Erosion resistant titanium based PVD coatings on CFRP

Carbon fibre reinforced plastics (CFRPs) are intensively used in aerospace applications due to their good strength to weight ratio. However, when subjected to solid particle erosion, wear rates of CFRP are more than one order of magnitude higher than steel. Protective coatings produced by physical vapour deposition (PVD) can increase the lifetime of CFRP components. In this work magnetron sputtering was used to deposit various pure titanium and Ti/TiN multilayer thin films on epoxy and PEEK based CFRP substrates to increase their erosion resistance. Erosion testing was performed at 90° impact angle and the mass loss was monitored. It was found that coatings with a film thickness below 10 μm failed due to a strong substrate influence. Coatings with a film thickness of 30 μm could withstand the erosive wear several times longer. Ductile coatings made of pure titanium showed the lowest mass loss on both substrates. However, for coated CFR-PEEK no reduction of mass loss could be achieved because the polymer had a high erosion resistance at normal impact angle. In contrast, the mass loss of CFR-epoxy could be reduced by a factor of 5 after 10 min of erosion testing which shows high potential of such coatings on CFRP.