Relationship between thermal process and microstructure during additive manufacturing of double-electrode gas metal arc welding

Wire arc additive manufacture of ER304L stainless steel was studied using double electrode micro-plasma arc welding. The effect of different bypass current and stacking sequence on the microstructure and properties of 304 stainless steel stacking samples were analyzed by microstructure observation and microhardness test. Combining with the thermal cycle curve measured in the process of additive manufacturing. The results show that when the bypass current is increased, the dendrite arm spacing of the stacking sample decreased firstly and then increased during additive manufacturing of double electrode micro-plasma arc welding. Meanwhile, the effect of stacking sequence on microstructure was that the different direction of heat dissipation leaded to the change of dendrite growth direction. The microhardness decreased slowly along the direction of stack height. And with the increase of the bypass current, the hardness increases firstly and then decreases. The stacking order had no obvious effect on the hardness.