高C-高Cr工具钢中残留奥氏体和马氏体回火行为的研究

发布时间：2018-02-23 23:02

本文关键词： 马氏体残留奥氏体含碳量中子衍射高C-高Cr钢　出处：《武汉科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文主要研究高C-高Cr工具钢中残留奥氏体和马氏体回火行为。淬火后的高C-高Cr工具钢组织成分主要包括板条状马氏体、残留奥氏体和碳化物。研究过程中将空冷淬火材和油冷淬火材在相同的回火条件下的实验结果作对比分析，主要采用OM、SEM/EBSD和TEM等分析方法对高C-高Cr工具钢的淬火材和回火材中的微观组织进行观察，并利用XRD和中子衍射等分析方法对残留奥氏体的体积分数及残留奥氏体和马氏体中含碳量进行计算分析。同时也研究了各种热处理条件下的材料硬度的变化。主要研究内容和结果如下：（1）在573K回火条件下，，块状残留奥氏体通过从马氏体中吸收碳原子从而使其体积分数增加，而条状残留奥氏体分解为铁素体和渗碳体，表明块状残留奥氏体和条状残留奥氏体有不同的回火特性；（2）在573-773K回火条件下，残留奥氏体的总体积几乎不变或略有上升，但此时的残留奥氏体是亚稳态的。当块状残留奥氏体回火后冷却至室温时，其转变成马氏体的临界回火温度为773K；（3）由于亚稳态残留奥氏体转变成马氏体的行为受试样形状和大小的限制，因此按照转变行为的难易程度来划分，首先发生在TEM薄片试样中，其次是在SEM/EBSD等块状试样的表面层，最后才是块状试样的中心层。TEM、SEM/EBSD、XRD和中子衍射实验都证实这一结果。
[Abstract]:In this paper, the tempering behavior of residual austenite and martensite in high C- high Cr tool steel is studied. Residual austenite and carbides. The experimental results of air-cooled quenched and oil-cooled quenched materials under the same tempering conditions were compared and analyzed during the study. The microstructure of quenching and tempering materials of high C- high Cr tool steel was observed by OMSEM / EBSD and TEM. The volume fraction of retained austenite and the carbon content in retained austenite and martensite were calculated and analyzed by means of XRD and neutron diffraction. The contents and results of the study are as follows:. 1) at 573K tempering condition, bulk residual austenite increases its volume fraction by absorbing carbon atoms from martensite, while strip residual austenite decomposes into ferrite and cementite. The results show that the bulk retained austenite and the strip retained austenite have different tempering characteristics. (2) under the tempering condition of 573-773K, the total volume of retained austenite is almost unchanged or slightly increased, but the residual austenite is metastable. When the bulk residual austenite is cooled to room temperature after tempering, the critical tempering temperature for transformation to martensite is 773K; (3) since the transformation of metastable residual austenite to martensite is limited by the shape and size of the sample, the transformation behavior is divided according to the degree of difficulty of the transformation behavior, which occurs first in the TEM sheet specimen and then in the surface layer of the bulk specimen such as SEM/EBSD. Finally, the central layer of the bulk sample. TEMN SEM / EBSD XRD and neutron diffraction experiments both confirm this result.
【学位授予单位】：武汉科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1;TG156.5

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