Abstract
Ni-base superalloy Inconel 706 which was developed from Inconel 718 has an economical advantage to save the major element Ni content less than Inconel 718. This alloy has such high strength, ductility and resistance against high temperature oxidation as equivalent to those of Inconel 718, but have a slight higher susceptibility to hot cracking. However the hot cracking susceptibility of Inconel 706 has not been investigated in detail.
The Trans-Varestraint test was conducted in order to examine the solidification cracking susceptibility of Inconel 706 as a function of Ni content in base metal. Three kinds of Ni-base alloys with three different levels of Ni content were used.
Typical dendrite structure was observed in the fractured surface of the specimen of Trans-Varestraint tested. Quantitative analysis of crack revealed that the solidification crack length and the temperature range in which hot cracking occurred (brittle temperature range, BTR) decreased with the increase of Ni content. Calculation of liquidus and solidus temperature of alloys by thermo-calc data indicated that the solidification temperature range also decreases with increase of Ni content.
On the basis of these results, it was deduced that the improvement of the solidification cracking susceptibility with Ni content was attributed to the decrease of the solidification temperature range of alloys.
