Hot Strength and Creep Resistance of a High Interstitial Austenitic CrMn Steel

The hot strength and short-time creep resistance of austenitic steel CN0.85 with about (mass%) 18Cr, 18Mn, 0.6N, and 0.25C was investigated up to 700 degrees C together with the corresponding structural changes of the solution annealed or cold worked initial states. In the primary creep range, the creep rate was rapidly reduced to the minimum creep rate and the more so after initial cold working. This also lowered the minimum creep rate but hardly the time to fracture. Precipitation of carbides and nitrides occurred in or near grain boundaries which gave rise to creep cracks. Precipitates within the grains, visible only in the overaged state, are assumed to have raised the resistance to creep. Comparing the creep strength of CN0.85 with standard hot work tool steel H11 points to an advantage of the former at service temperatures of >550 degrees C. However, tests in practice are required to back up the favorable results of this tentative study.