316LN不锈钢管状试样高温高压水的腐蚀疲劳行为

设计了一种管状疲劳试样,高温高压水流经试样内部,试样外部与空气接触。利用管状试样研究了316LN不锈钢高温高压水腐蚀疲劳性能,重点关注了应变速率对其疲劳性能的影响。实验结果表明,高温高压水环境降低了316LN不锈钢的疲劳强度,且疲劳寿命随应变速率降低而降低;管状试样与标准棒状试样获得的疲劳寿命相差不大,表明利用管状试样研究核电结构材料高温高压水环境疲劳性能是合理可行的。在低应变速率条件下,疲劳裂纹源区域为典型的扇形花样,呈现准解理开裂特征。疲劳裂纹扩展区为典型的疲劳辉纹特征。疲劳裂纹萌生阶段高温高压水环境效应更加显著。同时讨论了316LN不锈钢在高温高压水环境中的疲劳损伤机理。

Corrosion Fatigue Behavior of 316LN Stainless Steel Hollow Specimen in High-Temperature Pressurized Water

Environmentally assisted fatigue is an important factor in the design, safety review, and life management of key components used in nuclear power plants. Piping systems, valves, and smallbore pipes are sensitive to fatigue damage in nuclear power plants. In this work, a kind of hollow specimen for fatigue testing was designed. High-temperature pressurized water flows through the inside of the specimen, and the outside of the specimen is exposed to air. The corrosion fatigue behavior of 316LN stainless steel was investigated in high-temperature pressurized water using the hollow specimens. The experimental results show that the fatigue strength of 316LN stainless steel was reduced in a hightemperature pressurized water environment, and its fatigue life decreased with decreasing strain rate.The fatigue lives obtained by hollow and standard round bar specimens were comparable, which indicate that it is reasonable and feasible to use the hollow specimen to study the environmentally assisted fatigue performance of nuclear-grade structural materials in a high-temperature pressurized water environment. At low strain rate conditions, the fatigue crack initiation region is a typical fan-shaped pattern with quasi-cleavage cracking characteristics. The fatigue crack growth region is characterized by fatigue striation, and the environmental effects are highly significant in the stage of fatigue crack initiation. The fatigue damage mechanism of 316LN stainless steel in a high-temperature pressurized water environment is also discussed.