The effect of oxidizing environments on high temperature fatigue failure of 3CR12 alloy

3CR12 alloy is a titanium stabilized chromium containing corrosion resisting steel which was developed as a cost effective alternative material of construction in applications where low carbon and other structural steels have proved to have an inadequate combination of corrosion resistance and mechanical properties. Lately the use of 3CR12 was considered for components in the power generating and chemical industries operating under creep-fatigue loading conditions and oxidizing environments. The paper introduces a systematic study conducted in order to evaluate the effect of an oxidizing environment, in the form of an oxygen containing atmosphere, on the creep-fatigue failure of 3CRl2 at 600°C. The tests consisted of a creep tensile cycle and a plastic compression cycle and were conducted according to the CP mode of the strain range partitioning method. The strain ranges varied from 0.2% up to 0.4%. The results showed that the fatigue lives of 3CRl2 were greater in an atmosphere containing up to 200/0 oxygen than in an inert argon atmosphere indicating an adequate oxidizing resistance of the alloy under the cyclic loading conditions employed. The fatigue crack initiation and propagation mechanisms were studied by investigating the mechanical and chemical events occurring ahead of the crack tip using scanning electron microscopy, EDAX chemical analysis and X-ray diffraction.