20钢管高温钎焊与瞬时液相扩散焊接组织与性能

Microstructure and properties of 20 steel pipe joints by transient liquid phase bonding and high temperature brazing

采用镍基钎料BN i2和自主研制的铁镍基中间层合金进行了20钢管的焊接试验,以扫描电镜、能量散射X射线和电子探针分析了它们的焊缝组织形貌、成分分布以及焊接性能之间的差异。结果表明,采用镍基钎料BN i2高温钎焊20钢管,接头组织为典型的N i固溶体钎缝特征,与母材组织存在明显的钎缝界限,接头区成分分布不均匀且有S i脆性相存在,接头无韧性;采用铁镍基中间层瞬时液相扩散焊接20钢管,可获得与母材相似并连续的接头组织,接头成分分布均匀且无S i脆性相生成,接头强度、韧性均达到母材水平,其性能远远高于高温钎焊。

20 steel pipes were joined with a conventional nickel base brazing filler metal BNi2 and a novel iron-nickel base foil, and the mechanical properties and microstructure of them were investigated using scanning electron microscopy, energy dispersive X-ray analysis and electron probe microanalysis. The results showed that BNi2 brazing produced Ni solid solution joints with silicide precipitates and heterogeneity composition. In contrast, however, transient liquid phase bonding using iron-nickel base foil, resulted in homogenous joints with microstructure and composition similar to the parent metal and free of silicide precipitates. Mechanical tests showed that bonding properties of joints made using iron-nickel base foil were superior to those obtained using BNi2. When the iron-nickel base foil was used, bonding toughness was near parent toughness.