镍喷涂层下钛/钢电阻钎焊的接头形成机制

针对钛合金与不锈钢焊接时，接头中因大量Fe-Ti等金属间化合物生成而开裂的问题，尝试了一种涂层为匹配面的钛合金与不锈钢搭接电阻钎焊工艺.通过对不同厚度热喷涂层下钎焊接头力学性能的测定，以R接头区组织成分探查，研究了涂层参与反应的钎焊接头形成机制.结果表明，当合理厚度涂层介入时，其一定透过性的组织结构，降低了母材中Fe，Cr，Ti等原子在接头区的扩散浓度，涂层中Ni与Fe，Cr，Ti等原子发生扩散反应，使Fe-Ti，Cr-Ti等脆性金属间化合物数量明显下降，从而使接头力学性能得到显著提高.在涂层与钎料共同作用下，形成的多反应区显微组织实现了钛/钢间组织和性能上的过渡，这是其接头力学性能得到改善的主要原因.

Formation mechanism of titanium/steel brazing joints with thermally sprayed Ni layer

In the brazing joint of titanium alloy to stainless steel, a lot of Fe-Ti intermetallic compound can be easily formed to make joints cracking. To solve this problem, a procedure was developed that Ni coating was deposited as the lap joint face of titanium/steel in resistance brazing process. Meanwhile, the mechanical properties, the microstructure and the composition of the brazed joint with thermally sprayed layer with different thickness was studied. The formation mechanism of brazing joint with preplaced Ni layer was discussed. Experimental results showed, when a reasonable thickness of Ni layer acted as a part of the brazing joint, the concentration of diffused Fe, Cr, Ti and other atoms declineed due to the presence of Ni layer. Moreover, Ni atoms can combined with Fe, Cr, Ti and other atoms, making the number brittle Fe-Ti, Cr-Ti intermetallic compounds decreased obviously, therefore it improved the mechanical properties of the joint significantly. Under the combined effect of the coating and solder, a kind of microstructure induced by multiple reactions was formed, which played a transitional role in the joint, it is also the main reason for the mechanical properties improvement of joints.