Creep-properties and microstructure of austenitic steels containing manganese

The creep properties and the microstructure of two groups of austenitic steels containing manganese as a replacement for nickel have been studied at 700°C and for a range of stresses. In one-group, nitrogen was added to stabilize the austenite; in the other, the content of manganese was higher and the steels were expected to be stably austenitic without nitrogen. The objective of the programme was to demonstrate that austenitic steels containing manganese could be produced having creep properties comparable with those of the more conventional austenitic steels. The work has shown that in terms of life to rupture the present steels compare favourably with equivalent steels containing nickel. The addition of carbide- and nitride-forming elements such as tungsten, vanadium, and molybdenum gave a significant improvement in creep strength relative to the base compositions, and X-ray analysis of extracted residues has been used in order to identify the precipitates formed.