Improved fatigue behavior of low-carbon steel 20GL by applying ultrasonic impact treatment combined with the electric discharge surface alloying

详细信息    查看全文

• 作者：B.N. Mordyuk^a ; ^{mordyuk@imp.kiev.ua" class="auth_mail" title="E-mail the corresponding author} ; G.I. Prokopenko^a ; P.Yu. Volosevich^a ; L.E. Matokhnyuk^b ; A.V. Byalonovich^b ; T.V. Popova^c
• 关键词：Fatigue ; Low-carbon steel ; Chromium coating ; Electric discharge surface alloying ; Ultrasonic impact treatment
• 刊名：Materials Science & Engineering A
• 出版年：2016
• 出版时间：6 April 2016
• 年：2016
• 卷：659
• 期：Complete
• 页码：119-129
• 全文大小：3459 K

文摘

The effects of severe plastic deformation induced by ultrasonic impact treatment (UIT) and the electric discharge surface alloying (EDSA) with chromium on the stress-controlled fatigue response of low-carbon steel 20GL are studied. The surface microrelief and integrity were analyzed using light microscopy and scanning electron microscopy (SEM). The structural formations in the sub-surface layers were characterized by means of X-ray diffraction analysis and transmission electron microscopy (TEM). The steel specimens underwent UIT, and complex UIT+EDSA and UIT+EDSA+UIT processes demonstrate the fatigue strength magnitudes increased respectively by ~15, ~5 and ~30% on the base of 10⁷ cycles in comparison with that for the pristine specimen. SEM analysis of fracture surfaces reveals the subsurface crack nucleation in the UIT-processed specimens instead of superficial crack initiation observed in the pristine and EDSA-processed ones. TEM studies demonstrate that a dislocation-cell structure forms in ferrite grains and partial dissolution of cementite occurs in pearlite grains both at the surface after UIT and in the layer at a depth of 15–25 µm after the UIT+EDSA+UIT process. The enhanced fatigue strength and prolonged lifetime of the low-carbon steel specimens after UIT and UIT+EDSA+UIT processes are concluded to be associated with the subsurface crack nucleation achieved by the following factors: (i) minimized surface roughness and improved integrity of the modified layer; (ii) compressive residual stresses; and (iii) surface hardening coupled with the alloying by chromium and with the formation of the dislocation-cell structure containing the cell walls impenetrable to moving dislocations at cyclic loading.