Particle and rain erosion mechanisms on Ti/TiN multilayer PVD coatings for carbon fibre reinforced polymer substrates protection

Abstract PVD coatings have been studied as candidates for erosion protection of carbon fibre reinforced polymers. Thus, multilayer Ti/TiN coating stacks with different thicknesses ranging from 1.5 to 11 μm have been deposited by pulsed DC magnetron sputtering on carbon fibre reinforced polymers. The coatings were tested under particle erosion and rain erosion conditions showing opposite trends with thickness. The results show how different mechanisms dominate depending on the conditions used and revealing how thickness, surface finishing of the CFRP substrates and adhesion affect the performance of the coatings under different erosive conditions. In the case of sand erosion, thin coatings fail due to delamination in the vicinity of carbon fibres due to substrate deformation under impacts, while thick coatings are able to avoid substrate driven erosion, even if the adhesion is lower, and smooth erosive behaviour is obtained until the failure appears at specific spots. On the contrary, thin coatings show better behaviour under rain erosion conditions, as high speed impacts induces larger substrate deformation, even on the thicker coatings, that delaminates faster than thinner ones due to their poorer adhesion.