Computational fluid dynamics modelling of heat treatment of single crystal nickel based superalloys for turbine blade application

A numerical model based on computational fluid dynamics (CFD) is developed to simulate the vacuum heat treatment of single crystal turbine blades. Radiation and forced convection heat transfer are taken into account to model ramping-up, holding and gas fan quenching. This enables quantitative predictions to be made of temperature fields inside a laboratory-scale vacuum furnace. The uniformity of the expected temperature field is studied with a particular aim to predict hot spots or locations with higher risk of incipient melting. Simulation of the gas fan quenching process allows estimation of the quench rate to be made as a function of position within the furnace and critical furnace processing parameters. The effect of quench rate and ageing time on the microstructure of RR3010 superalloy has been characterised using scanning electron microscopy. Two representative structures with different average 7′ size have been tested in creep in three temperature regimes and with three different level of stresses, in an attempt to gain better understanding of the influence of microstructure on creep performance. Our results indicate that at lower creep testing temperatures, larger γ′ size confers longer time to rupture; however, as the testing temperature increases, the influence of microstructure is less pronounced.