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Mrs. Rebecca Strunk
Leibniz Institute for Materials Engineering - IWT

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0 residual stresses
0 surface integrity
0 Surface modifications
0 42CrMo4
0 Process Signature

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Journal article
Published: 10 July 2021 in Metals
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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.

ACS Style

Florian Borchers; Brigitte Clausen; Lisa Ehle; Marco Eich; Jérémy Epp; Friedhelm Frerichs; Matthias Hettig; Andreas Klink; Ewald Kohls; Yang Lu; Heiner Meyer; Bob Rommes; Sebastian Schneider; Rebecca Strunk; Tjarden Zielinski. The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes. Metals 2021, 11, 1102 .

AMA Style

Florian Borchers, Brigitte Clausen, Lisa Ehle, Marco Eich, Jérémy Epp, Friedhelm Frerichs, Matthias Hettig, Andreas Klink, Ewald Kohls, Yang Lu, Heiner Meyer, Bob Rommes, Sebastian Schneider, Rebecca Strunk, Tjarden Zielinski. The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes. Metals. 2021; 11 (7):1102.

Chicago/Turabian Style

Florian Borchers; Brigitte Clausen; Lisa Ehle; Marco Eich; Jérémy Epp; Friedhelm Frerichs; Matthias Hettig; Andreas Klink; Ewald Kohls; Yang Lu; Heiner Meyer; Bob Rommes; Sebastian Schneider; Rebecca Strunk; Tjarden Zielinski. 2021. "The Influence of Former Process Steps on Changes in Hardness, Lattice and Micro Structure of AISI 4140 Due to Manufacturing Processes." Metals 11, no. 7: 1102.

Journal article
Published: 04 May 2021 in Materials
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To generate advanced properties for the wear resistance and fatigue life of components and allow for an improved, application-oriented development of part specifications, a precisely tailored initial machining or manufacturing process is necessary. In addition, it is important to know how subsequent machining steps or operational loads affect the components’ condition. Residual stresses are a meaningful measurand for evaluating the modifications that a machining process induces into the material. The desired modifications should be specified regarding the final state for the required operational behavior. Thus, the stability of the modifications can be considered so that they can be beneficial in service. This investigation is part of fundamental research in the field of the Collaborative Research Center (CRC) “Process Signatures”. By applying defined selected loads, the effects on machined surface layers are investigated since machined components are exposed to further loads during use. For this reason, experimental process chains are applied in this work to grind-strengthened specimens as possible application cases and corresponding loads. These experimental process chains consist of defined mechanical and thermal loads, which are applied to the specimens using a thermal and mechanical testing system. Furthermore, it is investigated how these additional loads affect the modifications previously introduced by the grinding process. The influence of the additional loads is evaluated by using radiographic and electron microscopic examinations. It can be observed that the sequence, as well as the type of the applied loads, play a significant role in the development of the modifications.

ACS Style

Rebecca Strunk; Florian Borchers; Brigitte Clausen; Carsten Heinzel. Influence of Subsequently Applied Mechanical and Thermal Loads on Surfaces Ground with Mechanical Main Impact. Materials 2021, 14, 2386 .

AMA Style

Rebecca Strunk, Florian Borchers, Brigitte Clausen, Carsten Heinzel. Influence of Subsequently Applied Mechanical and Thermal Loads on Surfaces Ground with Mechanical Main Impact. Materials. 2021; 14 (9):2386.

Chicago/Turabian Style

Rebecca Strunk; Florian Borchers; Brigitte Clausen; Carsten Heinzel. 2021. "Influence of Subsequently Applied Mechanical and Thermal Loads on Surfaces Ground with Mechanical Main Impact." Materials 14, no. 9: 2386.

Journal article
Published: 05 July 2020 in Metals
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The surface and subsurface conditions of components are significant for their functional properties. Every manufacturing process step changes the surface condition due to its mechanical, chemical and/or thermal impact. The depth of the affected zone varies for different machining operations, and is predetermined by the process parameters and characteristics. Furthermore, the initial state has a decisive influence on the interactions that lead to the final surface conditions. The aim of the investigation presented here is to compare the influence of the load characteristics over the depth applied to manufactured components by several different machining operations and to determine the causing mechanisms. In order to ensure better comparability between the surface modifications caused by different machining operations, the same material was used (AISI 4140; German steel grade 42CrMo4 acc. to DIN EN 10083-3) and annealed to a ferritic-pearlitic microstructure. Based on interdisciplinary cooperation within the collaborative research center CRC/Transregio 136 “Process Signatures”, seven different manufacturing processes, i.e., grinding, turning, deep rolling, laser processing, inductive heat treatment, electrical discharge machining (EDM) and electrochemical machining (ECM), were used, and the resulting surface zones were investigated by highly specialized analysis techniques. This work presents the results of X-ray measurements, hardness measurements and electron microscopic investigations. As a result, the characteristics and depths of the material modifications, as well as their underlying mechanisms and causes, were studied. Mechanisms occurring within 42CrMo4 steel due to thermal, mechanical, chemical or mixed impacts were identified as phase transformation, solidification and strengthening due to dislocation generation and accumulation, continuum dynamic recrystallization and dynamic recovery, as well as chemical reactions.

ACS Style

Florian Borchers; Brigitte Clausen; Sandro Eckert; Lisa Ehle; Jeremy Epp; Simon Harst; Matthias Hettig; Andreas Klink; Ewald Kohls; Heiner Meyer; Markus Meurer; Bob Rommes; Sebastian Schneider; Rebecca Strunk. Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth. Metals 2020, 10, 895 .

AMA Style

Florian Borchers, Brigitte Clausen, Sandro Eckert, Lisa Ehle, Jeremy Epp, Simon Harst, Matthias Hettig, Andreas Klink, Ewald Kohls, Heiner Meyer, Markus Meurer, Bob Rommes, Sebastian Schneider, Rebecca Strunk. Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth. Metals. 2020; 10 (7):895.

Chicago/Turabian Style

Florian Borchers; Brigitte Clausen; Sandro Eckert; Lisa Ehle; Jeremy Epp; Simon Harst; Matthias Hettig; Andreas Klink; Ewald Kohls; Heiner Meyer; Markus Meurer; Bob Rommes; Sebastian Schneider; Rebecca Strunk. 2020. "Comparison of Different Manufacturing Processes of AISI 4140 Steel with Regard to Surface Modification and Its Influencing Depth." Metals 10, no. 7: 895.

Journal article
Published: 31 May 2020 in Procedia CIRP
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Since the term surface integrity was introduced in 1964 by Field and Kahles, the final processing step and its influence on the surface microstructure was heavily investigated. In particular, a lot of research on the surface microstructure and its connection to the functional properties of the workpiece like life time and wear resistance has been performed. However, the influence of the process chain on the final surface microstructure of the workpiece was in industrial applications most of the time not taken into account, although the former manufacturing steps do affect the final result. In this work, samples of ferrite-perlite 42CrMo4 steel (AISI 4140) were first processed by grinding with mechanical main impact (grind-strengthening) and then mechanically, thermally and thermo-mechanically treated to investigate the change in the microstructure depending on the chosen process chain. Electron backscatter diffraction (EBSD) measurements as well as backscatter electron images (BSE), secondary electron images (SE), energy dispersive spectroscopy (EDX) and transmission electron microscopy (TEM) were used to characterize the change in the surface modifications. The first applied grind-strengthening process caused a heavily deformed surface zone of ~4 µm with nano-crystalline grains and high dislocation densities in the following ~10 µm. Thermal treatment resulted in grain growth and dislocation annihilation due to static recrystallization whereas mechanical treatment either increased the dislocation density further or decreased the dislocation density by annihilation of dislocations and dislocation rearrangement. Thermo-mechanical treatment resulted in small equiaxed grains in the surface zone. Cementite lamellae of perlite grains were deformed, partly dissolved and formed spherical carbides at grain boundaries in the surface zone for all process chains including thermal treatment.

ACS Style

Lisa C. Ehle; Rebecca Strunk; Florian Borchers; Alexander Schwedt; Brigitte Clausen; Joachim Mayer. Influence of process chains with thermal, mechanical and thermo-mechanical impact on the surface modifications of a grind-strengthened 42CrMo4 steel. Procedia CIRP 2020, 87, 426 -431.

AMA Style

Lisa C. Ehle, Rebecca Strunk, Florian Borchers, Alexander Schwedt, Brigitte Clausen, Joachim Mayer. Influence of process chains with thermal, mechanical and thermo-mechanical impact on the surface modifications of a grind-strengthened 42CrMo4 steel. Procedia CIRP. 2020; 87 ():426-431.

Chicago/Turabian Style

Lisa C. Ehle; Rebecca Strunk; Florian Borchers; Alexander Schwedt; Brigitte Clausen; Joachim Mayer. 2020. "Influence of process chains with thermal, mechanical and thermo-mechanical impact on the surface modifications of a grind-strengthened 42CrMo4 steel." Procedia CIRP 87, no. : 426-431.

Article
Published: 06 June 2018 in Metallurgical and Materials Transactions A
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The newly proposed concept of Process Signatures enables the comparison of seemingly different manufacturing processes via a process-independent approach based on the analysis of the loading condition and resulting material modification. This contribution compares the recently published results, based on numerically achieved data for the development of Process Signatures for sole surface and volume heatings without phase transformations, with the experimental data. The numerical approach applies the moving heat source theory in combination with energetic quantities. The external thermal loadings of both processes were characterized by the resulting temperature development, which correlates with a change in the residual stress state. The numerical investigations show that surface and volume heatings are interchangeable for certain parameter regimes regarding the changes in the residual stress state. Mainly, temperature gradients and thermal diffusion are responsible for the considered modifications. The applied surface- and volume-heating models are used in shallow cut grinding and induction heating, respectively. The comparison of numerical and experimental data reveals similarities, but also some systematic deviations of the residual stresses at the surface. The evaluation and final discussion support the assertion for very fast stress relaxation processes within the subsurface region. A consequence would be that the stress relaxation processes, which are not yet included in the numerical models, must be included in the Process Signatures for sole thermal impacts.

ACS Style

Friedhelm Frerichs; Heiner Meyer; Rebecca Strunk; Benjamin Kolkwitz; Jeremy Epp. Development of a Process Signature for Manufacturing Processes with Thermal Loads. Metallurgical and Materials Transactions A 2018, 49, 3419 -3429.

AMA Style

Friedhelm Frerichs, Heiner Meyer, Rebecca Strunk, Benjamin Kolkwitz, Jeremy Epp. Development of a Process Signature for Manufacturing Processes with Thermal Loads. Metallurgical and Materials Transactions A. 2018; 49 (8):3419-3429.

Chicago/Turabian Style

Friedhelm Frerichs; Heiner Meyer; Rebecca Strunk; Benjamin Kolkwitz; Jeremy Epp. 2018. "Development of a Process Signature for Manufacturing Processes with Thermal Loads." Metallurgical and Materials Transactions A 49, no. 8: 3419-3429.