3DAP研究高碳高合金钢深冷处理过程的C偏聚行为  

CARBON SEGREGATION BEHAVIOR OF HIGHCARBON HIGH-ALLOY STEEL DURING DEEP CRYOGENIC TREATMENT USING 3DAP

作　　者：谢尘[1] 吴晓春[1] 闵娜[1] 沈贇靓 

机构地区：[1]上海大学材料科学与工程学院,上海200072

出　　处：《金属学报》2015年第3期325-332,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金资助项目51171104~~

摘　　要：将高碳高合金钢SDC99分别在1030℃奥氏体化30 min后油淬、在-196℃液氮中深冷处理8 h及210℃回火2 h.采用三维原子探针（3DAP）技术分析了淬火态、深冷态、回火态C原子的空间分布;用XRD研究了3种热处理状态下马氏体轴比、马氏体中含C量的变化;用SEM原位观察深冷前后碳化物的形貌.结果表明,C原子在深冷处理过程中偏聚于马氏体孪晶界,形成厚度为5~10 nm的偏聚区.210℃低温回火过程中,C进一步偏聚形成富C相或与合金原子形成M23C6型碳化物.Deep cryogenic treatment（DCT） is a supplement to conventional heat treatment, which usually involves cooling the material to liquid nitrogen temperature around-196 ℃ for a given soaking time and then heating back to the room temperature. As claimed in many pioneering researchers, DCT can evidently improve the hardness and wear resistance of high-carbon high-alloy steel and has been widely used to die steels, cutting tools,carburizing steels and barrels. The improvement of mechanical properties by DCT can be attributed to the transformation from retained austenite to martensite, the fine dispersion of nanoscale carbide precipitate and the removal of residual stresses. However, the nanoscale carbide precipitate is still lack of evidence and the interpretation of carbon segregation behavior during DCT is still unconvincing. In this work, the high-carbon high-alloy steel SDC99 is first austenized at 1030 ℃ for 30 min and then immersed in liquid nitrogen for 8 h and finally tempered at 210 ℃for 2 h. The spatial distributions of carbon atom and alloy element concentration in quenched, DCT treated and tempered samples are analyzed by three dimensional atom probe（3DAP）, respectively. In addition, the axial ratio and carbon content of martensite are studied using XRD and the carbide morphology before and after DCT are also observed in situ by SEM. The results indicate that after quenching from 1030 ℃ to room temperature, the volume fraction of retained austenite in SDC99 is about 21.1%. The retained austenite is soft and unstable which can easily transfer to martensite at lower temperatures. Carbon atoms will segregate slightly due to self-tempering. However, other alloy atoms do not segregated with carbon atoms. After quenching from 1030 ℃ to room temperature and then cooling in nitrogen for 8 h, the volume fraction of retained austenite in SDC99 will decrease to 7.4%. Carbon atoms will segregate along the twin boundary of martensite and form a segregation area with a thickness about 5~10 nm.There is no

关 键 词：高碳高合金钢 深冷处理 C偏聚 碳化物形貌 三维原子探针(3DAP) 

分 类 号：TG142.1[一般工业技术—材料科学与工程]