Influence of titanium on the creep properties of alloy D9

Alloy D9, an austenitic stainless steel containing 15% chromium, 15% Nickel 0.05 wt% carbon and specified amount of titanium, is the current choice of material for cladding and wrapper applications in Fast Breeder Reactors. The influence of varying the amount of titanium on the creep properties of cold worked Alloy D9 has been investigated Three different heats of this alloy, have been prepared containing 0.2,0.3 and 0.4 wt% titanium. Creep tests were carried out at 973 K at different stress levels in the range 125-200 MPa. The highest rupture life was obtained for the heat having the lowest titanium content Rupture ductility was in general very low. Metallographic investigation revealed extensive creep damage in the form of sharp w-type cracks. It is suggested that the cold-worked matrix coupled with precipitation of intragranular carbides favoured extensive formation of creep cracks leading to poor rupture ductility.