Welding of nickel-based alloy 617 using modified dip arc processes

The widespread application of nickel-based alloys as structural materials in chemical, nuclear and power generation industries is often limited due to weldability issues. Technological and metallurgical problems such as lack of fusion or hot cracking require specific welding guidelines as well as knowledge of the welding metallurgy to produce welds that fulfill high quality requirements. Due to the lower heat input modified dip arc welding is a potential alternative joining technique for hot crack sensitive nickel-based alloys. This paper contributes to the application of modified dip arc processes for butt welding of alloy 617 (2.4663). The influence of reduced heat input on microstructural and mechanical properties were investigated. Particular attention was given to the occurrence of hot cracking in the weld metal and base metal HAZ (heat-affected zone) using light optical microscopy, EDS analysis and electron probe microanalysis. The results indicate that the modified dip arc processes provide excellent weld quality and economic efficiency. However, microstructural observations showed that hot cracking in the form of microcracks could not be completely avoided. The modified dip arc welded joints exhibited good tensile strength and impact toughness. The mechanical properties are comparable to commonly GMA (gas metal arc) pulsed arc welding and are not influenced by the microcracks.