Shot peening of TWIP steel - influence on mechanical properties

Author:  C. Teichmann and L. Wagner
Source:  Conf Proc 2014: ICSP-12 Goslar, Germany (pgs.499-503)
Doc ID:  2014127
Year of Publication:  2014
Abstract:  
TWIP-steel with high manganese content of 15% was shot peened using an injector type facility. The peening media was spherically conditioned cut wire (SCCW14} and the peening pressure was changed resulting in various Almen intensities ranging from 0.15 mmA to 0.30 mmA. The influence on hardness, residual stresses and fatigue performance was studied. A marked enhancement in hardness could be achieved by shot peening. While peening with 0, 15 mmA already results in an increase of surface hardness from about 250 to about 470 HV0.1, peening at 0.22 mmA achieved an even higher hardness of up to 520 HV0.1. Highest hardness of about 550 HV0.1 was found after peening with 0.30 mmA. The residual stress measurements were carried out using the incremental hole drilling technique. The amount of residual compressive stresses can be increased by rising the Almen intensity. While the maximum values of the residual compressive stresses in specimens peened at 0.15mmA and 0.22mmA Almen intensities were about the same, the penetration depths differed. Whereas increasing the Almen intensity from 0,22mmA to 0,30mmA does not further increase the penetration depth the maximum compressive stresses significantly increase. Shot peening was found to increase the fatigue strength in rotating beam loading from 400 to 610 MPa. Presumably, the extraordinary high enhancement of surface hardness and fatigue performance due to shot peening results not only from the pronounced twinning induced plasticity but also from a phase transformation observed by optical microscopy.