Effect of interlayers on the structure and properties of TiAlN based coatings on WC-Co cemented carbide substrate

Abstract

Two interlayers (Ti and Cr) have been evaluated with respect to their influence on the structure and growth of TiAlN based coatings on WC-Co cemented carbide by a non-commercial hybrid PVD (physical vapor deposition) coater by Sichuan University in China. The structure and the growth morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The diffusion of interlayer was tested by Energy Diffraction Spectrum (EDS). Nanoindentation techniques and Rockwell HRC indentations were carried out to investigate the mechanical properties. The results show that the structure and the growth style change in the coatings on Cr interlayer, and this can be explained by thermodynamic theories. Cr interlayer exhibits a better diffusion compared with Ti interlayer, partly resulting in the transition from columnar crystal to equiaxed crystal. Columnar crystals disappear with the addition of Si, too. Due to the diffusion of Cr interlayer and the growth style changes in the coating, a transition zone is formed, and it is estimated to improve the adhesion. Good adhesion occurs in the coating with Cr interlayer. The hardness of TiAlN on Cr interlayer increases, and the Ti/(Ti,Si,Al)N coating shows the hardness as high as 40.0Gpa.