Toshihiko Yoshimura*
Sonoluminescence from various types of cavitation bubbles, namely those of water jet cavitation (WJC), water jet cavitation with a swirl flow nozzle (SFN-WJC), multifunction cavitation (MFC), ultrasonic cavitation (UC), and ultrahigh-temperature and highpressure cavitation (UTPC), wasinvestigated. The sonoluminescence measurements were compared with the surface modification characteristics imparted to Cr-Mo steel. The luminescence intensity of the various types of cavitation was measured using two types of photon counting head, whose detection sensitivity depends on the wavelength range. 2 UTPC had the highest light intensity, followed by MFC, UC, SFN-WJC, and WJC. The temperature inside the bubbles from the various types of cavitation could be estimated using the black-body emission method based on Planck’s law and the emission intensity, which was corrected for the sensitivity of the detector. UTPC, which had high luminosity and could treat surfaces at high temperatures, was found to increase compressive residual stress and decrease surface roughness compared to WJC and SFN-WJC, which had low luminosity and are forms of cold working. At higher cavitation temperature, more corrosion-resistant and oxidation-resistant films form on a steel surface. The magnitude of luminescence intensity for a cavitation process corresponds to the magnitude of corrosion potential (surface potential), which indicates corrosion resistance
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