Layer-by-layer laser cladding of crack-free Zr/Nb/Cu composite cathode with excellent arc discharge homogeneity

Cathode ablation shortens the cathode lifetime and hinders the development of arc heaters. Surface-modified Zr/Cu cathodes realize combinations of ablation-resistant surface and conductive matrix, while the cracking problem limits their applications. In this work, Nb cladding and Zr cladding were prepared on Cu matrix successively. The Nb cladding was effective in serving as a blocking layer against diluting of Cu and suppressing forming CuZr intermetallics. The surface Zr content reached as high as 85.6 at.% and no CuZr intermetallic was detected inside the cladding. Besides, the intermediate Nb cladding contributed to tight interlayer metallurgical bonding. The arc discharge behaviors of bi-layered Zr/Nb/Cu cathodes were investigated compared to Cu cathodes. The bi-layered Zr/Nb/Cu cathode exhibited an improved arc discharge homogeneity with shallow and smooth ablated areas. The cathode ablation rate (1.30 μg C−1) was 37.5 % lower than that of Cu cathodes. The Zr/Nb/Cu layered structure improved the cathodic arc ablation-resistance without cracking, which guaranteed its application in large-area manufacturing process.