Yang Peng,Yang Chen,Shen Hongying,et al.Effect of Nitrogen Infiltration on Microstructure and Properties of 12Cr Ferritic-Martensitic Steel[J].Special Steel,2026,47(02):134-139.
Yang Peng,Yang Chen,Shen Hongying,et al.Effect of Nitrogen Infiltration on Microstructure and Properties of 12Cr Ferritic-Martensitic Steel[J].Special Steel,2026,47(02):134-139. DOI: 10.20057/j.1003-8620.2025-00117.
Effect of Nitrogen Infiltration on Microstructure and Properties of 12Cr Ferritic-Martensitic Steel
The effects of nitrogen-hydrogen mixed atmosphere heat treatment on microstructure and properties of 12Cr ferritic-martensitic steel were studied by electron backscatter diffraction (EBSD) and microhardness (HV
0.025
). The results showed that the surface structure of the tube changed due to nitrogen infiltration after heat treatment, and a large amount of martensite was formed near the surface, which decreased with the increased of nitrogen diffusion distance.The nitriding layer would increase the surface hardness of the pipe. The microhardness analysis showed that the hardness value at 20 μm from the surface was 368HV
0.025
, and the transverse cracks was generated on the surface of the tube in the subsequent cold working deformation process. Based on the thermodynamic library TCFE11 and the kinetic library MOBFE6, a thermodynamic model of heat treatment time and N-directional diffusion distance in the matrix at the boundary was established to study the relationship between nitrogen infiltration and diffusion distance. The results showed that the nitrogen content gradually decreased with the increase of diffusion distance, and the decreasing trend slowed down after the diffusion distance reached 70 μm. By studying the effect of nitrogen infiltration on the microstructure and properties of 12Cr ferritic-martensitic steel, an annealing process for 12Cr ferritic-martensitic steel was developed, the pipe was heated in a hydrogen atmosphere to 860 ℃, holding it for 1 hour, and cooling it using a fan. Production verification confirmed that the surface hardness of the treated pipes was approximately 210HV
0.025
, meeting the requirements for cold working deformation.
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