Environmental effects on near-threshold fatigue crack propagation on a Ti6246 alloy at 500°c

Abstract

Abstract The cracking behavior of a Ti6246 alloy is studied in the near-threshold fatigue crack propagation regime with a special attention to possible coupled effects of corrosion and creep. Tests were conducted at 500°C in selected environmental conditions (high vacuum, controlled leak low pressure, controlled partial pressure of water vapor in pure argon) and at different frequencies. The near-threshold crack propagation is shown to be highly sensitive to the environment with a predominant detrimental influence of water vapor even under very low partial pressure. A modeling is proposed accounting for the influence of partial pressures of water vapor and oxygen, of test frequency and effective stress intensity factor, and introducing a single adjustable parameter accounting for the nature of the alloy and its sensitivity to environment. Applicability of this model is validated on an IMI834 alloy.