摘要
采用13%PAG(聚烷撑乙二醇)和油对60Si2Cr VAT弹簧钢进行淬火热处理,研究了不同淬火冷却速率对其轴向高周疲劳(r=-1)性能的影响。利用SEM、TEM和EBSD等方法对疲劳断口形貌、源区成分、显微组织进行表征。结果表明,13%PAG淬火后的疲劳极限(781.5 MPa)比油淬高67.5 MPa(714.0 MPa)。疲劳断口分析表明,疲劳破坏大部分起源于试样内部夹杂物和碳化物,形成"鱼眼"型撕裂的粒状亮区(GBF)。随裂纹源夹杂物处应力强度因子幅?Kinc的减小,疲劳寿命Nf增加,而GBF区边界的应力场强度因子幅?KGBF并不随Nf变化而改变,且13%PAG淬火试样的?KGBF大于油淬试样。实验钢13%PAG淬火试样组织中分布更多的纳米孪晶;马氏体板条块和板条更加细化,碳化物呈均匀细小弥散分布;而油淬碳化物较粗大,沿马氏体板条界和原奥氏体晶界分布。这些因素是PAG淬火后疲劳性能优于油淬的主要原因。
The effect of quench with two quenching media of 13% polyaleneglycol （PAG） and oil respectively on the high cycle fatigue behavior of spring steel 60Si2CrVAT was studied by applying alternatively uniaxial tension and compression. While the fatigue fractograph, source composition, microstructural evolution of the steel were examined by means of SEM, TEM and EBSD. The results indicate that the fatigue limit for the steel quenched with 13%PAG is 781.5 MPa; however that with oil is 714.0 MPa. Analysis results of fractograph show that fatigue damages mostly originate from the internal inclusions and carbides, while granular bright facets （GBF） are observed in the vicinity around the inclusions. Further investigation indicates that the stress intensity factor range at crack initiation site of inclusion ΔKinc trends to decrease gradually with increasing the fatigue life N1, while the stress factor range at GBF boundary ΔKGBF keeps almost constant with varying N1 and the ΔKGBF for the steel quenched with oil is smaller than that with 13% PAG. From microstructural observation results, it suggests that the beneficial effect on the fatigue property of the steel quenched with 13% PAG is caused by that there existed much more nanotwins, much finer individual lath and block, as well as finer carbides uniformly distributed in martensitic matrix for the steel quenched with 13% PAG rather than those with oil.
出处
《材料研究学报》
EI
CAS
CSCD
北大核心
2017年第1期65-73,共9页
Chinese Journal of Materials Research
基金
国家自然科学基金(51461006)
贵阳市科技支撑计划项目筑科合同(2013101)
贵州省科技重大专项(20146012)
贵州省重大专项黔科合(JZ[2014]2003)~~
作者简介
雷磊，男，1989年生，硕士
通讯作者,梁益龙，教授，liangyilong@126．com，研究方向为新型金属材料、材料强度与断裂及热加工装备
