通过拉伸变形5%及1100 ℃退火30 min的晶界工程(GBE)处理工艺, 将304奥氏体不锈钢低Σ重合位置点阵(CSL)晶界比例提高到75% (Palumbo-Aust标准)以上, 形成大尺寸的“互有Σ3ⁿ取向关系晶粒的团簇”显微组织. 采用钨极气体保护焊焊接样品, 对焊接后样品的HAZ区域进行显微组织表征和耐腐蚀性能测试. 结果表明, GBE处理过的304奥氏体不锈钢具有较好的晶界网络稳定性, HAZ区域内仍具有高比例低ΣCSL晶界, 并且晶粒尺寸并未明显变大. 在晶间腐蚀浸泡实验和电化学动电位再活化法(EPR)测试中, GBE处理的样品HAZ敏化区都表现出了更好的耐腐蚀性能, 表明晶界工程可以有效改善304奥氏体不锈钢焊接热影响区耐晶间腐蚀性能.

The heat-affected zone (HAZ) produced by welding in stainless steel has higher susceptibility to intergranular corrosion, which is attributed to the Cr depletion induced by grain-boundary carbide-precipitation. The grain boundary engineering can be used to control over the grain boundary structure, which has significant influence on the carbide precipitation and the associated Cr depletion and hence on the susceptibility to intergranular corrosion. The grain boundary network in a 304 austenite stainless steel can be controlled by grain boundary engineering (GBE) with 5% tensile deformation and subsequent annealing at 1100 ℃ for 30 min. The total length proportion of Σ3ⁿ coincidence site lattice (CSL) boundaries was increased to more than 75%, and the large-size highly-twinned grain-cluster microstructure was formed through the treatment of GBE. Specimens were welded by gas tungsten arc-welding. Then the microstructure and the corrosion resistance of HAZ were characterized. The result showed that the high proportion of low ΣCSL boundaries and the optimum grain boundary character distribution were stable in the HAZ of the grain boundary engineered stainless steel, and the grain size was nearly the same. The weld-decay region of GBE samples performed better intergranular corrosion resistance during the intergranular corrosion immersion experiment and electrochemical potentiokinetic reactivation (EPR) test. The reported results indicated that the grain boundary engineering can effectively improve the intergranular corrosion resistance of the heat-affected zone in 304 austenitic stainless steel.