Effect of Welding Current on Formability and Microstructure of Plasma Arc Cladding Titanium/Steel Dissimilar Metal Joint with Copper Intermediate Layer

Copper layer and TA0 titanium layer were sequentially deposited on the Q235B steel plate by plasma arc cladding. The effect of welding current (85, 90, 95, 100, 105 A) on formability and microstructure of the titanium/steel dissimilar metal welded joint was studied. The results show that this welding process could effectively suppress the formation of brittle phases and welding cracks when the welding current was higher than 90 A. With increasing welding current, the unfused area of the cladding layer decreased and the thickness uniformity increased. The cladding layers had the best formability at welding current of 100 A; the titanium layer, copper layer and steel substrate showed good metallurgical combination; the microstructures of titanium layer and copper layer were fine needle dendrite, columnar dendrite, respectively, and that of the heat-affected zone in steel substrate was fine pearlite + ferrite phase and coarse ferrite phase. At different welding currents, the hardness near the copper/titanium interface was the highest. In this area, the titanium and copper grains were interlaced, and a large number of low brittle intermetallic compounds such as CuTi₂ and CuTi precipitated.