Mechanism of the attack on metal surface in wear under ultrasonic cavtation

Abstract

Two series of tests of annealed metal materials — copper, brass L60 and aluminum-magnesium alloy AMg4,0 — were carried out. The first series consists first in upsetting the cylindrical samples of the listed above alloys on a press to a different strain rate, then cutting the deformed samples and measuring the microhardness of the area adjacent to the center of the samples. The first series results in constructing the calibration plots of microhardness as a function of strain. During the second series the tests of the same materials for cavitation wear were carried out in the fresh water on the ultrasonic vibratory apparatus. The frequency and amplitude of the apparatus horn vibration amount to 22 kHz and 28 μm respectively. The microhardness of the samples surface exposed to cavitation attack was measured after the definite spans of time within the incubation period and the maximum value of the microhardness was registered. Marking the maximum microhardness value on the calibration plot yields the strain rate reached on the surface under cavitation attack before the removal of wear particles begins. On the basis of the found values of the strain the stress state rigidity of the surface layers under cavitation attack was evaluated. The obtained coefficients of stress state rigidity allowed drawing the conclusion, that cavitation attack on the material being tested on the ultrasonic vibratory apparatus occurs through the microjets impacts.