Influence of the concentration of NaHCO3 solution on cavitation erosion of copper alloy

Abstract

Abstract To investigate the ultrasonic cavitation erosion in NaHCO3 solutions, experiments with copper alloy specimens were carried out. Three NaHCO3 solutions with concentrations of 0.3%, 3% and 6% were used as liquid mediums in which the vibration horn and the target specimen were mounted. A systematic evaluation and comparison of cavitation erosion effects were performed based on the cumulative mass loss, surface microstructure and three-dimensional morphology, residual stress and microhardness. The results indicate that the highest cumulative mass loss is attained in 6% NaHCO3 solution, while low solution concentration is responsible for low cumulative mass loss. Incubation periods of cavitation erosion in NaHCO3 solutions are relatively long compared to that in the deionized water. For the specimen eroded in 6% NaHCO3 solution for 120 min, large erosion pits and multiple cracks are observed. Regarding surface morphology, small erosion pits are well remained for 0.3% NaHCO3 solution as the erosion proceeds. For 6% NaHCO3 solution, small erosion pits are replaced with large and inter-connected erosion pits with the progression of cavitation erosion. Residual stress ascends to its maximum and then declines consistently during the erosion process. Overall residual stress on the eroded surface varies inversely with the solution concentration. Furthermore, the thickest hardened layer is produced in the specimen submerged in 0.3% NaHCO3 solution, which is substantiated by relatively high microhardness.