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1

Corrosion Resistance of High-Alloyed White Cast Iron

Kawalec M., Krawiec H.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 1

301--303

EN

The paper presents the results of corrosion resistance tests carried out on high-alloyed white cast iron. Tests were performed in 0.1 M NaCl by the technique of linear voltammetry. The test material was collected from six high-vanadium cast iron melts with a variable content of carbon and vanadium, and thus with different microstructure. Studies have confirmed that the type of crystallised microstructure has a very important effect on the alloy corrosion resistance. The highest corrosion resistance showed the alloy with a ferritic matrix containing the spheroidal precipitates of vanadium carbide VC, while the lowest had the eutectic alloy with a pearlitic matrix.

PL

W pracy przedstawiono wyniki badań odporności na korozję wysokostopowego żeliwa białego. Badania przeprowadzono w 0,1M roztworze NaCl techniką woltamperometrii liniowej. Materiał do badań pobrano z sześciu wytopów żeliwa wysoko-wanadowego o zmiennej zawartości węgla i wanadu, a tym samym o różnej mikrostrukturze. Badania potwierdziły, że rodzaj wykrystalizowanej mikrostruktury ma bardzo istotny wpływ na odporność na korozję stopu. Najwyższą odporność na korozję wykazał stop o osnowie ferrytycznej ze sferoidalnymi wydzieleniami węglików VC, natomiast najniższą - eutektyczny stop o osnowie perlitycznej.

2

Resistance to Abrasive Wear and Volume Fraction of Carbides in Cast High-manganese Austenitic Steel with Composite Structure

Tęcza G., Głownia J.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 4

129--133

EN

Cast Hadfield steel is characterised by high abrasion resistance, provided, however, that it is exposed to the effect of dynamic loads. During abrasion without loading, e.g. under the impact of loose sand jet, its wear resistance drops very drastically. To increase the abrasion resistance of this alloy under the conditions where no pressure is acting, primary vanadium carbides are formed in the metallurgical process, to obtain a composite structure after the melt solidification. The primary, very hard, carbides uniformly distributed in the austenitic matrix are reported to double the wear resistance of samples subjected to the effect of a silicon carbide-water mixture.

3

Anisotropic in Situ Metal Matrix Composite Reinforced with VC Carbide Fibres

Kawalec M., Górny M., Sikora G.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 1

21--24

EN

A eutectic reaction is a basic liquid-solid transformation, which can be used in the fabrication of high-strength in situ composites. In this study an attempt was made to ensure directional solidification of Fe-C-V alloy with hypereutectic microstructure. In this alloy, the crystallisation of regular fibrous eutectic and primary carbides with the shape of non-faceted dendrites takes place. According to the data given in technical literature, this type of eutectic is suitable for the fabrication of in-situ composites, owing to the fact that a flat solidification front is formed accompanied by the presence of two phases, where one of the phases can crystallise in the form of elongated fibres. In the present study an attempt was also made to produce directionally solidifying vanadium eutectic using an apparatus with a very high temperature gradient amounting to 380 W/cm at a rate of 3 mm/h. Alloy microstructure was examined in both the initial state and after directional solidification. It was demonstrated that the resulting microstructure is of a non-homogeneous character, and the process of directional solidification leads to an oriented arrangement of both the eutectic fibres and primary carbides.

4

Morphology of Carbides Crystallizing in Fe-C-V and Fe-C-V-Si Alloys

Kawalec M.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 3

1051--1054

EN

Fe-C-V alloys with high vanadium content are included in the family of white cast irons, because all carbon present in this material is bound into vanadium carbides. The study presents the results of microstructural examinations of the volume solidifying Fe-C-V and Fe-C-V-Si alloys containing carbon in the range of 1.38÷4.14%, vanadium in the range of 6.77÷16.34% and silicon in the range of 0÷3.10%. Attention was focused on near-eutectic alloys. In Fe-C-V and Fe-C-V-Si alloys, depending on the chemical composition, can crystallize eutectic composed of ferrite and VC-type carbides highly differentiated morphology. In these alloys were observed following types of eutectic: fibrous eutectic, spiral, quasi-regular and globular. Moreover, both these alloys are crystallized in the form of non-faceted dendrites primary carbides and faceted dendrites primary carbides. The paper presents examples of the different microstructures. Also in order to examine the shape of the primary carbides and eutectics in a closer detail the specimens were deep-etched with aqua regia and then examined in the SEM.

PL

Stopy Fe-C-V o wysokiej zawartości wanadu zaliczane są do grupy żeliwa białego, ponieważ cały węgiel związany jest w węgliki wanadu. W pracy przedstawiono wyniki szczegółowej analizy mikrostruktury stopów Fe-C-V oraz Fe-C-V-Si, o zawartości węgla w zakresie 1,38÷4,14%, wanadu w zakresie 6,77÷16,34% i krzemu w zakresie 0÷3,10%, krystalizujących w sposób objętościowy. Szczególną uwagę zwrócono na stopy okołoeutektyczne. W stopach Fe-C-V i Fe-C-V-Si, w zależności od składu chemicznego, może krystalizować eutektyka składająca się z ferrytu i węglików wanadu typu VC o bardzo zróżnicowanej morfologii. W stopach tych zaobserwowano występowanie następujących typów eutektyk: eutektyki włóknistej, spiralnej, quasi-regularnej oraz globularnej. Ponadto, w stopach tych krystalizują zarówno węgliki pierwotne w postaci dendrytów nieścianowych jak i ścianowych. Przykłady poszczególnych mikrostruktur zamieszczono w pracy. Dodatkowo, w celu szczegółowego przedstawienia morfologii krystalizujących eutektyk oraz węglików pierwotnych, stopy poddano głębokiemu trawieniu wodą królewską, a następnie obserwacji przy użyciu mikroskopu skaningowego.

5

Microstructure Control of High-alloyed White Cast Iron

Kawalec M.

Archives of Foundry Engineering

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2014

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Vol. 14, iss. 1

49--54

EN

This paper presents the results of studies of high-alloyed white cast iron modified with lanthanum, titanium, and aluminium-strontium. The samples were taken from four melts of high-vanadium cast iron with constant carbon and vanadium content and near-eutectic microstructure into which the tested inoculants were introduced in an amount of 1 wt% respective of the charge weight. The study included a metallographic examinations, mechanical testing, as well as hardness and impact resistance measurements taken on the obtained alloys. Studies have shown that different additives affect both the microstructure and mechanical properties of high-vanadium cast iron.

6

Effect of Microstructure of Fe-C-V Alloys on Selected Functional Properties

Kawalec M., Kozana J.

Archives of Foundry Engineering

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2014

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Vol. 14, iss. 3

33--36

EN

The cast alloys crystallizing in Fe-C-V system are classified as white cast iron, because all the carbon is bound in vanadium carbides. High vanadium cast iron has a very high abrasion resistance due to hard VC vanadium carbides. However, as opposed to ordinary white cast iron, this material can be treated using conventional machining tools. This article contains the results of the group of Fe-C-V alloys of various microstructure which are been tested metallographic, mechanical using an INSTRON machine and machinability with the method of drilling. The study shows that controlling the proper chemical composition can influence on the type and shape of the crystallized matrix and vanadium carbides. This makes it possible to obtain a high-vanadium cast iron with very high wear resistance while maintaining a good workability.

7

Modification of the high-alloyed white cast iron microstructure with magnesium master alloy

Kawalec M.

Archives of Foundry Engineering

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2013

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Vol. 13, iss. 2

71--74

EN

High-vanadium cast iron is the white cast iron in which the regular fibrous \gamma + VC eutectic with the volume fraction of vanadium carbide amounting to about 20% crystallises. This paper presents the results of studies on high-vanadium cast iron subjected to the inoculation treatment with magnesium master alloy. The aim of this operation is to change the morphology of the crystallising VC carbides from the fibrous shape into a spheroidal one. The study also examines the effect of the amount of the introduced inoculant on changes in the morphology of the crystallising VC carbides. To achieve the goals once set, metallographic studies were performed on high-vanadium cast iron of eutectic composition in base state and after the introduction of a variable content of the inoculant. The introduction of magnesium-based master alloy resulted in the expected changes of microstructure. The most beneficial effect was obtained with the introduction of 1.5% of magnesium master alloy, since nearly half of the crystallised vanadium carbides have acquired a spheroidal shape.

8

Alloyed white cast iron with precipitates of spheroidal vanadium carbides VC

Kawalec M., Górny M.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 4

95-100

EN

The paper presents the results of tests on the spheroidising treatment of vanadium carbides VC done with magnesium master alloy and mischmetal. It has been proved that the introduction of magnesium master alloy to an Fe-C-V system of eutectic composition made 34% of carbides crystallise in the form of spheroids. Adding mischmetal to the base alloy melt caused 28% of the vanadium carbides crystallise as dendrites. In base alloy without the microstructure-modifying additives, vanadium carbides crystallised in the form of a branched fibrous eutectic skeleton. Testing of mechanical properties has proved that the spheroidising treatment of VC carbides in high-vanadium cast iron increases the tensile strength by about 60% and elongation 14 - 21 times, depending on the type of the spheroidising agent used. Tribological studies have shown that high-vanadium cast iron with eutectic, dendritic and spheroidal carbides has the abrasive wear resistance more than twice as high as the abrasion-resistant cast steel.

9

Abrasive wear resistance of cast iron with precipitates of spheroidal VC carbides

Kawalec M., Olejnik E.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 2

221-226

EN

The paper presents the results of abrasive wear resistance tests carried out on high-vanadium cast iron with spheroidal VC carbides. The cast iron of eutectic composition was subjected to spheroidising treatment using magnesium master alloy. The tribological properties were examined for the base cast iron (W), for the cast iron subjected to spheroidising treatment (S) and for the abrasion-resistant steel (SH). Studies have shown that high-vanadium cast iron with both eutectic carbides and spheroidal carbides has the abrasion resistance twice as high as the abrasion-resistant cast steel. The spheroidisation of VC carbides did not change the abrasion resistance compared to the base high-vanadium grade.

10

The spheroidisation of VC carbides in high-vanadium cast iron

Kawalec M.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 3 spec.

111--116

EN

High-vanadium cast iron is a type of white cast iron, in which a regular fibrous γ + VC eutectic with about 20 vol.% of vanadium carbides crystallises. The paper presents the results of research during which the high-vanadium cast iron was subjected to spheroidisation treatment with magnesium Elmag 5800 master alloy. The purpose of this operation was to obtain the VC carbides of a spheroidal shape. The study also included metallographic examinations and testing of mechanical properties carried out on high-vanadium cast iron of a eutectic composition in as-cast condition and after the spheroidising treatment. The attempt to spheroidise the vanadium carbides has proved to be quite successful. The introduction of magnesium alloy has made nearly one half of the crystallised vanadium carbides acquire a spheroidal shape. The, obtained in this way, high-vanadium cast iron with vanadium carbides of a spheroidal shape showed very high mechanical and plastic properties. The tensile strength Rm increased by 60% compared to the as-cast alloy, while ductility increased more than twenty times. The presented results are based on the initial trials, but further studies of this new material are planned, mainly to check its resistance to abrasion, to impacts and corrosion. Tests are also planned to increase the fraction of spheroidal carbides and measure the effect of their content on the mechanical and tribological properties.

11

Structure and properties of the gradient tool materials based on a high-speed steel HS6-5-2 reinforced with WC or VC carbides

Dobrzański L. A., Kloc-Ptaszna A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

213-237

EN

Purpose: This paper concerns manufacturing and researching a new group of the gradient tool materials, manufactured by a conventional powder metallurgy method, consisting in compacting a powder in a closed die and sintering it. Design/methodology/approach: The materials were obtained by mixing the powders of the HS6-5-2 high-speed steel, tungsten carbide (WC), and vanadium carbide (VC). The mixes were poured one by one into the die, yielding layers with the gradually changing volume ratio of carbides within the high-speed steel matrix. Structural research by using the scanning and transmission electron microscopes, x-ray microanalysis and density, hardness and porosity tests, were performed. Structure and hardness of selected materials after heat treatment were also investigated. Findings: On the basis of the results of the research, it was found that it was possible to obtain gradient materials by the powder metallurgy methods, in order to ensure the required properties and structure of the designed material. It was shown that the new sintered graded materials were characterized by a multiphase structure, consisting of ferrite, primary carbides of the high speed steel, of the MC and M6C type, and dependently of the reinforcement phase, of the tungsten carbide WC or the vanadium carbide VC, which were introduced into the material, in the form of powder. Additionally in the structure of the WC-reinforced materials the W2C phase occurs. The gradient tool materials reinforced with the WC carbide were characterized by a higher hardness, and a lower porosity in relation to the materials reinforced with the VC carbide. It was found that the desired structure and properties (density, porosity and hardness) had the material containing 25% of the WC carbide in the surface layer, after sintering at the temperature 1210oC, for 30 minutes. The heat treatment application causes a significant increase of the surface layer hardness of the material. The highest surface layer hardness, equal to 71.6 HRC, shows the material austenitized at the temperature 1120şC, hardened and tempered twice at the temperature 530oC. Practical implications Developed material is tested for turning tools. Originality/value: The material presented in this paper has layers consisting of the carbide-steel with growing hardness on one hand, and the high-speed steel, characterized by a high ductility on the other.

12

Napawanie plazmowo-proszkowe warstw stopu Fe-Cr-W-Mo z węglikiem wanadu

Bober M., Senkara J.

Spajanie Metali i Tworzyw w Praktyce

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2007

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nr 1(16)

16-21

PL

Przedstawiono wyniki badań napawania plazmowo-proszkowego powłok o strukturze kompozytowej stop Fe-Cr-W-Mo-VC pod kątem doboru podstawowych parametrów procesu dla uzyskania optymalnego rozcieńczenia napoin materiałem podłoża (stal 18G2A). Zbyt niska energia liniowa procesu prowadzi do niedostatecznego związania z podłożem, zbyt wysoka do zmniejszenia udziału VC w napoinie. Przedstawiono graficznie kombinacje natężenia prądu łuku zewnętrznego, szybkości napawania i wydatku proszku, dla których uzyskuje się stopień rozcieńczenia rzędu 7% obj.

13

Effect of small additions of vanadium and niobium on structure and mechanical properties of ductile iron

Fraś E., Górny M., Kawalec M.

Archives of Foundry Engineering

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2007

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Vol. 7, iss. 1

89-92

EN

Results of investigations of influence of small additions of vanadium (up to 0,15% V) and niobium (up to 0,04% Nb) on structure of ductile iron is presented in this work. Effect of these additions on distribution of graphite nodule diameter, nodule count, fraction and carbide count have been determined. Investigations of effect of small additions of vanadium and niobium on mechanical properties taking into account tensile strength, yield strength and elongation have also been made.

14

Synteza nonocząstek węglika wanadu w żeliwie sferoidalnym

Fraś E., Blicharski M., Dymek S., Guzik E., Kawalec M.

Archiwum Odlewnictwa

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2006

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R. 6, nr 18/2

65--70

PL

W pracy opisano metodę syntezy nanocząstek węglika wanadu w żeliwie sferoidalnym. Wykazano, że po wysokotemperaturowej austenityzacji przy temperaturze 1095ºC, i następnym schłodzeniu z szybkością około 100ºC/min do temperatury 640ºC oraz wytrzymaniu żeliwa w tej temperaturze przez okres czasu 16 godz, otrzymuje się w ferrycie nanocząstki węglika wanadu o wymiarach do około 70 nm i bardzo dużej gęstości wynoszącej około 1,2 107 cząstek/mm-2.

EN

In work a method of synthesis of nanoparticles of vanadium carbides in ductile iron was presented. It has been proved that high-temperature austenitizing at temperature of 1095ºC with the following cooling with the speed of 100ºC/min up to temperature 640ºC where cast iron is held for 16 hr. gives nanoparticles of vanadium carbides embedded in ferrite to 70 nm in size and with high density in the range of 1,2 107 mm-2.