Coating Inspection of TIN by Scratch Testing
Coating inspection of residual stress in protective PVD/CVD coatings plays a critical role in the performance and mechanical integrity of the coated component. The residual stress derives from several major sources, including growth stress, thermal gradients, geometric constraints and service stresses. The thermal expansion mismatch between the coating and the substrate created during coating deposition at elevated temperatures leads to high thermal residual stress. Moreover, the TiN coated tools are often used under very high concentrated stresses, e.g. drill bits and bearings. It is critical to develop a reliable quality control process to quantitatively inspect the cohesive and adhesive strength of the protective functional coatings.