Fatigue Properties of Hydrided Titanium Condenser Tubes

Fatigue experiments have been performed on hydrided condenser tubes removed from a coastal power plant. Experimental phase of the study developed S-N data for hydride penetration depths ranging from 0 to 50 percent of wall thickness. This revealed about a 75 percent reduction in endurance limit with progressive hydriding over this penetration range. From the relationship between endurance limit and degree of hydriding, it was projected that a fracture mechanics evaluation could be applied where the hydride penetration depth was equivalent to a crack. It was concluded that residual fatigue strength of tubes hydrided to 50 percent of the wall thickness was approximately five times greater than the cyclic service stress plus a factor of safety.