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1

Structure of the S304H Steel after 20,000 Hours of Ageing

Wersta Robert, Zieliński Adam, Sroka Marek, Puszczało Tomasz, Sówka Karol

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 2

487--493

EN

The S304H steel is used in the construction of pressure components of boilers with supercritical operating parameters. The paper presents the results of the research on the microstructure after ageing for 20,000 hours at 650 and 700°C. The microstructure examination was performed using scanning and transmission electron microscopy. The precipitates were identifies using transmission electron microscopy. The influence of ageing time on microstructure changes and the precipitation process of the tested steel is described. The presented research results are an element of material characteristics of the new generation of steel, which are used in the design work of pressure devices of steam boilers and in diagnostic work during operation.

2

Influence of flame straightening on the properties of welded joints made of X2CrNi22-2 duplex steel

Lange Artur

Materials Science Poland

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2021

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Vol. 39, No. 3

446--457

EN

The study investigates the optimal conditions associated with flame straightening of welded joints in duplex steel grade X2CrNi22-2. The research aimed to assess the influence of heat, applied during flame straightening of welded structures in X2CrNi22-2 grade steel, on the properties of the welded joints. Based on the macroscopic, microscopic, and strength tests conducted on welding joints in X2CrNiN22-2-grade duplex steel that have been subjected to flame straightening, it was ascertained that post-welding flame straightening of this grade of steel, at a treatment temperature of 730°C, should not take place for >1 min. The temperature of 730°C has been chosen as a reference because of the assumption that the welded joints are heated to the temperature of 700–730°C during straightening with an acetylene-oxygen flame. The paper scrutinizes the questions of (i) what changes occur in the welded joints as a result of flame straightening carried out in this temperature range and (ii) what impact those changes have on the joint strength. The results of our study indicate that the duration of post-welding flame straightening of X2CrNiN22-2-grade duplex steel, at a treatment temperature of 730°C, should not exceed 1 min.

3

The sigma phase precipitation during high temperature deformation of the X2CrNiMoN25-7-4 duplex steel

Stradomski G., Jasińska J., Laber K., Sawicki S.

Hutnik, Wiadomości Hutnicze

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2018

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Vol. 85, nr 2

54--57

EN

Steels and other ferrous alloys are very well known as construction materials and still are widely used and in the near future this will not change. Duplex steels due to the two-phase construction combine high corrosion resistance and good mechanical properties. Both those parameters are at higher level than austenitic stainless steels and that why duplex steels are irreplaceable material in many fields like the petrochemical, power, pulp and paper, and food industry. This multiphase microstructure generates a lot of problems which have already been repeatedly presented in many works. Among the steels and cast steels resistant to corrosion most modern and dynamically developing group are ferritic-austenitic alloys, commonly known as duplex. The chemical composition of a steel containing about 0.02% C, 26% Cr, 6.5% Ni, 3% Mo, 1.4% Mn, 0.2% N guarantees that already after casting is obtained ferritic - austenitic structure. The paper present results of the X2CrNiMoN25-7-4 duplex steel physical tests made with the Gleeble 3800 machine. The research concerns problems of the influence of primary structure on the plasticity and sigma phase formation.

PL

Stale obok innych stopów żelaza są dobrze znanymi, szeroko wykorzystywanymi materiałami konstrukcyjnymi i sytuacja taka w najbliższej przyszłości nie ulegnie zmianie. Stale dupleks dzięki swojej dwufazowej budowie cechuje wysoka odporność korozyjna oraz wysokie właściwości mechaniczne. Obydwa te parametry są na wyższym poziomie niż stali austenitycznych i dlatego stale dupleks są niezastąpionym materiałem w wielu gałęziach przemysłu jak petrochemiczny, energetyczny, papierniczy czy w produkcji żywności. Taka budowa mikrostruktury powoduje pojawienie się wielu problemów, które już w wielu pracach były szeroko omawiane. Wśród stali i staliwa odpornego na korozję najszybciej rozwijającą się grupą są stopy ferrytyczno-austenityczne znane również jako dupleks. Skład chemiczny stali zawierającej 0,02% C, 26% Cr, 6,5% Ni, 3% Mo, 1,4% Mn, 0,2% N gwarantuje uzyskanie już w stanie lanym mikrostruktury ferrytyczno-austenitycznej. W pracy przedstawiono wyniki badań fizycznych przeprowadzonych z wykorzystaniem urządzenia Gleeble 3800 na stali X2CrNiMoN25-7-4. Badania dotyczą problemów wpływu mikrostruktury pierwotnej na plastyczność oraz wydzielanie się fazy sigma.

4

Effect of ageing time on microstructure and mechanical properties of SAF 2205 duplex stainless steel

Penha R. N., Silva L. B., Mendonça C. S. P., Moreira T. C., Melo M .L. N. M.

Archives of Materials Science and Engineering

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2018

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Vol. 91, nr 1

23--30

EN

Purpose: The aim of this study was to present the influence of mass concentration of the reinforcement phase on the structure and optical properties of the obtained composite thin films with a polymer matrix reinforced by SiO2, TiO2 and Bi2O3 nanoparticles, produced by the spin-coating method. Design/methodology/approach: To produce composite materials, 10% wt. polymer solutions of polyacrylonitrile (PAN) and N, N - Dimethyloformamide (DMF) were used, containing nanoparticles with a mass concentration ratio of, sequentially: 0, 4, 8, 12%. The morphology, structure and chemical composition of the obtained thin films were determined on the basis of surface topography images, taken using atomic force microscopy (AFM) and a scanning electron microscope (SEM) with EDX and QBSD spectrometers. In order to analyse the optical properties, UV-Visible spectroscopy (UV-Vis) was used. The width of the band gap was determined on the basis of the absorption spectra of radiation (UV-Vis). Findings: The carried out morphology and surface structure research showed that with increasing mass increased porosity of the produced coating surface was observed. In addition, the greater the diameter of the applied ceramic nanoparticles, the more noticeable this effect was. The analysis of the optical properties of the obtained nanomaterials, carried out based on the registered spectra in absorption function of the wavelength, revealed a strong absorption of this type of layers under ultraviolet radiation. Research limitations/implications: The nanostructured materials as components provides nanocomposite optical properties, such as absorption and width of the energy gap. In addition, nanoparticle content causes changes of the surface morphology, which is an important parameter of thin films in potential applications. Originality/value: The properties of films depend not only on the individual components used, but also on the morphology and the interfacial characteristics.

5

Korozja połączenia spawanego wykonanego na stali austenitycznej X2CrNi18-9 wywołana występowaniem fazy sigma

Lachowicz M., Nowak D., Lachowicz M.

Przegląd Spawalnictwa

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2017

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R. 89, nr 8

22--26

PL

W pracy przedstawiono wyniki badań przeprowadzonych w celu ustalenia przyczyny wystąpienia korozji elementu wykonanego ze stali austenitycznej gatunku X2CrNi18-9. Korozję obserwowano w szczególności w obszarach występowania złączy spawanych. Stwierdzono, że przyczyną powstania korozji była obecność fazy sigma wydzielonej podczas spawania badanych elementów konstrukcyjnych. Stwierdzono, że austenit wykazuje anodowy charakter w stosunku do fazy sigma, co prowadzi do inicjacji wżerów korozyjnych w wyniku powstającego efektu galwanicznego i dalszego rozwoju korozji.

EN

The paper presents results of the research performed in order to determine causes of corrosion of the part made of austenitic steel of the X2CrNi18-9 grade. In particular the corrosion was observed in the areas of welded joints. It has been found that the cause of the corrosion was presence of the sigma phase precipitated during welding of the tested structural components. Also, it has been found that austenite shows the anodic character in relation to the sigma phase, which led to initiation of corrosion pits, as a result of the galvanic effect created, and further development of the corrosion.

6

Wpływ fazy sigma na pękanie w warunkach ekspolatacyjnych zawiesi wykonanych ze stali żaroodpornej X8CrTi25

Lachowicz M. M., Lachowicz M. B.

Energetyka

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2017

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nr 10

635-637

PL

W artykule przedstawiono wyniki badań stali X8CrTi25 zastosowanej na zawiesia rurociągów przegrzewacza pary, które uległy wielomiejscowemu pęknięciu podczas eksploatacji z utworzeniem przełomów kruchych. Stwierdzono, że przyczyną powstawania kruchych pęknięć stali były zmiany w mikrostrukturze materiału prowadzące do utworzenia się fazy sigma w formie siatki po granicach ziaren. Doprowadziło to do uzyskania bardzo niskich właściwości plastycznych stali zastosowanej na zawiesia przy zachowaniu jej wysokich właściwości wytrzymałościowych i w konsekwencji do pękania zawiesi.

EN

The article presents the investigation results of X8CrTi25 steel used for slings of superheater pipelines. It has come for multiple crack during their exploitations with creating of brittle fractures. The cause of the steel brittleness was changes in the microstructure of the material, which lead to the formation of the sigma phase in the form of a grid on the grain boundaries. As a consequence, the very low plastic properties of the steel applied to the slings and their damage has archieved.

7

The Analysis of AISI A3 Type Ferritic-Austenitic Cast Steel Crystallization Mechanism

Stradomski G.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 3

229--233

EN

High-alloy corrosion-resistant ferritic-austenitic steels and cast steels are a group of high potential construction materials. This is evidenced by the development of new alloys both low alloys grades such as the ASTM 2101 series or high alloy like super or hyper duplex series 2507 or 2707 [1-5]. The potential of these materials is also presented by the increasing frequency of sintered components made both from duplex steel powders as well as mixtures of austenitic and ferritic steels [6, 7]. This article is a continuation of the problems presented in earlier works [5, 8, 9] and its inspiration were technological observed problems related to the production of duplex cast steel. The analyzed AISI A3 type cast steel is widely used in both wet exhaust gas desulphurisation systems in coal fired power plants as well as in aggressive working environments. Technological problems such as hot cracking presented in works [5, 8], with are effects of the rich chemical composition and phenomena occurring during crystallization, must be known to the technologists. The presented in this work phenomena which occur during the crystallization and cooling of ferritic-austenitic cast steel were investigated using numerical methods with use of the ThermoCalc and FactSage® software, as well with use of experimental thermal-derivative analysis.

8

The Cracking Mechanism of Ferritic- Austenitic Cast Steel

Stradomski G.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 4

153--156

EN

In the high-alloy, ferritic - austenitic (duplex) stainless steels high tendency to cracking, mainly hot-is induced by micro segregation processes and change of crystallization mechanism in its final stage. The article is a continuation of the problems presented in earlier papers [1-4]. In the range of high temperature cracking appear one mechanism a decohesion - intergranular however, depending on the chemical composition of the steel, various structural factors decide of the occurrence of hot cracking. The low-carbon and low-alloy cast steel casting hot cracking cause are type II sulphide, in high carbon tool cast steel secondary cementite mesh and/or ledeburite segregated at the grain solidified grains boundaries, in the case of Hadfield steel phosphorus - carbide eutectic, which carrier is iron-manganese and low solubility of phosphorus in high manganese matrix. In duplex cast steel the additional factor increasing the risk of cracking it is very "rich" chemical composition and related with it processes of precipitation of many secondary phases.

9

Wpływ struktury pierwotnej stali duplex X2CrNiMo25-6-3 oraz X2CrNiMoCuN25-6-3-3 na jej plastyczność

Stradomski G.

Hutnik, Wiadomości Hutnicze

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2015

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Vol. 82, nr 1

122--125

PL

Celem pracy było określenie wpływu mikrostruktury pierwotnej na własności plastyczne stali typu duplex. W pracy badano dwa gatunki różniące się jedynie zawartością miedzi X2CrNiMo25-6-3 oraz X2CrNiMoCuN25-6-3-3. Przedstawione wyniki wskazują bardzo wyraźnie, że zdolność do odkształcenia plastycznego badanych stopów jest bardzo silnie uzależniona od ich mikrostruktury. Innym czynnikiem, który wpływa na parametry plastyczne jest udział w strukturze i sposób wydzielenia się fazy sigma. Faza jak wykazali autorzy wielu prac cechuje się bardzo silnym oddziaływaniem niszczącym już na etapie stanu lanego.

EN

The aim of paper was to determine the influence of primary structure on the plasticity of duplex steels. In the paper were made analysis of two duplex X2CrNiMo25-6-3 and X2CrNiMoCuN25-6-3-3 steels grade with and without addition of copper. Presented results show clearly that on the plasticity of those materials have a very strong influence structure. Other parameter very strongly influencing this parameter is the presence and sigma phase method of formation. As it was presented by many authors this phase have a very strong destroying influence already at the stage of cast.

10

Kinetics of the σ Phase Precipitation in Respect of Erosion-corrosion Wear of Duplex Cast Steel

Brodziak-Hyska A., Stradomski Z., Kolan C.

Archives of Foundry Engineering

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2014

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Vol. 14, iss. 1

17--20

EN

The examined material comprised two grades of corrosion-resistant cast steel, namely GX2CrNiMoN25-6-3 and GX2CrNiMoCuN25-6-3-3, used for example in elements of systems of wet flue gas desulphurisation in power industry. The operating conditions in media heated up to 70°C and containing Cl- and SO4 ions and solid particles produce high erosive and corrosive wear. The work proposes an application of the σ phase as a component of precipitation strengthening mechanism in order to increase the functional properties of the material. The paper presents the results of examination of the kinetics of σ phase precipitation at a temperature of 800°C and at times ranging from 30 to 180 minutes. Changes in the morphology of precipitates of the σ phase were determined using the value of shape factor R. Resistance to erosion-corrosion wear of duplex cast steel was correlated with the kinetics of sigma phase precipitating.

11

Structural aspects of corrosion resistance in alloys based on the Fe3Al intermetallic phase in the cast state

Lachowicz M. M., Haimann K., Lachowicz M. B., Jasionowski R., Pawlak S.

Materials Science Poland

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2012

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Vol. 30, No. 3

217--225

EN

This paper presents the results of investigation of four cast alloys based on the Fe3Al intermetallic phase. Microstructure tests using light microscopy, electron scanning microscopy and X-ray diffraction methods, have been performed. On this basis, a presence of particles rich in zirconium and molybdenum, and in case of the alloy with 28 at.% aluminium and 5 at.% chromium - the presence of sigma phase (FeCr), has been found. Also, the results of the study of the microstructure influence on the electrochemical corrosion resistance in the 5 % NaCl solution have been presented. The Fe-26Al-2Cr-1Mo-0.1Zr-0.005B at.% and Fe-26Al-5Cr-1Mo-0.1Zr-0.005B at.% alloys exhibited increased corrosion resistance in comparison to the Fe-23Al-1Mo-0.1Zr-0.005B at.% alloy without chromium addition. The appearance of the sigma phase in the alloy of Fe-28Al-5Cr-1Mo-0.1Zr-0.005B at.% chemical composition resulted in lowering the corrosion resistance of this alloy and a change in corrosion character from the pitting to the intercrystalline one.

12

Development and verification of work hardening models for X2CrNiMoN25-7-4 super duplex stainless steel after sigma phase precipitation hardening used for FEM simulations.

Szabracki P., Bramowicz M., Lipiński T.

Journal of Power Technologies

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2012

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Vol. 92, nr 3

166--173

EN

The aim of this study was to develop numerical work hardening models for super duplex stainless steel X2CrNiMoN25-7-4. Each model accounts for changes caused by the precipitation of a known quantity (0, 20, 35, 38%) of FeCr intermetallic phase (s). The developed models were applied in FEM simulations of tensile tests for various geometries containing the same quantity of the sigma phase. Calculations were performed for two different geometries – flat and round tensile samples. Correlations between experimental and numerically simulated tensile curves were determined using Pearson's correlation coefficient. The obtained results revealed significant correlations (above 0.9955) between numerical and experimental data.

13

Optimization of sigma phase precipitates with respect to the functional properties of duplex cast steel

Stradomski Z., Brodziak-Hyska A., Kolan C.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 2

75-78

EN

The paper presents the results of examination concerning optimization of the \sigma phase precipitates with respect to the functional properties of ferritic-austenitic cast steel. The examined material comprised two grades of corrosion-resistant cast steel, namely GX2CrNiMoN25-6-3 and GX2CrNiMoCuN25-6-3-3, used for example in elements of systems of wet flue gas desulphurisation in power industry. The operating conditions in media heated up to 70 C and containing Cl- and SO4 ions and solid particles produce high erosive and corrosive wear. The work proposes an application of the \sigma phase as a component of precipitation strengthening mechanism in order to increase the functional properties of the material. Morphology and quantities of \sigma phase precipitates were determined, as well as its influence on the erosion and corrosion wear resistance. It was shown that annealing at 800 C or 900 C significantly improves tribological properties as compared with the supersaturated state, and the best erosion and corrosion wear resistance achieved due to the ferrite decomposition [...] was exhibited in the case of annealing at the temperature of 800 C for 3 hours.

14

Sigma phase in the cast alloy based on the Fe3Al intermetallic phase

Podrez-Radziszewska M., Lachowicz M., Haimann K., Jasionowski R.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 2

105-108

EN

The paper presents study results for cast alloy based on the Fe3Al intermetallic phase. The study material was Fe-28Al-5Cr-1Mo-0,1Zr- 0,005B% at. alloy in the cast state. The microscopic research, phase analysis with X-ray diffraction, bending test and observation of the alloy surface exposed to corrosion have been performed. It has been found that presence of the sigma phase in the material structure influences high hardness of the tested alloy, its susceptibility to brittle fracture and favours the intercrystalline corrosion.

15

The influence of sigma phase on erosion and corrosion properties of duplex steel

Stradomski Z., Brodziak A.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 3

85--88

EN

The paper presents the results of investigations concerning the influence of σ phase precipitating on the erosion and corrosion properties of ferritic-austenitic cast steel. The object of investigation have been two grades of corrosion-resistant cast steel: GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoN25-6-3. The examinations have involved measurements for obtaining potentiodynamic curves, examination of erosion and corrosion resistance, and microstructural analysis. The supersaturated cast steel and the material after heat treatment have been examined. It has been found that the tribological properties of supersaturated cast steel are worse than those of the supersaturated and annealed cast steel. The highest erosion and corrosion resistance has been achieved as a result of ferrite decomposition δ → γ’+ σ. The examinations of corrosion resistance have revealed that the ageing process after supersaturation do not cause significant changes in the anti-corrosive properties.

16

Assessment the possibility of enhancing the tribological properties of the ferritic-austenitic cast steel

Brodziak A., Stradomski Z.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 1 spec.

287--290

EN

The purpose of the research was to explore the possibility of enhancing the tribological properties of the ferritic-austenitic cast steel which is widely used in combustion gas desulphurization systems in the power industry. The subject of the research is the GX2CrNiMoN25-6-3 cast steel, a material for making pump rotors and other parts intended for operation at a temperature of up to 70 °C in a water suspension containing Cl- and SO4-2 ions and sand / gypsum particles. It seems that in some applications, at low dynamics of parts’ operation and a predominance of erosive phenomena over corrosive ones, there is a potential for using the σ phase as a structural constituent that enhances the tribological properties. However, due to the increased brittleness of the material, a need arises for optimizing the quantity of this phase and carrying out detailed research into the morphology of precipitates. To describe the tribological properties, the testing of the erosive and corrosive wear mechanism was used, which was carried out on a test stand of the authors' own construction. Metallographic and stereological examinations and hardness tests were performed, which enabled the understanding of the successive stages of tribological wear of the cast steel under investigation. The increasing volumetric share of the σ phase advantageously influenced the erosive wear resistance of the material.

17

The effect of deformation and annealing on sigma phase precipitation in duplex steels

Witkowska M., Ratuszek W., Ryś J., Zielińska-Lipiec A., Chruściel K.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 1

289-294

EN

The present work concerns the influence of deformation and annealing conditions on sigma phase precipitation in two model ferritic-austenitic steels of duplex type X1CrNi24-6 and X4CrNiMo24-6-2. After the preliminary thermo-mechanical treatment both steels were subjected to cold rolling up to 70% and 90% of reduction and subsequent annealing within the temperature range 600-800°C for various time. X-ray investigations included the phase analysis and texture measurements of the component phases, i.e. austenite (γ), ferrite (α) and sigma phase (δ). Microstructure observations were conducted by means of optical, scanning and electron microscopy. The results of texture and microstructure analysis indicate that the mechanisms of sigma phase precipitation; &alpha —> δ and α—> δ + γ', depend on chemical composition and degree of deformation as well as temperature and time of annealing.

PL

Prezentowana praca dotyczy analizy wpływu odkształcenia i warunków wyżarzania na wydzielanie fazy sigma w dwóch modelowych stalach ferrytyczno-austenitycznych typu duplex X1CrNi24-6 i X4CrNiMo24-6-2. Obie stale po wstępnej obróbce cieplno-mechanicznej poddano walcowaniu na zimno do 70% i 90% odkształcenia a następnie wyżarzano w zakresie ternperatur 600-800°C w różnym czasie. Badania rentgenowskie obejmowaty analizę fazową, pomiary tekstur składowych faz: austenitu, ferrytu i fazy sigma. Obserwacje mikrostruktury przeprowadzono przy użyciu mikroskopu świetlnego, skaningowego i elektronowego. Wyniki tekstury i analiza mikrostruktury wskazują na to, że mechanizm wydzielania fazy sigma α→δ i α→δ+γ' zależy od składu chemicznego, stopnia odkształcenia jak również temperatury i czasu wyżarzania.

18

Significance of the [sigma] phase for the erosive

Stradomski Z., Soiński M. S., Stradomska J., Dyja D.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 3

141-144

EN

The work presents a possibility of increasing the tribological properties of the ferritic-austenitic cast steel (the so called duplex cast steel) of GX2CrNiMoCu25-6-3-3 grade by taking an advantage of the mechanism of precipitation strengthening with the [sigma] phase arisen due to the eutectoidal ferrite decomposition. The examinations have been held using specimens cut out of both a massive casting (an impeller of about one-ton mass) and a thin-walled casting (of the wall thickness about 2 mm). The huge impeller has been made of cast steel containing 0.09% of carbon (i.e. exceeding the demands of the current standard), while the thin-walled casting has been of cast steel with extremely low carbon content (0.024%) due to applying the input material of a great purity. Employing the moulding material with alkaline phenolic binder hardened with CO_2 and using the zirconia coating has allowed for achieving about 20% fraction of [sigma] phase in the as-cast state of the casting. An increase in [sigma] phase fraction in the structure of duplex cast steel results in improving the abrasive wear resistance of the material. It should be stressed that despite the high fraction of the sigma phase in the material, the crack-free castings have been obtained. An addition of copper has made possible producing the high-quality thin-walled (as for cast steel) castings of smooth surfaces. No defects (including shrinkage porosity) have been found.

19

Changes of phase morphology in 29%Cr-6%Ni-3%Mo-3% Cu steel castings with varied wall thickness

Kalandyk B., Augustyn-Pieniążek J.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 1 spec.

175--178

EN

The article discusses the effect of wall thickness and temperature of solution treatment on the morphology of phases present in castings made from 29%Cr-6%Ni-3%Mo-3% Cu steel. The presence of acicular precipitates near the casting surface in as-cast condition was stated. The precipitates ceased to exist after the solution treatment, while volume fraction of the alloyed ferrite increased quite obviously. Compared with parallel investigations carried out on cast steel heats with lower concentration of Cr (24-25%), it has been started that high concentrations of Cr and Mo favour the occurrence of a brittle phase σ, both in as-cast condition and after solution treatment.

20

Influence of carbon content on the segregation processes in duplex cast steel

Stradomski Z., Dyja D.

Archives of Foundry Engineering

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2007

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Vol. 7, iss. 1

139-142

EN

The paper aimed at determination of increased carbon content influence on segregation processes in a duplex ferritic-austenitic cast steel. The analysis of raw cast steel structure was carried out using a Zeiss Axiovert 25 optical microscope. The chemical composition of selected areas was examined using a JEOL JSM 5400 scanning microscope equipped with an EDX microanalyser and the obtained results were verified using the Thermo-Calc software. The investigations carried out have shown that the lower carbon content causes the smaller amount of the intermetallic phases precipitates undesirable in the manufacturing process, which – affecting a clear deterioration in raw cast steel impact strength – promote origination of cracks in the castings. The increased, due to segregation processes, content of carbon, chromium and molybdenum within the solidification grain boundaries promotes precipitation of carbides already in the liquid state, what increases the propensity for hot cracking. The molybdenum content, in a cast steel of increased carbon content, varies from ~4% in the centre of solidification grain to ~6.5% in its boundary areas, and the chromium content from ~28% to 32%, respectively. Small enrichment of ferrite with molybdenum and chromium in boundary areas of cast steel solidification grains containing 0.02% carbon causes higher ferrite stability and prevents its decomposition in the temperature range from 600 to 900°C, what makes that the cast steel of lower carbon content features uniform ferritic-austenitic structure in as cast state.