Creep Rupture Properties of Nickel-base Heat Resisting Alloys in Two Impure Helium Environments of HTGR

Abstract

The creep rupture properties of nickel base heat resisting alloys are investigated in two types of impure helium o f He-2 and PNP-He at 1000 °C, simulating a high temperature gas-cooled reactor (HTGR) environment. The alloys examined are four new alloys developed for heat exchangers of nuclear steelmaking system using HTGR.
All the alloys are decarburized in some extent in PNP-He, while some of them are carburized in He-2 during the creep rupture testing, indicating that carbon activity of the gases is lower in PNP-He than in He-2 at 1000°C.
Decarburization is found to be the most important of the environmental effects deteriorating the creep rupture properties of the alloys. The environmental effects of the formation of internal oxides and the depletion of gamma prime and α-W precipitates beneath the alloy surface are also examined.