=Paper=
{{Paper
|id=Vol-2485/paper58
|storemode=property
|title=Processing of Graphic Information in the Study of the Microhardness of the Sintered Sample of Chromium-containing Waste"
|pdfUrl=https://ceur-ws.org/Vol-2485/paper58.pdf
|volume=Vol-2485
|authors=Evgeny Ageev,Sergey Khardikov
}}
==Processing of Graphic Information in the Study of the Microhardness of the Sintered Sample of Chromium-containing Waste"==
https://ceur-ws.org/Vol-2485/paper58.pdf
Processing of Graphic Information in the Study of the Microhardness of
the Sintered Sample of Chromium-containing Waste
E.V. Ageev1, S.V. Khardikov1
1
Southwest state University, Kursk, Russia
The results of graphic information processing and investigation of the microhardness of the sintered sample from chromium-
containing waste are presented. Currently, one of the main directions of development of engineering technology is the improvement of
existing and the development of new waste-free, environmentally friendly, material-saving production processes. Powder metallurgy is a
branch of technology, including the manufacture ofpowders from metals and their alloys and the preparation of blanks and products from
them without melting the main component. In most cases, new materials are created in order to provide the optimal combination ofproduct
price and operational characteristics. Microhardness is the resistance to plastic indentation (usually on a flat surface) of a solid tip in the
shape of a cone or a pyramid made of diamond. With the help of microhardness, they control very small parts, test and sort out watch,
instrument and other products. The aim of the work was to study the microhardness of a sintered sample.
Keywords: graphic information, sintered samples, chrome, spark-erosion powders.
method of electroerosive dispersion, we used a device for EED of
1. Introduction conductive materials developed by the authors of [11- 15] and ball-
bearing steel wastes. Waste was loaded into a reactor filled with a
One of the main directions of development of engineering
working fluid — distilled water; the process was carried out with
technology at the present time is the improvement of existing and
the following electrical parameters: capacitance of discharge
the development of new waste-free, environmentally friendly,
capacitors 65 pF, voltage 150-170 V, pulse repetition rate 110-120
material-saving production processes, that is, those processes that
Hz. As a result of local exposure to short-term electrical discharges
provide blanks with minimal allowances for subsequent machining
between the electrodes, the waste material was destroyed with the
or without them at the same time reducing consumption of scarce
formation of dispersed powder particles. The EED process is the
materials. In solving this problem, a specific role belongs to
destruction of conductive material as a result of local exposure to
powder metallurgy.
short-term electrical discharges between the electrodes. In the
Powder metallurgy is a branch of technology, including the
discharge zone, under the influence of high temperatures, heating,
manufacture of powders from metals and their alloys and the
melting, and partial evaporation of the material occur. To obtain
preparation of blanks and products from them without melting the
high temperature in a limited area of small volume, a large
main component. Using powder metallurgy methods, it is possible
concentration of energy is required. Achieving this goal is carried
to create materials from various components with sharply differing
out using pulsed voltage, and EED is carried out in a liquid medium
properties and melting points, new materials with a diverse set of
(working fluid), which fills the gap between the electrodes, called
physicomechanical properties. Powder metallurgy is used both to
the interelectrode gap.
create fundamentally new materials and products from them, and
Due to the fact that any smooth surface has its own macro- or
to manufacture the widest range of structural parts for general
microrelief, there will always be two points between two
purposes [1-6].
electrodes, the distance between which will be less than between
In most cases, new materials are created in order to provide
other points of the electrode surfaces. When a source of electric
the optimal combination of product price and operational
current is connected to the electrodes, a current begins to flow
characteristics. The obtained results contribute to the introduction
between the electrodes, and an electric field appears, the intensity
of powder metallurgy technologies into production, since this
of which in the area where the gap between the electrodes is
simplifies the technology for producing products, reduces material
minimal will reach its maximum value. The location of this section
loss, and can significantly improve the characteristics of products,
depends on local protrusions, irregularities on the electrodes, on
one of which is microhardness.
the presence and size of electrically conductive particles located in
Microhardness is the resistance to plastic indentation (usually
the interelectrode gap. To describe the processes occurring during
on a flat surface) of a solid tip in the shape of a cone or a pyramid
an electric discharge, we will divide them into three stages.
made of diamond. Much less often, microhardness tests are carried
The first stage of the EED process is the breakdown of the
out by scratching. The difference in microhardness tests from
interelectrode gap (formation of a discharge channel) as a result of
conventional hardness measurements is very small values of
the formation of a zone with high field strength. Under the action
pressing loads and small depth and dimensions of the print.
of the discharge, the working fluid is ionized in the gap through
With the help of microhardness, they control very small parts,
which electric current begins to flow. The second stage is the
test and sort out watch, instrument and other products. The study
formation of a gas bubble near the discharge channel from liquid
of the microhardness of rare and noble metals is possible on
and metal vapor, and heating of the electrodes. The development
quantities not sufficient for the manufacture of a sample for testing
of a discharge in the interelectrode gap is accompanied by the
for ordinary hardness. The fragility of surface layers, coatings (for
appearance of a shock thermal wave, which occurs in the initial
example, chromium plating) and very fragile materials can be
stages of the discharge and leads to the formation of a gas bubble
estimated by the number and nature of the location of cracks
in the working fluid. The third stage will be the cessation of
around the indent [7-10].
current, separation of the shock wave from the gas bubble and the
The aim of this work was to conduct research on the sintering
continuation of its expansion by inertia, the evacuation of erosion
of powders, obtained by electroerosive dispersion of chromium-
products.
containing wastes, and to study the microhardness of sintered
To study the properties of the obtained powder material, it was
samples.
sintered. One of the properties of a sintered sample is
2. Materials and techniques microhardness. The hardness of a material means its resistance to
local plastic deformation when another body penetrates into it that
To obtain powder from ball-bearing steel wastes by the is not subject to such deformation. From the definition it follows
Copyright © 2019 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
that the hardness of the implanted body must exceed that of the test diagonals of the imprint, obtained in the test surface by indenting
sample by a sufficient amount. Consider the definition of hardness a diamond tetrahedral pyramid with an angle at the apex of a =
by the Vickers method. 136°. The values of the diagonals are measured on a microscope.
All methods differ both in measurement technology and in the The main parameters for determining Vickers hardness are: load -
tools and devices used. The most common three methods for 30 kgf, holding time for steels - 10 ... 15 s, the dimension of the
determining the value of hardness: hardness number (kgf / mm2) is not set. Например, 420 HV
Resistance to indentation of a solid tip (indenter) in the test означает твёрдость, полученную при этих параметрах. If the
sample. The shape of the indenter can be very diverse - in the form parameters differ from the main ones (for non-ferrous metals, the
of a cone, ball, pyramid, etc. indenter exposure time for a load is 30 s), then, for example, 450
Scratch resistance with high strength reference samples. HV10 / 15 are recorded - it means that the Vickers hardness
Determination of the rolling resistance of the pendulum, where number 450 is obtained at a load of 10 kgf (98.1 N) applied to
the test body is the support of the tip of a certain shape. Most diamond pyramid for 15 s.
measurements are carried out on a flat surface of the test material.
Each of the methods for determining technical characteristics gives 3. Conduct
a certain error. For greater accuracy, compliance with the
Quanta 3D DualBeam microscope-FEI's most versatile
conditions for the size of the test sample, its minimum thickness,
microscope for 2D and 3D characterization and material analysis,
is required. In addition, each technique works only in a certain
Quanta 3D has three SEM imaging modes (high vacuum, low
range of measurement values. The method of determining Vickers
vacuum, and ambient mode) to enable you to match characteristics
hardness is based on the study of the dependence of the penetration
to a wide range of samples. The built-in focused ion beam (FIP)
depth of the diamond cone (indenter) into the material under study
adds the possibility of obtaining cross-sections of the sample,
on the force magnitude. After removing the force, an imprint
which extends the range of application of the microscope. Natural
remains on the surface of the sample corresponding to the
environment mode allows in situ study of the dynamic behavior of
immersion depth of the indenter. Due to the fact that the
materials at different levels of humidity, temperature and pressure.
geometrical dimensions of the indenter are known and strictly
Quanta 3D DualBeam (scanning electron microscope
regulated, instead of immersion depth, the imprint area in the
combined with focused ion beam system) opens up new
surface layer of the test material is determined.
possibilities and flexibility for engineers and researchers who need
Vickers hardness testing is possible for substances with the
to characterize materials, analyze faults and control processes. The
highest values, since a diamond pyramid is used as a test cone,
system combines traditional thermal scanning electron microscopy
which has the maximum known hardness.
(SEM) with focused ion beam (FIP) in addition to the existing
The indenter is made in the form of a quadrangular pyramid
instruments in your laboratory and extends the range of
with angles between the faces of 136 °. This angle was chosen in
applications for 3D research and nanoanalysis, TEM sample
order to bring the values of the Vickers method closer to the
preparation or structural modification of the sample surface at the
Brinnel method. Thus, the hardness values in the range of 400-450
nanometer scale. (figure 1).
units practically coincide, especially in the region of lower values.
The Quanta 3D DualBeam microscope is a combination of two
Vickers hardness is determined by pressing a pyramid into a test
systems:
sample under the action of a certain magnitude force. Knowing the
- scanning electron microscope (SEM), giving images of a
applied force and the area of the print, it is possible to determine
variety of samples in digital form with a magnification of more
the surface hardness of the test material.
than 100 000 times;
Instead of calculating the imprint area, the values of the
- focused ion beam (FIB), able to quickly and precisely
measured rhombus diagonals are used, between which there is a
remove the layer of the sample material, to expose the structure
direct relationship.
under the surface layer, create a section, place the layer of material,
The final hardness result is determined by the formula:
etc. in addition, ion beam, as well as electronic, can create a high
HV = 1.854-F/d2
resolution image.
In this formula, F - the value of force, and d - the diagonal of
The integration of both systems in one instrument forms a
the rhombus.
powerful analytical tool capable of analyzing a wide variety of
The magnitude of the load depends on the material being
samples in three-dimensional space. Switching between the two
measured (its estimated hardness). As harder the surface of the test
beams allows, on the one hand, fast and accurate navigation, and,
material sample, as greater the load. This is due to the desire to
on the other, the possibility of precision removal of layers of
reduce the error in determining the area and reduce the influence
material. The combination of electron and FIP beams on a short
of the viscosity of the material.
working segment allows the analysis to be carried out in the "cut
To reduce the error, restrictions are also imposed on the size
and saw" mode with high resolution. The workstation provides
of the test sample. The minimum thickness of the sample should
optimal performance, resolution, and automation. In addition, the
be in 1.2-1.5 times larger than the expected diagonal of the print
combination of FIP and SEM technologies in one device adds new
depending on the type of metal (a smaller value corresponds to
possibilities to the microscope:
steel, a larger one is for non-ferrous metals). The distance between
- creation of electron beam images of sections created with
the edge of the sample or the edge of the previous print and the
the help of FIP without erosion of the area of interest;
center of the print should be at least 2.5 diagonal values.
- real-time acquisition by electron beam of individual frames
Special requirements are also imposed on surface cleanliness.
and films simultaneously with removal of material layers by FIP;
Its roughness should not exceed 0.16 microns, which means the
- removal of the charge by the electron beam during removal
need for polishing the surface. The small linear dimensions of the
of the material using FIP;
sample require the use of a microscope to measure the size of the
- microanalysis of defect cross-section elements;
print, and as harder the sample, as more clear the picture must
- imaging of the sample surface by electron beam without
transmit the microscope to maintain measurement accuracy.
erosion or parasitic implantation of gallium ion beam;
Vickers hardness measurement is a universal method, but it
- preparation of samples for transmission electron microscope
gives the most accurate values when studying substances with high
(TEM).
hardness. Small efforts and, consequently, small linear dimensions
Basic advantages:
of the print allow practically not violating the surface of the
Increase visualization and analysis capabilities: capture
measured material.
surface and volume information and reconstruct image and
Vickers microhardness is determined by measuring the
analytical data in three dimensions
Increase throughput and explore larger areas with high current
Quanta FIB for rapid removal (bleed) of material
Empowerment in the field of nanocharacterization using
treatment (2 kV) PAM / nuclear probe / EBSD samples;
removing the amorphous regions without cleaning with argon
Improvement of registration and nanopatterned nonconductive
samples in the "neutralization of the charge"
Increase throughput for your samples with an automated
system for cutting FIP or preparing TEM samples
The ability to work with a wide range of materials, which is
provided by the presence of a large number of detector settings,
flexibility in setting up the system for samples of non-standard
shape or advanced experiments
Increased flexibility in the characterization of samples in a
dynamic environment; keeping samples wet or heating them for
ESEM experiments
Fig. 2. Photo of cross section of sintered specimen
Table 1. Vickers microhardness
Measurement number HV value at 50 g load
1 752
2 746
3 741
4 739
5 743
6 744
7 749
8 877
9 736
10 712
Fig. 1. Quanta 600 FEG microscope Average value 754
Hardness tests of the surface and transverse sections were
carried out using the DM-8 automatic microhardness analysis The spread of microhardness values over the surface is
system by the Micro-Vickers method with an indenter load of 50 associated with an uneven distribution of particles in the sintered
g using ten imprints with a free injection site in accordance with sample.
GOST 9450-76 (Measuring microhardness by indentation of Figure 3 shows a snapshot of one of the injection site with a
diamond tips ). The indenter loading time was 15 s. The diamond tip.
measurement results are shown in table 1. In image analysis it was established that there is an increase in
The results of the study of the sintered chromium- containing the hardness of sintered samples with an increase in sintering
sample microstructure, performed using a Quanta 600 FEG temperature. With increasing sintering temperature, the density
scanning electron microscope, are presented in Figure 2. and strength of the sintered products increase as faster as lower the
From image analysis 2 it was found that the sintered sample pressing pressure. At low temperatures, shrinkage is negligible,
consists of spherical particles, while small particles fill the voids since moisture evaporates, adsorbed gases are removed, and
between the large ones, therefore it is not very porous. This allows surface oxides are reduced. In the region of high temperatures, a
you to more accurately determine the cope of the sintered products significant increase in the metal contact between the particles
obtained. occurs, the pores become denser under the action of surface tension
From the analysis of the image of the microstructure of the forces and the compression shrinks. From the analysis of the image
sintered sample it can be seen that the sintered particles have an of the microstructure of the sintered sample it can be seen that the
equilibrium shape, the boundaries between the particles are sintered particles have an equilibrium shape, the boundaries
thinned, and their continuity is broken. This leads to the between the particles are thinned, and their continuity is broken.
appearance of qualitatively new contact areas with characteristic This leads to the appearance of qualitatively new contact areas with
metallic properties. characteristic metallic properties
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[9] Gusev, V.N. Anodic-mechanical processing of metals
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[10] Hertel N., Ferrous Metal. No 2, 50 (2012).
[11] Janitor M.I. Development of physico-chemical and
technological fundamentals of the processing of tungsten- cobalt
hard alloy by electroerosive dispersion: diss. ... cand. tech.
Sciences / Dvornik Maxim Ivanovich. - Khabarovsk, (2006) . - 116
p.
[12] Kazi I.H., Wild P.M.,. Moore T.N, Sayer M., Thin Solid
Films 515 No 4, 2602 (2006).
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No 1, 18 (2007).
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technology of sintered hard alloys (Moskow: Metallurgy: 1976).
[15] Wang Z., Qiu K., Electrochem. Commun. 8 No 7, 1075
Fig. 3. Photo of the indentation point of the tip (2006).
Thus, a study of the hardness of sintered samples confirms that
a lower fineness of the chromium-containing powder allows for
greater hardness at a lower sintering temperature.
4. Conclusion
The results of the work are as follows. According to the results
of studies of images of sintered samples of chromium- containing
steel, conducted on the microscope Quanta 600 FEG, it was found
that microhardness of sintered samples from powders, obtained by
electroerosive dispersion of chromium-containing waste in
lighting kerosene, is 754 HV. This allows you to determine the
scope of the resulting products.
From image analysis it was found that the sintered sample
consists of spherical particles, while small particles fill the voids
between the large ones, therefore it is not very porous. Thus, the
problem associated with the processing and reuse of chromium-
containing waste can be successfully solved by electroerosive
dispersion and subsequent isostatic pressing at a pressure of 250
MPa and sintering for 2 hours at a temperature of 1250 ° C in
argon.
As a result, by processing images from the microscope Quanta
600 FEG, it was possible to determine the important parameters of
the sintered products obtained from chromium- containing steels
obtained carbon-containing working fluid.
5. Acknowledgments
The work was supported by a scholarship of the President of
the Russian Federation to young scientists and graduate students
(SP-945.2019.1).
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10.05.2012. - 4 p.
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