2015 Volume 64 Issue 11 Pages 853-858
The effects of fine particle peening (FPP) on the torsional fatigue properties were investigated in the case of a transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steel that has potential for use in precision gears. FPP resulted in a significant increase in the torsional fatigue limit of the TBF steel, compared with that of a quenched and tempered SNCM420 steel. An increase in the torsional fatigue limit was larger than that in the rotating bending fatigue limit. In addition, the crack growth rate and the threshold stress intensity range of this steel were lower and higher, respectively, than those of its SNCM420 counterpart. These differences resulted from the TBF steel having a higher (1) Vickers hardness, (2) compressive residual stress, and (3) volume fraction of untransformed retained austenite in the surface hardened layer, which suppressed crack initiation and extension.
