梯度硬质合金与45钢的TIG焊研究

Research on TIG welding of gradient cemented carbide and 45 steel

选取YG8,YG15和YG20商用硬质合金与WC-5Co-25Ni硬质合金通过扩散烧结的方法制备梯度硬质合金,采用NiFe-C焊丝对梯度硬质合金与45钢进行TIG连接,通过扫描电镜观察、抗弯强度试验,对焊接接头的组织和力学性能进行了分析。结果表明:YG8/YG15/YG20/WC-5Co-25Ni四层结构梯度合金可以缓解焊接应力,与45钢TIG焊可以获得无开裂接头;垂直堆叠烧制的梯度合金焊接时易在焊缝底部界面位置形成η碳化物层,60°倾角倾斜堆叠烧制的梯度合金焊接时,界面位置不再形成有害碳化物层;由于η碳化物层的存在,垂直堆叠梯度合金的焊接接头抗弯强度仅为0. 74 GPa,倾斜堆叠梯度合金的焊接接头的抗弯强度提高到1. 29 GPa。

The gradient cemented carbide was prepared by selecting and diffusion-sintering the YG8,YG15 and YG20 commercial cemented carbide and WC-5Co-25Ni cemented carbide.Gradient cemented carbide and 45 steel were joined by TIG welding with Ni-Fe-C filler wire.The microstructures of welded joints were analyzed by scanning electron microscopy and mechanical properties of the joint were tested by bending strength test.The results show that the YG8/YG15/YG20/WC-5Co-25Ni four-layer structure gradient alloy can alleviate the welding stress,and crack free of TIG welding joint with 45 steel can be obtained.ηcarbide layer was easily formed at the interface of the bottom of the weld when the welded sintered gradient cemented carbide was vertically stacked,while no harmful carbide layer was formed at the interface location when the welded sintered gradient cemented carbide was stacked with 60°tilt angle.The bending strength of the welded joint of the vertically stacked gradient alloy was only 0.74 GPa due to the presence of theηcarbide layer,while the bending strength of the welded joint of the tilt-stacked gradient alloy increased up to 1.29 GPa.