表面纳米化对SS400钢应力腐蚀性能的影响

Effect of Surface Nanocrystallization on Stress Corrosion Cracking of SS400 Steel

采用高能喷丸技术对SS400钢表面进行纳米化处理,利用透射电子显微镜分析了表面纳米晶层的结构特征,同时对高能喷丸表面纳米化处理后残余应力沿厚度方向的变化进行了分析。结果表明:经过超声冲击处理后,试样表层的晶粒可细化至纳米尺度,且在表面形成厚度约为600μm的压应力层,压应力沿试样深度方向逐渐减小直至过渡到拉应力。在98±3℃温度下,Ca(NO3)257%+NH4NO33%溶液中进行的慢应变速率拉伸试验,结果表明,高能喷丸表面纳米化可以提高SS400钢的抗应力腐蚀开裂(SCC)性能。

A nanostructured surface layer was synthesized on SS400 steel by means of high energy shot peening （HESP）. The refined microstructure in the top surface layer was characterized by means of transmission electron microscopy （TEM）, and the residual stress variation along the depth of the treated sample was examined. Experimental results showed that after the HESP treatment the microstructure of the surface layer could be refined down into the nanoscale. The compressive stress induced by HESP decreased along the cross-section down to zero at about 600 μm. A compressive stress nanostrutured layer was achieved in the top surface of SS400 steel. The results of slow strain rate tests of SS400 steel in Ca（NO3）2 57%＋NH4NO3 3% solution at 98±3 ℃ indicated that the resistance of SS400 steel to SCC had been improved.