Mestrado em Engenharia Mecânica

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Agora exibindo 1 - 18 de 18

Análise da influência de tratamento térmico na resistência à corrosão-erosão do aço inoxidável AISI 304
(Universidade Federal do Espírito Santo, 2008-12-18) Louzada, Dímisson Abreu; Macêdo, Marcelo Camargo Severo de; Franco, Sinésio Domingues; Bozzi, Antônio César
This work intends to evaluate the damaged caused by the erosion-corrosion process of a stainless steels AISI 304, under four microstructures conditions, used in various applications by the erosion, corrosion, and erosion-corrosion rates. With these rates it is possible to verify if there is a synergistic effect under the test conditions. For that reason, a slurry pot tester was useful. The experiments were performed at an impact of 7,5 m/s at room temperature. The abrasive particles of quartz used are in granulometric range 150 μm and an average sand concentration of 4 % wt. The corrosion and erosion-corrosion tests were performed in a solution of sodium chloride and acetic acid with 10-3 mol/l of sodium thiosulfate which is used to simulate the effect of the H2S presence. The samples obtained from dowel steel are cylindrical with 4,76 mm diameter and were weighted before and after each test. The erosion rate is in good agreement with the literature and is higher for solubility samples. The erosion rate is higher than the corrosion rate. The synergistic effect was observed for the test conditions.
Análise da influência de tratamento térmico na resistência a corrosão-erosão do aço inoxidável AISI 304
(Universidade Federal do Espírito Santo, 2008-12-18) Louzada, Dímisson Abreu; Macêdo, Marcelo Camargo Severo de; Bozzi, António Cesar; Franco, Sinésio Domingues
This work intends to evaluate the damaged caused by the erosion-corrosion process of a stainless steels AISI 304, under four microstructures conditions, used in various applications by the erosion, corrosion, and erosion-corrosion rates. With these rates it is possible to verify if there is a synergistic effect under the test conditions. For that reason, a slurry pot tester was useful. The experiments were performed at an impact of 7,5 m/s at room temperature. The abrasive particles of quartz used are in granulometric range 150 µm and an average sand concentration of 4 % wt. The corrosion and erosion-corrosion tests were performed in a solution of sodium chloride and acetic acid with 10-3 mol/l of sodium thiosulfate which is used to simulate the effect of the H2S presence. The samples obtained from dowel steel are cylindrical with 4,76 mm diameter and were weighted before and after each test. The erosion rate is in good agreement with the literature and is higher for solubility samples. The erosion rate is higher than the corrosion rate. The synergistic effect was observed for the test conditions.
Análise de difusividade térmica em aço duplex UNS S32304 submetido a diferentes processos de soldagem TIG e tratamento térmico
(Universidade Federal do Espírito Santo, 2016-05-13) Bolsanello, Marilia Fernandes; Passos, Carlos Augusto Cardoso; Orlando, Marcos Tadeu D'Azeredo; Macêdo, Marcelo Camargo Severo de; Rossi, Jesualdo Luiz; Passamai Junior, José Luis
Thermal diffusivity of UNS S32304 stainless steel was evaluated with the purpose ofaggregate knowledge to the development of the radioactive material transportation containment receptacles project.The Flash Lased Method was used, which is based on unidimensional thermal diffusivity equation analytical solution. A carbon dioxide laser with Gaussian profile was used, with 10−6𝑚wavelength, 10√2𝑊𝑚2⁄intensity and 10√2𝑊𝑚2⁄diameter.A sample of material was analyzed as received, in order toobtain a reference diffusivity value, and to compare with the value provided by the supplier, which ensured the method effectiveness. Thereafter, a sample welded by TIG autogenous process, with argon shield gas, was tested to analyze the welding process influence under thermal diffusivity. A sample welded by the same procedure, but heat treated under 600 °C for 8 hours and cooled by air was also analyzed, to evaluate the effect of these steels exposure to high temperatures after welding. To do so, in both welded samples, points with variable distance to sample middle were taken, including molted zone, heat affected zone and base metal. Finally, obtained results were compared to previous optical microscopy, ray X diffraction characterization, micro hardness and residual stresses analysis. It could be observed that thermal diffusivity was affected not only by welding process but also by heat treatment. Most of the points presented reduced thermal diffusivity, assigned to a material thermal conductive reduction, harmful for the use in question, once it will respond slowly to thermal changes. The heat treated sample presented diffusivity values closer to the material as received, qualitative similar results were also observed on residual stresses tests, where thermal treatment equalized materials stress state. Besides that, the molting zone point, at the sample only welded, presented a thermal diffusivity value above the one founded at base metal, which can be related to structural changes caused by heating. Nevertheless, those are partial conclusions, reinforcing the need of deeper studies concerning stainless steel UNS S32304 thermal diffusivity.
Análise de difusividade térmica na junção metal/cerâmica UNS 32304/sílico-aluminosa 45-50
(Universidade Federal do Espírito Santo, 2018-05-07) Caliari, Hendricky Fassarella; Orlando, Marcos Tadeu D'Azeredo; Soares, Jacyra Ramos; Martins, Charles de Abreu; Passos, Carlos Augusto Cardoso
Fireclay bricks are widely used in industries where exist high temperature gradient from the working face to the cold face of the material. In the steel industry, for example, they are assembled in: blast furnaces runners, torpedo car, pig iron ladle, steel ladle, LD converter, etc.As ceramics, these materials are generally hard and brittle, have low tensile strength and impact resistance. This imposes limitations for applications when they are under mechanical stresses. In this way, an alternative is to combine the properties of the ceramic with the properties of the metals. With this objective in mind, in this dissertation, the joint of fireclay brick 45-50 in duplex stainless steel UNS 32304 was investigated. The thermal diffusivity measurements were performed with a carbon dioxide laser with Gaussian space profile, wavelength 10μ𝑚, intensity 10√2𝑊/𝑚2 and diameter equal to 2𝑚𝑚.Using UNS 32304 steel plates, several substrates with dimensions of 70x7x1,807𝑚𝑚were manufactured. Subsequently, these substrates were milled, producing rectangular channels with 2𝑚𝑚wide by 1𝑚𝑚deep. Silica-aluminous ceramics were cut with 70x2x3𝑚𝑚and coupled in these generated channels. Thermal diffusivity was measured with the flash laser method. The measurement results about thermal diffusivity in the metal / ceramic junction were close to those theoretically estimated, considering the hypothesis of additivity without interference between the compounds
Avaliação da resistência à corrosão localizada de cladding de aço inoxidável duplex UNS S39209 em aço carbono pela técnica eletroquímica de reativação potenciodinâmica de ciclo duplo (DL-EPR)
(Universidade Federal do Espírito Santo, 2018-08-30) Lima, Gustavo Fernandes Negris; Luz, Temístocles de Sousa; Macêdo, Marcelo Camargo Severo de; Ponzio, Eduardo Ariel; Cotta, Rômulo Almeida
The study of welding coating deposition technology is necessary because it is widely used in industries, combining good mechanical characteristics and high resistance to corrosion at low cost, both with regard to the manufacturing process (cladding) and the process of recovery, through over thickness.In this work the results obtained by DL-EPR techniques were evaluated in terms of the susceptibility to localized corrosion of duplex stainless steel cladding UNS 39209. The relationship between welding energy, dilution and sensitization was also sought.DL-EPR assays wereperformed in a 33% H2SO4solution + 0.5% HCl by volume, and a scan rate of 1.5 mV / s, in order to quantify the level of sensitization after the TIG welding thermal cycle fed with cold wire.With the results obtained, it was concluded that the increase ofthe dilution rate of the coating and the welding energy, increase the degree of sensitization and, consequently, increase the susceptibility to localized corrosion. This fact can also be observed in the proportion of ferrite-austenite and in the formationof phases such as secondary austenite and chromium nitrides
Avaliação da resistência à corrosão localizada de cladding de aço inoxidável duplex uns S39209 em aço carbono por meio de espectroscopia de impedância eletroquímica
(Universidade Federal do Espírito Santo, 2018-08-31) Sperandio, Bruno Filipe da Penha; Luz, Temístocles de Sousa; Macêdo, Marcelo Camargo Severo de; Ponzio, Eduardo Ariel; Cotta, Rômulo Almeida da
In this work electrochemical impedance spectroscopy tests were performed on the open circuit potential in samples of duplex steel UNS S39209 deposited by TIG welding on ASTM A36 steel sheets. A solution of 33% H2SO4+ 0.5% HCL with perturbations in the order of ± 10mV was used varying the frequency of 100Khz to 10mhz and 10 points per decade varying in potential. In order to evaluate the corrosion resistance of the duplex steel, relate to the ferrite / austenite volumetric fraction and compare with the results found by the DL-EPR technique.To reach the results an area adjustment was performed using the ferrite / austenite volumetric fraction. It was verified that the sample with lower dilution and austenite fraction presented higher resistance to corrosion than the others, consistent with the sensitization data. A tendency was observed for increasing the dilution and penetration of the addition metal with increasing welding energy. Deposition welding has proved to be an efficient option to increase the corrosion resistance of a material
Avaliação das propriedades mecânicas do aço inoxidável duplex UNS S32304 submetido à soldagem TIG e diferentes temperaturas de tratamento térmico
(Universidade Federal do Espírito Santo, 2019-03-11) Caetano, Gabriela Aksascki; Luz, Temístocles de Sousa; Orlando, Marcos Tadeu D'Azeredo; Furtado, Henrique Silva; Cavichini, Arthur Sant’Ana; Martinelli, Antonio Eduardo; Alves, Haimon Diniz Lopes
The duplex stainless steel UNS S32304 has been investigated as a candidate for external construction of areceptacle for transporting radioactive material associated with the future Brazilian Multipurpose Nuclear Reactor(RMB), as it presents the combination of excellent mechanical properties and high resistance to corrosion, as a consequence of its ferritic-austenitic biphasic structure.The outer shell construction of this receptacle provides for the use of welded UNS S32304 steel sheets.In order to evaluate the effect of post-weld heat treatments on the mechanical properties and to guarantee the reliability of the weld in this material, plates of UNS S32304 with a thickness of 1.8 mm were welded by autogenous GTAW process with pulsed current with direct polarity, shieldinggaswith a mixture of argon and 2% of nitrogen and an automatic drive system with digital control of the parameters.The specimens were heat treated for 8 h at 600, 650, 700 and 750 ° C in a programmable muffle furnace, with accuracy of ± 5 ° C followed by air cooling.The sampleswere submitted to stress tests in the thermal-mechanical simulator using Gleeble®model 3500 and 3800 in the Brazilian Nanotechnology National Laboratory and Brazilian Synchrotron Light Laboratory, located at the Brazilian Center for Research in Energy and Materials. Hardness measurements were made the Vickers microhardness test with load of 1006 gf for the profile and loads of 1 and 2 gf for phase individual analysis. The microstructural characterization was done stereoscopy, optical microscopy and scanning electron microscopy. Phase quantification was performed by image processing and analysis using the FIJI -ImageJ and SVRNA software. It was verified that the increase of the heat treatment temperature promoted the increase in the content of the austenitic phase and consequently the increase of the ductility, increase of the hardening coefficient, reduction of the hardness and reduction of the mechanical strength
Caracterização da deposição de pó cerâmico supercondutor de SmBa2Cu3O7-O em aço inoxidável lean duplex
(Universidade Federal do Espírito Santo, 2017-03-21) Lepich, Rodolpho Santos; Passos, Carlos Augusto Cardoso; Orlando, Marcos Tadeu D’Azeredo; Passamai Junior, José Luis; Scandian, Cherlio
Pre-prepared SmBa2Cu3O7-dpolycrystalline superconducting samples were deposited in lean duplex stainless steel and heat-treated withdifferent oxygen flows: 0.2 cm³/s, 0.5 cm³/s and 0.7 cm³/s. In addition, an attempt to heat treatment under an inert argon gas atmosphere was performed. The samples were labeled asA and B, due to the different synthesis processes to which they were submitted. So, to be deposited in the steel it was necessary to create a pit approximately 5cm long by 2mm wide. Through two different processes, corrosion and milling cutter, gave rise to the central channel. After visual analysis, it was noticed that the milling cutter process obtained higher quality and productivity. The superconducting ceramic powder was deposited on the steel and then the material was brought into the furnace for heat treatment. Afterwards, the samples were characterized by X-ray diffraction (XRD) and scanning electronmicroscopy (SEM), as well as the calculation of the mean size of the junction.From the XRD results, it was found that samples A did not form the desired stoichiometry, whereas samples B did. It was observed that the lower the oxygen flow, the greater themean size of the junctions. Consequently, the magnetic shielding is higher. The smaller sizes offer less resistance to the passage of electric current,therefore, thelower theprobability of forming hot spotsand degrading the grain boundaries.Finally, an ideal route for a creation of this composite was found: B synthesis process and thermal treatment under oxygen flow of 0.5 cm³/s. In this case, the desired stoichiometry with a relevant percentageof the orthorhombic and tetragonal phase was formed, however, none of the materials tested showed superconducting transition above 77K
Caracterização da deposição de pó cerâmico supercondutor de YBa2Cu3O7-d e SmBa2Cu3O7-d em aço inoxidável 316L
(Universidade Federal do Espírito Santo, 2019-03-15) Corteletti, Rodolpho Toniato; Passos, Carlos Augusto Cardoso; https://orcid.org/0000-0001-9627-7941; http://lattes.cnpq.br/2528679879816545; https://orcid.org/0000-0001-7963-7626; http://lattes.cnpq.br/7995155643932619; Passamai Junior, Jose Luis; https://orcid.org/0000-0001-6866-1460; http://lattes.cnpq.br/5445869592199028; Bolzan, Marcio de Sousa; https://orcid.org/0000-0002-5928-7670; http://lattes.cnpq.br/ 6504057484060757
In this work, microstructures of superconducting ceramics deposited in 316L stainless steel base were produced and characterized. The objective was to develop a fault currente limiter and evaluate the metal / ceramic junction and to change the mechanical properties of the superconducting ceramics. Thus, for this purpose in mind, YBa2Cu3O7-d and SmBa2Cu3O7-d polycrystalline ceramics were prepared by conventional method from the solid-state reaction. In addition, the 316L stainless steel plates were cut into rectangular pieces of approximately 72 mm x 10 mm x 2.5 mm. The yttrium-based superconducting ceramics deposited in the steel were named sample A and samarium-based ceramics were named sample B. Each of the samples were thermally treated with different isotherms. Sample A was maintained at a plateau of 1040 ° C and sample B at a plateau of 1060 ° C, followed by cooling to 520 ° C for 24 hours. It is then cooled to room temperature. All thermal process was under oxygen flow with 99.9% purity. The characterization of these samples was performed by X-ray diffraction, optical microscopy, scanning electron microscopy and dispersive energy spectroscopy. The results indicate that the ceramics covered steel body, there are recrystallized signals and presented a boundary size of grain outline. We conclude that the composite preparation process was effective in the control of grain boundary size.
Correlação entre a resistência à corrosão e as tensões residuais de um aço inoxidável lean duplex uns s32304 submetido à processo de soldagem TIG e diferentes condições de tratamentos térmicos e resfriamento
(Universidade Federal do Espírito Santo, 2016-02-24) Merlo, Panmela Pereira; Macêdo, Marcelo Camargo Severo de; Orlando, Marcos Tadeu D'Azeredo; Ponzio, Eduardo Ariel
Heat treatment and welding process can promote the precipitation of secondary phases in duplex stainsless steels, resulting in the phenomenon ofsensitization,whichis detrimental tothecorrosion resistance of the material. In this work, the UNS S32304 steel samples were subjected to heat treatments at temperatures of 475, 600 and 750 ° C for 8 hours, air or seawater cooled and the GTAW welding process followed by the same treatments. In order to evaluate the resistance to localized corrosion were performed electrochemical tests of the type DL-EPR. After DL-EPR was possible to calculate the degree of sensitization(DOS) of the samples and it was found in general that the elevated heat treatment temperature caused an increase in localized corrosion. The samples subjected to the welding processand heat treatment had a superior sensitizationthan the samplestreated only, and that the cooledair obtained DOS higher than cooled in seawater. The residual microstressesin ferrite introduced a compatible DOSbehavior in only treated samples
Efeito da temperatura de tratamento térmico na corrosão localizada do aço inoxidável duplex UNS S31803 avaliado por espectroscopia de impedância eletroquímica
(Universidade Federal do Espírito Santo, 2015-09-18) Helker, Paulo Victor Toso; Macêdo, Marcelo Camargo Severo de; Cotta, Rômulo Almeida; Ponzio, Eduardo Ariel
This study evaluated the comparative results obtained from the DL-EPR techniques and electrochemical impedance spectroscopy, in terms of behavior susceptibility to localized corrosion of UNS S31803 duplex stainless steel. Also sought the relationship between the heat treatment, microstructure and sensitization. For these samples were heat treated at the temperatures 645 ° C, 820 ° C and 960 ° C for 12 hours besides the sample under the condition "as received". These treatments resulted in the precipitation of sigma phase. DL-EPR tests were conducted in a 2 M H2SO4 solution + 0.5M NaCl + 0.01 M KSCN in order to quantify the degree of sensitization after heat treatment, and testing electrochemical impedance spectroscopy in the same solution, however the open circuit potential (OCP) and the potential of +350 mVsce where the samples are passive, in order to verify that the results were consistent with those obtained with DL-EPR. The samples suffered a considerable change in the proportion of ferrite-austenite due to heat treatment. Thus, the EIS results were evaluated with caution, in order to consider that effectively attacked areas experienced great variation, which should be appropriately compensated before evaluating the results
Efeito do tratamento térmico pós-soldagem no comportamento em corrosão e nas propriedades mecânicas do aço inoxidável duplex UNS S32304
(Universidade Federal do Espírito Santo, 2010-08-31) Silva, Samuel Deoteronio da; Tavares, Sérgio Souto Maior; Macêdo, Marcelo Camargo Severo de; Scandian, Cherlio; Londono, Antonio Jose Ramirez
abstract
Estudo da tensão residual através de difração de raios X em aço inoxidável duplex submetido a diferentes tratamentos térmicos
(Universidade Federal do Espírito Santo, 2012-12-07) Santos, Camila Zangerolame; Orlando, Marcos Tadeu D'Azeredo; Rossi, Jesualdo Luiz; Macêdo, Marcelo Camargo Severo de
The evolution of residual stresses in a duplex stainless steel with different thermal treatments was investigated by X-ray diffraction. In this work, samples of steel UNS S32304 were analyzed. These materials have a two-phase microstructure of ferrite and austenite in approximately equal volume fractions. The samples were characterized in detail by X-ray diffraction and AC magnetic susceptibility. To determine the residuals stresses in the phases, the method of sin2ψ was used. This method is based on the measurement of peak positions for a given hkl reflection and for various directions of the scattering vector. It was observed that due to heat treatment, there is a residual compressive stresses for both the ferritic phase and for the austenitic phase.
Estudo do desgaste por deslizamento de ligas de cobalto
(Universidade Federal do Espírito Santo, 2015-09-10) Falqueto, Leandro Entringer; Bozzi, Antônio César; Scandian, Cherlio; Mello, José Daniel Biasoli de; Milan, Júlio César Giubilei
Cobalt alloys are used in many industrial applications due to their good mechanical properties at high temperatures. Duringsupermartensitic stainless steel 13%Crseamless tubes manufacturing by Mannesmann process, the hot rolling guides, made of Co-Cr-Fe alloy, have a severe wear. To increase the life of these components, sliding wear tests were performed at room temperature and 500 °C inpin-on-disc configuration, without lubrication and varying the normal load. The pin was made ofsupermartensiticstainless steel 13%Cr. The discs were fabricated with the Co-Cr-Fe alloy. In addition to this, three coatings, Stellite 1, 6 and 12, applied by laser claddingprocess, were investigated, with a total of four materials. The wear surface was analyzed as to the worn volume through 3D profilometry. The micromechanisms were observed with a stereoscopic and scanning electron microscope. And, to assess the elemental composition of the wear track, analyzes were performed by energy dispersive spectroscopy. The results indicate that the samples coated with Stellite showed a betterperformance than the Co-Cr-Fe alloy. And, among the coatings, the Stellite 1 showed the best wear resistance, both at room temperature as in the tests performed at 500 °C. The Co-Cr-Fe, Stellite 6 and 12alloyspresented constitutively plasticmicromechanisms. WhereasStellite 1presented oxidative wear. In tests performed at room temperature, Co-Cr-Fe, Stellite 6 and 12alloyspresented a friction coefficient close to 0.3 for most normal loads. And, in the tests performed at 500 °C, in general, the coefficient of friction of all alloys showed an increasing trend with the increase of normal load
Estudo do efeito de parâmetros do processo GTAW pulsado na resistência à corrosão intergranular e por pite do aço inoxidável duplex UNS S32304
(Universidade Federal do Espírito Santo, 2011-12-21) Palácio, Felipe de Oliveira; Macêdo, Marcelo Camargo Severo de; Silva, Marcelo José Gomes da; Tavares, Sérgio Souto Maior
The duplex stainless steels, as well as austenitic and ferritic, are susceptible to intergranular corrosion. The chromium depleted regions adjacent to precipitates that can be formed in these steels is the most accepted mechanism for describing this phenomenon. Welding processes and heat treatments can cause such a mechanism and it is said that the material is sensitized. The welding processes generate inhomogeneous thermal cycles and this makes the material undergoes microstructural changes often unwanted. Regions near the fusion zone (FZ) are considered critical due to favoring the precipitation of new phases and microconstituents. The called heat affected zone (HAZ) can suffer a thermal cycling over a temperature range that favors the kinetics of formation of new phases. Several industrial processes adopt a post-weld heat treatment to minimize or even abolish these effects. This study aims evaluate the effect of welding process parameters GTAW (Gas Tungsten Arc Weld) pulsed on the resistance to pitting and intergranular corrosion of a duplex stainless steel UNS S32304. For this reason, polarization curves were performed and the method of double loop electrochemical potentiodynamic reactivation version (DLEPR) was also employed. It were obtained ten fillets weld without deposition of material on steel plates studied. A condition studied was conventional GTAW, and the parameters evaluated in the process pulsed were frequencies between 1 and 4 Hz, and the pulse on time. The mechanical properties were evaluated by microhardness testing and microstructural characterization of the material was performed by optical microscopy and scanning electron microscopy. The welded regions showed less susceptibility to intergranular corrosion when compared to the metal base (MB). And this in turn presented a higher pitting potential to others. The formation of precipitates in the HAZ did not cause a drastic effect on intergranular corrosion resistance, but on the other hand, the resistance to pitting corrosion was affected.
Estudo sobre corrosão localizada em junta de aço inoxidável duplex para uso em dessalinizador: efeito do gás proteção e temperatura de pré-aquecimento
(Universidade Federal do Espírito Santo, 2018-10-10) Borges, Francisco António Fortes; Luz, Temístocles de Sousa; Macêdo, Marcelo Camargo Severo de; Silva, Paulo Rogério Tavares da; Galdino, André Gustavo de Sousa
Recent studies show that the welding of duplex stainless steel sheets with preheatingallows a more efficient control of the phase balance, thus providing better characteristicsof the welded region. However, welding promotes microstructural changes that include themodification in the balance between ferrite and austenite, in proportions of approximate50 % each, in addition to the precipitation of secondary phases, such as the phase𝜎and the chromium nitride. In this context, the objective of this work is to evaluate themicrostructural changes and the corrosion resistance of duplex stainless steels subjected towelding process. The autogenous GTAW welding process was performed on UNS32205stainless duplex plates exposed to room temperature and preheated to 200∘C and 300∘C.After the welding, the plates were sectioned, prepared for the metallographic analysisof the morphology of austenite formed and for the quantification of the phases. Themicrostructural characterization was evaluated by optical microscopy and scanning electronmicroscopy (SEM). Besides this, double-cycle potentiodynamic electrochemical reactivation(DL-EPR) tests were performed to evaluate the corrosion resistance of the steel. The resultsshowed the presence of grain - bound allotriomorphic austenite, Widmanst ̈atten austeniteand intragranular austenite. It was observed that the preheating temperature and theshielding gas influenced the microstructural balance and the corrosion resistance. Finally,there was no evidence of pitting corrosion in samples immersed in the saline solution
Otimização da técnica eletroquímica de reativação potenciodinâmica de ciclo duplo (DL-EPR) para avaliação da resistência à corrosão localizada de cladding de aço inoxidável duplex UNS S39209 em aço carbono
(Universidade Federal do Espírito Santo, 2017-08-31) Canal, André; Luz, Temístocles de Sousa; Macêdo, Marcelo Camargo Severo de; Tavares, Sérgio Souto Maior; Pardal, Juan Manuel
Duplex stainless steels (AIDs) belong to a group ofmaterials of high mechanical and corrosion propertiesperformance.These achievements have been investigatedby several works on theapplication ofthe cladding weld with these materialsdue to the greater pitting resistance equivalente number (PREN) than conventional austenitic stainless steels and their lower costcompared withsuperalloys.During the deposition processthe cooling rate can influence the microstructural balance (δ and ) and the incidence of deleterious phases, which can decrease the performance of the deposited material.In this work the optimization of the parameters of theDouble Loop Electrochemical PotentiokineticReactivation(DL-EPR) for evaluatingquantitativelytheeffectof the dilution on the localizedcorrosion resistance ofcladding of UNS S39209 deposited by GTAWwelding with cold wire onASTM A36 steel.The microstructural characterization was performed by optical microscopy before and after the corrosion tests.Theefectsof thescanning rate and concentration of thedepassivator HCl in the solutionon the relationship betweenactivation and reactivation currents, which quantifies the corrosion resistance,were investigated.The results demonstrated that thesolution of33% H2SO4+ 0.5% HCl and scan rate of 1.5 mV/s can characterize the interactions between precipitation and chromium depletion of the deposited material.A decrease of the localized corrosion resistance was observed for higher austenite contents. The presence of secondary austenite and chromium nitrideswas detected in thespecimenof lower dilution. In the intermediate dilution specimenonly chromium nitrides were observed. However, these specimensshowna lower degree of sensitization than the specimenwith the highest dilution
Perfis de tensão residual do aço duplex UNS S32304 submetido a diferentes processos de soldagem TIG e condições de tratamento térmico
(Universidade Federal do Espírito Santo, 2015-01-01) Machado, Caruline de Souza Carvalho; Macêdo, Marcelo Camargo Severo de; Orlando, Marcos Tadeu D’Azeredo; Luz, Temistocles de Sousa; Martinez, Luis Gallego
Aiming the implementation of duplex UNS S32304 steel as a packed for radioactive material transport, TIG welded samples, with different shielding gas, were subjected to heat treatments at different temperatures, 475 °C, 600 °C and 750 °C, for 8 hours followed by air cooling, in order to examine the critical temperatures effect on the steel residual stress profile and microestruture. The X-ray diffraction was used as a non-destructive technique to determine the residual stresses at different conditions (samples received and only heat treated) and the profile of the total residuals stresses welded samples is analysed for each phase (austenite and ferrite). The residual stresses of the phases was determined by sen2ψ. For austenite phase it was used CuKα radiation source (<􀟣̅ > = 0.1542 nm) and for the ferrite phase it was used CrKα radiation (<􀟣̅> = 0.2291 nm). It was also measured the ferrite contents, Vickers microhardness and microstructure of the materials was investigated. These results were related to the obtained profiles. It was found that both, the temperature and the variation of the shielding gas, influence on the stresses profile for the different phases in the steel.

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