51316-7886-An Evaluation of Alloy Composition and Pre-Oxidation on High Temperature Coking

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Product Number: 51316-7886-SG

ISBN: 7886 2016 CP

Author: Jim Myers

Publication Date: 2016

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Coking is the process of carbon deposition from a gas phase that is encountered in many reforming cracking and other high temperature processes. Coking in certain petrochemical processes can lead to carbon build up causing reduced process efficiency as well as corrosive attack and degradation of the alloy. Components used in these processes are typically fabricated from austenitic stainless steels that utilize a complex chromia-based or alumina-based oxide layer to help protect against coking.An experimental high temperature coking atmosphere using H2 and CO process gases was constructed and used to evaluate the effects of alloy composition pre-oxidation condition and process parameters on the coking resistance of several stainless steel alloys including cast 25Cr-35Ni as well as an aluminum containing austenitic alloy. Coking was tracked using mass changes of the samples as a function of exposure times and conditions. The materials were analyzed using x-ray diffraction (XRD) scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy XPS after exposure to characterize the extent of attack and other microstructural changes. The results showed considerable difference in the coking behavior of the alloys evaluated and a strong influence of the pre-oxidation condition of the material.