Effect of beam current on microstructure, tensile properties and corrosion behaviour of electron beam welded zircaloy-4 joints

Abstract

ABSTRACT Butt joints of zircaloy-4 were made using electron beam (EB) welding. The effect of beam current (15–20 mA) on weld zone size, microstructure, porosity, mechanical and corrosion properties has been investigated. Local temperature and cooling rate were estimated, and the average cooling rate increased from 2.4 to 6.3°C ms–1 with a decrease in beam current in the said range. Joints prepared at lower beam current possessed smoother weld surface, narrow weld bead, and fine lamellar type widmanstätten structure in the fusion zone (FZ). The length of the α-Zr lamella (from 105 to 37 µm) and interlamellar space (from 0.8 to 0.3 µm) decreased with a decrease in beam current. The XCT result revealed that porosity increased with an increase in beam current, and large-size micro pores of 180 µm were present in joints prepared at high beam current. The hardness of the welded samples increased by 13–20% than the base metal. The joint prepared with a low beam current possessed higher ductility (29%) and a minimum corrosion rate (0.0085 mmpy in 3.5 wt-% of NaCl solution) than the joint made with a higher beam current.