Effective parameters for erosion caused by water droplet impingement and applications to surface treatment technology

Component materials in the steam environment of energy generation systems have severe problems of erosion caused by the impingement of water droplets. An evaluation of the resistance of such materials to erosion is very important in the maintenance of power plant systems and to prolong the life span of the components. A water-jet peening system, which is normally used for surface treatment technology, is based on the phenomenon of erosion damage. Parameters associated with water droplet impingement which dominate erosion rates are less controllable when a water-jet system is used. In this study, the use of a water-jet apparatus for erosion tests was conducted on an aluminum alloy to determine the effective parameters for erosion damage which are dependent on water pressure and the stand off distance between the nozzle and specimen. Parameters such as impact velocity, impact frequency and diameter of water droplets were examined by observations of craters formed on a thin aluminum film. Erosion damage was characterized with respect to incubation period and damage depth rate. Optimum surface treatment conditions were evaluated for an incubation period and damage depth rate after the incubation period. The incubation period and damage depth rate were greatly affected by the velocity and impact frequency of water droplets and the surface treatment technology should be sustained by the optimum impingement conditions which are controlled by the water pressure and stand off distance of the nozzle in the water-jet apparatus.