显微组织对0Cr13Ni5Mo不锈钢高周疲劳的影响机制

Influence of microstructure on high cycle fatigue damage behavior of 0Cr13Ni5Mo stainless steel

为揭示显微组织对低碳马氏体高强韧不锈钢疲劳损伤的影响规律,选取两种不同的工艺对0Cr13Ni5Mo钢(退火态)进行热处理:工艺1,淬火(1 050℃保温1 h,油冷)+回火(650℃保温2 h,空冷);工艺2,淬火(1 050℃保温1 h,油冷)+回火(700℃保温2 h,空冷)。用光学显微镜(OM)和电子显微镜(SEM)对不同热处理工艺下试板的显微组织、疲劳断口进行分析,通过拉伸、冲击和高周疲劳试验测试试板的力学性能。结果表明:两种热处理工艺下试板的组织均为板条状回火马氏体+逆变奥氏体+颗粒状碳化物,工艺2的显微组织中逆变奥氏体的量大大减少;试板经两种热处理后冲击功均大幅提升,工艺1试板的冲击功最大,为86 J,抗拉强度、屈服强度、高周疲劳极限均最高,分别为956.11、746.19、480 MPa;试样的S-N曲线在107周次左右时会出现平台,且当疲劳寿命小于107周次时,S-N曲线呈连续下降趋势,疲劳寿命随载荷的降低而增加;高周疲劳断口可以分为裂纹源区、裂纹扩展区和瞬断区。

In order to reveal the influence of microstructure on fatigue damage of low carbon martensite stainless steel with high strength,the 0Cr13Ni5Mo steel（annealed）was heated by two different heat treatment processes（process No.1：quenching（1050 ℃ for 1 h,oil cooled））＋tempering（650 ℃ for 2 h,air cooled）;process No.2：quenching（1 050 ℃ for 1 h,oil cooled））＋tempering（700 ℃ for 2 h,air cooled）. The microstructures of the test plates in different heat treatment processes were studied by means of optical microscope（OM）. Tensile,impact and high cycle fatigue tests were conducted to reveal the mechanical properties. High cycle fatigue fractograph was characterized by scanning electron microscope（SEM）. The results indicate that the microstructures of the test plates in different heat treatment processes are composed of striped tempered martensite＋reversed austenite＋granular carbides,and the content of reversed austenite in the trial plates under process No.2 is obviously reduced.The impact energy of the test plates in two different heat treatments is greatly increased compared with that of the base metal（annealed）. Compared with process No.2,the impact energy,tensile strength,yield strength and high cycle fatigue limit of the test plates in process No.1 are highest,the value is 86 J,956.11,746.19 and 480 MPa,respectively. In the 107 cycles,the platform will appear on the S-N curve of the plates. When the fatigue life is less than 107 cycles,the S-N curves show a continuous downward trend,and the fatigue life increases with the decrease of the load. In addition,the fatigue fracture can be divided into three regions：fatigue source zone,fatigue crack extension zone and transient fracture zone.