高氮不锈轴承钢碳化物分布与高温断裂机制  

Carbide distribution and high-temperature fracture mechanism of high nitrogen stainless bearing steel

作　　者：曹方 杨卯生[2] 杨树峰 李京社 罗志强[2] 刘威 CAO Fang;YANG Mao-sheng;YANG Shu-feng;LI Jing-she;LUO Zhi-qiang;LIU Wei(State Key Laboratory of Advanced Technology of Iron and Steel Metallurgy,University of Science and Technology Beijing,Beijing 100083,China;Special Steel Research Institute,Central Iron and Steel Research Institute,Beijing 100081,China)

机构地区：[1]北京科技大学钢铁冶金新技术国家重点实验室,北京100083 [2]钢铁研究总院有限公司特殊钢研究院,北京100081

出　　处：《钢铁》2022年第6期132-142,共11页Iron and Steel

摘　　要：通过高温拉伸试验研究高氮不锈轴承钢高温断裂行为,探究了170℃和470℃回火态钢中碳化物分布特征,分析了高温拉伸断裂及组织演变和碳化物分布规律。研究发现,回火温度从170℃升高至470℃,高氮钢中大于0.8μm的碳化物明显增加,高氮钢中M;C;强化增量提高了2.59 MPa,固溶强化增量下降了118.82 MPa,470℃回火态钢的室温抗拉强度降低、拉伸断口表现为准解理和少量撕裂韧窝;拉伸温度升高至300℃,试样断口表现为等轴型韧窝特征,170℃和470℃回火态试样起裂源断裂碳化物尺寸分别为2.8~3.6μm和5.5~6.7μm;450℃拉伸断口表现为塑孔韧窝特征,170℃和470℃回火态试样起裂源断裂碳化物尺寸分别为2.7~3.4μm和5.8~6.4μm。拉伸温度从300℃提高至450℃,钢的固溶强化和位错强化作用减弱,金属原子间结合能下降,碳化物与基体不连续应力分布加剧变形不协调性,碳化物承担较高应力而发生断裂。单纯热作用下钢中0.5~0.8μm尺寸碳化物数量比例增加;在热力耦合作用下,钢中应力所导致的位错增殖为碳元素扩散提供通道,钢中碳化物在晶界和位错线上形核析出0.2~0.8μm碳化物。裂纹沿着与拉伸方向45°角的最大剪力方向快速扩展而断裂,最终形成锯齿状的断口,小尺寸碳化物增多阻碍位错滑移导致塑性降低;钢中大尺寸碳化物不均匀分布在碳化物间形成大变形塑孔而增加钢的塑性。The high temperature fracture behavior of high nitrogen stainless bearing steel was studied by high temperature tensile test.The distribution characteristics of carbide in 170℃and 470℃tempered steel were investigated.The tensile fracture,microstructure evolution and carbide distribution law were analyzed.The results show that with the tempering temperature increasing from 170℃to 470℃,the carbide larger than 0.8μm in high nitrogen steel increases significantly,M;C;strengthening increment increases by 2.59 MPa,and solution strengthening increment decreases by 118.82 MPa.The tensile strength of 470℃tempering steel decreases at room temperature,and the tensile fracture behavior of the steel at room temperature is quasi-cleavage and a small amount of tear dimms.When the tensile temperature is increased to 300℃,the fracture surface of sample is equiaxed dimple,and the size of fracture source carbide of the 170℃and 470℃tempering samples is 2.8-3.6μm and 5.5-6.7μm,respectively.The tensile fracture at 450℃is characterized by plastic-pore dimples,and the size of fracture source carbide at 170℃and 470℃is 2.7-3.4μm and 5.8-6.4μm,respectively.When the tensile temperature increases from 300℃to 450℃,the effect of solution strengthening and dislocation strengthening is weakened,the interatomic bonding energy of metal decreases,the discontinuous stress distribution between carbide and matrix increases the deformation incompatibility,and the carbides bear higher stress then fracture occurs.Under the action of pure heat,the percentage of carbides of 0.5-0.8μm increased.Under the action of thermodynamic coupling,dislocation proliferation caused by stress in steel provides channels for carbon diffusion,and 0.2-0.8μm carbides are nucleated at grain boundaries and dislocation lines.The crack propagates rapidly along the maximum shear direction at angle of 45°with the tensile direction and then fractures.Finally,serrated fracture is formed.The increase of small carbides hinders dislocation slip and resu

关 键 词：高氮不锈轴承钢 高温断裂 塑性 高温硬度 碳化物 

分 类 号：TF762.4[冶金工程—钢铁冶金]