瞬时液相扩散焊双温和三温工艺下T91钢接头的显微组织与力学性能

Microstructure and Mechanical Properties of T91 Steel Welded Joint with Transient Liquid-Phase Bonding Two-step and Three-step Heating Process

分别采用瞬时液相扩散焊双温及三温工艺对T91钢管进行了焊接,采用扫描电镜、能谱仪、电子万能力学试验机、摆锤冲击试验机及弯曲试验机等研究了接头的显微组织、元素分布、力学性能等。结果表明:2种工艺下T91钢接头的成形质量均较好;双温工艺下接头焊缝近似直线,接头有钎焊特征,焊缝处镍元素富集导致黑色脆性相的生成;三温连接接头焊缝呈曲线状,镍元素得到均匀化扩散,接头的组织、成分与母材的相似;三温工艺下接头的抗拉强度为660MPa,冲击功为25.7J,三点弯曲180°而不裂,力学性能比双温工艺下的有显著提高;双温工艺下接头的断裂形式为韧-脆性混合断裂,三温工艺下的为典型的韧性断裂。

T91steel tube was bonded by transient liquid-phase bonding under two and three-step heating process,respectively.The microstructure,element distribution and mechanical properties of the joints were investigated by scanning electron microscopy,energy dispersive spectrometer,electronic universal testing machine,Charpy test device and bending testing machine.The results show that T91 steel joint had good formation quality under two heating processes.The joint under two-step heating process had the approximate line weld and brazing characteristics,and the Ni enrichment in weld resulted in the formation of black brittle phase.The weld of joint under three-step heating process was curved;Ni element distributed evenly;the microstructure and composition of the joint were the same with those of the base metal;the tensile strength was 660 MPa,the impact energy was25.7Jand the joint did not cracked during bending 180°;the mechanical properties were improved compared with that under two-step heating process.The fracture mode of the joint under two-step heating process was ductilebrittle mixed fracture,and the fracture mode under three-step heating process was typical ductile fracture.