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scientific edition of Bauman MSTU

SCIENCE & EDUCATION

Bauman Moscow State Technical University.   El № FS 77 - 48211.   ISSN 1994-0408

Metallurgical Engineering

Thermodynamic and Thermo-graphic Research of the Interaction Process of the Lisakovsky Gravity-magnetic Concentrate with Hydrocarbons
# 06, June 2015
DOI: 10.7463/0615.0780813
A.A. Мuhtar, E.V. Kochegina, Z.S. Khalikova, Z.B. Absat, A.B. Karimova, N.Zh. Rakhimzhanova, G.K. Mukicheva
pp. 438-445
Laws of Alloyed Cementite Particles Nucleation During Heat-Resistant Steels Carburizing
# 05, May 2014
DOI: 10.7463/0514.0710529
M.Yu. Semenov
The article uses numerical experiments to verify a previously hypothesized mechanism of dislocation nucleation particles of chromium- alloyed cementite during a process of carburizing heat-resistant steels, which contain, at least, 3 % chromium. It is shown that alloyed cementite particle nucleation occurs on the chromium and carbon concentration fluctuations in dislocations, thus eliminating the formation of cementite lattice. The proposed mechanism of nucleation explains the origin of the lattice formation when introducing a significant amount of nickel into steel and increasing the process temperature. The guidelines to choose the optimal parameters of carburized layers for hot-resistant steels, which contain nickel of 3% have been developed.
Porosity Design Procedure at the Directed Solidification of Castings
# 05, May 2014
DOI: 10.7463/0514.0709914
A.J. Korotchenko, M.V. Tverskoi, D.E. Khilkov
A series of special experiments using castings of the simple configuration (slabs and bars) defines a value of the feeding zone of a butt end and makes it out as the regressional dependences of the feeding butt end zone on the characteristic sizes of this or that casting. Thus, considerable material and time expenditures are demanded to define the value of the feeding butt end zone to be used further, including calculation of directional solidification of castings. The paper offers a design procedure to calculate a zone of the feeding butt end via computing simulation of solidification in the casting mould thereby sharply reducing expenditures for searching the desirable values. To reveal spaces in the casting, staggered with shrinkable porosity, the new criteria of porosity developed in BMSTU are used. The paper shows a possibility to use the effective size as a characteristic parameter of casting for the regressional dependence of the feeding butt end zone thus providing this dependence universality and a possibility to use it for making any shaped casting, but not just the castings of a simple configuration.
The maraging steel corrosion properties with hardening of different kinds after double aging
# 03, March 2014
DOI: 10.7463/0314.0699856
L.V. Tarasenko, M.V. Unchikova
The paper examines a possibility to apply the ÈP 678 and ÈP 817 martensitic-aging steels to manufacture the force-measuring resilient member in electronic strain-gauge balance. It proposes to use double aging, namely main and low-temperature one as a hardening heat treatment after hardening. Microstructure, X-ray microanalysis, X-ray diffraction, potentiodynamic researches have been conducted, and structure and properties of hard-ended samples after main and double aging have been compared. It is established, that double aging causes extra hardening of steels, but it has a different influence on corrosion resistance of steel, namely the corrosive properties of AP817 steel containing copper are improved due to formation of uniformly distributed cathode ε-Cu corpuscles; the corrosive properties of AP678 steel are deteriorated because of increased heterogeneity of structure.
The application of vacuum heat and thermo-chemical treatment to improve strength of different heavily loaded machine parts and engineering instruments
# 02, February 2014
DOI: 10.7463/0214.0700036
A.E. Smirnov, M.Yu. Semenov
The paper presents great technological capabilities of vacuum heat and thermo-chemical treatment provided by the universal equipment, which enables us to strengthen different heavily loaded machine parts and engineering instruments. A load-bearing capacity of the treated part is defined by the diffusion layer saturation, the structure of surficial region and heart. Technological factors of treatment processes with complicated mechanisms to influence on the resulting features make it reasonable to design the strengthening operating conditions using the calculation methods.
Comparative estimation of technological capabilities of polymer quenchants
# 03, March 2014
DOI: 10.7463/0314.0700099
S.Yu. Shevchenko
The paper presents a comparative estimation of technological capabilities of domestic polymer quenchants with different chemical composition such as UZSP-1, Kamgidrol-ZAK and Acresol. The influence of polymer concentration on cooling ability is presented. Intervals of working temperatures for each quenchant were defined and the influence of industrial pollution on the cooling ability was estimated. The paper makes evaluation of the operational stability and the effect of anti-corrosion additives on the cooling ability of each to the quenching medium. There are practical recommendations on application of quenchants in the industry.
New criterion for estimating probability of formation of microporosity in castings
# 08, August 2013
DOI: 10.7463/0813.0585558
S. Poliakov, V.M. Korovin, A.J. Korotchenko, J. Bast
This paper presents a new dimensionless criterion of formation of microporosity, which considers a set of essential technology factors, including atmospheric and metallostatic pressure, alloy’s gas saturation. The criterion is based only on the measured or controllable parameters and does not demand additional experimental data. A feature of the criterion is absence of the radius of a critical germ of a micropore. An estimation of the distance between secondary axes of dendrites is used instead. The criterion is recommended for using in systems of simulation of casting hardening for more accurate prediction of formation of microporosity.
Thermodynamic analysis of covering blades of gas-turbine engineы made of heatproof nickel alloys with protection diffusion coatings with tantalum undercoat
# 07, July 2013
DOI: 10.7463/0713.0583284
N.I. Artemenko, V.N. Simonov, B.G. Trusov
This work presents results of thermodynamic studies and searching for a rational chemical activation dopant for deposition of tantalum from the gaseous phase onto surfaces of parts of gas-turbine engines made of heatproof nickel alloys in order to increase the diffusion stability of heatproof aluminide coatings. Calculations showed a possibility of using nickel dichloride for tantalum and tantalum-chromium coating of nickel alloys. During this investigation several restrictions on the number of additional alloying elements in the saturating mixture were discovered. An effective amount of chromium for the combined process of tantalum-chromium coating was also determined.
Influence of ion nitriding and vacuum carburizing on wear resistance of VKS-7 and VKS-10 steels
# 06, June 2013
DOI: 10.7463/0613.0579264
S.A. Gerasimov, L.I. Kuksenova, V.G. Lapteva, R.S. Fahurtdinov, M.S. Alekseeva, I.A. Hrennikova, N.L. Boreiko, A.E. Smirnov, D.S. Krasovskii
Significant resources for improving the set of performance characteristics of essential machine parts are gathered in development of new technologies of thermal and thermochemical treatment, based on activation of processes of diffusion saturation and providing volumetric and surface ultra-finely-divided or nanostructured condition of constructional materials. Results of estimating wear resistance and micro-hardness of VKS-7 and VKS-10 steels after complex treatment, including two stages: 1 - preliminary plastic deformation by a warm compression method and 2 - ion nitriding or vacuum carburizing were presented. A conclusion on the correlation between hardness and wear resistance was drawn.
Thermodynamic analysis of covering blades of a gas-turbine engine made of heatproof nickel alloys with protection diffusion coatings with hafnium undercoat
# 06, June 2013
DOI: 10.7463/0613.0577291
N.I. Artemenko, V.N. Simonov, S.A. Muboyadjyan
This work presents results of thermodynamic studies and searching for a rational chemical activation dopant for deposition of hafnium from the gaseous phase onto the surface of gas-turbine engine’s parts made of heatproof nickel alloys in order to increase diffusion stability of heatproof aluminide coatings. Calculations showed impossibility of using a traditional activation dopant, that is nickel dichloride, for hafnium coating because liberation of gaseous hafnium compounds occurs at temperatures which are beyond reach for modern equipment for thermochemical treatment. During this investigation it was established that ammonium chloride could be used as an activation dopant. If hafnium consists one fifth of ammonium chloride in the saturating mixture, amount of gaseous hafnium chloride reaches its maximum.
Investigation of durability of VKS-7 and VKS-10 steels after vacuum carbonization and vacuum carbonitriding
# 05, May 2013
DOI: 10.7463/0513.0568124
S.A. Gerasimov, L.I. Kuksenova, V.G. Lapteva, R.S. Fahurtdinov, A.E. Smirnov, V.I. Gromov, V.V. Stupnikov
Development of new technologies of thermal and thermochemical treatment, based on the activation of cementation processes and which could provide volume and surface finely-divided or nanostructured state of constructional materials appeared to be a very powerful method to increase the durability of critical machine elements. Results of estimating the durability and micro-hardness of VKS -7 and VKS-10 steels were presented in this article after complex processing which consisted of two stages: 1 – preliminary plastic deformation by means of warm shortening and 2- plasma nitration or vacuum carbonization. Analysis of the relation between hardness and durability was carried out.
Aanalysis of kinetics of phase transformations in non-equilibrium solid solutions of systems such as Fe-2Cr (at.%), Fe-4 Cr (аt.%), Fe-24Cr (аt.%)
# 05, May 2013
DOI: 10.7463/0513.0566894
T.V. Kurihina, V.N. Simonov
In this work the authors calculated phase transformation kinetics in non-equilibrium solid solutions of binary alloys such as Fe-2 Cr (at.%), Fe-4 Cr (at.%), Fe-24Cr (at.%). In the literature [1] there is information on the impact of pre-heat treatment (PHT) on the size of iron nitrides after nitriding. Using the “Termodin” program [2, 3], they calculated cluster sizes, diffusion coefficients at temperatures of isothermal ageing, time of nucleation and time of the growth of the clusters, nucleation rate and growth rate of clusters which were formed at initial stages of decomposition of the supersaturated solid solution. Formation kinetics of a given volume fraction of the σ phase was also calculated. The obtained results allowed to control the structure of alloys, depending on heat treatment
Impact of galvanizing of couplings of tubings in the oil industry on the structure and properties of coatings
# 04, April 2013
DOI: 10.7463/0413.0559838
I.A. Chijov, E.A. Merkushkin, P.A. Pachkolina, V.V. Berezovskaya
Application of protective coatings is one of the promising areas to increase durability of the "pipe-coupling" threaded junction of tubing pipes for oil production. The authors investigated the structure, mechanical and corrosion properties of electroplating, thermal diffusion and hot zinc coatings on steel pipes 45, 30G2 and 37G2F 37G2S with a varying strength group. Thickness of the structure, phase composition, microhardness and pitting resistance of coatings were determined. Zinc coatings of different application techniques differ significantly in thickness, hardness, corrosion resistance and structure, but values ​​of these parameters within a single technology are virtually independent of the base metal. Hot Zn-coating of 100 microns is composed of several layers: T, T1-, δ1-, ζ - and η-phases with a  different content of zinc in accordance with the phase diagram of Fe-Zn. Thermal diffusion coating (40 m) is composed of phases D and T1 with a complex cubic lattice, and the δ1-phase with a hexagonal lattice. The composition of plating (20 microns) are η-phase - solid solution of iron in zinc, Zn and zinc oxide ZnO on the surface. GC and GVC coatings have significantly lower hardness as opposed to thermal diffusion, which is caused by the presence of the solid phase δ1. Pitting resistance of uncoated steel is lower than with coatings. Coating has a maximum resistance of MCC, which has zinc oxide on the surface, and a minimum - GC coating with a two-phase η + ζ-structure. The most resistant to pitting corrosion coating on steel was 37G2S doped by1% silicon, and the most unstable was on steel 45. It is shown that chemical composition and heat treatment of the investigated pipe steels have practically no influence on thickness of coatings, but steel after rolling provides a more uniform plating without obvious lamination.
Discussion of results of thermodynamic instability of materials structure
# 01, January 2013
DOI: 10.7463/0113.0530839
T.V. Kurihina, V.N. Simonov, E.A. Sergievskii
The authors propose an energy method for calculating degradation rate of a non-equilibrium structure while in opeartion. With the use of differential scanning calorimetry it is possible to determine the presence of phase transformations in case of alloy aging, decay of supersaturated solid solutions, secondary crystallization and also assess heat content of the system during the transient process from the non-equilibrium state into the thermodynamic equilibrium state with extra energy release. Differentiating the current value of extra energy with respect to time, it’s also possible to determine the value of the chemical activity coefficient during phase transformations in alloys at working temperatures. Estimated dependence of the rate of energy dissipation χ on the initial value of a superfluous chemical potential was derived for the first time.
Christon elastic fields in formation of bainitic ferrite lath structure
# 01, January 2013
DOI: 10.7463/0113.0529309
M.P. Kaschenko, K.N. Djemilev, V.G. Chaschina
The authors analyze elastic fields of a separate prismatic loop and a set of loops (special cases of christon) modeling shear deformation media in shear bands with orientations of the borders close to {558} γ. It is shown that christons can act as dislocation nucleation centers for lath crystals forming the composition of bainite macroplate. The obtained results support the dynamic picture according to which individual laths of ferrite crystals are formed like martensite laths. However, between stages of forming ferrite rods there occurs carbon diffusion redistribution. As a result, there arise new areas of austenite which are beneficial for rapid growth of the next generation of lath crystals.
Simulation of ion nitriding
# 01, January 2013
DOI: 10.7463/0113.0501016
S.A. Gerasimov, M.G. Krukovich, E.A. Baderko, N.P. Klochkov
The authors analyzed processes occurring in the saturating medium and work material; the analysis allowed to account for reasons of high rate of phase growth during ion nitriding. It was shown that the kinetic coefficient is a link between technological parameters and process output results. An algorithm for calculating process output characteristics is proposed.
Nanoclusters in solid solutions of iron-chromium and their influence on hardness of the nitrided layer of steel 38H2MYUA
# 11, November 2012
DOI: 10.7463/1112.0496806
S.A. Gerasimov, A.A. Novakova, V.S. Kraposhin, P.V. Bocharov
The authors established the influence of preliminary heat treatment (annealing at 950°C, 0.5 hrs, cooled with furnace + tempering at the interval of 500-700°C) on hardness of the nitrided layer of steel 38H2MYUA (nitriding at 500°C, 30 h). Similar results were obtained in a model of carbon-free alloy Fe-4% Cr. By the method of nuclear gamma resonance spectroscopy (the Mossbauer effect) on the model alloy it was established that Fe-Cr clusters are formed during the cooling process starting from 950°C and the subsequent tempering. Clustering affects the size and number of particles of chromium nitride formed during subsequent nitriding at 500°C. Depending on the heat treatment before nitriding, Fe-Cr clusters are characterized by different filling of chromium atoms of the first and second coordination spheres of iron. According to the Mössbauer spectra after annealing at 950°C and tempering at 550°C, during the following 10 hrs before nitriding in the structure of the solid solution clusters are formed, and they correspond to the crystalline structure of  the σ-phase Fe-Cr system: Frank-Kasper polyhedra with 14 vertices.
Calculation of thermal pre-treatment before nitriding on the size of the nuclei of iron nitride.
# 11, November 2012
DOI: 10.7463/1112.0496755
T.V. Kurihina, S.A. Gerasimov, V.N. Simonov
 The authors calculated the effect of temperature and time parameters of thermal pre-treatment of structural steels at the initial stages of formation of a fine structure before nitriding. With the program "Termodin" developed at the department "Materials science" in Bauman MSTU the authors calculated the critical radius of the nuclei of iron nitride, diffusion parameters, kinetic parameters of nucleation and growth phase Fe4N, time of formation of a given volume fraction of γ/ phase during isothermal holding in the high holiday for binary alloys Fe-5, 6% N by mass. Kinetic curves of decomposition of the supersaturated solid solution with formation of a given volume fraction of γ/ phase were built. The authors also calculated prediction modes of thermal pre-treatment on the size of hardening phases.
 
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