Effect of the Temperature of Pressure Welding of a Wrought EP975 Nickel Alloy and a Single-Crystal Intermetallic VKNA-25 Alloy on the Structure and Properties of the Welded Joints

This work is a continuation of the studies of the possibility of formation of a one-piece blisk unit for gas turbine engines by solid-phase pressure welding (PW) of a single-crystal [001] Ni3Al-based VKNA-type blade alloy with a wrought EP975 disk nickel superalloy. The influence of the PW temperature at a strain of 10 and 24% on the structure and mechanical properties of welded specimens at room temperature is investigated. An increase in the process temperature by 50 degrees C to 1175 degrees C is shown not to change the structure of the VKNA-25 alloy, and the gamma-phase grain sizes in the EP975 alloy increase from 7-8 to 15-18 mu m. During tensile tests, the welded specimens fail through the VKNA-25 alloy, and the strength of the welded specimens fabricated at 1175 degrees C is almost twice as high as that of the specimens fabricated by PW at 1125 degrees C at the same strain of the EP975 alloy. Electron backscatter diffraction (EBSD) analysis of the solid-phase bonding zone demonstrates that the VKNA-25 alloy retains its single-crystal structure.