Influence of Regimes Electrolytic-Plasma Processing on Phase Structure and Hardening of Steel 30CrMnSi

Skakov Mazhyn1,a, Zhurerova Laila1,b, Scheffler Michael2

1D. Serikbayev East Kazakhstan State Technical University, Ust-Kamenogorsk, Kazakhstan,

2Institute of Materials and Joining Technology of Otto von Guericke University, Magdeburg, Germany.

askakovmk@mail.ru., bleila_uka@mail.ru

Keywords: electrolytic-plasma cementation; microhardness; wear resistance; modified surface coating.

Abstract. The present work is devoted research of influence of various modes of electrolytic-plasma cementation on feature of change a structurally-phase conditions and hardening of a constructional steel 30CrMnSi. It is chosen scientifically proved low-power and resources-economy a processing kind which leads to formation stable ferrite-perlites structures, provides higher mechanical properties. Cementation process carried out with selection of different modes of electrolytic-plasma processing in the electrolyte containing water solution of 10 % of sodium carbonate and 10 % of glycerin.

As the basic methods of research in work we used metallographic the analysis with microscope application «NEOPHOT-21», X-ray analysis on diffractometer Х’PertPRO in monochromatic CrKα - radiation, tests for microhardness for device PMT-3. It is established that a microstructure of samples steel 30CrMnSi at different modes of processing consist from α - phases, particle carbides and retained austenite. Microhardness of the initial sample makes approximately 3000 МPа, and after processing its microhardness makes 6100 МPа that speaks about of a processing mode. The developed technology of electrolytic-plasma cementation of constructional steels in the conditions of the arc category in electrolyte is the optimal as provides reliable quality and demanded properties of details, working in variable loadings and often exposed to wear, forms the strengthened, modified surface coating.

Introduction

It is known that in modern applied materials technology the power saving up technologies promoting increase of productivity and working capacity plays very important role for scientific and technical progress in mechanical engineering. The urgency of this problem is especially obvious to manufacture of details of cars from к constructional alloyed steels which are intensively exposed to temperature-power influences of blankets and deterioration. Manufacturing of such details by various methods and modes of electrolyte-plasma processing leads to reduction of the expense of the electric power, labor intensiveness and increase of mechanical qualities. Therefore wide application of technologies of processing in electrolyte plasma is rather perspective direction in machine-building manufacture [1]. From this point of view represents huge interest increase of wear resistance of details of cars by methods of electrolyte-plasma processing.

Material and Methods

In connection with the above-stated, the purpose of the given work working out of an optimum mode of electrolyte-plasma cementation of a constructional steel 30CrMnSi and definition of mechanical properties. As a research material the steel 30CrMnSi in initial condition and after various modes of electrolyte-plasma cementation was used. Chemical compound of steel: 0,3 % of C; 0,8-1,1 % of Cr; 0,8-1,1 % of Мn; 0,8-1,1 % of Si; 0,025 % Р; 0,025 % S, other iron.

Advanced Materials Research Vol. 601 (2013) pp 79-83Online available since 2012/Dec/13 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.601.79

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On the figure 1 the chemical compound and distribution of elements in the sample of the investigated steel, received experimentally on scanning microscope in laboratories of University of Otto von Guericke (Magdeburg, Germany, November, 2011) is resulted.

Figure 1. The chemical compound and distribution of elements in the sample of the investigated steel.

Structural researches of samples of steel 30CrMnSi spent to scientific research institute Nanotechnology and new materials D. Serikbaev East Kazakhstan State Technical University and in scientific laboratories of Institute of materials technology and connecting technologies of University of Otto von Guericke (Magdeburg, Germany) by methods X-Ray analysis on diffractometer Х’Pert PRO in monochromatic CrKα - radiation (λ = 2,2897 Å), optical microscopy on NEOPHOT-21, mechanical tests for microhardness was spent on installation PMT-3 and on installation of measurement of wear resistance at a friction about flexible abrasive particles. Samples after mechanical polishing and polishing were exposed electrolytic to etching in electrolyte containing on 100 cm3 of the distilled water 10 g chromic anhydrite at room temperature, working pressure 6-20 V and density of current 0,1 [A/cm2].

Results and Discussion

Metallographic researches of the initial sample of steel 30CrMnSi, have shown that the steel possesses ferrite-perlite structure. Apparently from figure 2 a, grains perlite and ferrite settle down from each other in random way.

Figure 2. Microstructure (a) and X-ray pattern, line ruling x-ray (b) an initial condition of steel 30CrMnSi.

Approximately ~ 60 % of basic volumes on investigated steel occupy grains perlite. The average sizes of grains perlite make about 12.7 microns and mean sizes of grains on ferrite it has appeared slightly less and has made 9.4 microns. On the figure 2 b are resulted fragment X-ray diffractogramme and line ruling x-ray. Peaks X-ray pattern correspond α - Ғе to phase [2].

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Now we conduct researches on influence of various modes on formation process diffused layers at electrolyte-plasma of processing of constructional steels. Deeper studying of the general kinetics and formation mechanisms diffuses layers on surface processed details of cars in the course carrying out of electrolyte-plasma of processing with use of various electrolytes, will allow receiving the mechanism of formation on structure and properties of processed details. And as, possibility optimizes process of electrolyte-plasma of processing with a view improvement of quality on processed detail, stabilization of its physic-mechanical properties and increase of operational characteristics [1-3].

In connection with the above-stated according to the joint-stock company contract “Science Fund” the Republic of Kazakhstan on theme «Working out and introduction of innovative technologies of electrolyte-plasma hardening of material of the boring tool» have been made installation of electrolyte-plasma processing.

Installation of electrolyte-plasma processing consists of a strengthened detail (cathode), the anode from stainless steel, the drip pan, the pump, the heat exchanger, the power supply, the operated personal computer.

The way of electrolyte-plasma hardening of detail includes processing carrying out in glow-discharge plasma at temperature 850-950°С over 5-10 minutes with various maintenances of electrolyte depending on heating kind (cathode or anode), a chemical compound of processed detail and kind prospective on chemical-thermal treatment (cementation, nitrating, nitro-cementation, carbon-nitration).

Electrolyte-plasma cementation was carried out in water solution 10 %- sodium carbonate and 10 %- glycerin at regimes a) 850°С, 180 sec, 320-180 V; b) 850°С, 360 sec, 320-180 V; c) 950°С, 180 sec, 320-180 V; d) 950°С, 360 sec, 320-180 V. As we see from fig. 3 on borders grains at ferrite of iron carbides and oxides are located.

Figure 3. Microstructure of steel 30CrMnSi after electrolyte-plasma cementation.

On the figure 4 are shown microstructure and X-ray pattern of steel 30CrMnSi оn X-ray

diffractometer X'Pert PRO after electrolyte-plasma cementations. Processing mode 850°С, 180 sec, 320-180 V, water solution of sodium carbonate and glycerin.

Researches have shown that on borders of grains of ferrite iron carbides (Fe5C3) are located.

Figure 4. Microstructure and X-ray pattern of steel 30CrMnSi.

As we see from figure 3 on borders of grains of ferrite iron carbides and iron oxide are located. on X-ray scattering electron-microscope, after electrolyte-plasma cementations (850°С, 180 sec, 320-180 V, water solution of sodium carbonate and glycerin) [4].

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Figure 5. Element analysis surfaces of steel 30CrMnSi.

As have been investigated cross-section samples after various modes of electrolyte-plasma cementation. By results on X-ray scattering electron-microscope after processing depth of the saturated layer makes about 40-50 microns.

Figure 6. Element analysis sample cross-section of steel 30CrMnSi.

After electrolyte-plasma processing of samples of steel conducted tests for microhardness and on abrasive wear resistance.

Figure 7. Tests for microhardness and abrasive wear resistance surface coating sample of steel 30CrMnSi.

Microhardness it was measured on Vickers by loading of 1 N. On a figure 7 it began possible to see increase in microhardness after processing. Abrasive wear resistance of steel was defined on loss of mass on sample steels after processing (look fig. 7). Researches have shown that loss of mass has decreased at temperature 850°С, 180-360 sec [5].

Tests for microhardness measure on installation PМТ-3 on Vickers, load -1 N. Under the received diagramme it is possible to tell that the maximum increase in microhardness is reached at a modes 850°С, 180-360 sec.

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Conclusions

Thus, on the basis of the spent analysis of the received results of electrolyte-plasma processing, it is possible to draw following conclusions:

- electrolyte-plasma processing is the most effective and power saving up technology of processing;

- an optimum mode for reception diffused layer at electrolyte-plasma cementation, is 850°С, 180-360 sec;

- microhardness of steel 30СrMnSi after processing makes approximately 6100 МPa; - abrasive wear resistance on loss of weight of steel makes approximately 0.050-0.060 grams;

- the sated layer which consists from is α - Ғе, as there are iron carbides (Fe5C2) end iron oxides (FeO);

Acknowledgments

This work was supported in party by on the basis of the Agreement between D. Serikbayev East Kazakhstan State Technical University and University of Otto von Guericke Germany, 2008 accordance with the contract of Joint-Stock Company “Fund of Science” the Republic of Kazakhstan on “Development and implementation of innovative technologies electrolytic-plasma hardening of the material drilling tools”.

References

[1] I.V. Suminov, P.N. Belkin, A.D. Epelfeld, B. Ljudin, V.L. Crete, A.M. Borisov “Plazmenno-elektroliticheskoe modificirovanie poverhnosti metallov i splavov,” Moscow: the Technosphere, (2011), p. 464.

[2] J.F. Ivanov, E.V. Kozlov “Obemnaya i poverhnostnaya zakalka konstrukcionnoi stali-morfologicheskianaliz struktury,” Izvestiya vuzov. Phyzika, (2002), №3. p.p .5-23.

[3] P.N. Belkin “Elektrohimiko-termicheskaya obrabotka metallov i splavov,”.M: Mir, (2005), p. 336.

[4] P. Hirsh, А. Hovi, Р. Nicholson “Elektronnaya mikroskopiya tonkih kristalov,” М: Mir, (1968), p. 574.

[5] N.A. Sosnin, S.A. Ermakov, P.A. Topolyanskiy “Plazmennye tehnologiy. Svarka, nanesenie pokrytiy, uprochnenie,” M: Mashinostoenie, (2008), p. 406.

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Management, Manufacturing and Materials Engineering II 10.4028/www.scientific.net/AMR.601 Influence of Regimes Electrolytic-Plasma Processing on Phase Structure and Hardening of Steel

30CrMnSi 10.4028/www.scientific.net/AMR.601.79