Multiparticle Erosion of Pyrex Glass

Abstract

Multiparticle erosion tests were performed on Corning 7740 Pyrex glass using alumina powder of two grit sizes. Erosion was measured as a dimensionless parameter in terms of the loss in weight of the target per unit weight of particles impinged. The erosion characteristics of the Pyrex glass were investigated over a range of particle velocities, angles of impingement, and times of erosion. It was found that maximum erosion occurred at a normal angle of impact for the 240-grit powder (mean particle size ≃ 30 μm); however, with the 400-grit powder (mean particle size ≃ 10 μm), the maximum was found to occur at a slightly lower angle of about 80 deg. At all angles of impingement it was found that amount of erosion decreased as the erosion time increased. Erosion (E) was found to be dependent on the average particle velocity (V) by a power relationship of the form EαVn where n is a material constant. The values of the velocity exponent, n, in the present experiments were found to be between 2.2 and 2.7 and were independent of time of erosion. The time (t) dependence of erosion was also found to obey a power law relationship of the form Eαtc where c is a material constant. The time exponent c was found to be -0.1 under all conditions of velocity, particle size, and angle of impingement. The decrease in erosion with increase in time has been interpreted in terms of a change in the surface roughness. Scanning electron microscopy (SEM) has been used to establish that the effective average angle of impingement decreased as time of erosion increased until a constant surface roughness was achieved, at which time it was found that the average angle of impingement was about 55 deg instead of 90 deg. The experimental data obtained in the present work are discussed in terms of existing theories for the erosion of brittle materials.