Repeated impact test for characterization of hard coatings

The repeated impact test is an attractive method to evaluate different properties of hard coatings serving under the conditions subjected to cyclic loads. The main parameter leading to the failure of coatings has been attributed to the contacting load. However, the dynamic impact loading is characterized in the impact wave, which is much more severe than that of static loading, thus the load calculated by finite element method using the static stress is invalid. In this paper, the impact tests revealed two distinguished failure modes for CrN–Cu coatings: cohesive and interfacial. The primary mechanism for the coating failure is interfacial at low loading forces. The failure mode can change from adhesive to cohesive at the same loading force but with increasing velocity of the ball. It was shown that the applied kinetic energy absorbed and transformed to the plastic deformation energy has a strong relationship to the coating failure. Thus, the energy-cycles relation is a more suitable index to indicate the damage resistance of coatings.