Effect of cavitation erosion distance on the damage of hydraulic turbine materials

Abstract

Cavitation erosion could lead to material loss and structural damage in the flow components of hydraulic machinery, affecting the stable operation and efficiency of the equipment. This study established a cavitation erosion distance model for the gap in the cavitation field. High-speed cameras were used to capture the bubble distribution under different cavitation erosion distances. Additionally, the effects of cavitation erosion distance on the damage of stainless steel 06Cr16Ni5Mo, carbon steel 45#, and Q355B were investigated. The study revealed that when the cavitation erosion distance was short, the low number of cavitation bubbles in the gap volume reduced the impact frequency on the material surface. When the cavitation erosion distance was long, the attenuation of ultrasonic vibration propagation prevented gas nuclei at longer distances from developing into bubbles. Some small-volume bubbles further grew into larger-volume bubbles. The cavitation intensity distribution map obtained through image analysis showed that the maximum cavitation intensity occurring at the cavitation erosion distance of 1 mm. The maximum cumulative weight loss of three materials occurred at a cavitation erosion distance of 1 mm. The weight loss from highest to lowest was Q355B, 45#, and 06Cr16Ni5Mo. The cavitation damage of 06Cr16Ni5Mo was characterized by plastic deformation, with noticeable grain-boundary sliding and exfoliation. In contrast, the cavitation damage of 45# and Q355B was characterized by brittle spalling. The cavitation damage progression and failure mechanisms of the three hydraulic turbine materials were elucidated through comprehensive metallographic analysis. The experimental results provide guidance for enhancing the cavitation resistance of hydraulic turbine materials.