FORMATION OF SOLID-PHASE JOINT FROM EK61 AND EP975 NICKEL-BASED SUPERALLOYS

10.25712/ASTU.1811-1416.2022.03.012

Abstract

This paper presents the results of a study of the microstructure, energy dispersive analysis, and mechanical properties of solid-state joints after pressure welding of dissimilar nickel-based superalloys in the EK61//EP975 combination. Pressure welding was carried out in vacuum at a temperature of 925 °C and an initial strain rate of 10^-4 s^-1 according to the uniaxial compression scheme. The pressure welding conditions correspond to the conditions for the manifestation of low-temperature superplasticity for the EK61 superalloy. According to the results of the studies, it was found that a transition zone of diffusion interaction with a length of up to 20 μm is formed between the alloys as a result of mutual diffusion of elements. The strength of welded samples at a temperature of 650 °C is 0.51 of the strength of the EK61, and at room temperature 0.64. Significant changes are observed in the structure of the EK61 superalloy after pressure welding: the dissolution of the δ-phase and the coarsening of the matrix grains of the γ-phase occur. As for the more heat-resistant EP975 superalloy, the structure is stable. There were no changes, the size of the matrix grains of the γ-phase and relatively large particles of the γʹ-phase remains unchanged. Thus, it has been shown that the pressure welding is an effective method for obtaining solid-state joints from heat-resistant superalloys with different types of hardening.