Influence of shot peening on the fatigue life of Cu-Ni austempered ductile iron

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• 作者：A. Zammit^a ; ^{ann.t.triccas@um.edu.mt} ; M. Mhaede^b ; M. Grech^a ; S. Abela^a ; L. Wagner^b
• 关键词：Austempered ductile iron ; Fatigue behaviour ; Shot peening
• 刊名：Materials Science and Engineering ; A
• 出版年：2012
• 期刊代码：61_09215093
• 类别：ms
• 出版时间：30 May, 2012
• 卷：545
• 期：Complete
• 页码：78-85
• 文件大小：2730 K

摘要

Shot peening (SP) was carried out in order to improve the fatigue life of an austempered ductile iron alloyed with copper and nickel austenitised at 900 掳C for 2 h and austempered at 360 掳C for 1 h. The optimal peening intensity using S330 steel shot, was found to be 0.38 mmA producing residual compressive stresses with a maximum of approximately 1000 MPa at the surface. The microhardness at the surface was increased by SP from 370 to 535 HV. The fully reversed fatigue tests of SP-specimens showed a 61%increase in fatigue life over that of polished samples. The improvement in fatigue life is explained by the compressive residual stresses in the near surface shifting crack initiation to sub-surface. Fractography analysis showed multiple crack nucleation sites at the surface for the polished specimens, while SP-specimens showed sub-surface crack nucleation. In addition, a mixed fracture mode was also identified, with the graphite nodules and copper islands affecting crack propagation.