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

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 402
Author(s):  
Daniela Zander ◽  
Alexander Schupp ◽  
Oliver Beyss ◽  
Bob Rommes ◽  
Andreas Klink
Keyword(s):  
Sodium Nitrate ◽  
Mixed Oxide ◽  
Material Removal ◽  
Nitrate Solution ◽  
Electrochemical Machining ◽  
Metal Dissolution ◽  
Oxide Formation ◽  
Current Densities ◽  
Sodium Nitrate Solution ◽  
Anodic Metal Dissolution

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.

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

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2132
Author(s):  
Alexander Schupp ◽  
Oliver Beyss ◽  
Bob Rommes ◽  
Andreas Klink ◽  
Daniela Zander
Keyword(s):  
Mixed Oxide ◽  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Material Removal ◽  
Chemical Elements ◽  
Nitrate Solution ◽  
Electrochemical Machining ◽  
Process Efficiency ◽  
Negative Effect ◽  
Sodium Nitrate Solution

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.

Physico-chemical studies of DL-alanine in aqueous sodium nitrate solution

2015 ◽  
Vol 85 (1) ◽  
pp. 162-167 ◽  
Author(s):  
S. Roy ◽  
K. Mahali ◽  
S. Mondal ◽  
R. P. Mondal ◽  
B. K. Dolui
Keyword(s):  
Sodium Nitrate ◽  
Nitrate Solution ◽  
Aqueous Sodium ◽  
Physico Chemical ◽  
Chemical Studies ◽  
Sodium Nitrate Solution

Specific gravity of Opisthorchis viverrini eggs

1998 ◽  
Vol 72 (4) ◽  
pp. 359-361 ◽  
Author(s):  
T. Harnnoi ◽  
A. Wijit ◽  
N. Morakote ◽  
V. Pipitgool ◽  
W. Maleewong
Keyword(s):  
Specific Gravity ◽  
Sodium Nitrate ◽  
Gradient Centrifugation ◽  
Nitrate Solution ◽  
Opisthorchis Viverrini ◽  
Sedimentation Technique ◽  
Flotation Technique ◽  
Stool Specimens ◽  
Sodium Nitrate Solution ◽  
Human Stool

AbstractThe specific gravity of the eggs of the liver fluke Opisthorchis viverrini was determined using a sucrose gradient centrifugation and found to range from 1.2713 to 1.3043. The peak egg count was located at the sucrose fraction with a specific gravity of 1.2814. An attempt to float eggs in saturated sodium nitrate solution, sp.gr. 1.4, failed. Examination of human stool specimens for O. viverrini eggs by simple flotation in saturated sodium nitrate solution and the formol-ether sedimentation technique revealed that the flotation technique was not as efficient as the sedimentation technique. It was suggested that the flotation techniques were inappropriate for the detection of O. viverrini eggs in faeces or contaminated soil.

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