Cascading phase transformations in situ for the simulated coarse-grained heat-affected zone of P92 heat-resistant steel

Salient phase transformations in the coarse-grained heat-affected zone of P92 heat-resistant steel have been documented by confocal scanning laser microscope. It has been revealed that consecutive transformations (delta -> gamma -> martensite) take place, and the final microstructure is composed of transformed martensites with retained delta-ferrites. It is further demonstrated that martensite laths grow at a wide rate spectrum ranging from 86 to 354 mu m/s. The fast cooling rate may not allow complete transformation of delta-ferrite to gamma-austenite as the equilibrium condition is far from attained.

Automated summary

Salient phase transformations, including successive delta-gamma-martensite transformations, were observed in the coarse-grained heat-affected zone of P92 heat-resistant steel using a confocal scanning laser microscope. The final microstructure consisted of transformed martensites and retained delta-ferrites. The growth rate of martensite laths ranged from 86 to 354 μm/s, indicating a wide range of rates. The fast cooling rate prevented complete transformation of delta-ferrite to gamma-austenite due to the non-equilibrium condition.