Besides oxygen attack, at high service temperatures high temperature materials are frequently subject to attack by carbon. The carbon is usually formed by decomposition of hydrocarbons, carbon monoxide and carbon dioxide and diffuses into the material via the grain boundaries, where rapid diffusion of the carbon atoms takes place. The pick-up of carbon by the material may, inter alia, affect its mechanical properties and corrosion resistance. Therefore a wide variety of commercially available Ni- and Fe-base alloys were tested in a CH4/H2 gas mixture with a constant carbon activity of ac = 0.8 in the temperature range 550- 1200 °C. The tests were carried out in a 24-h cycle with a total test time of more than 1,000 hours. The weight change was determined and the average value for three tested specimens per alloy and test temperature was plotted versus time. This paper summarizes and compares the results with special emphasis on the influence of alloying elements on carburization resistance. The beneficial influence of nickel, molybdenum, silicon and aluminium could be proved for the prevailing environmental conditions.
Keywords: Carburization, Ni-base alloys, Fe-base alloys, Temperature Dependency of Carburization, Influence of Composition on Carburization