RELATIONSHIP BETWEEN SURFACE HARDNESS AND EROSION DAMAGE CAUSED BY SOLID PARTICLE IMPACT

A model for erosion caused by solid particles was studied and an equation based upon the relationship between dynamic indentation and the hardness of the material was proposed. This equation was established by the relationship between the surface hardness and the erosion damage to the materials. Erosion tests using a gas gun unit were conducted on five materials over a wide range of hardness values (Hv number 9-1100) up to an impact velocity of 150 m s-1. An increase in the hardness was seen on the fully eroded surfaces obtained in the cases of iron and aluminium, but a decrease was seen in the case of quenched carbon tool steel. No change in the hardness was seen in the cases of the acrylic resin and nylon. The hardness of the eroded surfaces, as opposed to that of the non-eroded surfaces, slightly improved the correlation with erosion damage, but it was not necessarily sound. The softening observed on the eroded surface of the quenched carbon tool steel specimen suggested that heat was generated during the impact of the particles and also that the surface hardness during the course of erosion was different from that both before and after erosion. The temperature increase of an iron leaf sample owing to the impact of a 3.18 mm steel ball or silica sand particles pointed to a transiently high temperature on the impacted surface and the possibility of softening during the course of the erosion process. As a result, the surface hardness of each material estimated with respect to work hardening and softening reasonably correlated with the erosion damage. Also, numerical formulation and the soundness of this equation were discussed through many erosion tests under various conditions.