Laser cladding of layered Zr/Cu composite cathode with excellent arc discharge homogeneity

Abstract

The surface-modified composite cathode is a promising candidate in alleviating arc ablation while retaining the matrix conductivity. In this work, mono-layered (ML) and bi-layered (BL) Zr/Cu claddings were prepared on the copper substrate through laser cladding. The arc ablation behaviors of BL Zr/Cu cathodes were investigated in the air atmosphere compared to ML Zr/Cu cathodes. The surface zirconium contents for the ML and BL Zr/Cu cathodes are 5.42 at.% and 65.91 at.%, respectively. The high-dilution Zr/Cu cladding serves as the intermediate buffer layer and promotes metallurgical bonding between the cladding and the matrix. The tight interlayer bonding is well maintained after long-term arc discharge. Cathode arc discharge homogeneity is improved as the surface zirconium content increases. The arc ablation rate of the BL Zr/Cu cathode (1.28 μg C−1) is 39.0% lower than that of the ML Zr/Cu cathode (2.10 μg C−1). The improved arc discharge behaviors are attributed to the surface ZrO2 layer. The ZrO2 layer homogenizes the arc discharge process with generating type 1 cathode spots while the copper matrix conducts the input energy flux. The layered structure realizes a combination of ablation-resistant surface and conductive matrix, which enhances the service life of the cathode.