Buckling-Induced Delamination of TiN Film on Stainless Steel in the Presence of Stress Concentration

TiN coating is provided by reactive magnetron coating on a 304 stainless steel sample with a notch introduced at the edge of the sample. The sample is subjected to a tensile stress close to that of yield strength of the stainless steel. Optical and scanning electron microscopy characterization showed the distribution of buckled and delaminated regions around the notch. The distribution of the size of the partially delaminated regions of the film on the substrate is determined by transient thermo-reflectance. The stress field due to the notch is represented by that of a circular hole present at the tip and the variation of compressive and shear strain as a function of radial and angular coordinates is determined. The distribution of buckled and delaminated regions is found to follow the compressive strain variation around the notch. The size of the partially delaminated film is found to be larger near the notch and decreased with distance from the notch. The results illustrate that structures with regions of stress concentration should not be provided with brittle protective coatings that will delaminate.