ON CORROSION FATIGUE MECHANISMS FOR S45C AND SCM435 STEELS IN ROTATING BENDING.

Morphology of surface damage and small cracks by the corrosion fatigue was studied for quenched and tempered carbon steel S45C and Cr-Mo steel SCM435 in a deionized water and 3% NaCl water environments under rotating bending at frequencies from 0. 03 to 30 Hz. In saline water the fatigue strength of the two steels decreased monotonously with increasing number of cycles and testing time, while in the pure water a kind of temporal fatigue limit was observed for frequencies higher than 3 Hz. In the latter case fatigue crack was arrested by the closure effect of corrosion porduct for certain periods but this was diminished by dissolution after enough long test duration.