Structure and properties of welds in electron beam welding of iron-chromium-nickel alloy EP718

Abstract

This article presents the results of a study focused on the formation of structural characteristics and properties of welded joints in the EP718 alloy with a 13 mm thickness (accounting for a 3 mm technological substrate). The study explores variations in electron beam welding parameters, such as beam current and the speed of its movement across the specimen’s surface, to determine the optimal welding mode for this alloy. This alloy is crucial in the production of high-pressure stators for aircraft engines, as the component operates under low-cycle loads at high stress levels, making its performance critical. Specimens that were welded with a beam speed (ν) of 0.0042 m/s and a beam current (i) of 85 mA exhibited a minimum tensile strength of 1160 MPa. On the other hand, specimens welded with ν = 0.006 m/s and i = 65 mA demonstrated a maximum tensile strength of 1270 MPa. However, it’s noteworthy that specimens welded at 0.006 m/s with beam currents of 120 mA and 75 mA experienced fracture along the weld, while specimens welded at 0.006 m/s with a beam current of 65 mA and at 0.0042 m/s with a beam current of 85 mA exhibited fracture in the heat-affected zone at a distance of 0.5–3.0 mm from the weld. Examination of the structure of specimens welded at ν = 0.006 and 0.0042 m/s and i = 120 mA, 75 mA, and 85 mA revealed expanded grain boundaries in the heat-affected zone. Consequently, the optimal welding mode was identified as having a beam speed of 0.006 m/s and a beam current of 65 mA. In this mode, no thickened grain boundaries were detected, and a maximum tensile strength of 1270 MPa was achieved.