Carbide precipitation in 12Cr1MoV power plant steel

The chemistry and other characteristics of carbide precipitates in 12CrlMoV steel of the type used in the power generation industry were studied using energy dispersive X-ray spectroscopy and electron and X-ray diffraction techniques, and the results have been compared against thermodynamic calculations. As a result of the much larger substitutional solute concentrations present in the alloy, unlike the carbides that occur in steels containing smaller concentrations of chromium and molybdenum, it is found that the equilibrium M23C6 carbide precipitates very rapidly during heat treatments of the kind used routinely for stress-relief purposes. The chemical compositions of carbides therefore do not change much during subsequent service at elevated temperatures.