Erosion-corrosion damage of aluminum alloy in a high-speed, high-temperature, two-phase flow

Abstract

A study of aluminum alloy damage by erosion-corrosion in a two-phase jet flow is presented. The jet flow was characterized by a temperature of 392 K and a speed of 177 m s −1 at the specimen location. Slip occurred between droplets and steam in the two-phase jet flow dispersed from a nozzle, and the relative velocities of steam to droplets were found 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 constant. We found that a nozzle with a long straight portion caused large droplet formation with large velocities at every volume flow rate ratio investigated. As a result, the mass loss was found to increase with 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 loss 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 the protective film of the alloy by droplet impingement.