Coating's applications: Assessment of coatings' brittleness by nano-impact tests

In the described investigations, nano-impact tests were conducted on PVD film surfaces previously subjected to micro-blasting at different pressures for constant duration. Micro-blasting improves the film mechanical properties due to the induced residual compressive stresses into the coating structure. The film mechanical properties as well as the ratio of the film yield to rupture stress (SY/SM) grow up to a certain micro-blasting pressure. The augmentation of SY/SM ratio increases simultaneously the film brittleness. For analyzing the effect of the SY/SM ratio on the film brittleness, a multi-layer 3D-FEM model simulating the nano-impact test was developed, employing the LS-DYNA software package. The FEM calculated results converge sufficiently with the attained experimental ones. Based on these results, the film's failure initiation and evolution can be predicted depending on the SY/SM ratio of the individual film layers.