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1

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.

2

Dry Sliding Wear Behavior of Super Duplex Stainless Steel AISI 2507: A Statistical Approach

Davanageri M., Narendranath S., Kadoli R.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 4

47--56

EN

The dry sliding wear behavior of heat-treated super duplex stainless steel AISI 2507 was examined by taking pin-on-disc type of wear-test rig. Independent parameters, namely applied load, sliding distance, and sliding speed, influence mainly the wear rate of super duplex stainless steel. The said material was heat treated to a temperature of 850°C for 1 hour followed by water quenching. The heat treatment was carried out to precipitate the secondary sigma phase formation. Experiments were conducted to study the influence of independent parameters set at three factor levels using the L27 orthogonal array of the Taguchi experimental design on the wear rate. Statistical significance of both individual and combined factor effects was determined for specific wear rate. Surface plots were drawn to explain the behavior of independent variables on the measured wear rate. Statistically, the models were validated using the analysis of variance test. Multiple non-linear regression equations were derived for wear rate expressed as non-linear functions of independent variables. Further, the prediction accuracy of the developed regression equation was tested with the actual experiments. The independent parameters responsible for the desired minimum wear rate were determined by using the desirability function approach. The worn-out surface characteristics obtained for the minimum wear rate was examined using the scanning electron microscope. The desired smooth surface was obtained for the determined optimal condition by desirability function approach.

3

The effect of silicon content on the pitting corrosion of duplex stainless steel weldment

Lee B.H., Lee H.J., Kang D.W., Lee H.W.

Archives of Materials Science and Engineering

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2014

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Vol. 67, nr 2

60--69

EN

In this study, the effect of Si content at a welded DSS on the pitting resistance was investigated. Design/methodology/approach: The δ-ferrite fraction increased due to addition of Si, and the amount of γ2 decreased. In the ferric chloride pitting test, the weight reduction range decreased due to an increase in the Si content. As to the location, pittings occurred intensively at the grain boundary or within the austenite grain due to the difference in PREN caused by the differential solid solubility in each phase. Findings: As a result of the potentiodynamic polarization test, while the Epit(Critical Pitting Potential) of all specimens depending on the temperature were observed to be similar at froom temperature up to 45°C, the reduction range of the Epit was found to be small at the temperature higher than 45°C as Si content increased. This was found to be because of formation of SiO2 in the passive film. Research limitations/implications: Higher the addition of Si, the more the number of pittings generated at the grain boundary decreased as the coherence of the passive film increased by the Si accumulated at the boundary. Originality/value: In this study, we intend to investigate the effect of Si element addition on the pitting resistance of the duplex stainless steel welding zone.

4

About heat treatment and properties of Duplex Stainless Steels

Rosso M., Peter I., Suani D

Journal of Achievements in Materials and Manufacturing Engineering

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2013

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Vol. 59, nr 1

26--36

EN

Purpose: of this paper is to review the effect of heat treatments and of strain hardening on microstructure and properties of superduplex stainless steels. Design/methodology/approach: Annealing and strain hardening treatments influences microstructures and properties. Findings: The characteristics and the properties of the industrially employed superduplex grade has been discussed, moreover the presence and the precipitation of sigma phase has been highlighted through ageing treatments. Research limitations/implications: : Based on the up to date achieved outcomes, it appears that a quite homogeneous and good mechanical properties can be obtained controlling the composition and the heat treatment and strain hardening parameters. Practical implications: The major implication is related to the transfer toward the proper choice of correct parameters for working the duplex grades. Originality/value: to supply deeper information with respect to those available in literature, which does not clearly indicate what amount of secondary phases existing in duplex stainless steel microstructure can be acceptable.

5

Zgrzewanie rezystancyjne punktowe stali stopowej typu duplex - założenia wstępne

Kliś B.

Prace Naukowe Politechniki Warszawskiej. Mechanika

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2009

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z. 229

155-162

PL

Na podstawie danych literaturowych przedstawiono krótką charakterystykę stali duplex, zestawiono jej zalety i problemy występujące podczas jej spawania. Opisano wyniki dotychczasowych prób zgrzewania rezystancyjnego punktowego stali 2205. W wyniku przeprowadzonej analizy postawiono tezę istnienia możliwości wykonania prawidłowego złącza stali duplex 2205 tą metodą.

EN

On the basis of literature data a short characteristic of duplex stainless steel was presented along with advantages and problems occurring during its fusion welding. To-date tests results of resistance spot welding of 2205 type steel were also described. As a result of analysis performed the thesis was formulated on the feasibility of obtaining proper 2205 duplex steel welds by resistance spot welding.

6

The influence of sintering time on the properties of PM duplex stainless steel

Brytan Z., Dobrzański L. A., Actis Grande M., Rosso M.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

387-396

EN

Purpose: The purpose of this paper is to analyse the effect of sintering time on the pore morphology, microstructural changes, tensile properties and corrosion resistance of vacuum sintered duplex stainless steel. Design/methodology/approach: In presented study PM duplex stainless steels were obtained through mixing base ferritic stainless steel powder with controlled addition of elemental alloying powders and then sintered in a vacuum furnace with argon backfilling at 1250°C for different time periods. Produced materials were studied by LOM/SEM metallography and the pore morphology was characterized. The mechanical properties were studied in tensile, hardness and Charpy impact tests. The corrosion resistance was evaluated by means of salt spray test and immersion in sulfuric acid. Findings: Prolongation of sintering time influenced on increase of density thus on the mechanical properties and microstructure balance. Practical implications: Mechanical properties of obtained PM duplex stainless steels are very promising, especially with the aim of extending their field of possible applications. Originality/value: The possibility of obtaining balanced austenitic-ferritic microstructure of stainless steel using elemental powders added to a stainless steel base powder. The vacuum sintering of such powder mixture results in good microstructural homogeneity.

7

Effect of microstructure on impact toughness of duplex and superduplex stainless steels

Topolska S., Łabanowski J.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 36, nr 2

142-149

EN

Purpose: of this paper is to study the effect of heat treatments and resulting changes in microstructure on mechanical properties, mainly impact toughness, of commercial 2205 duplex stainless steel and higher alloy superduplex 2507 grade. Design/methodology/approach: Both steels were submitted to ageing treatments in the temperature range of 500-900 °C with exposure time periods 6 minutes, 1 hour and 10 hours. Light microscope examinations, hardness measurements and impact toughness tests were performed in order to reveal microstructure and changes in mechanical properties. Findings: Obtained results confirm that high temperature service of duplex stainless steels should be avoided. Precipitations of secondary phases (mainly ó phase) strongly deteriorate mechanical properties of steels but some amounts of these phases could be acceptable in the microstructure depending upon the application of the steel. Research limitations/implications: Presence of secondary phases in duplex stainless steel microstructure can be very harmful for its corrosion resistance. This phenomenon is not considered in this study. Practical implications: The accidents during exploitation and errors in processing of duplex stainless steels can result in undesired temperature growth over 500°C. Such events brings question whether the steel can be still exploited or not. The aim of present study is to reveal the effect of thermal cycles on structural changes and mechanical properties of duplex stainless steel and establish the highest acceptable time-temperature conditions for safe operation of the steel. Originality/value: Information available in literature does not clearly indicate what amount of secondary phases existing in duplex stainless steel microstructure can be acceptable. The current study shows that duplex 2205 steel affected by thermal cycles and containing about 10% of sigma phase still exhibit acceptable mechanical properties.

8

The effect of starting orientations and initial morphology on texture formation in duplex steel SAF 2205

Ryś J., Witkowska M.

Archives of Metallurgy and Materials

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2009

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Vol. 54, iss. 3

789-803

EN

The present investigations concern the rolling texture formation and changes in morphology of two-phase structure in cold-rolled mid-alloy duplex stainless steel SAF 2205 with addition of nitrogen. The preliminary thermo-mechanical treatment included hot-rolling with subsequent solution annealing at the temperature 1150C. Afterwards the steel was cold-rolled within the wide range of reductions by applying two different variants, with rolling directions perpendicular and parallel to the direction of hot-deformation. Texture analysis indicates that austenite shows tendency to develop the textures similar to those in one-phase austenitic steels regardless of the applied cold-rolling variant and the final rolling textures of ferrite significantly differ from the typical textures of ferritic steels. Formation of the texture close to the {110}<112> alloy-type texture was observed in austenite and the orientation changes proceeded gradually over a wide range of reductions, especially for the cold-rolling variant perpendicular to the direction of hot-deformation. On the other hand the major component of the ferrite starting texture, i.e. the rotated cubic orientation {001}<110> and the character of texture spread, which is different for both rolling variants, remained essentially unchanged up to high deformations. It is concluded that the starting orientations of both constituent phases after the preliminary treatment and the band-like morphology of the ferrite-austenite structure considerably influence formation of the cold-rolling textures in the examined duplex type steel.

PL

Prezentowane badania dotyczą rozwoju tekstur walcowania i zmian morfologii struktury dwufazowej w walcowanej na zimno średnio-stopowej nierdzewnej stali duplex w gatunku SAF 2205 z dodatkiem azotu. Wstępna obróbka cieplno-mechaniczna obejmowała walcowanie na gorąco oraz wyżarzanie i przesycanie z temperatury 1150C. Stal poddano następnie walcowaniu na zimno w szerokim zakresie deformacji, stosując dwa różne warianty z kierunkami walcowania prostopadłym i równoległym do kierunku odkształcenia na gorąco. Analiza tekstur wskazuje, że niezależnie od zastosowanego wariantu walcowania na zimno austenit wykazuje tendencje do tworzenia tekstur odpowiadających tym w jednofazowych stalach austenitycznych natomiast końcowe tekstury walcowania ferrytu różnią się istotnie od typowych tekstur stali ferrytycznych. W austenicie obserwuje się rozwój tekstur zbliżonych do tekstury typu stopu {110}<112>, a w przypadku wariantu walcowania na zimno prostopadle do kierunku odkształcenia na gorąco zmiany orientacji zachodza stopniowo w szerokim zakresie odkształceń. Z kolei główna składowa tekstury początkowej ferrytu, tzn. orientacja skręcona sześcienna {001}<110> jak również charakter rozmycia tekstury ferrytu, odmienny dla obu wariantów walcowania, pozostają zasadniczo nie zmienione do wysokich odkształceń. Należy stwierdzić, że orientacje początkowe obu faz po obróbce wstępnej oraz pasmowa morfologia ferrytu i austenitu wywierają istotny wpływ na tworzenie się tekstur odkształcenia podczas walcowania na zimno badanej stali typu duplex.

9

Corrosion resistance of sintered duplex stainless steel evaluated by electrochemical method

Dobrzański L. A., Brytan Z., Actis Grande M., Rosso M.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

317--320

EN

Purpose: Purpose of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated. Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements. In the studies behind the preparation of mixes, Schaffler’s diagram was taken into consideration. Prepared mixes have been compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1h. After sintering two different cooling cycles were applied: rapid cooling with an average cooling rate of 245°C/min and slow cooling of 5°C/min in argon atmosphere. Findings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good corrosion properties. Corrosion resistance of sintered stainless steels is strictly connected with the density and the pore morphology present in the microstructure too. The highest resistance to pitting corrosion was achieved for composition with approximate balance of ferrite and austenite in the microstructure. Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for corrosion properties and microstructures, nevertheless further tests should be carried out in order to examine different cooling rates and sintering temperatures. Originality/value: The use of elemental powders added to a stainless steel base showed its potentialities, in terms of fair compressibility and final sintered density. In addition a good structural homogeneity and first of all corrosion resistance was achieved, also working with cycles possible for industries.