The erosion-corrosion performance of mild steel and SA213-T22 steel in low velocity conditions

The erosion-corrosion behavior of mild steel and T-22 steel were studied in a laboratory fluidized bed facility in the temperature range from 100 Centigrade up to 600 Centigrade. Tests were carried out in air using alumina particles of 560 μm average size. Impact velocities from 1.5 m/s to 4.5 m/s were used on pin specimens. For both steels, the trends of wear with temperature at velocities up to 1.5 m/s were similar; i.e. small weight gains were recorded. Erodent deposition was a dominant process at temperatures below about 300 Centigrade and velocities below 3 m/s, regardless the type of steel. A peak wastage temperature was observed for mild steel at about 300 centigrade and for the T-22 steel at about 350 Centigrade, but only within a certain velocity range for each steel. The wastage temperature curve observed in both cases suggested for temperature regions. On each one, a different erosion-corrosion regime operates. Scanning Electron microscopy revealed various wastage mechanisms, i.e. (a) oxide chipping, (b) development of a compact and adherent oxide scale, (c) oxide and metal removal, (d) buckling and detachment of scale fragments and (e) fracture and spalling within the oxide layer and at the scale/metal interface. In the present study, the latter mechanism was responsible for the high wastage observed on the steels and appeared at temperatures above about 450 Centigrade and impact velocities above 3 m/s for mild steel and 3.5 m/s for the T-22 steel. (Author)