A swirl flow nozzle attached to a water jet nozzle was developed in order to increase the
number and size of bubbles, and the generation of ultra-high temperature and pressure
cavitation (UTPC) by applying ultrasonic irradiation to water jet cavitation (WJC) was
evaluated theoretically and experimentally. In the swirl flow nozzle with the water jet
nozzle, the interior pressure of the swirling nozzle is lowered and the cavitation number
is decreased. Based on an estimation using the Rayleigh-Plesset equation, UTPC
processing provides the highest pressure and the highest temperature compared to WJC
and multifunction cavitation. The ferrite in the pearlite microstructure of a low alloy steel
was melted after UTPC processing. The surface potential of the UTPC specimen was
highest among other treatments, namely UC and WJC. The corrosion resistance was
improved by UTPC processing.