The effect of initial surface roughness on water droplet erosion behaviour

Water droplet erosion (WDE) is defined as the progressive loss of original material from a solid surface due to continuous impingements of water droplets or jets. Several factors are known to influence the WDE process, such as impact speed and water droplet size. The initial surface roughness was not given enough attention in the literature as a factor that may influence the WDE behaviour of materials. In this work the effect of initial surface roughness on the WDE of a special martensitic stainless steel (12%Cr-steel) and Ti6Al4V is investigated. Experiments were done by varying three parameters: initial surface roughness, test speed, droplet size. It was concluded that the initial surface quality influences the length of the incubation stage, and may influence the maximum erosion rate. The amount of asperities and irregularities on the surface of samples was found to be the main reason for the difference in the WDE erosion behaviour. Moreover, the importance of reporting the initial surface of tested samples was emphasised, especially when comparisons between the WDE resistance of different substrate materials and/or treatments are held.