Li Yang,Zhao Guangdi,Zang Ximin,et al.Effect of Boron on the Microstructure and Strength-Toughness of Fe-Cr-B-C Alloy after Heat Treatment[J].Special Steel,2024,45(05):25-33.
Li Yang,Zhao Guangdi,Zang Ximin,et al.Effect of Boron on the Microstructure and Strength-Toughness of Fe-Cr-B-C Alloy after Heat Treatment[J].Special Steel,2024,45(05):25-33. DOI: 10.20057/j.1003-8620.2023-00242.
Effect of Boron on the Microstructure and Strength-Toughness of Fe-Cr-B-C Alloy after Heat Treatment
In order to explore new methods for improving the strength-toughness matching of Fe-Cr-B-C alloy, the effect of B content on its microstructure, hardness, and impact toughness after heat treatment were investigated. The results showed that after air-cooling quenching at 1 050 ℃, a large amount of extremely fine secondary carbon-borides precipitated in the interdendritic region of low-B (0.000 6%) alloy, and fine dispersed secondary carbon-borides precipitated in the matrix of intermediate-B (0.51%) and high-B (2.89%) alloys. As the B content increased, the size of secondary carbon-borides increased but the particle density decreased. After air-cooling quenching at 1 050 ℃ plus tempering at 500 ℃, the number of secondary carbon-borides increased and the precipitation region expanded. For the low-B alloy, the dendrite arm was composed of coarse lath-like martensite, and the interdendritic region was composed of acicular martensite, high-density secondary carbon-borides and a small amount of solidification precipitates. For the intermediate-B alloy, the microstructure was composed of acicular martensite matrix with dispersed secondary carbon-borides, and network boron-carbides. For the high-B alloy, the microstructure was composed of γ matrix with a small amount of dispersed secondary carbon-borides, and denser network boron-carbides. The low-B alloy possesses the highest impact toughness and moderate Rockwell hardness. The intermediate-B alloy possesses the highest Rockwell hardness and moderate impact toughness. The high-B alloy possesses the lowest Rockwell hardness and impact toughness. Compared with the as-cast state, the solidification precipitates dissolved slightly after the quenching and tempering treatment, which resulted in the local rupture of netlike boron-carbides in intermediate-B and high-B alloys. Thus, after air-cooling quenching at 1 050 ℃ plus tempering at 500 ℃, the impact toughness of intermediate-B and high-B alloys improved obviously.
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