GH4738/GH3536异种高温合金钎焊接头的组织与性能

Microstructure and mechanical properties of brazed joints of GH4738/GH3536 dissimilar superalloys

采用BNi-2镍基钎料对GH4738和GH3536异种高温合金在1040℃×10 min条件下进行真空钎焊,通过扫描电子显微镜和能谱仪分析了钎焊接头的微观组织及物相组成,并测试了钎焊接头的高温强度。结果表明,钎缝与母材界面结合良好,且钎缝组织致密。在钎焊接头观察到3个特征组织区域,分别为元素扩散区、等温凝固区和非等温凝固区。等温凝固区由镍基固溶体组成,而非等温凝固区除了镍基固溶体外,还存在大量的Ni3Si相及少量的富含Cr,Mo的硼化物。在730℃高温条件下,钎焊接头抗拉强度为259 MPa。在拉伸过程中,钎焊接头沿非等温凝固区开裂,而Ni3Si及硼化物等脆性相内部形成的微裂纹促进了钎焊接头的断裂。

Vacuum brazing of GH4738 and GH3536 Ni-based superalloys was conducted with BNi-2 brazing filler metal under the condition of 1040℃×10 min.Microstructure and phase composition of GH4738/GH3536 brazed joints were performed by scanning electron microscope and energy dispersive spectrometer,respectively.High temperature mechanical properties of brazed joints were also tested.The results indicated that interface between brazing seam and base metal was well bonded,and microstructure of brazing seam was dense.Microstructure of brazed joints consisted of three distinct microstructural zones,including diffusion-affected zone(DAZ),isothermal solidification zone(ISZ)and athermal solidification zone(ASZ).ISZ was composed of Ni-based solid solutions,while ASZ contained Ni3Si intermetallic compounds and Cr-Mo rich borides in addition to Ni-based solid solutions.Tensile strength of brazed joints was 259 MPa at 730℃.Brazed joints fractured along ASZ during tensile process,and micro-cracks formed in brittle phases such as Ni3Si and borides promoted fracture of brazed joints.