Surface Modification of Ni-Cr-Mo Steel by Multifunction Cavitation

The multifunction cavitation (MFC) technique is referred to as a mechanical-electrochemical cavitation method because it includes both mechanical action by microjets (MJs), with high pressure from water jet cavitation (WJC), and electrochemical action by MJs, with the high-temperature reaction field of ultrasonic cavitation (UC). Recently, when MFC was applied to Cr-Mo (JIS-SCM435) steel, the corrosion resistance and compressive residual stress in rust were improved, and voids and cracks of the specimen interior were suppressed compared to that with WJC. It is of interest whether this phenomenon occurs similarly in other low-alloy steels processed by MFC. In the present study, MFC was applied to the modification of Ni-Cr-Mo steel (JIS-SNCM630) surfaces. SNCM630 processed by MFC exhibited improved corrosion resistance and compressive residual stress in rust, and voids and cracks in the interior were not generated from the specimen surface to any significant extent.