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Deep ro lling processes initiate p lastic deformat ions in the surface layer. The local characteristics of deformat ion are dependent on the induced stress expressed by the local stress tensor. Equivalent stresses above yield strength cause plastic deformat ion. Additionally the intrinsic energy, e. g. the dislocation density, is enhanced and the residual stress state is changed. The effects to a deep rolled surface from an increase in temperature are mainly dependent on the material, the microstructure, the initial residual stress state, the inclusion density, the distribution of soluted alloying elements and the plastic deformat ion. In the described experiments the interactions between deformation and temperature of the steel grade AISI 4140 (42 CrMo 4) used for all further experiments in a transregional Collaborative Research Center (CRC) were to be examined. The most simple investigation methods were chosen deliberately to allow a better statistical support of correlations between introduced strains and material react ions for a wide variat ion of process parameters. Since the visual effects by light microscopy in AISI 4140 were very s mall, the experiments were repeated with german grade 18 CrNiMo 7-6 (comparable to AISI 4820). Th is paper focuses on the micro structural changes in defined deep ro lled surface regions due to an increase in temperature. The work described is part of the Collaborative Research Center “Process Signatures”, collaboration between Bremen University, Technical University Aachen, Germany and Oklahoma State University Stillwater, USA.

Structural Changes in the Surface Layer of Deep Rolled Samples Due to Thermal Loads