Processing using multifunction cavitation (MFC) has recently enabled functional characteristics to be imparted to various materials. It is possible to process a material surface in the same manner as with conventional water jet (WJ) peening;however, the cavitation bubble temperature is different. To further improve this MFC technology, we examine the surface re-forming of low alloy steel (JIS-SCM435) using MFC with various modes of ultrasonic waves. The ultrasonic equipment used for MFC processing includes dual, single, pulse and frequency modulation (FM) ultrasonic modes. Improvement of the residual stress and corrosion resistance was confirmed for all modes. The dual mode showed the maximum values of residual compressive stress and surface potential. The sound pressure at the machining spot was the highest with dual mode, and the temperature in the bubble generated by the WJ nozzle was highest and the amount of dissolved oxygen was lowest. Improvement of the residual stress and corrosion resistance was promoted because the temperature and pressure in the bubble interior during processing was higher than in the other modes.
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