氯离子质量浓度对Inconel 740H合金应力腐蚀开裂性能的影响

Effect of chloride ion concentration on the stress corrosion cracking performance of Inconel 740H alloy

采用慢应变速率拉伸试验和应力腐蚀裂纹扩展试验方法,研究了630~700℃高参数先进超超临界机组候选镍基合金Inconel 740H在0、1、20 mg/L氯离子水环境中的应力腐蚀开裂性能及规律,并探讨了高质量浓度氯离子促进应力腐蚀裂纹的萌生和扩展的相关机理。结果表明:高质量浓度氯离子促进740H合金的应力腐蚀开裂,合金应力腐蚀敏感性指数断后伸长损失I_(scc(δ))随氯离子质量浓度升高而增大;当氯离子质量浓度升高至20 mg/L时,断口中部和断口边缘均呈沿晶脆性断裂特征,断口附近有大量沿晶二次裂纹,此时合金发生了应力腐蚀开裂。在20 mg/L氯离子水环境中裂纹平均扩展速率达1.15×10^(–6) mm/s,是高纯水中裂纹平均扩展速率的111.7倍。

The effect of chloride ion concentration on the stress corrosion cracking of Inconel 740H,a candidate nickel based alloy for high parameter ultra-supercritical units at 630~700℃,were investigated by slow strain rate tensile testing and stress corrosion crack propagation testing.Results showed that high concentration of chloride ions promoted stress corrosion cracking of 740H alloy,and the stress corrosion sensitivity index I_(scc(δ))of the alloy increased with the increase of chloride ion concentration.When the concentration of chloride ions increased to 20 mg/L,both the middle and edge of the fracture exhibited intergranular brittle fracture characteristics,with a large number of secondary intergranular cracks near the fracture.At this point,the alloy experienced stress corrosion cracking.The average crack propagation rate in a 20mg/L chloride ion water environment reached 1.15×10^(-6) mm/s,which is more than 100 times the average crack propagation rate in high-purity water.And the relevant mechanism of high concentration chloride ions promoting the initiation and propagation of stress corrosion cracks was explored.