Analysis of rain erosion resistance of electroplated nickel–tungsten alloy coatings

The erosive influence of liquid and solid particles is a serious problem for aircraft. Especially components made from fibre reinforced polymers (FRP) undergo substantial damage during takeoff, flight and landing. Metallic layers can offer good erosion protection. This study presents the liquid impact behaviour of electroplated nanocrystalline nickel–tungsten (Ni–W) onto composite material. The results are compared and contrasted with an electroplated nickel coating and a tungsten plate. The W content of the alloy was 23.2 at.%. Rain erosion experiments were carried out using a pulsating jet erosion test rig (PJET) at a droplet velocity of 255 m s− 1. The coatings or bulk material were impacted by 2 mm equivalent diameter water droplets. The number of impacts was increased stepwise up to a maximum of 150 000 for each specimen. Ni-based coatings could withstand 150 000 impacts without failure, although small depressions and changes of roughness were found on the surface. W exhibited similarly good rain erosion resistance. In addition to the mechanical damage of the surface and in contrast to the unalloyed metals, oxidation of the Ni–W alloy surface was observed. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis showed that NiO, WO2 and WO3 were formed by water droplet impacts.