Effects of Cu content on the microstructures and properties of Cr–Cu composite coatings fabricated via mechanical alloying method

• Chrome–copper composite coatings were prepared on pure Cu substrate.
• The copper content has effects on roughness and adhesion of coatings.
• A multilayered structure was formed after treatment in copper-rich powder.
• The fabricated coatings could largely strengthen the substrate surface.

Cr–Cu coatings with a composite structure were fabricated by means of mechanical alloying. Powders with various Cr–Cu ratios were used to fabricate coatings. Microstructures and chemical compositions of as-synthesized coatings were analyzed by SEM and EDS. Phases and microstructural features of ball milled powders were identified by XRD and SEM. The results indicated that large amount of initial Cu powder addition led to the excess of pure Cu after Cu–Cr mechanical alloying, which prevented particles from being fractured and thus resulted in the increase of surface roughness. Coatings with a multilayered structure could be detected in the cross-section micrographs. The formation mechanism of the coating was discussed. Adhesion behaviors of the coatings were determined through the combination of scratch tests and SEM equipped with EDS. Mechanical properties such as microhardness and friction and wear resistance were also tested. The test results provided an evidence of the surface reinforcement of as-synthesized coatings. Taking into consideration surface roughness, coating adhesion and mechanical properties including microhardness and friction and wear resistance, the optimal Cr–Cu ratio of starting powder was about 13:7 at the selected mechanical alloying processing parameters.

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