Effect of ultrasonic surface rolling process(USRP)on the corrosion resistance of 304 stainless steel surface was investigated.The surface morphology,microstructure,residual stress and surface roughness were analyzed by means of scanning electron microscopy,X-ray diffraction analysis,and metal surface roughness meter,respectively.The corrosion resistance and integrity of the oxide film was assessed using electrochemical tests and o-phenanthroline color development experiments.The results indicate that the value of Ra for the 304 stainless steel is reduced from 0.60 µm to 0.28 μm after USRP treatment.The surface grain size is reduced from 23.13 μm to 20.80 nm,and the surface residual stress is changed from 20 MPa to-329 MPa.Compared with the untreated specimen,the minimum corrosion current density Icorr of the USRP treated specimen is 0.94 × 10-5 A/cm2,which is reduced by 71％.The oxide film resistance Rp is 2.59 x 106 Ω·cm2,increased by 2 times.The range of color rendering value of phenanthroline is narrowed and the color rendering area is decreased,indicating that the surface defects are reduced and the quality of the surface oxide film is improved.For the 304 stainless steel,USRP treatment promotes the grain refinement near the surface layer,produces residual compressive stress,reduces surface defects,denseres oxide film,and then blocks the electrochemical reaction process,and improves the corrosion resistance.
ultrasonic surface rolling process304 stainless steelsurface residual stresscorrosion resistance
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