Stability of permanent connection of deformable high-temperature nickel based and cast intermetallic alloys obtained by pressure welding under superplasticity conditions

The article presents a study of welded joints of cast intermetallic single-crystal rhenium containing VKNA-25 alloy with crystallographic orientation [001] and deformable high-temperature disk nickel alloy EP975, depending on the parameters of pressure welding under superplasticity conditions and standart heat treatment for high-temperature disk nickel alloy with regulated single-phase cooling. The study was carries out for the interdendritic region. The results of X-ray micro-spectral analysis of a solid-phase joint in the welding zone and at distances of up to 140 μm are presented in comparison with the initial chemical composition of the alloys. Found that before and after heat treatment in the welding zone and near-weld zone particles of topologically cloth-packed phases are not observed. Balance of alloying is better maintained in deformable high-temperature disk nickel alloy EP975 and this is natural, since pressure under superplasticity conditions takes place due to the disk alloy and at cast intermetallic single-crystal alloy only diffusion processes take place. Thus, high-quality one-piece connection of a disk and a blade for blisk-type structures is feasible under superplasticity only of one deformable fine-grained disk alloy and it is relevant for blisk type constructions. Blade intermetallic alloy VKNA-25 keeps thermally stable single-crystal structure.