Mass Loss and Advanced Periods of Erosion

Abstract

This chapter is devoted to the advanced stages of erosion characterized by a mass loss curve of a sample exposed to cavitation as a function of exposure time. Depending upon materials, erosion devices, and operating conditions, different regimes of erosion may be identified on the mass loss curve including incubation, acceleration, deceleration, and steady-state periods. Typical mass (or volume) loss curves obtained for different materials using ultrasonic cavitation, cavitating jets, and a high-speed cavitation tunnel are discussed. They can be normalized by introducing a characteristic volume loss and a characteristic time, which are unique functions of the material and the cavitating field condition. By computing the ratio of characteristic volume loss and characteristic time, the characteristic erosion rate can be deduced for allowing material ranking. The ranking deduced from vibratory cavitation tests and from cavitating jet tests is generally in agreement. Some materials, however, do not rank the same way in a cavitating flow of relatively low aggressiveness (such as vibratory cavitation) as compared to the cavitating flow of higher aggressiveness (high speed cavitating jets).