钎焊温度对纯Fe真空钎焊接头组织及硬度的影响

Effects of Brazing Temperature on Vacuum Joint Microstructure and Microhardness of Pure Fe

采用BNi-7+9%Cu复合钎料对纯Fe进行真空钎焊,研究不同钎焊温度对焊接接头的影响。运用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)、X射线衍射分析及显微硬度分析对焊接接头进行研究。结果表明,接头主要由等温凝固区、非等温凝固区和扩散影响区组成。等温凝固区为富Cr、Fe的γ(Ni,Cu)固溶体,非等温凝固区由γ(Ni)+Ni-P共晶组织和Ni-Cr-P金属间化合物组成。当钎焊温度为940℃时,由于扩散影响区部分液体凝固缓慢,形成许多大的空洞,焊缝中心的显微硬度为870MPa;当钎焊温度为960℃时,焊缝和母材得到很好结合,焊缝中心的显微硬度为800MPa;当钎焊温度为980℃时,由于Fe与Ni原子的扩散速度不同,在扩散影响区形成了柯肯达尔孔洞,焊缝中心的显微硬度为760MPa。

BNi-7＋9% Cu composite solder was used to braze pure Fe in vacuum. Influence of brazing tempe- rature on the welded joints was studied. The welded joints were studied by optical microscopy （OM）, scanning elec- tron microscopy （SEM）, electronic data systems （EDS）, X-ray diffraction and microhardness analysis. The results show that brazing joints are mainly consists of isothermally solidified zone, athermally solidified zone and diffusion-af- fected zone. Isothermally solidified zone is 7（Ni,Cu） solid solution that solutes the rich of Cr,Fe, athermally solidified zone is ＂/（Ni）q-Niz-P eutectic and Ni-Cr-P metal compounds. Diffusion-affected zone forms many large voids at 940 ℃, the reason is that the part of liquid solidify slowly, the microhardness is 870 MPa at the center of weld;the weld and the base material get the fine combination at 960 ℃ ,the microhardness is 800 MPa at the center of weld; diffusion- affected zone forms Kirkendall voids at 980 ℃, the reason is that Fe and Ni have different spread speed, the microhard- ness is 760 MPa at the center of weld.