Cavitation Erosion Mechanisms and Its Quantitative Evaluation Based on Erosion Particles.

Abstract

Cavitation erosion mechanisms were studied through the observation of erosion particles for carbon steels. In the initial period and the incubation period, many small sharply-edged particles were produced by single impact loads. In the accumulation period and the steady-state period, large striated particles were observed due to cyclic loads. The volume fraction of fatigue fracture is 70% to 80% in these periods incubation pure copper and pure aluminum. The exponent of the crack growth rate observed on the cross section of the eroded specimen is almost the same as that obtained from a regular fatigue test. The fatigue crack growth rate for many metals depends on a reciprocal of the square of Young's modulus (1/E2). The particles fall off from the tip of uneven surface. The maximum diameter of erosion particle decreases inversely to the square root of Vickers hardness (1/HV1/2), thus the volume is proportional to 1/HV3/2. Therefore, the volume loss rate in the steadystate period corresponds well with the 1/(HV3/2·E2). It was concluded that cavitation erosion can be evaluated in the terms of the material hardness and the fatigue crack growth.