HR3C/T91异种耐热钢焊接接头的力学性能及界面蠕变失效行为研究

Mechanical Properties and Interfacical Creep Failure Behaviors Between HR3C/T91 Dissimilar Heat-resistant Steel Welded Joints

针对新型奥氏体不锈钢HR3C与细晶粒强韧马氏体耐热钢T91异种钢焊接接头,采用手工氩弧焊接工艺、高温加速模拟、高温持久和常温力学性能试验研究HR3C与T91异种钢焊接接头的力学性能变化、高温强度、界面蠕变损伤及破坏特征。研究结果表明,焊前预热448 K,焊后不进行热处理条件下,接头的力学性能优异。加速模拟运行3 004 h后,接头的力学性能仍然良好。而加速模拟运行5 012 h后,HR3C/T91界面发生了蠕变失效,蠕变裂纹在管接头内表面焊缝/T91界面形核、扩展,然后在管接头外表面T91的临界热影响区内发展,最后导致接头蠕变失效。拉伸和弯曲试验过程中,接头的强度和塑性下降严重,断裂位置均在焊缝/T91界面区域。因此,焊缝/T91界面容易发生早期蠕变失效。

The properties, creep rupture strength, interracial creep damage and rupture characteristics of dissimilar welded joint between austenitic heat-resistant steel （HR3C） and martensitic heat-resistant steel （T91） were investigated by means of argon arc welding, high temperature accelerated simulation, creep rupture test, mechanical properties test and microstructure analysis. The research results indicate that the properties of joint are good with the preheat temperature of 448 K and no post welding heat treatment after accelerated operation 3 004 h. But the interfacial creep failure occures at HR3C/T91 interface after accelerated operation 5 012 h. Creep crack nucleates at HR3C/T91 interface, and propagates along HR3C/T91 interface in the internal face of tube joint. However, creep crack develops in heat affected zone of T91 in the outer face of tube joint. The tensile strength and plasticity of joint decrease obviously, fracture locations are all near the HR3C/T91 interface. Metallographic observations fred that the microstructures of HR3C are austenites and carbides, and coarsen seriously, grain boundary are also coarsening. And there are no creep cavities and cracks. However, ＇ grains at HR3C/T91 interface zone are coarsening, creep damages are serious, and interfacial creep cracking occures. Therefore, HR3C/T91 interface is the weakest part of HR3C/T91 welded joint.