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Effect of carbon on the sulphidation of cobalt‐tantalum alloys
Author(s) -
ElDahshan M. E.,
Hazza M. I.,
AlMutaz I. S.
Publication year - 1988
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19880390705
Subject(s) - tantalum , cobalt , carbon fibers , materials science , alloy , metallurgy , layer (electronics) , composite material , composite number
The sulphidation of cobalt‐tantalum‐carbon alloys containing 10 and 15 wt% Ta and carbon in the range 0–1 wt%, was carried out in H 2 ‐H 2 S mixture containing 10% by volume H 2 S. The reaction kinetics at 800–1000°C were followed thermo‐gravimetrically and the scale products examined in detail using metallographic and X‐ray diffraction techniques. In these sulphidation conditions (10% H 2 S – 90% H 2 ) addition of 10 and 15% Ta to cobalt was unable to suppress the formation of liquid cobalt‐rich sulphides; consequently, very rapid rates of alloy consumption were attained. Decreasing the temperature resulted in the distribution of the tantalum sulphides in a fine scale. Transport of cobalt through the inner layer was sufficiently rapid to form an outer, molten sulphide layer. The inability of tantalum‐rich sulphides to develop into a continuous layer appears to be responsible for the disappointing effect of tantalum on the sulphidation resistance. Increasing carbon contents in the alloy increase the sulphidation rate, but the increase is not very dramatic.