Microstructure and microhardness of solid-state joints of high-temperature nickel-based alloys obtained by pressure welding

Abstract

The task of joining dissimilar heat-resistant nickel-based alloys (superalloys) is relevant to the mass reduction of aircraft engine parts. The paper presents the results of the microstructure and  microhardness studies of solid-state joints of the heat-resistant nickel-based superalloys obtained by pressure welding under superplastic conditions in the following combinations: EK61//EP741NP, and EK61//EP975, EP741NP//VKNA-25 and EP975//VKNA-1V. Pressure welding was performed in vacuum at 850 ℃ for EK61//EP741NP and EK61//EP975, and at 1125 ℃ for EP741NP//VKNA-25 and EP975//VKNA-1V. After pressure welding at 850 ℃, the initial microstructure of the joined EK61//EP741NP and EK61//EP975 superalloys remains stable. During high-temperature (1125 ℃) pressure welding in the combination of EP741NP//VKNA-25 and EP975//VKNA-1V superalloys, an increase in the grain size of the γ-phase from 5–6 to 7–8 μm is observed for EP741NP superalloy and from 6–8 to 9–10 μm . At the same time the monocrystalline structure is maintained in the VKNA-25 and VKNA-1V alloy. The microhardness of all solid-state joints is at the average level between the joined materials.