Effect of oxygen boost diffusion treatment on fatigue behavior of Ti-4Al-2V alloy

An attempt has been made to determine the influence of oxygen boost diffusion (OBD) treatment on the fatigue behavior of Ti-4Al-2V alloy. In order to study the effect of OBD treatment, specimens were thermally oxidized at 450 degrees C in air for 2 h. Pre oxidized samples were put in the vacuum furnace (1 x 10(-3) Pa) at 850 degrees C for 7, 14, and 21 h. Rotary bending fatigue tests were performed on specimens before and after OBD treatments. The results revealed that OBD treatment led the fatigue endurance limit to be increased up to 85%. X-ray diffraction studies revealed that OBD treatment gave rise to large lattice expansion and high amount of residual compressive stresses, as result of dissolving oxygen atoms as interstitial in the titanium lattice. It is believed that the fatigue endurance limit improvement is mainly due to the residual compressive stress (RCS) filed and fatigue crack closure mechanisms. (C) 2010 Elsevier B.V. All rights reserved.