抄録
Large residual stress is formed in the coating of ceramic material deposited on a metal substrate because of difference in thermal expansion coefficient between the film and the substrate and of some other reasons. The residual stress greatly influences the mechanical properties of the film and the coated material. Therefore, the residual stress is one of the most important factors on evaluating the strength of coated materials.
In the present investigation, we studied the residual stress in TiN film deposited on a substrate of spring steel by a multi-arc method as a function of depositing temperature and film thickness. The residual stress in the substrate layer near the interface was also investigated.
The TiN film exhibited highly {111}-orientation, i.e., [111] of TiN crystals orients parallel to the surface normal of the substrate within ±10 degrees. The residual stress in the TiN film could be evaluated by the two-exposure method with getting the lattice strains for 222 diffraction at φ=0° and 70.5° determined by the relation of crystallographic orientation. The results revealed the compressive residual stress of -5.5--3.5GPa which is very large compared with the thermal residual stress due to the thermal strain mismatch between the film and the substrate. The residual stress value was greatly depended on the depositing temperature; it decreased with increasing temperature, and thickness of TiN film and increased with increasing film thickness. The residual stress in the substrate was compressive and below -30MPa probably due to the implantation of Ti ions into a shallow layer of the substrate.
