CORROSION BEHAVIOUR OF A HEAT RESISTANT STEEL IN THE STRESS FREE AND THE STRESSED STATE UNDER SIMULATED COAL GASIFICATION CONDITIONS
The corrosion behaviour of an austenitic 20Cr-32Ni steel, Alloy 800H, was studied in several S-O-C bearing gas mixtures, simulating coal gasification environments at 700 C for up to 4000 h. The investigations showed that small differences in oxygen and sulphur activities of the environment simulating that of coal gasification can cause severe changes in the corrosion behaviour of Alloy 800H. Whereas in the modest environment a more or less protective oxide scale was formed, the most severe gas caused catastrophic sulphidation. It is clear that for technical systems, which will always suffer variations in environmental conditions, any prediction of material response must be considered carefully. Concerning corrosive attack under superimposed creep deformation, it was found that corrosion can be accelerated significantly along grain boundaries lying perpendicular to the stress axis. This observation can be related to selective cracking of the oxide scale in combination with enhanced grain boundary diffusion. This clearly shows the necessity to judge the corrosion behaviour of a material not only for the stress free state, but also for the stressed state.
Bibliographic Reference: PAPER PRESENTED: ELEVENTH INTERNATIONAL CORROSION CONGRESS, FLORENCE (IT), APRIL 2-6, 1990 AVAILABLE FROM COMMISSION OF THE EUROPEAN COMMUNITIES, DG XIII-C-3, L-2920 LUXEMBOURG AS PAPER EN 35170 ORA
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Record Number: 1989128095100 / Last updated on: 1990-11-02
Original language: EN
Available languages: en