CONTENTS

 

Effect of energy fluxes on materials

 

L.V. Baran

Effect of the boron ions implantation on the structure, phase composition, and mechanical properties

of chrome-fullerite-chrome films...................................................................................................................................................5

Effect of implantation with boron ions on the structure, phase composition, and mechanical properties

of chromium-fulleritechromium films has been studied. The films were obtained by a resistive method

in a vacuum. Oxidized monocrystalline silicon with (111) surface orientation was used as the substrate.

The thickness of the layers was chosen in such a way that the maximum of radiation defect distribution

was not far from the Cr-60 interface between the upper Cr film and fullerite one, so the ion range was

less than second C60-Cr interface occurrence depth. The films were implanted with boron ions with

energy of 80 keV, fluence of implantation was 51017 ion/cm2 at the ion current density of 3.5 μA/cm2.

Structure of the films was investigated with the help of atomic force microscopy (AFM) using

supersharp cantilevers with a needle tip curvature radius less than 3 nm. Phase composition of the films

was monitored by means of X-ray diffraction method using a DRON-4.13 X-ray diffractometer.

Hardness of the films was measured by nanoindentation technique using the Berkovich triangular

indenter. From the results of AFM investigation it is ascertained that as-condensed films have a

globular structure with an average size of structural elements of 20 nm. X-ray diffraction analysis

shows a partial mixing of Cr and fullerite layers already at the stage of specimen preparation.

Implantation of chromium-fullerite-chromium films with boron ions leads to increasing in the size

of structural elements in near the surface layers up to 30 nm, intensive mixing of chromium and

fullerite layers with formation of intercalated chromium of the fullerite phase. Nanohardness of

implanted films is increased from 0.56 to 1.2 GPa.

Keywords: chrome-fullerite films, ion implantation, structure, phase composition, mechanical properties,

atomic force microscopy.

 

Plasmochemical methods of production and treatment of materials

 

A.M. Kruchinin, V.F. Kubarev, E.S. Ryazanova, A.Yu. Chursin

Calculation of heat transfer characteristics of an arc in a gas stream of plasma-arc furnaces................................................13

Within the framework of the heat exchange model of the electric arc, the arc characteristics in the

gas jet of the melting plasmotron are calculated in the approximation of the interaction of a semi-

infinite isothermal jet with a wall. The temperature profile, structure, and values of the heat fluxes

of a part of the arc column in the melting space of the plasma arc furnace are determined to a

distance from the cathode. For the given power and composition of plasma-forming gas, the

electric and thermal characteristics of the plasmotron and its geometry are established. Examples

are given of calculation of arc characteristics in argon and argon-hydrogen mixture in the initial

period of melting of solid charge with stable arc combustion taking into account the influence of

electric circuit parameters. The results on the temperature profile of the arc in a gas jet are presented.

Keywords: electric arc, arc steel-smelting furnaces, theory of electric arc heating.

 

A.A. Nikolaev, D.E. Kirpichyov, A.V. Nikolaev

Power-technological characteristics of a plasma-arc reducing fusion of leucoxene concentrate.............................................18

The plasma-arc reduction melting of the leucoxene concentrate containing 36% SiO2 has been

investigated with the variation of the boundary conditions of the bath. The process is based on

the carbothermic reduction of SiO2 to SiO with the subsequent evaporation of SiO from the melt,

the product of melting is synthetic rutile. The experiments were carried out in a laboratory

plasma-arc DC furnace for reducing fusion of oxide materials in crucibles of various designs up

to 100 mm in diameter. The melt in a crucible was anode of the arc and cathode was a graphite

electrode with an axial channel through which a mixture of concentrate with carbon and argon

was fed into the bath. Melting of the charge containing 10-20% was carried out in hot graphite

and cold copper crucibles at an arc power of 10.2 kW. It is established that the best results are

obtained by refining in a cold copper crucible. A mathematical model for anode spot formation

at leucoxene temperature in a spot not below Si evaporation temperature (2000 K) is considered.

The temperature fields in the bath of hot graphite and cold copper crucibles were calculated taking

into account the radiation of the bath and the heat of physical and chemical processes. The results

of the calculations are consistent with the experiment. It is shown that diameter of the anode spot

in the graphite crucible is larger and the current density and temperature of material in the spot

are smaller than these values in the copper spot. It is the reason for the worst concentrate refining

in graphite crucible. Specific energy consumption of concentrate treatment in a graphite crucible

is almost twice as high as in a copper crucible, and the coefficient of useful energy use is three

times less.

Keyword: plasma, arc, anode, spot, reduction, leucoxene, silicon, rutile.

 

Functional coatings and surface treatment

 

S.Yu. Kornilov, N.G. Rempe, N.N. Smirnyagina

Non-vacuum surfacing of protective coatings with a low-energy electron beam.......................................................................26

The results of electron-beam surfacing in air of protective coatings by a low-energy (120 keV)

electron beam produced by an electron gun with a plasma emitter are presented. There is a two-

stage differential pumping system for the electron beam extraction from the area with the pressure

of 104 Torr to the air. The gun is mounted on an industrial robotic manipulator KUKA, which allows

the electron beam to be moved to the atmosphere along a given trajectory without electromagnetic

sweep. The combined (SHS-process and electron-beam surfacing) method for obtaining coatings

from reaction mixtures TiO2:2.1C and TiO2:0.3Cr2O3:3.3 is realized at this unit. The optimum

composition of the reaction mixtures and the deposition regimes are determined by thermodynamic

modeling using the TERRA program. The obtained coatings with a thickness of 120-200 μm

have a microhardness of 12 GPa. It is established that the coatings and the transition layer have

good heat resistance up to a temperature of 900C. Noticeable changes in the weight characteristics

of coatings occur at temperatures above 1000C.

Keywords: electron beam, plasma emitter, gas-discharge, electron gun, differential pumping

system, self-propagating high-temperature synthesis, electron-beam surfacing, microhardness,

carbide coatings.

 

G.A. Pribytkov, A.V. Baranovskiy, I.A. Firsina, V.G. Durakov, M.G. Krinitsyn

Formation of the coatings structure under electron-beam facing

of TiC+high speed steel binder SHS composite powders.......................................................................................................36

Metal matrix composite powders TiChigh-speed steel (HSS) with from 20 to 50 vol.% steel

binder content were obtained by self-propagating high-temperature synthesis (SHS). The resulting

powders were used for electron-beam cladding of coatings. It is established that the dispersion

of carbide inclusions in the granules of the composite powder decreases monotonically with

increasing content of the steel binder in reactive powder mixtures. This behavior is typical for

SHS products synthesized from the mixtures containing thermally inert components, which in

this case is HSS. In spite of considerable scatter of the composite powder granules microhardness

values which is explained by the pores inside the granules, there is a tendency of the microhardness

to decrease with increasing of the HSS content in the granules. Coatings formed by multi-pass

electron-beam cladding have a characteristic structure including the original granules of the

composite powder and individual carbide particles in a steel binder. A metallographic study

of the deposited coatings showed that the average size of the granules in the deposited coatings

depends both on the original size of the granules of the composite powders and on the content

of the steel binder in the granules. The average of the granules size values in the coatings cladded

by a coarse powder (200-315 μm) decreases with increasing binder content in the composite powders.

The average size of the granules in the coatings cladded by fine powder (125-200 μm) remains

constant at the level of 125 μm. A detached carbide inclusions in a steel binder have a double origin.

The main part of them before seated is in the peripheral region of the granules and released at the

melting of the steel binder which held the carbide particles inside the granules. A smaller fraction

of the carbide inclusions are precipitated during cooling from liquid-metal solution supersaturated

by carbon and titanium.

Keywords: metalmatrix composite, titanium carbide, high speed steel, self-propagating high

temperature synthesis, burning temperature, dispersion, hard facing, microstructure.

 

Composite materials

 

G.S. Burkhanov, N.B. Kolchugina, A.A. Lukin, Yu.S. Koshkidko,

J. Cwik, K. Skotnicova, V.V. Sitnov

Structure and magnetic properties of Nd-Fe-B magnets prepared from powder mixtures with DyH2 hydride additions..........44

Sintered magnets were prepared by powder-mixture technique using a strip-casted alloy

24 Nd-6.5 Pr-0.5 Dy-1.0 B-0.2 Al-65.8 Fe (wt.%) and 2 wt.% dysprosium hydride DyH2.

After optimum heat treatment (500C, 1 h), the magnets demonstrate high hysteretic characteristics:

magnetic induction Br=1.29 T, coercive force jHc=1309 kA/m, critical field Hk=1220 kA/m,

maximum energy product (BH)max=322 kJ/m3. The hysteretic characteristics were found to be stable

(unchanged) in the course of subsequent stepped annealing or progressive heating in a temperature

range of 250-500 at a total holding time of 20 h. This fact is the advantage of the magnets

prepared with hydride-containing powder mixture. Conditions of low temperature annealing

which leads to the degradation and subsequent recovery of hysteretic characteristics were

determined. X-ray diffraction analysis and electron-microscopic studies allowed us to demonstrate

the evolution of the microstructure and phase composition of magnets in the course of used heat

treatments. Correlation between the observed structural changes and hysteretic characteristics

of the magnets is discussed.

Keywords: Nd-Fe-B permanent magnets, coercive force, strip-casting, dysprosium hydride,

low-temperature treatment, grainboundary diffusion.

 

S.G. Vadchenko, M.I. Alymov, I.V. Saikov

Ignition and combustion of metal-Teflon mixtures......................................................................................................................55

Mixing method and heating rate dependence the parameters for ignition process and product

structure generation in metal W-Ti, Ti-B, Ti-Cu, and Ni-Al powder mixture with Teflon (Tf)

was investigated. The adiabatic temperature, the quantity of forming melt and product proportion

were calculated for focused systems at adiabatic combustion temperature. Mixing were made both

by usual method in Turbula type mixer and in mechanoactivator in isopropyl alcohol. The

samples from the powder mixture with 3 mm diameter and 0.3-1 mm thickness were pressed for

high temperature gradient cancellation. The ignition of samples was carried out in thermal explosion

regime in argon at atmospheric pressure. The samples temperature at heating and ignition were

measured by thermocouples rolled from WRe5/WRe20 wires to 15-20 μm thickness. An increase

in the heating rate was found to have little or no influence on the ignition temperature of Ti-B-Tf

and Ti-Cu-Tf mixtures but strongly affected product structure toward elevated amount of the melt.

The ignition temperature weakly depends on heating rate for investigated samples except Ni-Al-Tf

mixture. Mixtures whose combustion was accompanied by vigorous gas release either lost their

integrity (W-Ti-Tf mixtures) or yielded highly porous combustion products (Ni-Al-Tf mixtures).

The high level of homogeneity obtained by mechanical activation doesnt promote for consolidation

of combustion product particles also. The activation energy of interaction process combustion

estimated for mechanical activated Ti-Cu-Tf mixtures (E=17 kJ/mol) greatly low than for common

mixtures (E=28 kJ/mol). This effective value characterizes the whole process shows the increase

of process by improvement of contacts between reagent particles during mechanical activation

of mixture.

Keywords: metal-Teflon mixtures, ignition, combustion, product patterning, reaction kinetics.

 

New methods of treatment and production of materials with required properties

 

S.N. Anuchkin, E.K. Kazenas, V.A. Volchenkova, N.A. Andreeva, T.N. Penkina

Investigation of the form of existence of zirconium in Ni melts containing exogenous oxide refractory nanophases...............63

With the help of atomic emission spectrometry with inductively coupled plasma method and Mars5

autoclave microwave

system for dissolution of samples, new methods have been developed for quantifying the content

of various forms of zirconium in nickel: zirconium dissolved in metal and zirconium in the form

of brazilite ZrO2. The influence of a matrix element (nickel) and methods of its elimination are

studied. It is determined that the nickel content up to 10 g/l does not affect the analytical signals

of solutions containing more than 2 ppb of zirconium. It was shown that under introduction of

0.40 wt.% ZrO2 nanoparticles in the melt the ratio Zr both in solution and in the form of ZrO2 is

1:80, i.e. about 99% Zr is in the form of ZrO2. Concentration of nanoparticles in the preform of

composite material is found to have an effect on the processes of nanoparticles assimilation by melt

and uniformity of its distribution in liquid nickel. When the composite material 97.5% Ni+2.5% ZrO2

was introduced into liquid nickel, a uniform distribution of the nanoparticles was observed throughout

the entire volume and the degree of assimilation averaged 86.5%. With zirconium oxide concentration

in the composite material increasing, the assimilation processes decreased to 9.7% and concentration

of ZrO2 in the upper part of the ingot was 1.64 times greater than in the lower part. It was found that

lyophobic relatively to nickel ZrO2 nanoparticles on the meltpreform boundary have trend to

agglomeration with the formation of a high-temperature carcass of ZrO2.

Keywords: nanoparticles, zirconium, zirconium oxide, Ni, forms of occurrence, methods of analysis,

atomic emission spectrometry with inductively coupled plasma.

 

N.A. Dormidontov, A.G. Dormidontov, Yu.S. Koshkidko

Peculiarities of the heat treatment of (Sm,Zr)(Co,Cu,Fe)z alloys..............................................................................................70

The effect of heat treatment on the properties of (Sm, Zr)(Co,Cu,Fe)z-based permanent magnets has

been studied. It was noted that in using the selected manufacturing procedure the increase in the

density of blanks does not finish at the sintering stage but continues in the course of solid-solution

heat treatment. It was shown that the dynamics of magnetic hardening of magnets prepared from

the studied alloy, in whole, corresponds to available concepts on phase transformations in five-

component precipitation-hardened Sm-Co-based alloys during heat treatment. Peculiarities of the

studied compositions consist in the fact that the coercive force magnitude of magnets quenched

from the isothermal aging temperature is higher by an order of magnitude than those available in

the literature.

Keywords: rare-earth permanent magnets, precipitation hardening, sintering, heat treatment,

coercive force.

 

V.N. Mironenko, V.V. Vasenev, M.I. Vedernikova, I.V. Myshlyaev, Zh.A. Karpova, E.A. Shorstova

Structure and mechanism of deformation of stamping of hypereutectic silumines....................................................................78

The possibility of quasi-hydrostatic forging of hypereutectic silumines (up to 45 wt.% Si and

3 wt.% Ni, the value of linear thermal expansion coefficient is (10-15)106 grad.1) is presented.

Methods of optical microscopy, X-ray diffraction, and X-ray spectral analysis have been used to

study the structure of hot-pressed briquettes and blanks of stamped parts made from composites

obtained by mixing or mechanical alloying the matrix powder and disperse silicon. Mechanical

tests were carried out with the use of conventional techniques. Deformation of composites is found

to be increased significantly under three dimensional compression condition. At the pressure of

125-1000 MPa, deformation rate <7.5103 s 1, and temperature of 490-520, ductility of composites

is sufficient to provide the structural integrity of material under the strain of 50%. The structure of

briquettes from mechanically activated powder mixture represents the matrix from sintered particles

with 50 mm Si precipitations on the boundaries. Al3Ni phase particles with the size of 1-3 mm are

uniformly distributed in a-Al. In matrix of stamping, the powder particles are elongated along the

direction of applied stress while the arrangement of the particles of mechanically alloyed silicon

takes place. The volume of a-Al phase is increased and coagulation of Al3Ni phase is happened.

The structure of mechanically alloyed composite becomes more disperse due to repeated milling

and aggregation, and Si particles with the size of 10-15 mm are distributed more uniformly in the

matrix. During the compacting, silicon-free zones of a-Al are formed on the borders of powder

particles and formation of lines and clusters of Al3Ni takes place. When the deformation in stamping

is developed, the volume fraction of a-Al zones is increased and they turn into stripes. On early

stages of deformation, Al3Ni particles look like lines and clusters. In the course of deformation,

Al3Ni particles are gathered in clusters and next the transformation of the particles into stripes

oriented along the direction of deformation occurs and the lines become thinner. It is proposed

that under the 3D compression, deformation of composites is carried out by means of directional

diffusion transfer in a field of the stress gradient which is accompanied by self-consistent diffusion-

viscous flow on grain boundaries. It provides the material integrity, formation of a-Al stripes, and

deformation develop by those stripes. Deformation of mechanically alloyed composite is also

accompanied by grain boundary sliding with Al3Ni-stripes occurring on grain boundaries.

Keywords: hypereutectic powder silumines, hydrostatic forging, mechanical alloying, diffusion

mass transfer, grain boundary sliding.