Cavitation Wear of Polymers

Cavitation wear tests on six polymers belonging to different classes: polytetrafluoroethylene, low-pressure polyethylene; polymethyl methacrylate, block polyamide (caprolon), polyurethane, and epoxy compound K-153 have been performed. The experiments on an ultrasonic magnetostrictive vibrator in soft fresh water at a temperature of 20 ± 3°C have been carried out. The frequency and amplitude of oscillations of the vibrator concentrator end were 22 kHz and 28 μm, respectively. The samples had a cylindrical shape, the end surfaces of which, subject to testing, were ground and polished using the same technology for all polymers. Before the tests, the density, sound velocity in polymers, and Shore hardness (type D) have been measured. During the tests, the mass loss of the samples and the surface roughness have been measured, and the dependence of the mass loss and the arithmetic mean deviation of the surface profile on the duration of the cavitation effect has been plotted. The wear of all polymers occurred with an incubation period. A viscous–brittle transition has been observed in the dependences of the incubation period duration and the wear rate on the Shore hardness, while in the viscous fracture region, the effect of the polymer hardness on their cavitation wear resistance is opposite to that in the brittle fracture region. It has been found that both in the viscous and brittle fracture regions, the cavitation wear resistance of the polymer decreases with increasing acoustic resistance. It has been concluded that in order to ensure the greatest cavitation wear resistance, it is necessary to select polymers with a hardness value that would ensure viscous–brittle fracture of the polymer at Shore hardness in the range of 65–70.