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High Temperature Corrosion & Materials Applications
 
High-Temperature Corrosion
 
Carburization and Metal Dusting
 
Metals and alloys are generally susceptible to carburization when exposed to environments containing CO, CH4, or other hydrocarbon gases at elevated temperatures. Carburization typically results in the formation of internal carbides in the matrix as well as at grain boundaries, causing an alloy to lose room-temperature ductility and/or creep-rupture strengths. Fe-Ni-Cr alloys are widely used for processing equipment to resist carburization in the petrochemical industry. Increasing nickel in Fe-Ni-Cr alloys improves carburization resistance. In addition, chromium, silicon and aluminum are very effective in improving the alloy’s carburization resistance, which is attributed to the formation of Cr2O3, SiO2 and Al2O3 scales, respectively.

Metal dusting is another form of carburization attack; it typically causes an alloy to suffer pitting attack and/or thinning. The metal beneath the pitted area generally shows carburization. The corrosion products typically consist of carbon soot, metal particles, carbides, and oxides. The environment in which metal dusting occurs generally contains H2, CO, CO2, and H2O with high carbon activities (i.e., ac > 1). Stagnant gas conditions can be conducive in initiating metal dusting attack. The metal temperatures at which metal dusting occurs are between 430 and 900 °C (800 and 1650 °F).

Materials problems due to carburization and metal dusting can be encountered in chemical and petrochemical processing, coal gasification, and heat-treating industry. The resistance to carburization and metal dusting for a wide range of commercial alloys is presented and discussed in great detail in my book.

 
 
 
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