Effects of fine particle peening on fatigue strength of a TRIP-aided martensitic steel

• Published in: International journal of fatigue 2017-07, Vol.100, p.206-214
• Main Authors: Sugimoto, Koh-ichi, Mizuno, Yuta, Natori, Masahiro, Hojo, Tomohiko
• Format: Article
• Language: English
• Subjects: Fatigue strength; Fine particle peening; Residual stress; Retained austenite; TRIP steel
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2017.03.022

Fine particle peening increased fatigue limits and lowered notch sensitivity of a TRIP-aided martensitic steel. It also increased the threshold stress intensity factor range in stage I, and decreased the crack propagation rate in stage II in the steel. [Display omitted] The effects of fine particle peening on the fatigue properties of a transformation-induced plasticity-aided martensitic steel with a chemical composition of 0.2% C, 1.5% Si, 1.5% Mn, 1.0% Cr, and 0.05% Nb (mass%) were investigated for applications in precision gears. When this steel was subjected to fine particle peening after heat treatment, higher fatigue limits and lower notch sensitivity were achieved compared with those of SNCM420 martensitic steel. The increased fatigue limits are principally associated with higher hardness and compressive residual stress on and just below the surface, as well as low surface roughness. Fine particle peening also increased the threshold stress intensity factor range in stage I, and decreased the crack propagation rate in stage II in this steel. The crack propagation behavior was mainly suppressed by (1) high hardness and high compressive residual stress, and (2) the strain-induced martensite transformation of retained austenite and high internal stress resulting from a difference in flow stress between the soft martensite matrix and the finely dispersed hard MA-like phase that developed during fatigue deformation.