Abstract
This study was carried out quantitatively to evaluate the hot cracking susceptibilities of various Ni-base superalloys and the effect of grain size on hot cracking susceptibility during laser welding.
Ni-base superalloys used were Inconel 718, Inconel X-750, Inconel 617, Inconel 625, Nimonic 90 Waspaloy, Hastelloy X. The grain size of Inconel 718 varied from about 10 to 110 μm. In this study, the hot craking susceptibility was evaluated by a modified U-type hot cracking tester during CO2 laser welding. Samples were solution heat-treated before welding and welded with laser powers of 3 and 5 kW and with a traveling speed of 0.5 to 3 m/min.
The hot cracking occurring in the weldment during the bead on plate test was reproduced on the U-type hot cracking test. Consequently, the liquation cracking susceptibilities of various Ni-base superalloys decreased in the order of Waspaloy, Inconel 617, Inconel 718, Hastelloy X, Inonel 625, Inconel X-750 and Nimonic 90. Liquation cracking susceptibility of Inconel 718 increased with an increase in grain size.
