Predictive tools for the design of erosion resistant coatings

Aerospace industry is seeking to develop high performance coatings for the protection against erosion by solid particles. However, with many new materials used and tested for different applications and operation under different conditions, conducting experiments for each one of them is becoming increasingly difficult. In the present work, we propose practical semi-empirical and numerical predictive methods to determine erosion resistance of tribological coatings. The paper presents data obtained by finite element (FE) calculations that can be compared with those obtained by classical theories developed for the erosion of materials. The simulation-based approach allows one to express the functional dependence of erosion on the coating properties, and to quantitatively predict the erosion rate. We determined a proportionality coefficient for a wide range of hard coatings. This coefficient was then used, in combination with the semi-empirical expression derived from FE simulations, to determine the erosion rate of different coatings. In addition to the existing erosion theories that tend to emphasize hardness, H, and Young's modulus, E, as the main parameters defining erosion resistance, we focus here on the role of the H/E and H3/E2 ratios. We demonstrate that the latter characteristics allow one to rank coatings with respect to their erosion performance.