超声滚压对LZ50钢疲劳性能及短裂纹行为的影响  

Effect of Ultrasonic Surface Rolling Processing on Fatigue Properties and Short Crack Behavior of LZ50 Steel

作　　者：宋江杰 杨冰[1] 周旻昊 肖守讷[1] 王明猛[1] 陈东东 SONG Jiangjie;YANG Bing;ZHOU Minhao;XIAO Shoune;WANG Mingmeng;CHEN Dongdong(State Key Laboratory of Traction Power,Southwest Jiaotong University,Chengdu 610031,China)

机构地区：[1]西南交通大学牵引动力国家重点实验室,成都610031

出　　处：《中国表面工程》2022年第6期98-106,共9页China Surface Engineering

基　　金：国家自然科学基金(51675446);四川省国际科技创新合作(2022YFH0075);牵引动力国家重点实验室自主课题(2022TPL-T03)资助项目。

摘　　要：针对超声滚压(USRP)对材料短裂纹行为影响规律不明的问题,对LZ50钢开展USRP试验,对比分析USRP对材料表面形貌、表层显微组织、表层显微硬度、残余应力分布和疲劳寿命的影响,并在340MPa应力水平下开展旋转弯曲复型试验,研究USRP对疲劳短裂纹萌生和扩展的影响。结果表明:USRP能使材料表面发生塑性变形,有效改善材料表面状态,降低表面粗糙度;处理后的LZ50钢表层铁素体、珠光体组织显微硬度平均值分别从200 HV和240 HV提升至304 HV和357 HV,表层残余压应力从-103 MPa提升至-720 MPa,且表层显微硬度和残余压应力沿深度方向呈梯度分布,影响层深约为300μm。在340MPa应力水平下,USRP试样平均疲劳寿命提升385.54%,疲劳短裂纹突破晶界障碍、珠光体带状组织,出现第一、第二次显著降速时的平均寿命分数f分别从0.068和0.469延后至0.172和0.604,短裂纹的萌生和扩展得到明显抑制与延缓。研究结果有助于明确USRP在抑制材料疲劳裂纹萌生与扩展上发挥的积极作用,可为工程材料表面强化工艺的选择提供参考。For the problem that the influence law of ultrasonic surface rolling processing(USRP)on short crack behavior of materials is unknown,USRP test is carried out on LZ50 steel.The effects of USRP on surface morphology,surface microstructure,surface microhardness,residual stress distribution and fatigue life are compared and analyzed.The effects of USRP on the initiation and propagation of short fatigue cracks are studied by replica test under 340 MPa rotating bending load.The results show that USRP causes plastic deformation on the material surface,and effectively improves the material surface state and reduces the surface roughness.After USRP,the microhardness of ferrite and pearlite on the surface of LZ50 axle steel increases from 200 HV and 240 HV to 304 HV and 357 HV,and the surface residual compressive stress increases from-103 MPa to-720 MPa,and the surface microhardness and residual compressive stress are gradient distributed along the depth direction,and the affected layer depth is about 300μm.Under the stress level of 340 MPa,the average fatigue life of the specimens after USRP is increased by 385.54%.When the short fatigue crack breaks through the grain boundary barrier and pearlite banded structure,the average life fraction f at the first and second deceleration is delayed from 0.068 and 0.469 to 0.172 and 0.604 respectively.The initiation and propagation of short fatigue cracks are restrained and delayed.The results are helpful to clarify the positive role of USRP in inhibiting fatigue crack initiation and propagation,and can provide reference for the selection of surface strengthening process of engineering materials.

关 键 词：LZ50钢 超声滚压 疲劳性能 疲劳短裂纹 

分 类 号：O346[理学—固体力学]