STEPWISE EROSION AS A METHOD FOR INVESTIGATING THE WEAR MECHANISMS AT DIFFERENT IMPACT ANGLES IN SLURRY EROSION

Abstract

In the present work, stepwise erosion technique was carried out to investigate in detail the influence of impact angle on the erosion process of AISI 5117 steel. The impact sites number and their morphology at different impact angles were investigated using SEM examination and image analysis. In addition, the SEM images of eroded surface using stepwise technique were used presented for better understanding of material removal at different angles. The tests were carried out with particle concentration of 1 wt %, and the impact velocity of slurry stream was 15 m/s. Silica sand has a nominal size range of 250 – 355 µm was used as an erodent, using whirling-arm test rig. The results showed that the number of craters as expected increases with the increase in the mass of erodent for all impact angles and that this number decreases with the increase of the impact angle. In addition, the counted number of craters is larger than the calculated number of particles for all impact angles and at any stage. The effect of impact angle based on the impact crater shape can be divided into two regions; the first region for θ ≤ 60o and the second region for θ ≥ 75o. In the first region the length of the tracks decreases with the increase of impact angle. The calculated size ranges from few micrometers to 100 micrometer for the first region and to 50 micrometers in the second region. Chipping of the former impact sites by subsequent impact particles plays important role in developing erosion.