The sand erosion performance of coatings

This paper reviews studies of the performance of polymeric, metallic and ceramic including diamond coatings on steel and ceramic substrates when subjected to water–sand jet impingement erosion conditions. The coatings tested have been deposited by the thermal spray, electroless plating, PVD and CVD routes. The erosion conditions covered include sand impact velocities between 10 and 30 m/s with sand sizes 60–235 ?m and at jet impingement angles of 30° and 90°. Tests compared the performance of the substrate material carbon steel AISI 1020 with the various polymeric, metallic and ceramic coatings. Coating and substrate erosion rates are plotted against mean particle impact energy, Ek or EkVp0.5 allowing easy surface selection once the erosion conditions of an application are known. The effect of jet impingement on the erosion resistance of selected coatings is presented. As with bulk materials, the slurry jet impingement angle and mean Ek must be considered in coating selection. Of the softer coatings tested the flexible polyurethane coatings seem to have promise for future use in fluid-borne sand particle erosion environments. Pure epoxy coatings show typical brittle erosion behaviour, with fusion-bonded epoxy having mixed ductile and brittle behaviour and glass fibre reinforced epoxy showing strong ductile behaviour. CVD deposited coatings of either boron carbide or diamond are the most resistant surfaces tested and outperform bulk ceramics such as silicon carbide by orders of magnitude for Ek<8 ?J and 90° jet impingement angle. Areas requiring further research to allow accurate prediction of coating life are highlighted