We developed a new nozzle in order to greatly increase the temperature and pressure of multifunction cavitation (MFC) [1, 2], so allowing ultra-high temperature and pressure cavitation (UTPC) [3, 4] to take place, which produces a new metal surface. The ultrasonic radiation is imparted to the cavitation cloud generated by a high pressure waterjet. In this method, the microjets generate mechanical action, but so-called “hot spots” at which chemical reactions can occur are also formed. As the ultrasonic cavitation proceeds, isothermal expansion takes place once the pressure is above the Blake threshold value. Following this expansion, Rayleigh shrinkage occurs.  Repeated expansion and shrinkage leads to cavitation, which in turns results in high pressure collapse and the generation of high temperature hot spots. This high-temperature and high-pressure cavitation was named as Multifunction cavitation, because this cavitation processing provides various function to the surface. In order to generate the high-temperature and high-pressure cavitation, a swirl flow nozzle, which is placed on a water jet nozzle, was evaluated experimentally and theoretically. This swirl flow nozzle increase the number of bubble and the size of bubble. As a result, the temperature and pressure of bubbles extremely increases and UTPC could be generated.
From microstructural examination of specimen surfaces or sides and from the mechanical properties resulting from compressive residual stress using Cr-Mo steel (SCM435) [5], Ni-Cr-Mo steel (SNCM630), Ti-6aAl-4V and Inconel (UNSN06601) processed by WJC (Water Jet Cavitation) and UTPC. The microstructure of the WJC-processed specimen revealed that voids and cracks tended to occur in the depth region of 0.5–1 mm from the topmost surface. The microstructure of the UTPC-processed specimen showed the spheroidization of cementite observed in the depth region of 0.5–1 mm from the topmost surface. In addition, voids and cracks were not observed in the specimen bulk. The Charpy impact energy of UTPC had the highest value of 101 J, because the ductile layers were formed by UTPC (Ultra-high Temperature and Pressure cavitation) processing. Stress relaxation behavior of various processed materials at a temperature of 500℃ was investigated. A compressive residual stress of more than -100 MPa was retained after annealing both the WJC and UTPC processing specimens for 5 hours. After stress relaxation testing, cracks owing to thermal stress do not occur at the grain boundary in the UTPC material having a tenacious tough layer inside. The so-called, micro forging (UTPC) is promising for high temperature oxidation of low alloy steel, Titanium alloy and Inconel. 
Furthermore, UTPC and MFC were applied to Aluminium alloy (Al-Mg-Si, AC4CH) in order to treat various kind aging. The Mg2Si, which should be G. P. zone or θ’ was detected by X-ray structural analysis, was recognized in the specimen processed  by MFC and UTPC. As same as the Mg concentration in the crystal grain Al-Mg-Si alloy processed by T6 aging, the Mg concentration in the crystal grain Al-Mg-Si alloy increases by MFC processing. The MFC processing provides not only the increase of surface hardness but also surface compressive stress.