Abstract
The effect of tempering temperature on microstructure and mechanical properties of plasma welded martensitic heat-resistant steel P92 was investigated by tempering heat treatment process (tempering temperature range was 550–750°C, temperature interval was 100°C). The results show that with the increase of tempering temperature, the microstructure of welded joint coarsens, the tensile strength and hardness decrease, and the toughness is improved.In the tempering process, M23C6 and Laves phases are produced in the welded joint. A certain amount of M23C6 precipitates can strengthen the mechanical properties of the welded joint. Excessive M23C6 carbides lead to the softening of martensite and the decrease of hardness; the formation of Laves phase can inhibit the excessive precipitation of M23C6, but the excessive precipitation of the Laves phase will lead to coarsening at the grain boundary and the formation of voids at the grain boundary. When the welded joint temperature is 650°C, the comprehensive mechanical properties of the welded joint are the best.
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