The erosion of aluminum by solid particle impingement at oblique incidence

Abstract

The erosion of coarse-grained aluminum by 1.58 mm diameter WC-6wt.%Co spheres was investigated over a range of impact angles and velocities by means of a rotating-arm apparatus. Eroded specimens were studied by scanning electron microscopy, surface profilometry and weight loss measurements. Experimental data on crater dimensions were compared with the predictions of a computer model of the process of crater formation by oblique impact. It is concluded that this model successfully predicts the ways in which crater depth and volume vary with impact angle and velocity, but that it tends to underestimate crater length at the shallower impact angles and higher impact velocities where the pile-up of displaced material at the exit end of the crater is most pronounced. The scanning electron microscopy studies suggest that material removal occurs at all impact angles by a single mechanism that involves the detachment of thin platelets by ductile rupture. These platelets are formed by the extrusion of raised portions of the specimen surface between subsequently impacting spheres and the underlying work-hardened substrate. In addition, it is shown that the velocity exponent of erosion, which is greater at an impact angle of 30° than for impacts normal to the specimen surface, decreases with increase in the number of impacts per unit area. Finally, it is demonstrated that the threshold number of impacts required to initiate erosion varies with impact angle and velocity in the opposite manner to the steady state erosion.