A series of doctoral and diploma investigations which have been carries out at the Institute of Reactor Materials of the KFA are reported. The influence of both thermal exposure and carburisation at 800 °C and above on the room temperature tensile properties of INCOLOY 800 H, INCONEL 617, HASTELLOY X and NIMONIC 86 has been studied and the results have been compared with literature data. It is shown that the room temperature ductility of INCOLOY 800 H is much less sinsitive to carburisation than that of the nickel-base alloys. This is attributed to the greater volume fraction of carbide formed in the nickel-base alloys for a particular bulk carbon content. In the nickel-base alloys carbide volume fractions are higher than in iron-base alloys due to the lower solubility of carbon and to the formation of M6C carbides. The ductility of reformer and intermediate heat exchanger (IHX) tubes after long service times in a process heat high temperature reactor has been estimated using carburisation rates found in corrosion experiments. The data indicate that a reformer tube of INCOLOY 800 H should retain a room temperature ductility equivalent to 5 % tensile elongation - a normal minimum requirement in conventional engineering design over the anticipated service life of 140000 h. For the IHX tubes, the impurity concentrations in the primary coolant must be carefully controlled in order to avoid embrittlement by carburisation. Alternatively, a design concept to allow the use of low ductility tubes will be required. Suggestions are given for future work, in particular for alloy development to produce alloys which are less severely embrittled by carburisation
