Research on the Cracking Control of Laser Additive Repaired K465 Superalloy

The damaged aeroengine turbine blades made of K465 nickel-based superalloy were repaired by a laser additive repairing technique. Then the cracks characteristics and cracking mechanism of the laser additive repaired K465 superalloy were investigated. The cracks were eliminated successfully by taking some effective measures. Results show that the cracks originate from the heat affected zone of the laser additive repaired specimens, and extend to the repaired zone along the grain boundaries. The continuous liquid film is derived from the liquation of larger γ' particles at the grain boundaries and γ-γ' eutectics appear during grain boundary liquation. Stress field simulation results of the Ansys software demonstrate the existence of large thermal stresses between the substrate and the molten pool. Through preheating the substrates synchronously and adopting the optimized processing parameters, the laser additive repaired specimens with the structure of single track and multi layers without any cracks are obtained.