Modelling the crack growth behaviour of a single crystal nickel base superalloy under TMF loading with long dwell times

The influence of hold time on the crack growth behaviour of a single crystal nickel base superalloy under in phase thermomechanical fatigue is investigated. Two da/dt models were calibrated using creep crack growth tests in the temperature range 750-950 degrees C: one based on K and the other on (C-t)(avg). The models were applied, in combination with a cycle dependent model, to predict da/dN of in-phase thermomechanical fatigue crack growth tests with 1-6 h hold time. The predictions based on K were inaccurate and generally non-conservative, whereas the predictions based on (C-t)(avg) were accurate. da/dt vs (C-t)(avg) followed a single trendline for all temperatures.Funding Agencies|Siemens Energy AB in Finspang, Sweden; Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy ProcessesSwedish Energy Agency [KME-702]