scholarly journals Deterioration of surface layers of tungsten and steel-containing materials in current collection sliding against molybdenum

2021 ◽  
Vol 64 (2) ◽  
pp. 122-128
Author(s):  
M. I. Aleutdinova ◽  
V. V. Fadin
Keyword(s):  
Electrical Conductivity ◽  
Iron Oxides ◽  
Electrical Contact ◽  
Bearing Steel ◽  
Wear Intensity ◽  
Oxide Content ◽  
Molybdenum Oxides ◽  
Sliding Surface ◽  
Surface Layers ◽  
Current Collection

The possibility of improving the characteristics of a dry sliding electrical contact with a current density higher than 100 A/cm2 by using a molybdenum counterbody is considered. It is shown that tungsten or metallic materials containing bearing steel (1.5 % Cr) in sliding against molybdenum at a speed of 5 m/s under electric current, forms a contact with low electrical conductivity and high wear intensity. This observation served as the basis of this work. Using optical and electron microscopy of sliding surfaces it was found that strong adhesion in the interface was the main reason for rapid surface layers deterioration and high wear intensity. A well-known statement was taken into account that adhesion is due to the low oxide content between the contact surfaces. Visual study of molybdenum sliding surface made it possible to establish formation of a thin transfer layer and absence of traces of oxide formation. The same was observed on sliding surface of tungsten that was caused by high temperature of tungsten and molybdenum oxides formation. A layer of iron oxides was observed on sliding surface of steel containing materials. In addition, traces of a thin tribolayer were find out. An increase in concentration of steel in the primary structure led to a slight increase in iron oxides on the sliding surface, but did not lead to a significant increase in electrical conductivity and wear resistance of the contact. Unsatisfactory characteristics of the contact allowed us to conclude that it is impossible to significantly improve sliding parameters with current collection against molybdenum and inappropriateness of its use as a counterbody for these conditions.

Wear behaviour of metals in dry sliding against molybdenum with current collection

2020 ◽  
pp. 118-125
Author(s):  
M. I. Aleutdinova ◽  
V. V. Fadin
Keyword(s):  
Electrical Conductivity ◽  
Electrical Contact ◽  
Wear Behaviour ◽  
High Wear Resistance ◽  
Dry Sliding ◽  
High Electrical Conductivity ◽  
Current Collection ◽  
Ferrous Metals ◽  
Non Ferrous Metals ◽  
Sliding Electrical Contact

The possibility of high electrical conductivity of dry sliding electrical contact against molybdenum counterbody was studied. It was found that metals W and Cu were not able to form a sliding electrical contact with high wear resistance at current density higher 100 A/cm2 . The characteristics of the contacts of iron containing metals were slightly better than the contact characteristics of non-ferrous metals due to weaker adhesion. Using X-ray phase analysis, it was shown the absence of oxides in the sliding zone of non-ferrous metals. This led to their strong wear and contact’s low electrical conductivity. In the contact zone of iron containing samples the formation of FeO was observed that made it possible to reduce wear. This means that high electrical conductivity is unattainable in sliding with current collection against molybdenum.

scholarly journals CHARACTERISTICS OF DRY SLIDING ELECTRIC CONTACT OF METALS IN CONDITIONS OF CATASTROPHIC WEARING

2019 ◽  
Vol 62 (2) ◽  
pp. 103-108 ◽  
Author(s):  
M. I. Aleutdinova ◽  
V. V. Fadin
Keyword(s):  
Current Density ◽  
Niti Alloy ◽  
Wear Intensity ◽  
Contact Temperature ◽  
Structural Defects ◽  
Dry Sliding ◽  
Sliding Surface ◽  
Surface Layers ◽  
Strong Adhesion ◽  
Steel 1020

The authors have studied the relation between wear intensity, average contact temperature and phase composition of the surface layers ofAISI 1020 steel, copper and NiTi alloy in dry sliding against the steel counterbody under electric current of density higher than 100  A/cm2 . These contact characteristics are considered carefully at the beginning of catastrophic wear, when the surface layers transit to the utmost state. It was noted that relaxation of stresses in the surface layers was due to the structural transformation in normal wear regime. It leads to tribolayers formation. The high strength of the copper tribolayer is first of all due to the formation of FeO oxide on the sliding surface, which prevents adhesion in contact. In addition, signs of a  liquid phase were observed on the copper contact surface. It promoted the low rate of formation and accumulation of structural defects. Emergence of areas of melt and FeO oxide on the sliding surface provides high contact wear resistance. These factors, combined with the high thermal copper conductivity, have caused the tribolayer transition to the limit state at high current density and low contact temperature. The absence of oxides on the sliding surface of the NiTi alloy has caused strong adhesion in the contact, high rate of formation and accumulation of structural defects. Therefore, the tribolayer quickly deteriorates and high wear intensity and rapid increase in the contact temperature are observed with current density increase. Therefore, the catastrophic wear of the NiTi alloy begins at a temperature about 350  °C and at low current density. The sliding surface of AISI 1020 steel contained FeO oxide, therefore strong adhesion is not manifested. Formation of FCC-Fe in tribolayer of AISI steel 1020 is detected, that promotes its accelerated deterioration. Therefore, the tribolayer of AISI steel  1020 transites to the utmost state at a relatively low current density and at a  higher temperature. The presented contact temperatures corresponding to the beginning stages of the utmost state of the tribolayer do not exceed 350  °С. Comparison of these temperatures with the known contact temperatures of other metals made it possible to assert that raising of the contact temperature of any metal higher than 400  °С leads to its utmost state. Therefore the characteristics of metals contact at temperatures of sliding contact higher than 500  °С is not of practical interest.

Interaction of tungsten in dry sliding against steel under high density electric current

2019 ◽  
pp. 101-109 ◽  
Author(s):  
M. I. Aleutdinova ◽  
V. V. Fadin ◽  
Yu. P. Mironov
Keyword(s):  
Electrical Contact ◽  
Analysis Data ◽  
Dry Sliding ◽  
Sliding Surface ◽  
X Ray ◽  
Sliding Surfaces ◽  
Quenched Steel ◽  
Sliding Electrical Contact ◽  
A Current ◽  
Tungsten Steel

The possibility of creating a wear-resistant dry sliding electrical contact tungsten/steel was studied. It was shown that tungsten caused severe wear of the quenched steel counterbody due to unlimited plastic flow of its surface layer at a current density up to 150 A/cm2 . This indicated the impossibility of achieving satisfactory characteristics of such a contact. Low electrical conductivity and wear resistance of the contact tungsten/steel were presented in comparison with the known high copper/steel contact characteristics under the same conditions. X-ray phase analysis data of the steel sliding surfaces made it possible to state that the cause of the unsatisfactory sliding of tungsten was the absence of the necessary concentration of FeO oxide on the sliding surface of the steel. 

scholarly journals Multi-material braids for multifunctional laminates: conductive through-thickness reinforcement

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Caroline O’Keeffe ◽  
Laura Rhian Pickard ◽  
Juan Cao ◽  
Giuliano Allegri ◽  
Ivana K. Partridge ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Carbon Fibre ◽  
Electromagnetic Interference ◽  
Design Tool ◽  
Electrically Conductive ◽  
Current Collection ◽  
Wide Range ◽  
Predictive Design ◽  
The Right ◽  
Metal Wires

AbstractConventional carbon fibre laminates are known to be moderately electrically conductive in-plane, but have a poor through-thickness conductivity. This poses a problem for functionality aspects that are of increasing importance to industry, such as sensing, current collection, inductive/resistive heating, electromagnetic interference (EMI) shielding, etc. This restriction is of course more pronounced for non-conductive composite reinforcements such as glass, organic or natural fibres. Among various solutions to boost through-thickness electrical conductivity, tufting with hybrid micro-braided metal-carbon fibre yarns is one of the most promising. As a well-characterised method of through thickness reinforcement, tufting is easily implementable in a manufacturing environment. The hybridisation of materials in the braid promotes the resilience and integrity of yarns, while integrating metal wires opens up a wide range of multifunctional applications. Many configurations can be produced by varying braid patterns and the constituting yarns/wires. A predictive design tool is therefore necessary to select the right material configuration for the desired functional and structural performance. This paper suggests a fast and robust method for generating finite-element models of the braids, validates the prediction of micro-architecture and electrical conductivity, and demonstrates successful manufacturing of composites enhanced with braided tufts.

scholarly journals Salinity Status of Lajas Valley Soils

1969 ◽  
Vol 41 (1) ◽  
pp. 25-34
Author(s):  
Juan A. Bonnet ◽  
Eduardo J. Brenes
Keyword(s):  
Electrical Conductivity ◽  
Hydraulic Conductivity ◽  
Soil Layer ◽  
Soil Surface ◽  
Exchangeable Sodium Percentage ◽  
Exchangeable Sodium ◽  
Surface Layers ◽  
Alkali Soils ◽  
The World ◽  
Sodium Percentage

1. The area of soils surveyed in Lajas Valley was 24,656 acres. 2. The soils were classified into normal, saline, saline-alkali, and non- saline-alkali at depths of 0 to 8, 8 to 24, 24 to 48, and 48 to 72 inches, respectively. 3. A large percentage of normal soils was found in the upper soil layer and of saline-alkali soils in the lower layers. 4. Normal soils occupied about 86 percent of the surface area to a depth of 8 inches and about 63 percent at a depth of 8 to 24 inches. 5. Soils with a salinity problem increased from 9 percent at a depth of 8 inches to 28.3, 58.8 and 68.5 percent, respectively, at depths of 8 to 24, 24 to 48, and 48 to 72 inches. 6. The soils with a salinity problem were largely of the saline-alkali class. 7. In four soil-profile samples taken from Lajas Valley, the saturation percentage varied from 58 to 191, the electrical conductivity from 0.8 to 28.4 millimhos per centimeter, the exchangeable-sodium percentage from 2.2 to 46.0, the soil pH from 8.1 to 8.9, the content of gypsum from 0 to 21.9 tons per acre-foot, the gypsum requirement from 0 to 23.8 tons per acre-foot, and the hydraulic conductivity from less than 0.005 to 6.24 inches of water per hour. Higher gypsum contents were found in the deep subsoil layers of two soils (profiles 1 and 4). Amounts of gypsum varying from 9.9 to 20.3 tons per acre-foot of depth, are required for the reclamation of the surface layers of these two profiles. In general, the hydraulic- conductivity values show that the soil-surface layers are more permeable than the subsoil layers. 8. The procedure and methods used in this paper were found to be accurate, simple, rapid, and practical. They are recommended for the coordination of data related to the classification and reclamation of soils affected by salinity problems in the different countries of the world.

scholarly journals Accumulation Characteristics on a Cold, High-Alpine Firn Saddle from a Snow-Pit Study on Colle Gnifetti, Monte Rosa, Swiss Alps

1983 ◽  
Vol 29 (102) ◽  
pp. 260-271 ◽  
Author(s):  
W. Haeberli ◽  
U. Schotterer ◽  
D. Wagenbach ◽  
H. Haeberli Schwitter ◽  
S. Bortenschlager
Keyword(s):  
Electrical Conductivity ◽  
Strong Influence ◽  
Early Summer ◽  
Swiss Alps ◽  
Saharan Dust ◽  
Surface Layers ◽  
Place Of Origin ◽  
Monte Rosa ◽  
Accumulation Characteristics ◽  
Sedimentation Processes

AbstractIn a snow pit, incorporating about 2.5 a of accumulation, on the 4 450 m high Colle Gnifetti, Monte Rosa, various snow characteristics, isotopes (δ18O, 3H), electrical conductivity, dust, trace elements, and pollen were investigated. The aim of this study was to develop a key for the stratigraphic interpretation of cores from cold, high-alpine firn areas. It appears that the strong influence of wind results in mixing and re-sedimentation processes in the surface layers. Nevertheless, by interpreting several parameters in a combined way, it is possible to classify a large number of the layers according to their season and sometimes to their place of origin. Apart from the melt layers, which only appear in early summer to summer layers, other prominent features are the (Saharan) dust falls, characterized by dust and conductivity peaks.

Metallurgical investigations of dry sliding surface layers in phosphorus iron/steel friction pairs

Wear ◽  
2002 ◽  
Vol 252 (3-4) ◽  
pp. 269-275
Author(s):  
Y.Z Zhang ◽  
S.J Wu ◽  
W.M Liu ◽  
Y Chen ◽  
B Shang Guan ◽  
...  
Keyword(s):  
Dry Sliding ◽  
Sliding Surface ◽  
Surface Layers ◽  
Phosphorus Iron

Effect of SnO2 Particle Size on Properties of Ag-SnO2 Electrical Contact Materials Prepared by the Reductive Precipitation Method

2014 ◽  
Vol 936 ◽  
pp. 459-463 ◽  
Author(s):  
Zhi Jie Lin ◽  
Xu Dong Sun ◽  
Shao Hong Liu ◽  
Jia Lin Chen ◽  
Ming Xie ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Particle Size ◽  
Citric Acid ◽  
Electrical Contact ◽  
Precipitation Method ◽  
Precipitation Process ◽  
Composite Powders ◽  
Contact Materials ◽  
Electrical Contact Materials ◽  
Ag Particle

Performances of Ag-SnO2 electrical contact materials can be strongly affected by the microstructure. In this work, Ag-SnO2 composite powders were synthesized by chemical reductive precipitation method. During the precipitation process, Ag particle was deposited onto the surface of SnO2 particle with the assistance of citric acid. The microstructure and properties were analyzed for the prepared Ag-SnO2 electrical contact materials. Our research reveals that the particle size of SnO2 has significant influence on the morphology of the Ag-SnO2 composite powders, and therefore on the microstructure and physical properties of the electrical contact materials. With the decrease of particle size of SnO2, hardness of the Ag-SnO2 electrical contact materials increases, while electrical conductivity decreases.

Structure and Worn Surface Morphology on Copper Containing Composites under Dry Sliding with High Contact Current Density

2016 ◽  
Vol 712 ◽  
pp. 137-142
Author(s):  
Viktor V. Fadin ◽  
Marina I. Aleutdinova ◽  
Valery E. Rubtsov ◽  
Valeriya A. Aleutdinova
Keyword(s):  
Surface Layer ◽  
Liquid Phase ◽  
Surface Morphology ◽  
Current Density ◽  
Wear Intensity ◽  
Dry Sliding ◽  
Sliding Surface ◽  
Worn Surface

Dry sliding of the sintered composites of compositions Cu-graphite-Fe and Cu-Fe against steel at the contact current density higher 100 A/cm2 has been carried out. The presence of FeO oxide in surface layer was shown. The low content of FeO oxide resulted in high wear intensity. Formation of a liquid phase on a sliding surface was observed. Wear intensity was low in the presence of a liquid phase on the worn surface.

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