, N)-based cermets. Additionally, the surface coatings improve the fracture toughness of Ti(C, N)-based cermets, as shown by an increase from 9.8 +/- 0.18 MPam(1/2) for the uncoated cermet to 10.5 +/- 0.08 and 10.8 +/- 0.05 MPam1/2 for the AlTiN-and AlTiN / AlCrN-coated cermets, respectively. The surface coatings with higher hardness and H-3 / E-2 ratios significantly improve the wear resistance of the Ti(C, N)-based cermets, among which the lowest wear rate of 2.8 x 10(-6) mm(3) / (Nm) is achieved by the AlTiN / AlCrN-coated Ti(C, N)-based cermets. Furthermore, the Ti(C, N)-based cermets coated with AlTiN and AlTiN / AlCrN demonstrate excellent oxidation resistance, and their oxide-layer thickness reduces to similar to 185 and similar to 65 nm after oxidation at 800 C for 5 h, respectively. Owing to their combination of higher hardness, lower friction coefficient, and excellent oxidation resistance, the Ti(C, N)-based cermet tools coated with AlTiN / AlCrN exhibit a cutting life that is similar to 75% higher than that of the uncoated tools. This study reveals the effect of surface coatings deposited via PVD on the wear resistance, high-temperature oxidation resistance, and cutting life of Ti(C,N)-based cermets, which can be applied to improve the comprehensive performance of Ti(C,N)-based cermets. These findings provide a theoretical basis and technical support for the development and design of high-performance Ti(C, N)-based cermet tools and further promote their large-scale application in high-speed machining.