Path to single-crystalline repair and manufacture of Ni-based superalloy using directional annealing
T. Kalfhaus, H. J. Schaar, F. Thaler, B. Ruttert, D. Sebold, J. Frenzel, I. Steinbach, W. Theisen, O. Guillon, T.W. Clyne, R. Vaßen.
Surface and Coatings Technology, 405, 126494, (2021)
Advanced methods for the repair of single-crystalline (SX) Ni-based superalloys are of special interest for the gas turbine industry. Polycrystalline repair approaches show promising results, while the repair of SX materials is still challenging. Directional annealing experiments resulted in large columnar grains by imposing thermal gradients at the abnormal grain growth temperature of a specific Ni-based superalloy. A numerical model of the Bridgman process is applied to provide an insight into the temperature evolution during zone annealing of the Vacuum-Plasma-Spray (VPS) repair coatings with the aim of promoting grain growth from the SX substrate. The results presented here suggest that this is a promising approach to repair or manufacture SX turbine blades.
Keyword(s): Thermal spray, Superalloy, Nickel alloys, Annealing, Bridgman technique