Microstructural characterization of modified 25Cr–35Ni centrifugally cast steel furnace tubes

Almeida, Luiz Henrique de; Ribeiro, A.F.; May, Iain

doi:10.1016/s1044-5803(03)00013-5

Cited by 165 publications

(88 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The Cr-Ni-Nb-Si rich phase appeared to be transformed from NbC, and the area covered by this phase appeared to increase as distance from the inner diameter increased. The instability of NbC precipitates at temperatures of 700-1050°C has been well reported in the literature [1,[22][23][24][25][26][27]. The product of the transformation is generally identified as G-phase, which has a commonly reported composition of Ni 16 Nb 6 Si 7 , and an FCC structure with a lattice parameter of 1.12 nm [1,23,24].…”

Section: Cr-ni-nb-si Rich Phasementioning

confidence: 95%

“…The current literature on the NbC-to-G-phase and NbCto-g-carbide transformations in HP-Nb alloys is constrained to ex-service reformer tubes [8,22,[25][26][27] and a limited number of laboratory-aged studies [1,[23][24][25]. Based on the available literature and data from laboratoryaged HP-Nb alloys, Buchanan [10] concluded that the NbC-to-G-phase and NbC-to-g-carbide transformations in aged HP-Nb alloys are dictated by the aging temperature.…”

Section: Cr-ni-nb-si Rich Phasementioning

confidence: 99%

See 1 more Smart Citation

Microstructure and Carburization Detection in HP Alloy Pyrolysis Tubes

McLeod

Bishop

Stevens

et al. 2015

Metallogr. Microstruct. Anal.

View full text Add to dashboard Cite

A highly carburized HP40-Mod alloy ethylene pyrolysis tube was characterized by means of scanning electron microscopy with backscatter electron imaging, electron back-scattered diffraction, energy dispersive spectroscopy, and etching using the NACE International Standard Test Method for evaluation of carburization of ethylene pyrolysis tubes. The response of the tube to eddy current non-destructive testing was measured using the carburization crawler under development at Quest Integrity NZL Ltd. The matrix was significantly depleted of chromium, as low as 4 wt% Cr at the inner wall. M 23 C 6 carbides transformed to M 7 C 3 at the inner wall region and NbC carbides partially transformed to the chromium-rich g-carbide at the outer wall region, both of which likely contributed to the chromium depletion of the matrix. The present results indicate that the NACE etchant attacks the austenitic matrix where chromium content is below approximately 12wt%. A comparison to other ex-service tubes indicates that matrix chromium content and the location of the M 23 C 6 /M 7 C 3 transformation front are useful microstructural characteristics for interpreting eddy current NDT response.

show abstract

Section: Cr-ni-nb-si Rich Phasementioning

confidence: 95%

Section: Cr-ni-nb-si Rich Phasementioning

confidence: 99%

Microstructure and Carburization Detection in HP Alloy Pyrolysis Tubes

McLeod

Bishop

Stevens

et al. 2015

Metallogr. Microstruct. Anal.

View full text Add to dashboard Cite

show abstract

“…Regarding the Nb and Si effect, the formation of intermetallic niobium-nickel-silicides (G-phase) is expected to decrease the creep resistance of the cast material 7,8 . On the other hand, the role of Mn in the mechanical properties is not clear.…”

Section: Methodsmentioning

confidence: 99%

Use of titanium and zirconium in centrifugally cast heat resistant steel

Caballero¹,

Imizcoz²,

López³

et al. 2007

Materials Science and Technology

View full text Add to dashboard Cite

) 2 AbstractLow carbon 25% Cr-35% Ni steel (HP type steel) modified with titanium and zirconium has been produced by centrifugal casting. The different phases present in the as-cast and aged conditions were described by light optical and scanning electron microscopy with secondary electron imaging and energy dispersive spectroscopy (EDS). Results suggest that the use of titanium as a microalloying element reduces secondary precipitation during aging. Moreover, secondary precipitates in the microalloyed steel are much finer and more evenly distributed. On the other hand, zirconium oxides was found to be potential nucleation sites for primary titanium-rich carbides contributing to an optimum distribution of these carbides in the tubes. These differences together with the higher stability of the titanium containing primary carbides are responsible for the improvement on ductility and creep resistance found in this work.

show abstract

“…

Abstract:The purpose of this study was to determine the impact of niobium addition as an inoculation element on the microstructure and electrochemical properties of EN-FGL250 gray cast iron. Niobium additions are in a powder form and have a 0.5 mm particle size at dfferent proportions of 1wt.% and 3wt.%.

…”

mentioning

confidence: 99%

“…I t is well established that the variety of applications of cast iron is attributed to the presence of chemical elements in the solid solution as interstitial or substitutional form, such as so-called addition elements Ni, Cu, Ti, Cr, V and Nb [1][2][3][4] , and inoculation elements Al, Si, Ca, Sr, Mn, Zr, P, Sn and Ce [5][6][7] .…”

mentioning

confidence: 99%

Niobium addition effect in molds at last cooling step on EN-GJL250 gray cast iron: Microstructural changes and electrochemical behavior

et al. 2018

View full text Add to dashboard Cite

I t is well established that the variety of applications of cast iron is attributed to the presence of chemical elements in the solid solution as interstitial or substitutional form, such as so-called addition elements Ni, Cu, Ti, Cr, V and Nb [1][2][3][4] , and inoculation elements Al, Si, Ca, Sr, Mn, Zr, P, Sn and Ce [5][6][7] .In the foundry, additions are done by controlling the Abstract:The purpose of this study was to determine the impact of niobium addition as an inoculation element on the microstructure and electrochemical properties of EN-FGL250 gray cast iron. Niobium additions are in a powder form and have a 0.5 mm particle size at dfferent proportions of 1wt.% and 3wt.%. The addition was done during casting of the metal in the mold at the last cooling step of the melt cast iron. These additions have a significant impact on the phenomenon of solidification as the metal powder deposited in the sand molds creates new centers of germination and absorbs a lot of heat. The cooling rate directly affects the microstructure and electrochemical behavior. This is confirmed by SEM observations and electrochemical tests. Furthermore, the addition of niobium transforms the microstructure of gray cast iron from cellular structure into totally dendritic structure. As a consequence, the niobium addition affected the shape and size of graphite, thus considerably reducing the corrosion current density by increasing the polarization resistance R p . chemical composition of the melt rather than equivalent carbon, alloying elements and inoculation products. The minor additions of alloying elements for their affinities to carbon can be used to improve the mechanical properties of the cast iron mainly by the formation of M 7 C 3 , M 3 C and MC type carbides. Filipovic et al. [4] have shown that variable proportions of additions of niobium and vanadium to the hypoeutectic white cast iron containing 19% chromium modify its microstructure and affect its wear and hardness properties. Kesseri et al. [3] have also shown that the addition of niobium in chromium-rich cast irons improves the mechanical properties by the formation of MC-type niobium carbides. Similarly, the inoculation elements have a strong affinity to oxygen and sulfur [8][9][10][11] . Thus, oxides and sulphides of a homogeneous or heterogeneous nature formed in the melt give the graphite nucleation sites [12][13][14] . Some authors suggested that the Mn/S ratio affects the nucleation and morphology of graphite [15,16] . Other authors [17,18] indicated that the inoculations elements *M. O. Azzoug Male, born in 1979, Teacher (assistant master) at University of Sciences and Technology Houari Boumedienne Algiers, Algeria, also Ph.D student in Materials Science and Engineering. He is currently working on the development of a surface treatment process for gray cast irons directly in the manufacturing stage of parts without resorting to conventional (physical or chemical) surface treatments by metal deposition process or surface treatment. The influence of additions in ...

show abstract

Microstructural characterization of modified 25Cr–35Ni centrifugally cast steel furnace tubes

Cited by 165 publications

References 7 publications

Microstructure and Carburization Detection in HP Alloy Pyrolysis Tubes

Microstructure and Carburization Detection in HP Alloy Pyrolysis Tubes

Use of titanium and zirconium in centrifugally cast heat resistant steel

Niobium addition effect in molds at last cooling step on EN-GJL250 gray cast iron: Microstructural changes and electrochemical behavior

Contact Info

Product

Resources

About