Impact toughness of high-chromium martensitic steel with low nitrogen and high boron content
DOI:
https://doi.org/10.54708/26587572_2026_822575Keywords:
creep-resistant steels, heat treatment, impact toughness, structure, secondary phase particlesAbstract
This paper examines the impact response of a novel high‑chromium martensitic steel alloyed with 0.0007 wt.% nitrogen and 0.015 wt.% boron over a broad temperature interval. The heat‑treated microstructure consists of tempered martensite laths (mean width 320±30 nm) with a dislocation density of 1.5 × 1014 m−2 and no δ‑ferrite. Secondary phases include M23C6 carbides (~70 nm average), sporadic M6C, and fine NbX precipitates. At ambient temperature, the impact toughness exceeds 200 J/cm², well above the standards for boiler and turbine applications. The ductile‑to‑brittle transition temperature (defined as the midpoint between upper and lower shelf energies) is 0 °C. Above –20 °C, the crack initiation energy becomes virtually constant at 60±7 J, whereas the propagation energy rises steadily owing to growing ductile fracture contribution. Fractographic observations show that with increasing temperature the stable crack growth region widens and the unstable propagation zone shrinks, vanishing completely at 60 °C. The combination of high room-temperature toughness (~200 J/cm²) and a transition temperature of about 0 °C makes this 10Cr–3Co–0.2Re steel with low N and high B a promising candidate for ultra-supercritical steam power-plant components.References
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