Effect of rare earth alloying on creep rupture of economical 21Cr-11Ni-N heat-resistant austenitic steel at 650 °C

The effect of rare earth (RE) on creep rupture of economical 21Cr-11Ni-N heat-resistant austenitic steel was investigated at 650 °C under different stress levels. It was found that RE could increase the time to creep rupture, especially at long-term creep duration. The logarithm of the time to creep rupture (lgtr) was a linear function of the applied stress (σ). RE addition was favorable to generating a high fraction of low-coincidence site lattice (CSL) boundaries which was a possible cause for improving the creep rupture resistance. The fracture surface of RE-added steel exhibited less intergranular cracks suggesting the alteration on the nature of grain boundaries due to the presence of RE. RE addition changed the morphology of the intergranular chromium carbides from continuous network shape to fragmentary distribution which was another cause for longer creep duration. These results strongly suggested that the effect of RE alloying played a crucial role in improving the creep rupture resistance.

Graphical AbstractLinear relation between σ and lg trFigure optionsDownload as PowerPoint slide