A thermal outgassing method (t.o.m.) To measure the hydrogen diffusion coefficients in austenitic, austeno-ferritic and ferritic–perlitic steels

Iacoviello, Francesco; Galland, J.; Habashi, M.

doi:10.1016/s0010-938x(97)00145-5

Cited by 31 publications

(7 citation statements)

References 7 publications

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“…El fenómeno de difusión ha sido estudiado a través de métodos electroquímicos, para determinar la permeabilidad de hidrógeno en el acero asociado a heterogeneidades microestructurales, las cuales pueden actuar como sitios colectores de hidrógeno, que afectan la movilidad del hidrógeno dentro de la red cristalina [8][9][10][11][12][13][14][15][16] .…”

Section: I In Nt Tr Ro Od Du Uc Cc Ci Ió óN Nunclassified

“…Las características microestructurales del metal base y del cordón de soldadura descritas anteriormente, coinciden con las obtenidas en el acero estudiado cuando se somete a un proceso de soldadura por resistencia eléctrica. Este tipo de soldadura se caracteriza por no utilizar material de aporte, por lo que la zona de fusión y la zona afectada por el calor alcanzan extensiones muy pequeñas [16] .…”

Section: I In Nt Tr Ro Od Du Uc Cc Ci Ió óN Nunclassified

“…La difusión de los átomos de hidrógeno en aceros ocurre, principalmente, a través de sitios intersticiales, siendo los sitios tetraédricos los que se ocupan a bajas temperaturas [16] . Sin embargo, es bien sabido que todos los materiales contienen imperfecciones que tienen un efecto profundo sobre el comportamiento de los mismos.…”

Section: I In Nt Tr Ro Od Du Uc Cc Ci Ió óN Nunclassified

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Hydrogen damage of a welded API 5L X52 steel

Réquiz¹,

Camero²,

Aristizabal³

et al. 2008

Rev. metal.

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Las tuberías de acero API 5L X52, utilizadas para el transporte de crudo y gas, pueden sufrir diversos tipos de corrosión y, por consiguiente, experimentar una pérdida considerable de sus propiedades mecánicas cuando están en contacto con medios agrios. Específicamente, cuando estos aceros al carbono y aquellos de baja aleación son expuestos a medios acuosos contaminados con H 2 S son susceptibles al fenó-meno conocido como daño por hidrógeno. Este fenó-meno, que se refiere a la modificación de ciertas propiedades mecánicas debido a la presencia o interacción con el hidrógeno atómico, puede manifestarse en presencia de esfuerzos aplicados o residuales [1 y 2] .El hidrógeno es absorbido por el metal de forma atómica (H), causando su fragilización, agrietamiento y/o ampollamiento. El agrietamiento inducido por hidrógeno es altamente influenciado por parámetros metalúrgicos como: inclusiones, bandas de segregación de elementos (P, Mn), bordes de grano, dislocaciones, entre otros. También ejercen una marcada E Es st tu ud di io o d de el l d da añ ño o p po or r h hi id dr ró óg ge en no o e en n u un ni io on ne es s s so ol ld da ad da as s d de e u un n a ac ce e--r ro o A AP PI I 5 5L L X X5 52 2 (R. Réquiz * , S. Camero ** , V. Aristizabal * y A. Rivas * R Re es su um me en n En la presente investigación se estudió la susceptibilidad al daño por hidrógeno en un acero API 5L X52 soldado por resistencia eléctrica. Para ello, se emplearon técnicas de permeación y de carga catódica de hidrógeno. El material fue caracterizado mediante microscopía electrónica de barrido y de transmisión. La susceptibilidad al daño por hidróge-no fue similar tanto en el metal base como en el cordón de soldadura. Este comportamiento se vincula a la microestructura homogénea constituida por perlita y ferrita, que presentan ambos, aun cuando existen diferencias en el tamaño de grano. El cordón de soldadura tenía dimensiones muy pequeñas, donde la zona de fusión y la afectada por el calor poseen espesores de 5 mm y 1 mm, respectivamente. El daño inducido por hidrógeno se presentó en forma de ampollas en la superficie del material, asociado, principalmente, a la presencia de inclusiones globulares y semiglobulares ricas en aluminio. Además, se manifestó una disolución parcial de las inclusiones y/o un ataque de la matriz en la zona adyacente a la inclusión. P Pa al la ab br ra as s c cl la av ve eAcero API 5L X52. Soldadura por resistencia eléctrica. Daño por hidrógeno. Permeación. Ampollamiento.H Hy yd dr ro og ge en n d da am ma ag ge e o of f a a w we el ld de ed d A AP PI I 5 5L L X X5 52 2 s st te ee el l A Ab bs st tr ra ac ct tThe main objective of the present investigation was to study the susceptibility to hydrogen damage on a type API 5L X52 steel welded by electrical resistance. Several techniques, such as hydrogen permeation and cathodic charging were used. The metallic material was characterized using SEM and TEM. The base metal microstructure was very similar to that one corresponding to the welded area. This microstructure ...

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Section: I In Nt Tr Ro Od Du Uc Cc Ci Ió óN Nunclassified

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Hydrogen damage of a welded API 5L X52 steel

Réquiz¹,

Camero²,

Aristizabal³

et al. 2008

Rev. metal.

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“…For stainless steel systems with no leaks and where no process gas is introduced, the gas load is primarily from hydrogen outgassing from the steel [50]. There are numerous reports of successful reduction of the outgassing rate via moderate [51][52][53][54][55][56][57] and high temperature [56][57][58][59][60][61][62][63] heat treatments, which serve to reduce hydrogen outgassing. There are also numerous reports of coatings such as titanium nitride (TiN) [64][65][66][67][68][69], boron nitride [69,70], silicon [71,72], or silicon oxide [73] that may reduce the outgassing rate by acting as diffusion barriers.…”

Section: Introductionmentioning

confidence: 99%

Thin film studies toward improving the performance of accelerator electron sources

Mamun

2016

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Future electron accelerators require DC high voltage photoguns to operate beyond the present state of the art to conduct new experiments that require ultra-bright electron beams with high average current and higher bunch charge. To meet these demands, the accelerators must demonstrate improvements in a number of photogun areas including vacuum, field emission elimination in high voltage electrodes, and photocathodes. This dissertation illustrates how these improvements can be achieved by the application of suitable thin-films to the photogun structure for producing ultra-bright electron beams.This work is composed of three complementary studies. First, the outgassing rates of three nominally identical 304L stainless steel vacuum chambers were studied to determine the effects of chamber coatings (silicon and titanium nitride) and heat treatments. For an uncoated stainless steel chamber, the diffusion limited outgassing was taken over by the recombination limited process as soon as a low outgassing rate of ~1.79(0.05)  10 -13 Torr L s -1 cm -2 was achieved. An amorphous silicon coating on the stainless steel chambers exhibited recombination limited behavior and any heat treatment became ineffective in reducing the outgassing rate. A TiN coated chamber yielded the smallest apparent outgassing rate of all the chambers: 6.44(0.05)  10 -13 Torr L s -1 cm -2 following an initial 90 °C bake and 2(20)  10 -16 Torr L s -1 cm -2 following the final bake in the series. This perceived low outgassing rate was attributed to the small pumping nature of TiN coating itself.Second, the high voltage performance of three TiN-coated aluminum electrodes, before and after gas conditioning with helium, were compared to that of bare aluminum electrodes and electrodes manufactured from titanium alloy (Ti-6Al-4V). This study suggests that aluminum electrodes, coated with TiN, could simplify the task of implementing photocathode cooling, which is required for future high current electron beam applications. The best performing TiNcoated aluminum electrode demonstrated less than 15 pA of field emission current at -175 kV for a 10 mm cathode/anode gap, which corresponds to a field strength of 22.5 MV/m. Third, the effect of antimony thickness on the performance of bialkali-antimonide photocathodes was studied. The high-capacity effusion source enabled us to successfully manufacture photocathodes having a maximum QE around 10% and extended low voltage 1/e lifetime (> 90 days) at 532 nm via the co-deposition method, with relatively thick layers of antimony (≥ 300 nm). We speculate that alkali co-deposition provides optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali.In summary, this research examined the effectiveness of thin films applied on photogun chamber components to achieve an extremely high vacuum, to eliminate high voltage induced field emission from electrodes, and to generate photocurrent with high quantum yield with an extended operational lifetime. Simult...

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“…For stainless steel systems with no leaks and where no process gas is introduced, the gas load is primarily from hydrogen outgassing from the steel 5 . There are numerous reports of successful reduction of the outgassing rate via moderate [6][7][8][9][10][11][12] and high temperature [11][12][13][14][15][16][17][18] heat treatments which serve to reduce hydrogen outgassing. There are also numerous reports of coatings such as titanium nitride (TiN) [19][20][21][22][23][24] , boron nitride 24,25 , silicon 26,27 , or silicon oxide 28 that may reduce the outgassing rate by acting as diffusion barriers.…”

Section: Introductionmentioning

confidence: 99%

Effect of heat treatments and coatings on the outgassing rate of stainless steel chambers

Mamun¹,

Elmustafa²,

Stutzman

et al. 2013

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The outgassing rates of three nominally identical 304L stainless steel vacuum chambers were measured to determine the effect of chamber coatings and heat treatments. One chamber was coated with titanium nitride (TiN) and one with amorphous silicon (a-Si) immediately following fabrication. The last chamber was first tested without any coating, and then coated with a-Si following a series of heat treatments. The outgassing rate of each chamber was measured at room temperatures between 15 and 30 °C following bakes at temperatures between 90 and 400 °C. Measurements for bare steel showed a significant reduction in the outgassing rate by nearly a factor of 20 after a 400 °C heat treatment-12 Torr L s -1 cm -2 prior to heat treatment, reduced to 1.7×10 -13 Torr L s -1 cm -2 following heat treatment). The chambers that were coated with a-Si showed minimal change in outgassing rates with heat treatment, though an outgassing rate reduced by heat treatments prior to a-Si coating was successfully preserved throughout a series of bakes.The TiN coated chamber exhibited remarkably low outgassing rates, up to four orders of magnitude lower than the uncoated stainless steel, but the uncertainty in these rates is 2 large due to the sensitivity limitations of the spinning rotor gauge accumulation measurement and the possibility of a small pump speed due to inhomogeneity in the TiN coating. The outgassing results are discussed in terms of diffusion-limited versus recombination-limited processes.3

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A thermal outgassing method (t.o.m.) To measure the hydrogen diffusion coefficients in austenitic, austeno-ferritic and ferritic–perlitic steels

Cited by 31 publications

References 7 publications

Hydrogen damage of a welded API 5L X52 steel

Hydrogen damage of a welded API 5L X52 steel

Thin film studies toward improving the performance of accelerator electron sources

Effect of heat treatments and coatings on the outgassing rate of stainless steel chambers

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