Characteristics of Ni-Based Superalloy Powders Used for the Gradient Integral Turbine Blisk by the Ultra-transient Solidified Additive Manufacturing Ⅱ: Blade Alloy Powders

The characteristics of superalloy powders used for the gradient integral turbine blisk by the ultra-transient solidified additive manufacturing were investigated. According to the temperature capacity of the alloy and the phase equilibrium diagram calculated by JMatPro, DZ4125 was selected as the blade material, whereas K418 alloys were selected as the disk rim material for integral turbine blisk. The superalloy powder were prepared by vacuum induction melting and argon gas atomization (VIGA) and sieved to the particle size range of 53~105 μm. The differential scanning calorimeter (DSC), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), laser diffraction particle size analyzer, dynamic image analysis system and comprehensive powder property analyzer were used to systematically characterize the phase transformation temperatures, microstructure, precipitated phase composition, element segregation, particle size and shape, apparent density, tap density and flowability of the selected superalloy powders. The results show that DZ4125 possesses wider solid-liquid temperature range than K418 alloy. The liquidus temperature and MC carbide initial precipitation temperature of the transition zone DZ4125+K418 hybrid composition alloy are between that of the two alloys, and the γ' onset precipitation temperature is equivalent to the two alloys. The morphology of DZ4125 alloy powders is mainly spherical and nearly spherical. The surface and cross-section microstructures are mainly dendritic structure. For the selected alloy powders, the elements Hf,Ta, Ti, Mo and W exhibit strong segregation tendency, while the elements with weak segregation tendency include Ni, Cr, Co and Al. There are fine MC carbides distributed in the interdendritic zone of the powder, and the size is about 200 nm. The particle size distribution of powders measured by laser diffraction and dynamic image analysis methods is similar. The D50 values of DZ4125 powder are 70.2 and 72.8 μm. The dynamic image analysis result shows that the DZ4125 alloy powders possess good sphericity, and the SPHT and b/l values are 0.91 and 0.86, respectively. The DZ4125 superalloy powders have good apparent density, tap density and flowablity. The apparent density and tap density of the alloy powders can reach 52% and 63% of the theoretical density of the DZ4125 alloy, respectively. In addition, the DZ4125 superalloy powders possess compressibility of 17.7% and flowability of 20.79 s•(50 g)^-1.