Solid Particle Erosion of Brittle Materials (Part 5)

Abstract

The erosion tests were performed for nine kinds of ceramics such as SiC, Si3N4 and Al2O3 and window glass using SiC, Al2O3 and glass powders as abrasive at the impingement angle (θ) of 90-20 degrees. The erosive wear (V) for many target and abrasive particle pairs is almost proportional to the square of the impingement angle as proposed by Bitter. However, there were several pairs for which the exponent n in V∝(sinθ)n deviates greatly from two. The pair of Si3N4 (9S) target and Al2O3 abrasive has a small n, 0.8. The small n value is explained by the fact that the erosive wear by brittle erosion mechanism in the high impingement angle region is suppressed because of large toughness of the target and that the erosive wear by scratching in the low impingement angle region is significant. The n's large than two were observed in glass abrasives. This is caused by a large change of effective stress with changing the impingement angle, and the larger change in stress resulted from the slip of abrasive particle on the surface of target which is caused by the melting of glass by the rubbing heat at the instant of impingement. The melting phenomenon of particles and/or targets was observed also for Al2O3. The exponent n for SiC particles are always larger than that for Al2O3 particles for the same target. Changing the impingement angle in the erosion test is considered to be effective for finding some clue to understand the erosion mechanism and mechanical or chemical phenomena occurring at a minute area of impingement.