Application of hydrogen-as-a-probe to evaluate the metallurgical condition and imperfections of a 13CrMo4-5 ex-service steam header component from a power plant

Hydrogen-as-a-probe, via thermal desorption spectroscopy (TDS), is a proposed highly sensitive technique for detecting early-stage material degradation. In this work, hydrogen-as-a-probe was applied to a 13CrMo4-5 ex-service (ES) component that operated for over three decades at 60 bar and 783 K, offering rare insight into creep cavitaty-type damage (<1.7 µm) under real service conditions. To establish reference hydrogen desorption patterns and support method reliability, 13CrMo4-5 AS and artificially aged plates were investigated. A holistic methodology combining microstructural characterisation and finite element method-based analysis was employed to assess creep strain evolution. The main findings relate to the formation of a distinct desorption pattern (peak 2 at T = 541 K in charged samples), with hydrogen concentration directly proportional to the volumetric creep cavity number density—both features present only in the ES extracted samples. Peaks 1, 3, and 4 appeared consistently across all material conditions and showed minimal sensitivity to material condition evolution. These findings highlight the high sensitivity and potential of hydrogen-as-a-probe via TDS to detect sub-micron creep cavity-type damage and differentiate microstructural changes arising from distinct metallurgical histories. These results demonstrate the potential of hydrogen-as-a-probe as a sensitive mechanistic framework for detecting early small-scale damage, providing a reference for future development of NDT or minimally invasive diagnostic methods beyond conventional inspection limits. It represents a significant advancement in diagnostic capabilities, enabling the prevention of progressive damage and catastrophic failures in high-value engineering applications, while optimising performance and ensuring safe, sustainable operations.