Carbide precipitation law in vacuum carburized 18CrNiMo7-6 steel

doi:10.13251/j.issn.0254-6051.2022.05.028

Abstract

Abstract: Using quenching dilatometer for simulation, carbide precipitation law during cooling of the vacuum carburized 18CrNiMo7-6 steel was studied by characterizing the microstructure and hardness distribution. The results show that after austenitizing at 980 ℃ for 30 min, the carbides are completely dissolved. After cooling quickly to 600 ℃ and holding for 20 min, the infiltration layer microstructure is fully transformed into fine lamellar microsturcture with pearlite morphology. Then after heating to 830 ℃ and holding for 20 min and cooling with protective atmosphere at 20 ℃/s to room temperature, carbides with different shapes appear, and the martensite is finer than that in the original microstructure before the heat treatment. Besides, the hardness is higher and the depth of hardened layer is deeper than those before the heat treatment.

Key words: vacuum carburizing, 18CrNiMo7-6 steel, carbide, heat treatment, microstructure, depth of hardened layer

CLC Number:

TG156.1

Zhang Minghao, Han Haoyuan, Xu Yueming, Li Qiao, Gao Zhi, Zhou Leyu. Carbide precipitation law in vacuum carburized 18CrNiMo7-6 steel[J]. Heat Treatment of Metals, 2022, 47(5): 171-176.

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