Mechanical Fatigue of Wall Surface Caused by Liquid Droplet Impingement

Pipe wall thinning caused by water or steam flow was observed associated with oxide layer inside of the pipe. Interaction between oxide formation and corrosion or erosion due to the water or steam flow may be an essential phenomenon of the wall thinning. Thinning rate of the wall therefore depends on the formation of the oxide. In the case of wall thinning caused by liquid droplet impingement (LDI) erosion models, mechanical fatigue of the layers is of interest from estimation of the wall thinning rate. In this paper, from a fundamental point of view, to examine parameters related to adhesion strength of the interface in the model equation of material removal from the wall by multiple droplet impingements, evaluation of adhesion strength between piping material and surface oxide layer was carried out using a laser shock method. Several model oxide layers were prepared at elevated temperatures in oxidizing environments on a carbon steel. Results from the measurements of the adhesive strength of the oxide layer formed on the carbon steel at elevated temperatures, the interface had a comparative strength or less of the yield stress of the carbon steel. It was found that reputation of the loading by laser shots up to 10⁴ times did not affect the adhesive strength so far. A kinetic modeling of the wall thinning caused by the LDI was suggested higher cycle mechanical fatigue.