The effect of heat treatment on the microstructure and mechanical properties of a (in wt. %) 10 Cr-3Co-3W-0.2Re martensitic steel was investigated. The microstructure and mechanical properties of the steel subjected to the normalizing at 1050 °C and tempering at different temperatures ranging from 750 to 800 °C were studied. After normalizing at 1050 °C, the average size of prior austenite grains was 59 ± 5 μm and no evidence of δ-ferrite was observed. The tempering temperature strongly affected the tempered martensite/ferrite lath structure: the lath width increased from 280 ± 30 to 710 ± 70 nm and dislocation density decreased from to 3 × 1014 to 1.5 × 1014 m-2 when tempering temperature increased from 750 to 800 °C. The boundary M23C6 and M6C carbides and randomly distributed within matrix Nb-rich MX carbonitrides were detected. Increasing the tempering temperature led to the significant growth of all secondary phase particles. No depletion of Re from the solid solution during tempering under any temperatures was revealed. Impact toughness was independent of tempering temperature, whereas tensile properties and hardness decreased with increasing tempering temperature. This steel tempered at 770 °C was subjected to the short-term creep tests at 650 °C under the applied stresses ranging from 200 to 140 MPa with a step of 20 MPa. High creep resistance of this steel under short-term creep testing was revealed which is attributed to the stability of tempered martensite/ferrite lath structure.Keywords: Martensitic steel, heat treatment, microstructure, mechanical properties, precipitation
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