Abstract
Due to their mechanical and corrosive properties, nickel-based alloys are very important in several industrial sectors like power stations, chemical apparatus, and the oil industry. While flux-cored arc welding (FCAW) of carbon steels often uses flux-cored wires (FCW), the use of Ni-based flux-cored wires is industrially less common. The reasons for this include the lower degree of recognition and the higher material costs compared to solid wires. In comparison to solid wires, flux-cored wires have some technological benefits such as the possibility of welding without pulsed arc technology using low-cost standard mixed gases, which has a much lower tendency to weld defects due to high penetration depth. Depending on the slag, the flux-cored wires have a good weldability and excellent mechanical properties. Based on the self-stressed and externally stressed hot crack tests, the basic FCW showed a higher hot cracking susceptibility, contrary to the original assumption. Even if the causes have not yet been finally clarified, a negative influence of the comparatively high sulfur and oxygen contents in the basic FCW is suspected. The weld metal of the solid wires showed the highest hot crack resistance.
Highlights
Welding of nickel-based alloys is often problematic because of their sensitivity to the occurrence of hot cracks and lack of fusion in the welds [1, 2]
The characterization of the welding consumables showed that all flux-cored wires are form-fitted and differ only in the overlap length
It can be denoted that the pure weldment of the solid wires has the highest hot crack resistance
Summary
Welding of nickel-based alloys is often problematic because of their sensitivity to the occurrence of hot cracks and lack of fusion in the welds [1, 2]. The metallurgical causes of the high susceptibility of segregation-induced hot cracks are mainly the low solubility and diffusion rate of polluting elements such as sulfur, phosphorus, and boron in the face-centered cubic lattice structure of the Ni-based alloys. Other reasons for the high hot crack sensitivity of Ni-based alloys are:. & The high thermal expansion with low thermal conductivity, which results in larger strain and shrinkage reactions in the temperature range of hot cracking [7],. & The mostly cellular solidification of the weld metal, which supports the formation of segregation-induced hot cracks [4], and. A sufficiently high temperature at the weld flanks has a favorable effect here [9]
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