1982 Volume 68 Issue 3 Pages 477-485
A study has been made of the effect of a simulated HTR (High Temperature Gas-cooled Reactor) coolant atmosphere on the creep-rupture properties of Inconel 617 at 1 173K.
Carburization during creep in helium accelerated the growth of surface cracking, and led to losses in rupture life and ductility. This was characterized by the early onset of tertiary creep, and which was explained in terms of the reduction of net cross-sectional area by surface cracking. Similar premature failure was observed also in air. But the effect of air atmosphere diminished for the test durations longer than 1 Ms, when the internal cracks became dominant in the rupture processes. With increasing the amount of carburization the matrix strengthening became significant and increased the rupture life. For the test durations of 3 to 4 Ms the rupture life in helium became superior to that in air when the increase in bulk carbon contents exceeded 0.15%.
The variation of rupture mode, increased amount of carburization and coarsening of carbide in long-term creep test were discussed to predict the creep strength in a simulated HTR helium under lower stresses.