航空齿轮钢C69高温渗碳后的组织性能

通过OM、SEM、TEM以及显微硬度计等设备研究了1050 ℃下不同渗碳工艺对航空齿轮钢C69组织及性能的影响。结果表明,经渗碳、深冷和回火处理后,渗碳层表层的显微硬度最高可达约950 HV0.3,组织为针状马氏体,马氏体上观察到M₃C、M₂C碳化物,晶界处有M₇C₃碳化物分布,次表层组织为针状马氏体和板条马氏体,心部显微硬度约为630 HV0.3,组织主要为板条马氏体。循环渗碳的渗碳效率更高,随循环次数增加,试验钢的表面碳含量和渗碳层深度不断提高,且晶界处M₇C₃尺寸和数量逐渐增加。4次循环渗碳的表面碳含量为1.14%,渗碳层深度约为3.0 mm。

Microstructure and properties of C69 gear steel for aviation after high temperature carburizing

Effect of different carburizing processes at 1050 ℃ on microstructure and properties of gear steel C69 for aviation was studied by using OM, SEM, TEM and Vickers hardness tester. The results show that after carburizing, cryogenic and tempering, the surface hardness of the carburized layer can reach about 950 HV0.3, and the microstructure is acicular martensite where the M₃C and M₂C carbides precipitate, and the M₇C₃carbides precipitate at grain boundary. At the sub-layer of the carburized surface, microstructure is composed of acicular martensite and lath martensite. At the core, the microstructure is lath martensite and the hardness is about 630 HV0.3. The cyclic carburizing has higher carburizing efficiency. With the increase of carburizing cycle, the thickness of carburized layer and surface carbon concentration increase continuously, and the size and quantity of the M₇C₃ at the grain boundary also increase. After four cycles carburizing, the surface carbon concentration is 1.14%, and the thickness of carburized layer is about 3.0 mm.