Metallurgical and Stress State Factors Which Affect the Creep and Fracture Behavior of 9% Cr Steels

Figure 12

Analysis of the N : Al ratio on tempering behavior for specific casts of Grade 91 steel. Note that although steel J4 starts with the lowest initial hardness value, as demonstrated in the 760°C (1400°F) for 10 hours experiments, it exhibits the highest resistance to tempering and a more consistent (i.e., lower standard deviation) hardness for each examined tempering treatment.