A COMPARISON OF PARTICLE IMPACT IN GAS-SOLID AND LIQUID-SOLID EROSION

The sizes of craters formed on cylindrical, electro-polished, OFHC cop per erosion specimens subjected to impact by closely-sized glass beads , average diameter 540 mu m, suspended in diesel oil in a slurry-pot e rosion tester operating at nominal rotation speeds of 18.7, 14.0 and 9 .35 m s(-1) have been compared with those produced in an identical app aratus operating at the same speeds, in which the glass beads were sus pended in air. Crater sizes were measured at the cylinder stagnation l ine and at location angles of 15 degrees, 30 degrees, 45 degrees, 55 d egrees and 65 degrees on either side of it. Impact craters formed unde r liquid-solid erosion conditions were found to be smaller than those formed in gas-solid erosion at the same nominal test speed. Crater siz es were related to impact velocities using diameter measurements from craters produced under slow loading conditions. The differences in nor mal impact velocities during gas-solid and liquid-solid erosion are di scussed and the values compared with predictions from a mathematical m odel. The relative retardation of impacting particles in liquid-solid erosion is ascribed to fluid dynamic effects on particle velocities an d trajectories, including squeeze-film retardation of particles immedi ately prior to impact. In both air and diesel oil the effective free-s tream velocity was found to correspond with the nominal test speed. Im pact crater eccentricity was measured for tests conducted at 18.7 m s( -1) in air and diesel oil. Eccentricity was consistently greater for c raters formed in diesel oil. Ripple pattern formation, owing to the di splacement of material by plastic deformation, during the wear of copp er subjected to repeated impact by glass beads suspended in diesel oil at 18.7 m s(-1), is reported.