Формирование твердофазных соединений жаропрочного дискового никелевого сплава с ультрамелкозернистой стрктурой и монокристального лопаточного сплава на основе Ni3Al

Abstract

The work is aimed at obtaining highly efficient one-piece units of gas turbine aircraft engines - disks with blades (blisks). Intermetallic γ΄ + γ alloys based on γ-Ni3Al phase of the VKNA type selected as blade material and Ni-based high alloy EP975 selected for discs have similar initial melting temperatures ( ~ 1340 and ~ 1300 °C, respectively). Solid-phase joints (SPJ) "EP975 //VKNA " are obtained at the homologous temperatures of 0.86-0.91 Tm (K). Fundamental differences in the SPJ structure and that of the adjacent areas for both alloys are determined by the intensity of diffusion processes at the homologous temperatures in intermetallic single-crystals of a thermally stable structure and in the deformed Ni-based alloy of an ultrafine-duplex (γ + γ΄) structure. The structure of single-crystal intermetallic alloys does not basically change either in the process of solid-phase welding at 1125-1200ºC (ε = 8-9%), or under the compression at 1125-1200ºC (ε = 8-9%), or during the subsequent annealing at 1200 °C. The SPJ material structure and properties are determined by the diffusion flows at the interface of the two alloys: Co, Cr, Co, W, Nb diffusing from the Ni-based alloy of the disk into the intermetallic alloy of the blade, on the one hand, and Ni diffusing into the disk alloy, on the other. The diffusion of W and Nb into the intermetallic alloy and Mo and Al into the Ni-based alloy is impeded. High-alloyed γ-solid solution based on the Ni alloy of variable composition (enriched with Al by the intermetallic alloy, wider from the Ni alloy side) is formed at the interface. The weld joint tensile strength on the flat surface varies at room temperature from 0.42 to 0.67 of that of the high tensile strength alloys welded.