Effect of cerium on microstructure, eutectic carbides and Laves phase in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel

The dendrites, eutectic carbides, Laves phase and microsegregation of alloying element in electroslag remelted 15Cr-22Ni-1Nb austenitic heat-resistant steel with varying cerium contents were studied. The liquidus and solidus temperatures of the steel were determined to reveal the effect of cerium on solidification temperature interval and local solidification time of the steel. The secondary dendrite arm spacing decreases from 57.10 to 40.18 mu m with increasing the cerium content from 0 to 0.0630 wt.%. The eutectic NbC and Laves phase in as-cast ingots exhibit blocky and honeycomb morphology, respectively. The area fractions and sizes of eutectic NbC and Laves phase in as-cast ingots decrease with the increase in cerium content. The atomic percentage of Laves phase-forming element (Ni, Nb, Cr, Mo and Si) decreases with the increase in cerium content of the steel. The microsegregation of Mo, Ni, Si, Cr and Nb decreases with increasing the cerium content, which is favorable to reducing both the amount and sizes of eutectic NbC and Laves phase in as-cast ingots. The solidification temperature interval and local solidification time of the steel decrease as the cerium content is increased from 0 to 0.0630 wt.%, which inhibits the growth of dendrites, eutectic NbC and Laves phase.