Low-carbon 9-12Cr heat-resistant ferritic/martensitic steels were fabricated by SEBM using two types of powders (Ar gas- and N gas-atomized powders). Both the as-built Ar- and N-components showed a tempered and fine lath-like ferritic/martensitic microstructure, high tensile strength (approximately 1300 and 1167 MPa for the as-built N-component and the as-built Ar-component, respectively), and tensile elongation of approximately 8%. The high N content (0.44 wt%) of the as-built N-component resulted in a refined lath martensite phase and promoted the precipitation of a fine M2X phase which give rise to higher strength. SEBM is a suitable and rapid method for fabricating low-C martensite steels with a fine lath martensitic microstructure and enhanced mechanical properties for use in power plants without employing welding.
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