The Creep Ductility and Fracture of Carburised Alloy 800H at High Temperatures
The conjoint action of stress and environmental degradation in high temperature process plant increasingly determines the material selection, process efficiency and economic viability. Degradation through carburisation is evidenced at the microscopical level in high temperature reactors and reformers and, at a much greater level, in many coal conversion processes and ethylene pyrolysis furnaces. Metallic materials utilised in such processes and coming into contact with the carburising atmospheres are normally operating under stress in the high temperature creep regime. One commonly used metallic structural material is the austenitic Fe-Ni-Cr Alloy 800 H and, as it has been established that this alloy’s room temperature ductility is destroyed through carburisation (1–3) while its creep ductility at the very high temperature of 1000°C is, if anything, enhanced (4), it is necessary to account for such adifference and, equally importantly, to assess the behaviour at intermediate temperatures. A temperature more consistent with coal conversion processes, 800°C, is chosen as the main focal point of the present study but it is recognised that ductile/brittle transitions need to be discovered for thermal cycling characterisation and results from tests down to 600°C are added for comparison.
KeywordsStress Rupture Rupture Time Creep Life Alloy 800H Creep Ductility
Unable to display preview. Download preview PDF.
- 1.R.C. Hurst and J.F. Norton, “The Effect of high temperature carburisation upon the ambient temperature ductilityof Alloy 800H”, High Temp. Tech., Vol. 6, 1983, p. 319.Google Scholar
- 2.D.A. Wenschhof and J.A. Harris, “The Influence of Carburisation on the Mechanical Properties of Wrought Nickel Alloys” in “Corrosion 77”, Paper n° 9, San Francisco 1977.Google Scholar
- 3.P. J. Ennis and H. Schuster, “The Mechanical Properties of Alloys in High Temperature Reactor Environments”, in “Corrosion and Mechanical Stress at High Temperature”, eds. V. Guttmann and M. Merz, Applied Science Publishers, 1981.Google Scholar
- 4.V. Guttmann and R. Bürgel, “The Effect of a Carburising Environment on the Creep Behaviour of Some Austenitic Steels” in “Corrosion Resistant Materials for Coal Conversion Systems” (eds. D.B. Meadowcroft and M.I. Manning) Appl. Sc. Publ., London, 1982, p.423.Google Scholar
- 6.G.L. Swales, “Materials selection considerations for petrochemical furnace tubes”, Proc. Conf. “Behaviour of High Temperature Alloys in Aggressive Environments” (eds. I. Kirmen et al.) Metal Soc., 1979, p.45.Google Scholar