40Cr钢循环离子渗氮工艺及渗层硬度研究

目的探索循环离子渗氮与常规恒温离子渗氮技术的工艺效果。方法先对试样进行调质处理,分组进行离子渗氮,固定氨气和乙醇的流量,改变渗氮时间和渗氮温度两种工艺参数及渗氮工艺,分别测定渗氮后各试样的表面硬度及渗层厚度,观察其金相组织,并分析每组试样渗氮层的性能。结果循环离子渗氮530 6 h℃试样的表面硬度最高,随着渗氮温度的升高和渗氮时间的延长,试样的表面硬度增加,但是当温度超过530℃、时间超过6 h后,试样的表面硬度反而降低。循环渗氮550 10 h℃试样的渗层厚度最厚,随着渗氮温度的升高和渗氮时间的增加,试样的渗层厚度变厚,但时间超过6 h后,渗层厚度的增加较缓慢,6、8、10 h试样的渗层厚度差别不大。相同的渗氮温度下,循环渗氮6 h的试样的渗层厚度基本与常规恒温渗氮10 h试样的渗层厚度一样,相同渗氮时间内,循环渗氮510℃的试样的表面硬度高于恒温渗氮550℃试样的表面硬度,且两者的渗层厚度相差不多。结论循环离子渗氮工艺优于常规的恒温离子渗氮,循环离子渗氮550 8 h℃试样的综合性能最好。

Study on Surface Circular Plasma Nitriding Technology and Nitrided Layer Hardness of 40Cr Steel

The work aims to explore the process effects of circular plasma nitriding and conventional constant temperature plasma nitriding technology. Firstly, the specimen quenching and tempering was carried out. Plasma nitriding was conducted by groups. The flows of ammonia and ethanol were fixed. The two technological parameters (nitriding time and nitriding tempera-ture) and nitriding technology were changed to respectively measure the surface hardness and nitriding thickness of each speci-men after nitriding. The metallographic structure of each specimen was observed and the nitrided layer performance of each group of specimens was analyzed. The surface hardness of circular plasma nitrided 530℃ 6 h specimen was the highest. With the increase in the nitriding temperature and the prolonged nitriding time, the surface hardness of specimens was increased. However, when the temperature exceeded 530℃ and the time was over 6 h, the surface hardness of specimens would be re-duced instead. The nitrdied layer thickness of the circularly nitrided 550℃ 10 h specimens was the maximum. With the increase in nitriding temperature and nitrding time, the nitrided layer of the specimen would become thicker. However, when the time exceeded 6 h, the nitriding thickness was increased more slowly. The nitriding thicknesses at 6 h, 8 h and 10 h were of little dif-ference. At the same nitriding temperature, the nitrding thickness of specimen circularly nitrdied for 6 h was basically the same with that of the specimen subject to 10 h conventional constant temperature nitriding. Within the same nitriding time, the surface hardness of the circularly nitrided specimen at 510℃ was higher than that of the nitrided specimens at the constant temperature 550℃ , and both nitriding thicknesses were almost the same. Circular plasma nitriding technology is superior to the convention-al constant temperature plasma nitriding and the circular plasma nitrided 550℃ ×8 h specimens have the best overall perfor-mance.