Impact of rim zone modifications on the surface finishing of ferritic–pearlitic 42CrMo4 using electrochemical machining

Zander, Daniela; Schupp, Alexander; Mergenthaler, Stefanie; Pütz, René Daniel; Altenbach, Christoph

doi:10.1002/maco.202012213

Cited by 3 publications

(4 citation statements)

References 36 publications

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“…It is assumed that the increased carbide density at the surface of the ferritic–pearlitic 42CrMo4 leads to a lower charge yield compared to the carbide-poor, martensitic 42CrMo4 due to an increased oxygen evolution. In contrast to Haisch et al [ 8 , 17 , 22 ] it is considered that the cementite phase is not electrochemically inert, but dissolves significantly slower than the ferritic phase [ 23 , 24 , 25 , 26 ]. Taking into account that the XPS measurements ( Figure 9 ) showed no enrichment of the rim zone with carbides for ECM-B, also the thickness of the mixed oxide layer has to be considered.…”

Section: Discussionmentioning

confidence: 99%

“…The quotient of the real and the idealized material removal is thereby defined as the charge yield η. η is thus an important measure of the efficiency of material removal. The calculation of η and the idealized mass removal via Faraday’s law has already been described in a previous publication in more detail [ 26 ].…”

Section: Methodsmentioning

confidence: 99%

“…However, an enhanced selective dissolution of the ferrite phase compared to the cementite phase was also demonstrated by Klocke et al [ 23 , 24 ] and Harst [ 25 ]. The investigations of Zander et al [ 26 ] of ground, ferritic–pearlitic 42CrMo4 compared to EDM-processed (electrical discharge machining), partially austenitic 42CrMo4 revealed a lower material removal efficiency for the ground ferritic–pearlitic compared to the partially austenitic steel. This also was associated to the stronger oxygen reaction related to the cementite.…”

Section: Introductionmentioning

confidence: 99%

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Insights on the Influence of Surface Chemistry and Rim Zone Microstructure of 42CrMo4 on the Efficiency of ECM

et al. 2021

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The electrochemical machining (ECM) of 42CrMo4 steel in sodium nitrate solution is mechanistically characterized by transpassive material dissolution and the formation of a Fe3−xO4 mixed oxide at the surface. It is assumed that the efficiency of material removal during ECM depends on the structure and composition of this oxide layer as well as on the microstructure of the material. Therefore, 42CrMo4 in different microstructures (ferritic–pearlitic and martensitic) was subjected to two ECM processes with current densities of about 20 A/cm2 and 34 A/cm2, respectively. The composition of the process electrolyte was analyzed via mass spectrometry with inductively coupled plasma in order to obtain information on the efficiency of material removal and the reaction mechanisms. This was followed by an X-ray photoelectron spectroscopy analysis to detect the chemical composition and the binding states of chemical elements in the oxide formed during ECM. In summary, it has been demonstrated that the efficiency of material removal in both ECM processes is about 5–10% higher for martensitic 42CrMo4 than for ferritic–pearlitic 42CrMo4. This is on one hand attributed to the presence of the cementite phase at ferritic–pearlitic 42CrMo4, which promotes oxygen evolution and therefore has a negative effect on the material removal efficiency. On the other hand, it is assumed that an increasing proportion of Fe2O3 in the mixed oxide leads to an increase in the process efficiency.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Insights on the Influence of Surface Chemistry and Rim Zone Microstructure of 42CrMo4 on the Efficiency of ECM

et al. 2021

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“…The high flow of electrolytic solution is also used for the metal dissolution process, which serves as a conductive medium. The anodic metal ions are usually observed to dissolve under the region of low potential difference (2-25V) between the electrodes [4][5]. Intrinsic ionic charges of the electrolytes generally compensated the movement of ions from anodic-metal surfaces to the cathode tool according to Faraday's law of electrolysis [6][7].…”

Section: Introductionmentioning

confidence: 99%

Study of anodic dissolution of 100Cr6 Steel during electrochemical machining in oxidizing and reducing electrolytic environments.

Upadhyay

Chakraborty²,

Majhi³

et al. 2023

Preprint

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Electrochemical machining (ECM) has been widely recognized as a promising technique that plays an important role in the fabrication of micro textured surfaces of engineering materials. The advantageous features of ECM, like high material removal rate (MRR) and surface finish, have been found effective to improve the efficiency of machining components compared to the other processes. However, the machining precision of ECM has still limited due to the formation of a passive adherent oxide layer over the specimen surface. These factors adversely affect the MRR and surface roughness (Ra). The high current density (20-150 A/cm2) can be used to enhance the MRR, but the process becomes vulnerable to energy consumption, resulting in poor surface finish. These limitations of ECM can be minimized by employing a suitable electrolytic environment. This paper shows the anodic dissolution characteristics of 100Cr6 Steel in oxidizing and reducing electrolytic solutions. The reducing electrolyte containing CuSO4 mixed NaCl that maintains the low valence state of substrate metal ion which, in turn, facilitates higher MRR and improves the surface finish quality. Similarly, the oxidizing electrolytic solution composed of K2Cr2O7 mixed with NaCl allows higher anodic dissolution but ensuing Cr2O7—ion form a passive layer on the metal surfaces. In two different electrolytic environments, transpassive anodic dissolution was found to occur. Comparable dissolution mechanisms have been studied using cyclic voltammetry (CV) technique and UV-visible spectrophotometry. Micro-images of scanning electron microscopy (SEM) emphasize that metal surfaces are exposed more in existing oxidizing environments and less in reducing environments.

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Oxide Formation during Transpassive Material Removal of Martensitic 42CrMo4 Steel by Electrochemical Machining

et al. 2021

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The efficiency of material removal by electrochemical machining (ECM) and rim zone modifications is highly dependent on material composition, the chemical surface condition at the break through potential, the electrolyte, the machining parameters and the resulting current densities and local current density distribution at the surfaces. The ECM process is mechanistically determined by transpassive anodic metal dissolution and layer formation at high voltages and specific electrolytic compositions. The mechanisms of transpassive anodic metal dissolution and oxide formation are not fully understood yet for steels such as 42CrMo4. Therefore, martensitic 42CrMo4 was subjected to ECM in sodium nitrate solution with two different current densities and compared to the native oxide of ground 42CrMo4. The material removal rate as well as anodic dissolution and transpassive oxide formation were investigated by mass spectroscopic analysis (ICP-MS) and (angle-resolved) X-ray photoelectron spectroscopy ((AR)XPS) after ECM. The results revealed the formation of a Fe3−xO4 mixed oxide and a change of the oxidation state for iron, chromium and molybdenum, e.g., 25% Fe (II) was present in the oxide at 20.6 A/cm2 and was substituted by Fe (III) at 34.0 A/cm2 to an amount of 10% Fe (II). Furthermore, ECM processing of 42CrMo4 in sodium nitrate solution was strongly determined by a stationary process with two parallel running steps: 1. Transpassive Fe3−xO4 mixed oxide formation/repassivation; as well as 2. dissolution of the transpassive oxide at the metal surface.

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Impact of rim zone modifications on the surface finishing of ferritic–pearlitic 42CrMo4 using electrochemical machining

Cited by 3 publications

References 36 publications

Insights on the Influence of Surface Chemistry and Rim Zone Microstructure of 42CrMo4 on the Efficiency of ECM

Insights on the Influence of Surface Chemistry and Rim Zone Microstructure of 42CrMo4 on the Efficiency of ECM

Study of anodic dissolution of 100Cr6 Steel during electrochemical machining in oxidizing and reducing electrolytic environments.

Oxide Formation during Transpassive Material Removal of Martensitic 42CrMo4 Steel by Electrochemical Machining

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