INFLUENCE OF TITANIUM ON THE CREEP-PROPERTIES OF ALLOY D9

Alloy D9, an austenitic stainless steel containing 15% chromium, 15% N ickel 0.05 wt% carbon and specified amount of titanium, is the current choice of material for cladding and wrapper applications in Fast Bree der Reactors. The influence of varying the amount of titanium on the c reep properties of cold worked Alloy D9 has been investigated Three di fferent 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 o btained for the heat having the lowest titanium content Rupture ductil ity was in general very low. Metallographic investigation revealed ext ensive creep damage in the form of sharp w-type cracks. It is suggeste d that the cold-worked matrix coupled with precipitation of intragranu lar carbides favoured extensive formation of creep cracks leading to p oor rupture ductility.