scholarly journals IMPROVING THE SURFACE STRUCTURE OF MASSIVE PARTS BY THE PLASMA METHOD

2021 ◽  
Author(s):  
I.M Kossanova.Т.Кanayev,A А.U.Аkhmedyanov,I.P. Mazur,
Keyword(s):  
Structural Changes ◽  
Surface Plasma ◽  
High Temperature Region ◽  
Heating Rates ◽  
Plasma Hardening ◽  
Fine Grained ◽  
Kinetics Of ◽  
New Phase ◽  
Phase And Structural Changes ◽  
Structural Zones

An increase in the reliability of the operation of large-sized and massive parts by plasma hardening of their surfaces is substantiated. It has been established that the formation of several structural zones of different microhardness is observed in detail along the depth of hardening, indicating the formation of a gradient-layered structure. It has been proved that at ultrafast heating rates, which occur during surface plasma hardening, phase and structural changes move to the high temperature region, changing the kinetics of the appearance and growth of new phase nuclei. In this case, fine-grained austenite is formed, which is transformed into a highly dispersed martensitic structure, which increases the strength and reliability of the surfaces of the parts.

APPLYING SURFACE PLASMA HARDENING FOR IMPROVING THE TRIBOLOGICAL CHARACTERISTICS OF STEEL PARTS

Tribologia ◽  
2019 ◽  
Vol 283 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Bauyrzhan RAHADILOV ◽  
Laila ZHUREROVA ◽  
Zhuldyz SAGDOLDINA
Keyword(s):  
Wear Resistance ◽  
Experimental Studies ◽  
High Hardness ◽  
Hardened Layer ◽  
Heating Time ◽  
Tribological Characteristics ◽  
Surface Plasma ◽  
Initial State ◽  
Plasma Hardening ◽  
Fine Grained

This work presents the results of experimental studies on the application of surface plasma hardening to improve the tribological characteristics of steel marks of 40CrNi, 20Cr2Ni4A, and 34CrNi1Mn. According to the obtained results, it was established that, after plasma treatment, a modified layer with a thickness of 1–1.2 mm with high hardness and wear resistance is formed, consisting of a hardened layer of fine-grained martensite and, an intermediate layer of perlite and martensite. It was determined that, after treatment with a heating time of 3 min, the microhardness of steels 40CrNi and 20Cr2Ni4A doubles, and the steel 34CrNi1Mn increases 1.6 times, depending on the initial state, and the wear resistance of all steel samples increases, on average, 30 times.

Increase of Wear Resistance and Contact-Fatigue Strength of Wheel Steel by Plasma Hardening

2018 ◽  
Vol 284 ◽  
pp. 1144-1150 ◽  
Author(s):  
A.T. Kanayev ◽  
A.V. Bogomolov ◽  
A.A. Kanayev
Keyword(s):  
Structural Phase ◽  
Contact Fatigue ◽  
Internal Stresses ◽  
Surface Zone ◽  
Surface Plasma ◽  
Heating Rates ◽  
Near Surface ◽  
Plasma Hardening ◽  
Metastable Structure ◽  
High Level

Metallographic studies of structural-phase states formed in the section of the flange of the wheel band during surface plasma hardening were conducted. It is shown that the formation of several structural zones of different micro hardness is distinctly observed in the depth of hardening, which indicates the formation of a graded-layered structure. It has been confirmed that at superfast heating rates that occur during surface plasma quenching, phase and structural transformations are shifted to high temperatures, greatly changing the kinetics of nucleation and growth of the new phase (austenite). This forms a fine-grained austenite, which turns into a highly disperse martensitic structure, unattainable by traditional methods of heat treatment. It is shown that the main factor leading to strong hardening of the surface layer during plasma treatment is the formation in the near-surface zone of a nonequilibrium metastable structure, which goes over to a narrow zone of complete and incomplete quenching with an inhomogeneous and distorted structure of highly disperse martensite with a high level of internal stresses. The complete wear of the unstressed flange of the tire wheel band is 1.9 mm in 1.1 years, and for hardened flanges, wear is 0.7 mm for 2.6 years.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

Biofilm Structure – An Important and Neglected Parameter in Waste Water Treatment

1989 ◽  
Vol 21 (8-9) ◽  
pp. 805-814 ◽  
Author(s):  
F. R. Christensen ◽  
G. Holm Kristensen ◽  
J. la Cour Jansen
Keyword(s):  
Wastewater Treatment ◽  
Structural Changes ◽  
Waste Water Treatment ◽  
Experimental Investigations ◽  
Biofilm Reactors ◽  
Substrate Removal ◽  
Treatment Processes ◽  
Laboratory Reactor ◽  
Biofilm Structure ◽  
Kinetics Of

Experimental investigations on the kinetics of wastewater treatment processes in biofilms were performed in a laboratory reactor. Parallel with the kinetic experiments, the influence of the biofilm kinetics on the biofilm structure was studied at macroscopic and microscopic levels. The close interrelationship between biofilm kinetics and structural changes caused by the kinetics is illustrated by several examples. From the study, it is evident that the traditional modelling of wastewater treatment processes in biofilm reactors based on substrate removal kinetics alone will fail in many cases, due to the inevitable changes in the biofilm structure not taken into consideration. Therefore design rules for substrate removal in biofilms used for wastewater treatment must include correlations between the removal kinetics and the structure and development of the biological film.

scholarly journals Thermal Stability and Decomposition Kinetics of 1-Alkyl-2,3-Dimethylimidazolium Nitrate Ionic Liquids: TGA and DFT Study

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2560
Author(s):  
Jianwen Meng ◽  
Yong Pan ◽  
Fan Yang ◽  
Yanjun Wang ◽  
Zhongyu Zheng ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Density Functional Theory ◽  
Ionic Liquids ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Nitrogen Atmosphere ◽  
Decomposition Kinetics ◽  
Heating Rates ◽  
Functional Theory ◽  
Kinetics Of

The thermal stability and decomposition kinetics analysis of 1-alkyl-2,3-dimethylimidazole nitrate ionic liquids with different alkyl chains (ethyl, butyl, hexyl, octyl and decyl) were investigated by using isothermal and nonisothermal thermogravimetric analysis combined with thermoanalytical kinetics calculations (Kissinger, Friedman and Flynn-Wall-Ozawa) and density functional theory (DFT) calculations. Isothermal experiments were performed in a nitrogen atmosphere at 240, 250, 260 and 270 °C. In addition, the nonisothermal experiments were carried out in nitrogen and air atmospheres from 30 to 600 °C with heating rates of 5, 10, 15, 20 and 25 °C/min. The results of two heating modes, three activation energy calculations and density functional theory calculations consistently showed that the thermal stability of 1-alkyl-2,3-dimethylimidazolium nitrate ionic liquids decreases with the increasing length of the alkyl chain of the substituent on the cation, and then the thermal hazard increases. This study could provide some guidance for the safety design and use of imidazolium nitrate ionic liquids for engineering.

scholarly journals Pyrolysis and Oxidation of PAN in Dry Air. Thermoanalytical Methods

1970 ◽  
Vol 17 (1) ◽  
pp. 38-42
Author(s):  
Anna BIEDUNKIEWICZ ◽  
Pawel FIGIEL ◽  
Marta SABARA
Keyword(s):  
Temperature Increase ◽  
Heating Rates ◽  
Linear Change ◽  
Dry Air ◽  
Isothermal Conditions ◽  
Gaseous Products ◽  
Heterogeneous Processes ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
Kinetics Of

The results of investigations on pyrolysis and oxidation of pure polyacrylonitrile (PAN) and its mixture with N,N-dimethylformamide (DMF) under non-isothermal conditions at linear change of samples temperature in time are presented. In each case process proceeded in different way. During pyrolysis of pure PAN the material containing mainly the product after PAN cyclization was obtained, while pyrolysis of PAN+DMF mixture gave the product after cyclization and stabilization. Under conditions of measurements, in both temperature ranges, series of gaseous products were formed.For the PAN-DMF system measurements at different samples heating rates were performed. The obtained results were in accordance with the kinetics of heterogeneous processes theory. The process rates in stages increased along with the temperature increase, and TG, DTG and HF function curves were shifted into higher temperature range. This means that the process of pyrolysis and oxidation of PAN in dry air can be carried out in a controlled way.http://dx.doi.org/10.5755/j01.ms.17.1.246

Effects of additives on the cure kinetics of vinyl ester pultrusion resins

2021 ◽  
pp. 002199832110015
Author(s):  
Alexander Vedernikov ◽  
Yaroslav Nasonov ◽  
Roman Korotkov ◽  
Sergey Gusev ◽  
Iskander Akhatov ◽  
...  
Keyword(s):  
Vinyl Ester ◽  
Mean Squared Error ◽  
Cure Kinetics ◽  
Zinc Stearate ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Different Temperatures ◽  
Predicted Values ◽  
Kinetics Of ◽  
Final Degree

Pultrusion is a highly efficient composite manufacturing process. To accurately describe pultrusion, an appropriate model of resin cure kinetics is required. In this study, we investigated cure kinetics modeling of a vinyl ester pultrusion resin (Atlac 430) in the presence of aluminum hydroxide (Al(OH)3) and zinc stearate (Zn(C18H35O2)2) as processing additives. Herein, four different resin compositions were studied: neat resin composition, composition with Al(OH)3, composition comprising Zn(C18H35O2)2, and composition containing both Al(OH)3 and Zn(C18H35O2)2. To analyze each composition, we performed differential scanning calorimetry at the heating rates of 5, 7.5, and 10 K/min. To characterize the cure kinetics of Atlac 430, 16 kinetic models were tested, and their performances were compared. The model based on the [Formula: see text]th-order autocatalytic reaction demonstrated the best results, with a 4.5% mean squared error (MSE) between the experimental and predicted data. This study proposes a method to reduce the MSE resulting from the simultaneous melting of Zn(C18H35O2)2. We were able to reduce the MSE by approximately 34%. Numerical simulations conducted at different temperatures and pulling speeds demonstrated a significant influence of resin composition on the pultrusion of a flat laminate profile. Simulation results obtained for the 600 mm long die block at different die temperatures (115, 120, 125, and 130 °C) showed that for a resin with a final degree of cure exceeding 95% at the die exit, the maximum difference between the predicted values of pulling speed for a specified set of compositions may exceed 1.7 times.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

scholarly journals The poly(ADP-ribose)-dependent chromatin remodeler Alc1 induces local chromatin relaxation upon DNA damage

2016 ◽  
Vol 27 (24) ◽  
pp. 3791-3799 ◽  
Author(s):  
Hafida Sellou ◽  
Théo Lebeaupin ◽  
Catherine Chapuis ◽  
Rebecca Smith ◽  
Anna Hegele ◽  
...  
Keyword(s):  
Dna Damage ◽  
Structural Changes ◽  
Cellular Responses ◽  
Dna Lesions ◽  
Fast Kinetics ◽  
Important Player ◽  
Chromatin Relaxation ◽  
Kinetics Of ◽  
Laser Microirradiation

Chromatin relaxation is one of the earliest cellular responses to DNA damage. However, what determines these structural changes, including their ATP requirement, is not well understood. Using live-cell imaging and laser microirradiation to induce DNA lesions, we show that the local chromatin relaxation at DNA damage sites is regulated by PARP1 enzymatic activity. We also report that H1 is mobilized at DNA damage sites, but, since this mobilization is largely independent of poly(ADP-ribosyl)ation, it cannot solely explain the chromatin relaxation. Finally, we demonstrate the involvement of Alc1, a poly(ADP-ribose)- and ATP-dependent remodeler, in the chromatin-relaxation process. Deletion of Alc1 impairs chromatin relaxation after DNA damage, while its overexpression strongly enhances relaxation. Altogether our results identify Alc1 as an important player in the fast kinetics of the NAD+- and ATP-dependent chromatin relaxation upon DNA damage in vivo.

Magnetic Properties, Nanostructure, and Ordering Kinetics of Nb Additive FePtCu Films

2010 ◽  
Vol 638-642 ◽  
pp. 1743-1748
Author(s):  
G.J. Chen ◽  
Y.H. Shih ◽  
Jason S.C. Jang ◽  
S.R. Jian ◽  
P.H. Tsai ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Activation Energy ◽  
Magnetic Properties ◽  
Heating Rates ◽  
Fept Alloy ◽  
Ordering Kinetics ◽  
Nb Content ◽  
Kinetics Of ◽  
Nb Addition ◽  
Microstructure And Magnetic Properties

In this study,the (FePt)94-xCu6Nbx (x=0, 2.87, 4.52, 5.67) alloy films were prepared by co-sputtering. The effects of Nb addition content and heat treatment on the microstructure and magnetic properties of the polycrystalline FePtCu films are reported. Our previous experiments showed that the ordering temperature of the (FePt)94Cu6 films reduced to 320 °C, which is much lower than that of the FePt alloy. However, the grain growth after heat treatment limited the practical application in recording media. By adding the Nb content in the (FePt)94Cu6 film, the grain sizes of the films can be adjusted from 50 to 18nm, even for the films annealed at temperature as high as 600°C. DSC traces of as-deposited disorder films at different heating rates, to evaluate the crystallization of the order phase, revealed that the addition of Nb enhanced the activation energy of ordering from 87 kJ/mol to 288 kJ/mol for the (FePt)94-xCu6Nbx (x=0 and 2.87, respectively) films. The reduction of the grain size and the corresponding increase in the activation energy of the Fe-Pt-Cu-Nb films might result from the precipitation of the Nb atoms around the ordering FePt phase. The (FePt)94-xCu6Nbx (x=2.87) film showed a coercive force of 13.4 kOe and the magnetization of 687 emu/cc.

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