Applying Water Cavitation as an Alternative to Shot Peening for Aerospace Component Surfaces

A novel process for applying compressive residual stresses to the surface of metal parts has been developed as a new alternative to shot peening. Cavitation Water Jet Peening (CWJP) is based on the phenomenon of the violent phase transformation of water cavitation vapor bubbles, which can be created under certain conditions through a high-pressure water stream flowing through a specially designed nozzle that nucleates and amplifies the effect of cavitation. It was discovered and developed through scientific studies made of the primary weapon used by an amazing sea creature called the mantis shrimp.
When water vapor transforms back to liquid, a forceful discharge is created that can be directed towards metal part surfaces submerged inside a tank of water. The effect of the treatment is very similar to conventional shot peening, except that process does not have to be directed entirely line-of-site due to the somewhat omni-directional blast of the shock waves through the water.
The lower power process has already been used by industry to clean unwanted debris, but higher energy CWJP also leaves behind a significant amount of compressive residual stress above/below the surface of aerospace metal components that can be the equivalent or better than that created with conventional shot peening media. Since the CWJP process makes use of only water inside of a closed loop system, is a completely environmentally friendly process.
CNC machines have recently been built and are currently undoing trials to determine process speeds and the CWJP capability as a shot peening replacement for titanium, aluminum, CRES, nickel-based metals and superalloys.
Several recently completed case studies will be shared as examples of the application of CWJP, along with the technical data that has been collected for the evaluation of surface roughness, residual stress and fatigue performance.