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Abstract

In the complex and unusual environments characteristic of SNG plants, sulphidation may be anticipated as a major corrosion problem, recognizing the low or very low oxygen potentials which are likely to exist. In these atmospheres, the partial pressures of sulphur are also likely to be considerably less than atmospheric, perhaps as low as 10**-11 atm. Little information concerning the sulphidation behaviour of conventional HT alloys in such environments is available. The present studies have been conducted on four commercial HT alloys AISI 314, Incoloy 800H, Hastelloy X and H39W, all MCrX-type alloys containing Fe, Ni and/or Co (M) and other reactive elements (X) such as Si, Mn, Mo, Nb, A1 and Ti generally present as minor (<= 1-2 %) additions. The sulphidation behaviour of these alloys has been ascertained in H-2/H-2S atmospheres at 825 degrees C for exposure periods of up to 50 h, such that pS-2 = 10**-6 or 10**-11 atmospheres (1.0 x 10**-1 Nm**-2 or 1.0 x 10**- 6- Nm**-2, respectively). The influence of sulphur partial pressure has been shown to be very marked, weight gains associated with the higher sulphur potential being up to two orders of magnitude larger than those derived from the atmosphere of very low sulphur potential. Such large weight gains were associated with thick heterophasic scales which readily exfoliated from alloy substrates and were of complex morphology and composition constituted by (Fe, Cr, Ni) sulphides. Thick subscales were also formed. In contrast thin single-layered scales grew on alloys during sulphidation in the environment of very low pS-2 containing Cr and S, but essentially free of any appropriate elements constituting the alloys' base. In detail the patterns of scaling, including internal sulphidation, have also been shown to be sensitive to specimen surface finish and minor alloying element content, especially in the atmosphere of very low sulphur potential.

Additional information

Authors: STRAFFORD K N, SCHOOL OF MATERIALS ENGINEERING, NEWCASTLE UPON TYNE POLYTECHNIC (UK);JRC PETTEN ESTAB. (THE NETHERLANDS);CHAN W Y, SCHOOL OF MATERIALS ENGINEERING, NEWCASTLE UPON TYNE POLYTECHNIC (UK);JRC PETTEN ESTAB. (THE NETHERLANDS);NORTON J F SCHOOL OF MATERIALS ENGINEERING, NEWCASTLE UPON TYNE POLYTECHNIC (UK), SCHOOL OF MATERIALS ENGINEERING, NEWCASTLE UPON TYNE POLYTECHNIC (UK);JRC PETTEN ESTAB. (THE NETHERLANDS);JRC PETTEN ESTAB. (THE NETHERLANDS), SCHOOL OF MATERIALS ENGINEERING, NEWCASTLE UPON TYNE POLYTECHNIC (UK);JRC PETTEN ESTAB. (THE NETHERLANDS)
Bibliographic Reference: CORROSION RESISTANT MATERIALS FOR COAL CONVERSION SYSTEMS, SUDBURY HOUSE, LONDON (UK), MAY 5-7, 1982. PROCEEDINGS: PP. 517-549 - WRITE TO APPLIED SCIENCE PUBLISHERS LTD., RIPPLE ROAD, BARKING, ESSEX (ENGLAND)
Record Number: 1989122037000 / Last updated on: 1987-01-01
Category: PUBLICATION
Available languages: en
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