Thermally activated reactions of multi-walled carbon nanotubes reinforced aluminum matrix composite during the thermal spray consolidation

Highlights: ► The interfacial reactions of MWCNT reinforced Al composite in the HVOF spraying process are investigated. ► The MWCNTs reacted with oxygen at their defect sites, and were gasified into carbon oxide gas. ► A reaction between Al and carbon produced Al4C3 at the defect sites on the MWCNT surface. ► These reactions result in the deterioration of the reinforcement in the composite. ► The interfacial reaction mechanisms of the MWCNTs are discussed based on microstructural and thermodynamic analysis. - Abstract: The interfacial phenomena of multi-walled carbon nanotubes (MWCNTs) embedded in an Al matrix during high-velocity oxygen fuel (HVOF) spraying were investigated. The high thermal energy supplied from the high temperature gas flow of HVOF spraying activated the interfacial reactions of MWCNTs with oxygen and Al, such as MWCNT oxidation and aluminum carbide formation. Interfacial reactions deteriorated the contribution of the MWCNTs to the coating properties by destroying the intrinsic structure of the MWCNTs. In this study, the interfacial reaction mechanisms of the MWCNTs are discussed based on microstructural and thermodynamic analysis.