M50钢中M_(2)C一次碳化物高温转变机制  

High-Temperature Decomposition Mechanism of M_(2)C Primary Carbide in M50 Steel

作　　者：马芳 陆星宇 周丽娜 杜宁宇 类承帅 刘宏伟[3] 李殿中[3] MA Fang;LU Xingyu;ZHOU Lina;DU Ningyu;LEI Chengshuai;LIU Hongwei;LI Dianzhong(School of Mechatronics Engineering,Harbin Institute of Technology,Harbin 150001,China;AECC Harbin Bearing Co.Ltd.,Harbin 150025,China;Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China)

机构地区：[1]哈尔滨工业大学机电工程学院,哈尔滨150001 [2]中国航发哈尔滨轴承有限公司,哈尔滨150025 [3]中国科学院金属研究所沈阳材料科学国家研究中心,沈阳110016

出　　处：《金属学报》2024年第7期901-914,共14页Acta Metallurgica Sinica

基　　金：国家重点研发计划项目No.2018YFA0702900;国家自然科学基金项目No.52031013;中国航发自主创新专项资金项目No.ZZCX-2020-027。

摘　　要：以双真空冶炼的M50钢为研究对象,通过SEM、EPMA及TEM对铸态及高温扩散后M50钢中的一次碳化物进行了详细表征,系统研究了合金成分及温度对铸态M_(2)C一次碳化物高温转变机制的影响,揭示了在1160~1250℃下M_(2)C一次碳化物的高温分解机制。研究结果表明:M50钢中的M_(2)C一次碳化物主要有3种形态,分别是棒状、片层状与块状,成分上表现出Fe元素含量依次降低、Mo元素含量依次升高的分布规律。合金成分的差异导致M_(2)C一次碳化物在1160~1250℃高温扩散处理时表现出不同的热稳定性及不同的组织转变机制。其中,1160~1180℃保温时Fe元素含量较高的M_(2)C碳化物快速回溶到基体中,部分M_(2)C碳化物转变为MC碳化物,MC碳化物长大速度较慢;1210℃保温时M_(2)C碳化物几乎完全溶解,一次碳化物数量明显减少,但部分MC碳化物快速长大,形成球形大尺寸MC碳化物;1250℃保温时,M_(2)C碳化物完全溶解,未发现大尺寸MC碳化物,但存在基体组织熔化现象,此时基体中的Mo、V合金元素向形成的液相中扩散,并在凝固后形成呈球形分布的新生M_(2)C碳化物。M50 steel is primarily used for manufacturing the main shaft bearings of aero engines.However,the fatigue property of M50 steel affects the service life of shaft bearings owing to their operation in the environment with high temperature,high rotation speed,and high contact stress.Inclusions and large-sized carbides are proved to be the primary reasons that cause fatigue cracking.Nevertheless,inclusions in M50 steel and fatigue failure due to inclusions are substantially reduced with the rapid development of metallurgical technology and metallurgical equipment in recent years.M50 steel contains high fractions of Cr,Mo,and V elements,which are easily enriched and can form primary carbides.The primary carbides in M50 steel are hard and brittle and cause stress concentration under external load,thereby accelerating the initiation and propagation of fatigue cracks.Currently,the large-sized primary carbides in M50 steel play an important role in reducing the service life of bearings and have attracted substantially research attention.The present investigation focuses on the decomposition mechanism of large-sized M_(2)C primary carbide in M50 steel to reveal the carbide-refinement mechanism during high-temperature heat treatment.In addition,M_(2)C primary carbide in M50 steel was systematically characterized by SEM,EPMA,and TEM,and its decomposition mechanism at 1160-1250℃ was studied.The difference in chemical composition of different M_(2)C primary carbides and its effect on the decomposition mechanism were also explored.Three forms of M_(2)C carbides in M50 steel were revealed:the rod-like carbide,the lamellar-like carbide,and the block-like carbide.In these three M_(2)C carbides,the content of Fe increased,while the content of Mo decreased successively.The difference in chemical composition and morphology of these three M_(2)C carbides led to the different microstructure-evolution process when heat-treated at elevated temperature.When the steel was heat-treated at 1160-1180℃,only the M_(2)C carbides with high Fe

关 键 词：M50钢 M_(2)C一次碳化物 高温扩散 转变机制 

分 类 号：TG142.1[一般工业技术—材料科学与工程]