=Paper=
{{Paper
|id=Vol-2485/paper60
|storemode=property
|title=Problems of Analyzing Microstructure Images in Assessing the Impact of Technological Parameters of Combined Strain Wave Hardening on the Quality of the Surface Layer
|pdfUrl=https://ceur-ws.org/Vol-2485/paper60.pdf
|volume=Vol-2485
|authors=Andrey Kirichek,Dmitriy Solovyev,Aleksandr Khandozhko,Svetlana Fedonina
}}
==Problems of Analyzing Microstructure Images in Assessing the Impact of Technological Parameters of Combined Strain Wave Hardening on the Quality of the Surface Layer==
https://ceur-ws.org/Vol-2485/paper60.pdf
Problems of Analyzing Microstructure Images in Assessing the Impact of
Technological Parameters of Combined Strain Wave Hardening on the
Quality of the Surface Layer
A.V. Kirichek1, D.L. Solovyev2, A.V. Khandozhko1, S.O. Fedonina1
avkbgtu@gmail.com|murstin@yandex.ru|chandosh@yandex.ru|fedonina.sv2015@gmail.com
1
Bryansk State Technical University, Bryansk, Russia;
2
Vladimir State University, Murom branch, Murom, Russia
The problems of analyzing metallographic images and the method of their solution using modern software for the analysis of
metallographic images are described. There is given an analysis of microstructure images as the main indicator of the surface layer quality
by the example of studying the research results of strain wave hardening combinations and chemical-thermal treatment, in particular the
influence of previous strain wave hardening and subsequent thermal and chemical- thermal treatment on the alloy steel microstructure or
previous thermal and chemical- thermal treatment and subsequent strain wave hardening. On the basis of the analysis the effectiveness of
strain wave hardening and chemical and thermal treatment is established
Keywords: analysis, image, hardening, surface plastic deformation, surface layer, carburization, chemical and thermal treatment,
microstructure
the case of combined types of processing - both in size and phase
1. Introduction components. Taking into account FST peculiarities, the hardened
Constant development of computer technologies and methods layer in most cases has an implicit boundary, the detection of which
of digital processing of images allows to accelerate and simplify depends not only on the quality of preparing the microsection and
research in all fields of science and technology. Using image the correct selection of pickling solution, but also on the
analysis in assessing the quality of the surface layer gives the physiological data of the researcher. When conducting a simpler
opportunity to identify the best processing methods that would best study that is comparing several images of microstructures, there are
meet the requirements of the surface layer. not only the problems mentioned above, but also the problem of
The study of microstructure is one of the main tasks of obtaining the original image. Even with completely identical
materials science, which allows not only to vary the mechanical preparation and processing of microsections, the final images of
properties of the surface layer and the performance properties of microstructures may differ in brightness and color rendering, which
the finished part with a change in the phase composition, but also significantly complicates the processing and analysis of the data
to create innovative materials or improve the properties of existing obtained by the researcher. Thus, the main tasks of implementation
materials. The effectiveness of the metallographic analysis depends of microstructure studies, are segmentation, filtering of defects and
on many factors, ranging from the quality of preparation of samples selection of objects from the background, determining the limits of
to the subjectivity of observations and low speed of the research objects, as well as image recognition [1,4].
process [1]. When conducting research, especially on metallographic
2. Main Part equipment, which does not allow to change such object
Images of microstructure are a combination of various characteristics as intensifying the image sharpness and brightness,
structural components with the most common geometric segmentation is quite problematic. Special software is required to
dimensions and shapes, distributed unevenly and differently improve the image quality, allowing to select all structural objects
oriented. The combination of these structural components often [5, 8-10]. However, this does not solve all the problems of
gives a complex result, which is difficult to interpret without a metallography. Even with a very long and high-quality preparation
sufficient level of training. Therefore, the main requirement for the of samples micro-scratches may remain on the surface of the
qualitative analysis of images is to select phase components on the microsection, for example, when studying the modes of applying a
microstructure image under study, followed by classification and softer and more plastic material (bronze) on a steel part. When
analysis according to the most significant quantitative processing the resulting image, the program may evaluate such
characteristics. These can be both geometrical parameters of grains defects incorrectly, which will negatively affect the final analysis
and percentage ratio of structural components in the investigated of the microstructure. Therefore, when using auxiliary programs for
image or on the desired depth of a sample. When studying not one research, it is still impossible to rely on the software fully [6] and
image, but several linked images, it is possible to obtain complete there should be an ability for the operator to change and adjust the
information about the change in the phase composition of the data during running of the program.
microstructure at the sample depth concerned, for example, when One of the most promising ways to solve these problems is to
studying the hardening of the surface layer. In this case, at the depth use auxiliary software that analyzes the images in order to increase
depending on the type of applied finishing and strengthening the efficiency of quantitative analysis.
treatment (FST), structural components should vary either in size At present there are a sufficient number of programs for
and orientation or phase components of the microstructure, and in speeding up and simplifying the research process. The most
Copyright © 2019 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
effective are considered the following: PHOTOM, OPTIMUS, of parts was processed by surface plastic deformation – strain wave
VIDEOTEST, IMAGE EXPERT PRO, IMAGE, AVISO, hardening (SVH) [2], and then subjected to chemical-thermal
SMARTEYE and many others. These programs have all necessary treatment (CTT), and in the second case previously hardened by
algorithms for processing technical images: high-frequency and CTT surface layer was then strengthened by wave deformation.
low-frequency filtering, selection of image boundaries, arithmetic CTT hardening was carried out in several stages: 1. double-ended
and logical operations, brightness/contrast correction, etc. Image carburization; 2. interrupted quenching: I-quenching at temperature
processing in this case is not aimed at improving visual perception, of 930°, II-quenching at temperature of 790°, with cooling in oil; 3.
but at preparing it for further analysis [1,7,11,12]. backing. Depending on the combination, surface plastic
The result of metallographic studies using specialized software deformation hardening was carried out before or after CTT [3].
is the statistical analysis obtained in the process of measuring the The samples under study were compared according to the
characteristics of objects and determining the mean of these values, microstructure of the hardened layer, Figure 1. The images obtained
as well as the construction of graphical dependencies for well characterize the problems of metallographic studies described
visualization of the analysis process. However, it is not possible to above: different color rendition of images, identification of
rely entirely on the results obtained by the software without further structural components and boundaries of the hardened layer. These
analysis of the data obtained in terms of evaluation of materials images do not allow to define reliably the ratio value of structural
science. components and their distribution over the entire depth of
The problems of analyzing microstructure images in assessing hardening. Taking into account the complex combined processing
the quality of the hardened surface layer of parts is shown by the of parts it is problematic to determine the depth range of hardening
example of studies on hardening of alloy steel 10XSND. The study with great accuracy, as there is no significant difference between
is carried out on a metallographic microscope to determine the the grain size and the change of phase composition. In this case, the
phase composition of the hardened metal, the characteristic grain hardening boundary smoothly passes into the microstructure of the
size, grain density, depth of hardening, as well as the detection of sample core. Images were processed without using auxiliary
defects in the hardened surface layer. The study objective is to software for analysis and preparation of images, which complicated
identify the most optimal combination of hardening of the part the process of comparison and analysis of microstructures. All
surface layer. these measurements were carried out using a metallographic
Samples identical in size and thickness were gradually microscope.
subjected to different FST types. In the first case, the surface layer
Hardening by CTT+SVH Hardening by SVH+CTT
Depth of the hardened layer, х158
Subsurface layer of samples
Depth 220…320 microns
Depth 1400…1500 microns
Sample cores
Fig. 1. Comparison of microstructures of 10KHSND steel samples hardened according to various schemes, х2550
Processing, analysis and assessment of the samples revealed sorbite. At the depth of 400 microns, the microstructure is needle-
the main features of microstructures. The microstructure of the like, there is a slight increase in the size of the needles up to 4-5
subsurface layer of the sample, hardened according to CTT+SVH microns, there is a large number of sorbite bands. At the depth of
type, is finely dispersed, but the grains are elongated of martensite. 1400 microns, the microstructure is combined of three components
tempering. At the depth of about 220 microns, the combined - fine-needled, densely-packed martensite, fine grains and sorbite
structure begins: fine-needled martensite appears more clearly, the bands. No obvious martensite needles were found deeper than
needles are up to 3 microns, there are a few small implicit bands of
1500...1600 microns, the microstructure gradually passes into the [7] Bodla KK, Murthy JY, Garimella SV. Microtomography-based
structure of the sample core. simulation of transport through open-cell metal foams. Numer Heat
The microstructure of the subsurface layer, hardened according Transfer Part A 2010;58(7):527.
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number of crystallization centers.
The use of auxiliary software, which gives the opportunity to
analyze the image of microstructures, would allow to assess the
ratio of phase structures and determine the ranges of changes in the
phase composition better. The availability of these data
significantly facilitates and supplements the studies.
3. Conclusion
Thus, the use of modern technologies and analysis of
microstructure images can significantly speed up and simplify the
research process. The study gives the opportunity to determine that
carburization of surface, pre-hardened by wave deformation
provides a more finely dispersed, even and densely-packed
microstructure than hardening by wave deformation of previously
carburized surface. This helps to improve the mechanical properties
of the hardened surface and allows to provide for their smooth
distribution over the whole section of the part.
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