Heat Treatment of Metals ›› 2023, Vol. 48 ›› Issue (11): 143-148.DOI: 10.13251/j.issn.0254-6051.2023.11.022

• PROCESS RESEARCH • Previous Articles     Next Articles

Effect of cryogenic treatment on microstructure and hardness of carburized gear steel

Song Shaowei1,2, Yu Wenchao2, Shi Jie2, Wang Maoqiu2, He Xiaofei2, Zhou Yun1   

  1. 1. Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming Yunnan 650093, China;
    2. Research Institute of Special Steels, Central Iron and Steel Research Institute Company Limited, Beijing 100081, China
  • Received:2023-06-08 Revised:2023-10-09 Online:2023-11-25 Published:2023-12-27

Abstract: Microstructure and hardness of 20Cr2Ni4A and 17Cr2Ni2MoVNb carburized gear steels were characterized by means of metallographic microscope, X-ray diffractometer, EBSD and Vickers hardness tester, and the effect of cryogenic treatment on microstructure and hardness distribution of the tested steels was studied. The results show that the maximum hardness in the carburized layer of the two tested steels increases obviously after cold treatment at -75 ℃, and it increases a little further after cryogenic treatment at -196 ℃. After cold treatment at -75 ℃, the contents of retained austenite in the carburized layers of the 20Cr2Ni4A and 17Cr2Ni2MoVNb steels are decreased from 34% to 19% and 25% to 20%, respectively, and they are further decreased to 11% and 13% after cryogenic treatment at -196 ℃. There is a more amount of large-sized retained austenite in the 20Cr2Ni4A steel, which is decreased more easily after cryogenic treatment. Large-sized retained austenite has a significant effect on hardness of the carburized layer.

Key words: carburized gear steel, cryogenic treatment, microstructure, retained austenite, hardness

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