Cavitation erosion and corrosion behaviour of laser surface melted 316L stainless steel

Cavitation erosion is a form of erosive wear occurring on the metal surface which encounters high fluid flow velocity. Typical examples of cavitation erosion can be found on high speed impellers, pump casings, ultrasonic mixers in the food and pharmaceutical industries, etc. Austenitic stainless steels AISI 316L is widely used as pumping components for marine and urban water supply systems. 316L stainless steel has poor cavitation erosion resistance despite its high pitting corrosion resistance in marine condition. Surface modification of 316L stainless steel was achieved by surface melting the specimens by a 2 kW CW Nd-YAG laser to produce a rapidly quenched surface layer. The cavitation erosion characteristic of laser surface melted 316L stainless steel was studied by means of a 20 kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 μm in 3.5% NaCl solution at temperatures 23° and 50 °C. Its pitting corrosion behaviour was also studied at 23 °C by electrochemical method. The cavitation erosion resistance of 316L stainless steel was found to be improved by 22% at 23 °C after laser melting. The pitting potential of laser melted 316L also increased from 359 to 452 mV at 23 °C. The deformation mechanism by cavitation erosion and the pitting morphology of laser melted 316L stainless steel were also be examined.