2520不锈钢开裂原因分析与研究

Analysis and Study on Crack Cause of 2520 Stainless Steel

通过宏观、金相、扫描电镜和化学分析技术对2520不锈钢膨胀接头开裂缺陷进行分析。结果表明:膨胀接头管壁存在严重减薄、高温氧化、逐层剥落及蠕变孔洞等现象。一方面是工作热质对管内壁的冲蚀,使管壁减薄到一定程度而不能承受出风管的系统应力而开裂;另一方面是2520钢在高温环境中长期使用会析出对晶间腐蚀敏感的σ相和晶间碳化物,易造成晶间脆性断裂。此外,高温下管壁内部位错攀移形成蠕变孔洞,蠕变孔洞长大并连接成蠕变裂纹;蠕变孔洞和蠕变裂纹降低了膨胀接头强度,提升了工作热质对管壁的冲蚀速度。

According to the results of visual examination,metallographic examination,scanning electronic microscope examination and chemical analysis,the severe thinning,high temperature oxidation,spalling layer upon layer,creep voids were found on the tube wall of the expansion joint of 2520 stainless steel.The results show that,the main reasons for crack are erosion corrosion of thermal mass on the tube,which can lead to severe thinning;滓 phase and intergranular carbide precipitating in high temperature environment is the cause of intergranular embrittlement fracture.In addition,high-temperature creep voids are caused by dislocation climb,which grow and connect with each other into creep cracks.The creep voids and creep cracks can decrease the strength of expansion joint,and improve the erosion speed of thermal mass on the tube.