不同应力比下沉淀硬化不锈钢的超高周疲劳断裂机制  

Ultra-high Cycle Fatigue Fracture Mechanism of a Precipitation Hardening Stainless Steel at Different Stress Ratios

作　　者：冯博[1] 李煜佳[1] 梅林波 轩福贞[1] 

机构地区：[1]华东理工大学、承压系统与安全教育部重点实验室,上海200237 [2]上海电气电站设备有限公司上海汽轮机厂,上海200240

出　　处：《机械工程材料》2017年第3期29-32,38,共5页Materials For Mechanical Engineering

基　　金：国家自然科学基金资助项目(51325504)

摘　　要：在100℃含氧量小于1mg·L^(-1)的饱和蒸汽环境中,对Custom 450沉淀硬化型不锈钢在三种应力比(-1,-0.6,0.1)下进行了轴向等幅力控制的超高周疲劳试验,观察了疲劳断口形貌并研究了其疲劳断裂机制。结果表明:试验钢的S-N曲线没有水平段,始终保持下降趋势,其疲劳极限消失;疲劳断口呈现从表面缺陷、内部夹杂物和内部结构不连续三个位置处形成裂纹源的起裂模式;随着应力比的提高,表面形成裂纹源的概率增大,内部形成裂纹源的概率降低。In the saturated steam with oxygen content less than 1 mg· L -1 at 100℃, axial constant-amplitude force controlled fatigue tests were conducted on the precipitation hardening stainless steel Custom 450 with three stress ratios （-1, -0. 6, 0.1）. The fatigue fracture morphology was observed, and the ultra-high cycle fatigue fracture mechanism was investigated. The results show that the S-N curves of the tested steel presented a continuous decline shape without a horizontal asymptote, indicating that the tested steel had no fatigue limit. Three crack initiation patterns, namely forming crack sources at surface defects, internal inclusions and internal defects, were observed on the fracture surfaces. With the increase of stress ratio, the probability of the surface crack initiation increased while that of the internal crack initiation decreased.

关 键 词：沉淀硬化不锈钢 超高周疲劳 S-N曲线 疲劳断裂机制 

分 类 号：TB301[一般工业技术—材料科学与工程]