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

Metals

Yang Lu¹  Lisa C. Ehle²  Bob Rommes³  Andreas Klink³  Sebastian Schneider³  Heiner Meyer⁴  Ewald Kohls⁴  Jérémy Epp⁴  Florian Borchers⁴  Tjarden Zielinski⁴  Friedhelm Frerichs⁴  Rebecca Strunk⁴  Marco Eich⁴  Brigitte Clausen⁵  Matthias Hettig⁵ 

[1] BIAS—Bremer Institut für Angewandte Strahltechnik GmbH, 28359 Bremen, Germany;Gemeinschaftslabor für Elektronenmikroskopie (GFE), RWTH Aachen University, 52062 Aachen, Germany;Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University, 52062 Aachen, Germany;Leibniz-Institute for Materials Engineering, IWT, 28359 Bremen, Germany;MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany;

关键词: surface integrity;    influencing depth;    XRD;    SEM;    EBSD;    hardness;   

DOI  :  10.3390/met11071102

来源: DOAJ

【 摘 要 】

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

【 授权许可】

Unknown