Changes in microstructure and properties of TP347HFG steel aged at 700 ℃

doi:10.13251/j.issn.0254-6051.2025.02.036

Abstract

Abstract: By using SEM, EDS, TEM, universal testing machine and Brinell hardness tester, the changes in microstructure and properties of TP347HFG steel in as-received state and different aged states (aged at 700 ℃ for 500, 800, 1500, 2500, 3650 h) were analyzed. The results show that the relationship of total amount of precipitated phases vs aging time during the aging process of the TP347HFG steel at 700 ℃ is as follows: y=0.060-9.956×10^-5x+2.912×10^-7x²-2.707×10^-11x³-7.719×10^-15x⁴. The precipitated phase of the as-received TP347HFG steel is fine primary phase Nb(C, N). After aging for 500 h, M₂₃C₆ carbides precipitate and grow at the grain boundaries, and a small amount of σ phase appears after aging for 3650 h. After aging for 500 h, the fine second phase on the grain boundaries inhibits grain boundary slip, improves the hardness and strength, but reduces the material plasticity. After aging for 800 h, the precipitation of hard and brittle M₂₃C₆ carbides and the decrease in twinning quantity reduce the strength of the steel. After aging for 1500 h, the fine secondary Nb(C, N) plays a role in dispersion strengthening, increasing the strength and reducing the plasticity of the steel. When aged to 3650 h, with the coarsening of precipitated phases, the hardness value of the steel is decreased, the strength is slightly decreased, and the plasticity is slightly improved.

Key words: TP347HFG steel, aging, microstructure, mechanical properties

CLC Number:

TG142.1

Song Tao, Xing Honggen, Wang Zhiwu, Zhang Yonglin. Changes in microstructure and properties of TP347HFG steel aged at 700 ℃[J]. Heat Treatment of Metals, 2025, 50(2): 230-234.

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