| LI Ruixin,WU Chongzhong,WANG Yimin,LIU Dayong,YAN Wenji,DING Yanchao,QU Minggui,LYU Zhiqing.Effect of Controlled Pressure Nitriding Process on the Microstructure and Properties of 42CrMo Steel[J],54(7):180-188, 202 |
| Effect of Controlled Pressure Nitriding Process on the Microstructure and Properties of 42CrMo Steel |
| Received:July 23, 2024 Revised:December 18, 2024 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2025.07.015 |
| KeyWord:gas nitriding pressurized nitriding 42CrMo steel microstructure surface hardness nitrided layer |
| Author | Institution |
| LI Ruixin |
Key Laboratory of Advanced Forging and Stamping Technology and Science of Ministry of Education, School of Mechanical Engineering, Yanshan University, Hebei Qinhuangdao , China |
| WU Chongzhong |
Fujian Wind Power Generation Co., Ltd., China General Nuclear Power, Fuzhou , China |
| WANG Yimin |
Key Laboratory of Advanced Forging and Stamping Technology and Science of Ministry of Education, School of Mechanical Engineering, Yanshan University, Hebei Qinhuangdao , China |
| LIU Dayong |
Fujian Wind Power Generation Co., Ltd., China General Nuclear Power, Fuzhou , China |
| YAN Wenji |
Fujian Wind Power Generation Co., Ltd., China General Nuclear Power, Fuzhou , China |
| DING Yanchao |
Fujian Wind Power Generation Co., Ltd., China General Nuclear Power, Fuzhou , China |
| QU Minggui |
State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Hebei Qinhuangdao , China |
| LYU Zhiqing |
Key Laboratory of Advanced Forging and Stamping Technology and Science of Ministry of Education, School of Mechanical Engineering, Yanshan University, Hebei Qinhuangdao , China;State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Hebei Qinhuangdao , China |
|
| Hits: |
| Download times: |
| Abstract: |
| For the purpose of preparing a uniformly nitrided layer with stable mechanical properties on the surface of 42CrMo alloy structural steel within a relatively short time at a relatively low temperature, the temperature and holding time parameters of the gas nitriding process were regulated. Meanwhile, the pressure parameter was introduced to investigate the evolution of the mechanical properties and microstructure of the surface layer of 42CrMo alloy structural steel after nitriding. The surface hardness, nitrided layer thickness, compound composition, and distribution of N element of the samples after controlled-pressure nitriding were analyzed and tested. By observing the hardness and microstructure morphology, it was found that the microstructure of the nitrided sample consisted of a white bright layer on the surface, and N diffusion zone, and a matrix. The nitrided layer was significantly affected by pressure. Compared with the normal pressure state, the pressurized state could accelerate the nitriding process, making the nitrided layer thicken faster and distribute more uniformly. However, when the pressure increased from 0.3 MPa to 0.5 MPa, the improvement effect on nitriding was not pronounced. In contrast to a higher temperature, increasing the holding time at a lower temperature could more effectively improve the hardness and gradient distribution of the nitrided surface layer. Similarly, in the short-term nitriding process, the improvement in the nitriding effect by increasing the temperature was more significant compared with that in the long term. The increase in temperature and time had a significant impact on the diffusion of nitrogen concentration, with the effect of nitriding temperature being more prominent. The nitriding parameters had a relatively small impact on the nitrogen content of the outermost compound layer. When the nitriding temperatures were 480 ℃ and 510 ℃, the N atom concentration on the surface could reach about 10% (mass) under different nitriding pressures and time. The nitride content gradually decreased with the increase in the depth of the nitrided layer. The increase in nitriding temperature and nitriding time had a great impact on the thickening of the N concentration diffusion region and the N concentration decreased in a gradient trend. As the nitriding time increased, the N diffusion region thickened significantly, and the proportion of the ε-Fe2-3N phase in the near-surface region also increased. The increase in nitriding temperature had an even more significant impact on the N concentration diffusion region. Under the conditions of temperature of 510 ℃, pressure of 0.3 MPa, and time of 5 h, a favorable nitriding effect could be achieved through the controlled-pressure nitriding process, with a maximum hardness of 790HV, a uniformly distributed compound layer, and N concentration, showing that the diffusion zone depth exceeded 180 μm. There were high-N-concentration compounds formed by the combination of N atoms and Fe atoms on the surface of the nitrided sample, including ε-Fe2-3N and γ′-Fe4N. The outermost layer phase of the sample was basically ε-Fe2-3N phase, and the proportion of the γ′-Fe4N phase increased with the depth of the nitrided layer. Compared with the traditional gas nitriding process, the controllable pressure nitriding process not only makes the structure of the nitrided layer more uniform but also enhances the comprehensive mechanical properties. |
| Close |
|
|
|