Why does cavitation occur in multi-stage centrifugal pumps?

During the use of multi-stage centrifugal pumps, cavitation always occurs. What is the reason for this? The manufacturer of multi-stage centrifugal pumps is here to discuss this issue.
Research on the impact of gasification pressure shows that as gasification pressure increases, cavitation damage first increases and then decreases. As gasification pressure increases, the number of unstable bubble nuclei formed in the fluid also increases, leading to an increase in the number of bubble ruptures, an increase in shock wave intensity, and an increase in cavitation rate. But if the gasification pressure continues to increase, causing the number of bubbles to reach a specific limit, the bubble group forms a "layer spacing" effect, preventing the shock wave from traveling and weakening its strength, and the degree of cavitation damage will gradually decrease.
When other factors remain unchanged, reducing the surface tension of the fluid can reduce cavitation damage, because as the surface tension of the fluid decreases, the intensity of the shock wave generated by bubble collapse weakens, and the cavitation rate decreases.
The influence of temperature on the physical properties of gas erosion, such as gasification pressure, gas solubility, surface tension, etc., will be significantly affected by changes in temperature in the fluid. From this, it can be seen that the mechanism of temperature's influence on cavitation is relatively complex and needs to be judged based on actual situations.
Taking the AISI304 material impeller as an example, cavitation can cause work hardening and phase transformation of the impeller material, inducing martensitic steel. This change will in turn prevent further cavitation of the material. The resistance of work hardening and phase transformation induced martensitic steel to cavitation mainly depends on the hardness of the impeller material.
In the actual use of multi-stage centrifugal pumps, due to extremely complex operating conditions, the inlet flow rate and pressure of the pump constantly change. Therefore, there is often a significant deviation between the actual operating conditions of the centrifugal pump and the experimental and designed operating conditions, and the possibility of cavitation may be greater than the expected experimental results.