超声表面滚压工艺对304不锈钢耐腐蚀性的影响

Effect of ultrasonic surface rolling process on corrosion resistance of 304 stainless steel

采用超声表面滚压工艺(USRP)对304不锈钢进行表面处理,研究了其对304不锈钢耐蚀性的影响。利用扫描电镜、X射线衍射仪和金属表面粗糙度仪对表面形貌、微观结构、残余应力和粗糙度进行分析。采用电化学测试、邻菲啰啉显色试验评估了氧化膜的耐腐蚀性和完整性。结果表明,经USRP处理后,304不锈钢表面粗糙度R_a由0.60μm降低到0.28μm,表面晶粒尺寸从23.13μm降低到20.80 nm,表面残余应力由20 MPa转变为-329 MPa。与未处理试样比较,超声表面滚压试样的自腐蚀电流密度I_(corr)最小为0.94×10^(-5)A/cm^(2),降低了71%;氧化膜层电阻R_(p)达到2.59×10^(6)Ω·cm^(2),提升了2倍;邻菲啰啉显色值范围变窄,显色面积减小,表明表面缺陷减少,表面氧化膜的质量得到提高。分析认为,超声表面滚压处理促使304不锈钢近表面层晶粒细化、产生残余压应力,使表面缺陷减少、氧化膜更加致密,进而阻滞304不锈钢的电化学反应进程,提高了材料的耐腐蚀性。

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 R,for the 304 stainless steel is reduced from 0.60μm to 0.28μm after USRP treatment.The surface grain size is reduced from 23.13μm 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 l_(corr) of the USRP treated specimen is 0.94×10^(-5) A/cm^(2),which is reduced by 71%.The oxide film resistance R_(p)is 2.59×10^(6)·cm^(2),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.