Environmentally assisted fatigue crack nucleation in Ti-6Al-2Sn-4Zr-6Mo

摘要

An unexplained feature was observed at the fatigue crack origin of a number of alpha/beta titanium specimens tested at 450 degrees C in the low cycle fatigue regime. The origin was discoloured blue but this was not a result of temper colouration; this feature sometimes resulted in large reductions in fatigue lives. A number of specimens were examined to determine the cause and formation mechanism of these "blue spots." This feature was associated with elevated oxygen and chloride levels and the presence of sodium. A mechanism based on hot-salt stress-corrosion cracking is proposed and the implications for service components are discussed. (C) 2015 Elsevier Ltd. All rights reserved.