Cold-sprayed Cu-WC/Cu/Cu-Ni@W multilayer deposits for high-quality repair of Cu alloy electromagnetic rails

In electromagnetic launch systems, the harsh service conditions coupling of electrical arc erosion, high temperature friction and high frequency of thermal shock make the surface of the high strength Cu alloy rail easily damaged. The conventional high-strength alloy repair layer faces challenges in balancing electrical conductivity with wear and arc erosion resistance. Addressing this challenge, in the present work, a novel multilayered repairing strategy is introduced by cold spraying pure Cu and Cu-based composite deposits for synergistically improving/balancing the adhesion, electrical conductivity and surface protection performance. The effects of the multilayered deposit structure design, strengthening particle surface modification, and heat treatment on adhesion, electrical conductivity, wear and arc erosion resistance of the deposits are investigated. An optimized multilayered structure composed of a Cu-WC bond coat, a pure Cu middle layer and a composite top layer deposited with Cu-Ni-clad W (Ni@W) powder is achieved. As compared with spraying pure Cu, an increase in adhesion from 14 MPa to 66 MPa is achieved via introducing Cu-WC composite bond coat on the CuCrZr substrate. For the top composite layer, as the Ni@W particles are used to strengthen pure Cu, the friction coefficient and wear rate decreases from 0.37 and 3.2 × 10⁻⁵ mm³·(N·m)⁻¹ to 0.14 and 2.3 × 10⁻⁵ mm³·(N·m)⁻¹, respectively, and the arc erosion depth and area decreased by 31.1 % and 81.0 % with the breakdown intensity improved by 50.6 % relative to the CuCrZr substrate. Meanwhile, a high electrical conductivity of 77.7 %IACS through the thickness direction is detected for the optimized multilayered deposit. Finally, a practical repair demonstration done on V-grooved CuCrZr substrates confirms the structural integrity and machinability of the cold sprayed multilayer composite deposit. The present work is attempted to offer a viable solution for improve the service performance and extending the service life of the metallic structures used in coupled harsh conditions.