The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes

The surface and subsurface conditions of components are critical for their functional properties. Every manufacturing process modifies the condition as a consequence its mechanical, chemical, thermal impact or combinations three. depth affected zone varies different machining operations is related to parameters characteristics. Furthermore, initial material state has decisive influence on modifications that lead final conditions. With this knowledge, collaborative research center CRC/Transregio 136 “Process Signatures” started first joint investigation analyze several uniformly premanufactured samples in broad study. present paper focusses four defined chains which were analyzed detail regarding resulting function state. Two workpiece geometries same (AISI 4140, 42CrMo4 (1.7225) classified according DIN EN ISO 683-2) treated two heat treating lines. Samples annealed ferritic-perlitic microstructure additionally deep rolled starting condition. Quenched tempered induction hardened before further application. These states then submitted six processes, i.e., grinding (with mainly mechanical impact), precision turning (mainly mechanical), laser processing thermal), electrical discharge (EDM, thermal) electrochemical (ECM, chemical impact). investigated after each step chain by specialized analysis techniques residual stresses, microstructure, hardness distribution. Based knowledge systematic characterizations, characteristics depths modifications, well underlying mechanisms causes, investigated. Mechanisms occurring within AISI 4140 steel (42CrMo4) due thermal, mixed impacts identified work hardening, stress relief, recrystallization, re-hardening melting, grain growth, rearrangement dislocations.