Effect of N-heterocyclic carbene surface modification on the oxidation and mechanical performance of low-pressure cold-sprayed copper coatings

Abstract:

Achieving durable corrosion-resistant coatings remains a key objective in many thermal spray applications. Copper-based deposits are therefore widely utilized; however, the presence of native surface oxides on feedstock particles remains a critical limitation, as it impedes particle deformation and reduces inter-particle bonding during deposition. This study investigates a surface engineering approach based on N-heterocyclic carbene (NHC) chemistry to reduce surface oxygen levels of copper feedstock powders prior to spraying. Commercially available copper powders (Dv(50) = 12 µm, Sigma-Aldrich) were subjected to a mechanochemical treatment pathway designed to activate the powder surface, promote oxide removal, and establish an organic capping layer intended to stabilize the modified surface. Coatings were deposited using a low-pressure cold-spray process onto carbon steel substrates to evaluate the influence of engineered surface chemistry under representative application conditions. The research is structured to elucidate the relationship between tailored powder surface states and coating formation, with particular focus on particle–particle interactions, bonding mechanisms, and coating integrity. The coatings underwent comprehensive characterization, such as microstructural examination and mechanical adhesion/cohesion assessment via scratch testing. Overall, this work seeks to establish a fundamental processing–surface chemistry framework for chemically tailored copper powders, providing guidance for the design of next-generation feedstocks aimed at improving the reliability and performance of coatings.

Keywords: Copper powders, N-heterocyclic carbene (NHC), Surface engineering, Cold spray coatings, Oxidation resistance