Solid particle erosion mechanisms of protective coatings for aerospace applications

The design of the appropriate material system for a given tribological application must be guided by an accurate understanding of the degradation mechanisms and the surface response to loading and deformation. In this review article, a detailed overview of the material loss mechanisms during solid particle erosion (SPE) which occurs when hard particles are entrained by an air flow and impact exposed surfaces will be presented. In the first part of the paper, several methodological considerations essential for the assessment of multi-parameter correlations necessary for the accurate interpretation of SPE data will be discussed. Then, the ductile and brittle SPE mechanisms, the transitions between these different material removal processes and the effect of particle properties on overall erosion behavior will be examined. Finally, in the last section of the paper, the various coating material systems proposed in the literature for protection against SPE are reviewed with a focus on the two main categories of TiN-based and carbon-based coatings. Concluding this review is a discussion on the effects of coating system microstructure and architecture on the SPE mechanisms of vapor deposited coatings. It will be shown that to significantly impact the future technological development of SPE protective coatings, novel highly resolved characterization methodologies need to be developed and employed.