Effect of electroplated interlayers on bonding mechanism of cold-sprayed copper on SS316L steel substrate

Abstract

Cold-spray technology is being actively considered to develop copper (Cu) coatings to shield the plasma-facing components in Tokamaks, however, adequate adhesion is yet difficult to achieve. In the current study, interlayers of nickel and copper were introduced by electroplating SS316L steel substrate in order to improve the adhesion. Subsequently, thick copper coatings were deposited on the electroplated substrate by cold-spraying. The effect of these electroplated interlayers on the adhesion mechanism between cold-sprayed copper and the steel substrate was explored. The deposited copper coatings were subjected to adhesion/shear strength testing. To investigate the bonding mechanism of the coatings with the substrates, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses were done on the interfacial surfaces; exposed after the adhesion testing. Additionally, single-particle deformation behavior of copper particles cold-sprayed on copper electroplated (CE), nickel electroplated (NE) and as-received (AR) substrate surfaces was evaluated by using SEM/EDS. NE steel substrate resulted in a better adhesive strength as compared to the AR and CE steel substrates, which could be attributed to its strong metallurgical and mechanical bonding with cold-sprayed copper.