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渗碳20CrMnMoAl钢表面硬贝氏体的制备及其组织特征

期刊名称：金属学报
时间：0
页码：1038-1045
语言：中文
分类：TG142.1[金属学及工艺—金属材料;一般工业技术—材料科学与工程;金属学及工艺—金属学]
作者机构：[1]燕山大学亚稳材料制备技术与科学国家重点实验室,秦皇岛066004
相关基金：国家杰出青年科学基金项目50925522,国家自然科学基金项目50871094和50821001及河北省杰出青年基金项目E2009001632资助
相关项目：厚板和锻件用纯净高强度准贝氏体钢中氢扩散与氢脆机理

关键词：硬贝氏体, 渗碳, 等温淬火, 低碳钢, hard bainite, carbonization, austempering, low carbon steel

中文摘要：

在渗碳20CrMnMoAl钢表面通过热处理获得了硬贝氏体组织,对其组织结构特征进行了研究.首先,利用自行设计的滴注式可控气氛全自动渗碳炉,在930℃对20CrMnMoAl钢渗碳处理8 h,使钢表面的C含量达到0.81%（质量分数）.将经过渗碳处理的试样在930℃保温20 min进行奥氏体化处理,然后淬入温度分别为220,250和300℃的盐浴中,并分别保温0.5—50 h后空冷.利用OM,TEM,XRD及显微硬度计对热处理后渗碳层的组织和性能进行分析研究.结果表明,该钢经过220和250℃保温一定时间后,试样表层为超细硬贝氏体,由平均尺寸为70—100 nm的贝氏体层片和分布于片间平均厚度为几纳米到几十纳米的残余奥氏体膜组成,试样表面硬度达到630HV;试样心部是低碳板条马氏体;过渡层是硬贝氏体和低碳马氏体的混合组织.

英文摘要：

A new technology was developed based on carburization and succedent low-temperature austempering to produce hard bainitic microstructure in the surface layer of low-carbon steel 20CrMnMoAl.The microstructure and property of the hard bainite were investigated.The samples were carburized in a gas carburizing furnace at 930℃ for 8 h.The carbon content in the surface layer increased to 0.81%（mass fraction） after carburization.The carbonized samples were heated at 930℃ for austenitization and then isothermally quenched at different temperatures in salt bath.The microstructures were investigated by OM,TEM and XRD,and the hardness was tested by HV-sclerometer.The results show that for the samples which were isothermally quenched at 220 and 250℃ultrafine hard bainite was obtained in the surface layer with a hardness of 630 HV.The plate of ultrafine bainitic ferrite was as thin as 70 nm and film of retained austenite had a thickness of several nanometers.Low carbon lath martensite was obtained in the center and mixstructures of the ultrafine bainite and low carbon martensite in the transition layer.