Influence of process chains with thermal, mechanical and thermo-mechanical impact on the surface modifications of a grind-strengthened 42CrMo4 steel

Influence of Subsequently Applied Mechanical and Thermal Loads on Surfaces Ground with Mechanical Main Impact

“…A comparison clearly shows that the residual stresses at the surface are reduced or rearranged, but the FWHM at the surface are not affected. This indicates that reduction of the residual stresses might be caused by a rearrangement of dislocations as the sub-grain boundaries are sharper in case of the application of σ maxFP (see Ehle et al [ 8 ]). On the other hand, the FWHM seems less affected because the microstructural differences at the surface are not very pronounced [ 8 ] although the residual stresses are reduced.…”

“…After relief, the plastically deformed (“longer”) core elongates elastically the surface layer and therefore relaxes the compressive residual stresses. In the FP-condition, according to Ehle et al [ 8 ], the dislocation density within the subgrains is reduced which indicates the occurrence of dynamic recovery as an additional mechanism behind the reduction of the residual stresses. The QT-condition has a higher dislocation density due to the heat treatment, which is further increased by grind-hardening.…”

“…The differences in the residual stress states of the two microstructures are not very pronounced. Dynamic recrystallization is the predominant mechanism, as shown in the investigations of Ehle et al [ 8 ].…”

“…This approach allowed a higher magnified view on the microstructure. More detailed investigations of the specimens in FP-condition can be found in Ehle et al [ 8 ].…”

“…The investigated material is AISI4140 (42CrMo4) German-grade steel. The microstructural changes of the ferritic-perlitic annealed specimens of this investigation are discussed intensely by Ehle et al [ 8 ].…”