Effect of different variants of filler metal S Ni 6625 on properties and microstructure by additive layer manufactured using CMT process

Abstract

The influence of arc energy and different filler metal composition on the mechanical properties and macro- and microstructure of additively welded thin-walled structures of Ni-based alloy were investigated using four different variants commercially available solid wire electrodes of type S Ni 6625. As the welding process, the Cold Metal Transfer (CMT) process was used. The heat input and cooling rate were varied by adjusting wire feed and travel speed. The results show that an increase in arc energy leads to longer t10/6 cooling times. This leads to an increase in the dendrite arm spacing and thus to a reduction in the strength values and hardness of the thin-walled structures. The higher Fe-containing variant of S Ni 6625 produces the highest strength and hardness values, while the W-alloyed solid wire electrode produces the lowest values. The porosity in the walled structures was very low, and unacceptable weld defects, hot cracks and lack of fusion did not occur. Segregations occur in all weld metal specimens. While niobium, molybdenum and titanium are the preferred segregations in the Nb-alloyed Ni 6625 type weld metal, only Mo is present in the W-alloyed Ni 6660 type weld metal.