ABSTRACT This study systematically evaluates the potential of Raman spectroscopy for the microstructural analysis of advanced martensitic steels, using creep‐resistant 9CrWMo steel as a case study. The core objective was to establish the detection thresholds and applicability of this nondestructive technique for identifying key secondary phases, such as M 23 C 6 carbides, MX carbonitrides (NbX, VX), and the Fe 2 (W, Mo) Laves phase. The phase evolution during high‐temperature creep was investigated in parallel by thermodynamic modeling and transmission electron microscopy (TEM) to provide validation. Raman spectroscopy successfully detected grain‐boundary M 23 C 6 carbides in all material states. It revealed Laves phase particles after creep exposure when their average size exceeded ~80 nm (volume fraction ~0.2%) and identified MX carbonitrides only when their particle size was greater than ~50 nm with a volume fraction above 0.2%. A comparative analysis confirmed good qualitative agreement between the Raman spectroscopy data and the results from TEM and modeling. Beyond detection, Raman spectroscopy indicates the increased structural disorder in coarsening M 23 C 6 carbides and enhanced crystallinity of the Laves phase with prolonged creep. The work quantitatively defines the detection limits of Raman spectroscopy for critical precipitates in complex steel microstructures and demonstrates its utility as a rapid, complementary tool for assessing microstructural degradation.
Fedoseeva et al. (Thu,) studied this question.