Cavitation is not welcome in pumps. One of the most problematic effects of cavitation is the reduction in performance, but this is not the only problem! Cavitation can also cause damage to blades and create noise while the pump is working.
Perhaps, the most universal problem caused by cavitation is the material damage that bubbles can cause when they collapse in the vicinity of a solid surface. The problem is complex because it involves the details of a complicated unsteady flow combined with the reaction of the particular blade material.
As we’ve seen before, cavitation bubble collapsing is a violent process. It generates highly and localized large amplitude disturbances and shocks in the fluid when they collapse. When this collapse occurs close to a solid surface, intense disturbances generate highly localized and transient surface stress.
Repetition of this loading due to a multitude of bubble collapses can cause local surface fatigue failure and the detachment of piece of material. The typical damage of cavitation damage has a crystalline and jagged appearance of fatigue failure. An example is shown here, where the blade is referred to a mixed-flow pump with aluminum-based alloy.