Surface Alloying and Surface Compositing of Copper Alloy Castings Using Mold and Core Coatings

Abstract This study presents a technique for simultaneous surface alloying and surface compositing (SASC) of C89836 brass castings. Core surfaces were coated with a slurry of Cu, Ni, and Ni-coated graphite powders before casting. During solidification, Ni and Cu dissolved into the melt and enriched the surface, while graphite particles were embedded in the matrix, forming a composite layer. Microstructural characterization by optical microscopy, SEM, and XRD confirmed uniform Ni enrichment and graphite incorporation. Electrochemical and Inductively Coupled Plasma Mass Spectrometry tests showed SASC castings had reduced corrosion rates and lower lead leaching, while machinability improved through the formation of short, granular chips instead of long, spiral chips. Compared with both the base alloy and Ni/Cu surface alloyed castings, SASC provided simultaneous improvements in corrosion resistance, lead leaching mitigation, and machinability. These findings demonstrate the potential of SASC technique for producing safer, high-performance brass components by integrating alloying and compositing in a single step.