Interactions between creep deformation and hot gas corrosion

The paper starts with a short explanation of the basic processes during the high temperature corrosion and of deformation under creep stress. Corrosion may give rise to an increase or a decrease of creep resistance, or it may result in an increase of the stress applied. The individual mechanisms are explained and, as far as possible, illustrated by examples. As a rule, however, several factors act simultaneously. The concerted action is further complicated by back effects of a creep deformation on the corrosion processes. In the case of iron and nickel base alloys there exist obviously critical strain rates beyond which corrosion is enhanced and then proceeds more pronouncedly at the grain boundaries. It is also possible that then internal corrosion processes are triggered, in particular, in the grain boundary regions. While a qualitative assessment of the relationhips between corrosion and creep deformation is possible, the feasibility of a quantitative description is still far away. As a rule, however, the aspect of a strength decrease will prevail although, in principle, corrosion may give rise to a strengthening, too. (orig.)