In service embrittlement of cast 20Cr32Ni1Nb components used in steam reformer applications

Knowles, David; Thomas, Charles W.; Keen, D.J; Chen, Q.Z

doi:10.1016/j.ijpvp.2003.12.025

Cited by 27 publications

(7 citation statements)

References 2 publications

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“…The changes of alloy chemistry, combined with segregation associated with the casting process, lead to different mechanical properties. It has been reported that fatigue or creep fatigue have occurred in manifold systems at different plants [1]. To understand the mechanical performance, however, it is important that the microstructure of the newly developed cast materials in as-cast and particularly in-service conditions is fully characterised.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of 20Cr32Ni1Nb alloys in as-cast and Ex-Service conditions by SEM, TEM and EDX

Chen

Thomas

Knowles

2004

Materials Science and Engineering: A

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Section: Introductionmentioning

confidence: 99%

Characterisation of 20Cr32Ni1Nb alloys in as-cast and Ex-Service conditions by SEM, TEM and EDX

Chen

Thomas

Knowles

2004

Materials Science and Engineering: A

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“…11). G phase was fragile, and it has been reported in the literature that the G phase was harmful to mechanical properties [30,31]. Therefore, the formation of a large number of G phases during SHT impaired the impact properties of the weld metal.…”

Section: Effect Of Precipitation Behavior On Mechanical Propertiesmentioning

confidence: 99%

Effects of Stabilization Heat Treatment on Microstructure and Mechanical Properties of Si-Bearing 15Cr–9Ni–Nb Austenitic Stainless Steel Weld Metal

Chen

et al. 2022

Acta Metall. Sin. (Engl. Lett.)

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Two 15Cr-9Ni-Nb austenitic stainless steel weld metals with 2.5% Si and 3.5% Si (namely 2.5Si and 3.5Si samples, respectively) were designed and prepared through tungsten inert gas (TIG) welding and then hold at 800 °C or 900 °C for 3 h for stabilization. The microstructure and mechanical properties were investigated both for the as-welded and after-stabilization heat treatment (SHT) weld metals. There are 3.0-4.0% martensite and 2.5-3.5% δ ferrite in the 2.5Si as-welded weld metal and 6.0-7.0% δ ferrite in the 3.5Si as-welded weld metal. After SHT, a large amount of martensite formed in the 2.5Si weld metal, and δ → γ transition occurred during the SHT process both for the 2.5Si and 3.5Si weld metals. There were a large amount of coarse NbC and few nanoscale NbC in the as-welded weld metal. During the SHT, a large amount of nanoscale NbC formed in the matrix, while a large number of G phases formed at the austenite grain boundaries and the δ/γ interfaces. The decrease in solid solution C and δ ferrite content led to the decline of the yield strength of the weld metal after SHT. The martensite formed in 2.5Si weld metal after SHT had less effect on strength because of its low carbon content. The G phases formed during the SHT reduced the impact energy of the weld metal because it promoted the intergranular fracture, while the δ → γ transition reduced the amount of the δ/γ interfaces and avoided the intergranular fracture, which was beneficial for the impact toughness of the weld metals.

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“…In the reformer furnace, the required operating temperature is elevated. The skin temperature of the reformer tubes is approximately 850 to 950 o C and gas outlet temperatures are approximately 760 to 850 o C [2]. A lot of engineering failures have been reported including creep, thermal fatigue or creep-fatigue fracture in manifold systems at different plants [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

An Improved Omega-Based Method for Creep Life Prediction Using Hyperbolic Sine Stress Correlation

Yang

Barrett

Leen

et al. 2019

KEM

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This paper is concerned with the creep life prediction of cast 20Cr32NiNb alloy, an alternative candidate material to wrought Inconel alloys for use in the gas collector pipes of CO reformers which suffer from long-term creep damage due to high temperatures and stresses. Uniaxial creep tests of 20Cr32NiNb alloy were performed at 890 °C and 950 °C for different stresses. The Omega method for creep life prediction is applied to the 20Cr32NiNb tests and shown to give reasonably accurate prediction, particularly at low stress levels. A new method, based on the use of a hyperbolic sine function for stress correlation at specific temperatures for identification of the characteristic Omega parameters is presented and validated.

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In service embrittlement of cast 20Cr32Ni1Nb components used in steam reformer applications

Cited by 27 publications

References 2 publications

Characterisation of 20Cr32Ni1Nb alloys in as-cast and Ex-Service conditions by SEM, TEM and EDX

Characterisation of 20Cr32Ni1Nb alloys in as-cast and Ex-Service conditions by SEM, TEM and EDX

Effects of Stabilization Heat Treatment on Microstructure and Mechanical Properties of Si-Bearing 15Cr–9Ni–Nb Austenitic Stainless Steel Weld Metal

An Improved Omega-Based Method for Creep Life Prediction Using Hyperbolic Sine Stress Correlation

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