混合钎料对镍基单晶高温合金大间隙钎焊接头组织和性能的影响

Influence of mixed brazing filler metal on microstructure and mechanical properties of wide gap brazed joints of nickel-based single crystal superalloy

【目的】采用一种新型镍基钎料和母材成分一致的高熔点合金粉混合的方法制备出混合钎料,研究了添加的高熔点合金粉的粒径和配比对钎缝微观组织和力学性能的影响。【方法】采用扫描电子显微镜对钎焊接头的析出相、元素分布、微观组织进行了分析,并对钎焊接头的硬度及持久性能进行了测试。【结果】研究表明,接头主要由钎料合金区(FAZ)、界面连接区(IBZ)和扩散影响区(DAZ)三部分组成。钎料合金区主要由M3B2和M8B型硼化物及γ/γ′相组成。界面连接区由γ和γ′沉淀强化相组成。当合金粉粒径为44μm和75μm时,均可得到无缺陷的焊接接头;但当合金粉粒径尺寸达177μm时,钎缝内会形成孔洞缺陷。【结论】随着合金粉比例的提高,接头连接区的显微硬度有所上升。当合金配比由30%到50%,接头的持久寿命由15 h增加至34 h;但进一步提升比例至60%时,接头的持久寿命下降至0.6 h。该文的结果可为实现高温热端零部件的连接和修复工程应用提供理论依据和参考价值。

[Objective]A method combining a new type of nickel-based brazing filler metal with high-melting-point alloy powder that matched composition of base material was used to create mixed brazing filler metal.Effect of particle size and proportion of added high-melting-point alloy powder on microstructure and mechanical properties of brazed joints was explored.[Methods]Precipitated phase,element distribution and microstructure of brazed joints were analyzed by scanning electron microscope,and hardness and creep life of brazed joints were tested.[Results]It revealed that brazed joints mainly consisted of filler alloy zone(FAZ),interface bonding zone(IBZ)and diffusion affected zone(DAZ).FAZ predominantly comprised M3B2 and M8B type borides,along withγ/γ′phases.IBZ was composed ofγandγ′precipitation-strengthened phases.When alloy powder particle size was 44μm and 75μm,defect-free brazed joints were obtained.However,pores defects formed in brazing seam when particle size reached 177μm.[Conclusion]As the proportion of alloy powder increased,there was a rise in microhardness of bonding area of brazed joints.When alloy ratio was increased from 30%to 50%,creep life of brazed joints extended from 15 h to 34 h.However,further increasing proportion to 60%led to a reduction in creep life of brazed joints to 0.6 h.The results of this study provided a theoretical basis and reference value for realizing connection and repair of high-temperature hot-end components in engineering applications.