The inner wall oxide layer of 12Cr1MoV steel pipe for long－term operation of superheater

Scanning electron microscopy analysis, energy spectrum analysis, X－ray diffraction analysis, transmission electron microscopy analysis, X－ray photoelectron spectroscopy analysis and mechanical performance testing were used to study the inner wall oxide layer of 12Cr1MoV steel pipes for long－term operation of superheaters. The results show that under high temperature service conditions, Cr₂₃C₆ carbides with a face centered cubic structure were precipitated at the grain boundaries of 12Cr1MoV steel pipes, and they were dispersed, strengthening the grains boundaries. There was no obvious layering phenomenon at the interface between the steel pipe substrate and the inner wall oxide layer. With the prolongation of service time, the Cr₂₃C₆ carbides at the grain boundaries exhibited a chain like aggregation distribution, with more carbides and larger particle sizes. The oxide layer structure was loose, and there was a clear interface between the carbides and the metal matrix.