Permanent Joint Stability of Heat-Resistant Deformable Nickel and Cast Intermetallic Alloys Obtained under Superplasticity Conditions (Part II)

Welded joints of casting intermetallic single-crystal rhenium-containing VKNA-25 alloy with crystallographic orientation [001] and wrought high-temperature disk nickel alloy of brand EP975 were studied depending on the parameters of pressure welding under superplasticity conditions and the influence of standard heat treatment for disk high-temperature nickel alloy with controlled cooling from a single-phase area. The study was carried out on the interdendritic regions of a single-crystal alloy. The results of X-ray microanalysis in the solid-state compound zone (SSC) and at distances up to 140 μm from this zone are presented in comparison with the initial chemical composition of the alloys. It has been found that, both in the samples before heat treatment and in the heat-treated samples in the SSC zone of welded samples EP975//VKNA-25 and also near this near-weld zone, no appearance of topologically close-packed (TCP) phases is observed. The alloying balance is better maintained in the deformable disk nickel alloy EP975, which is natural, since deformation under superplasticity conditions occurs owing to the disk high-temperature alloy, and only diffusion processes occur in the cast single-crystal material. Obtaining a high-quality permanent connection from EP975//VKNA-25 nickel-based alloys, which is relevant in relation to blisk-type constructions, is feasible in the process of pressure welding under superplasticity conditions (realized only in the deformable fine-grained disk alloy EP975). At the same time, the blade intermetallic alloy VKNA-25 retains a thermally stable single-crystal structure.