EROSION-CORROSION DAMAGE OF ALUMINUM-ALLOY IN A HIGH-SPEED, HIGH-TEMPERATURE, 2-PHASE FLOW

A study of aluminum alloy damage by erosion-corrosion in a two-phase j et how is presented. The jet flow was characterized by a temperature o f 392 K and a speed of 177 m s(-1) at the specimen location. Slip occu rred between droplets and steam in the two-phase jet how dispersed fro m a nozzle, and the relative velocities of steam to droplets were foun d to depend on the length of the straight portion of the nozzle outlet , even though the mean velocities of the liquid and steam were held co nstant. We found that a nozzle with a long straight portion caused lar ge droplet formation with large velocities at every volume flow rate r atio investigated. As a result, the mass loss was found to increase wi th increases in the length of the straight portion. A small number of pits were caused by just corrosion, and there was little mass loss of the aluminum alloy in the static hot condensate of the two-phase fluid . Although a large number of pits were induced by the flow, the mass l oss corresponding to pit volumes calculated from their shapes was not so large. We believe that the alloy damage was mainly due to erosion, and subsequent corrosion follows owing to small cracks generated in th e protective film of the alloy by droplet impingement.