Fabrication of Ti–Cu–Al coatings with amorphous microstructure on Ti–6Al–4 V alloy substrate via high-energy mechanical alloying method

Abstract

A high-energy planetary ball mill was applied to fabricate Ti–Cu–Al coating on Ti–6Al–4V alloy substrate. The microstructure and elemental and phase composition of coatings were studied. The surface SEM images showed that the rough but densified coating surfaces, the cross-section microstructures as well as the related EDS line scan results illustrated different structures in the coatings, and the XRD results as well as TEM and corresponding SEAD pattern provided evidences of the existence of amorphous phase in the coatings. Mechanical properties including microhardness and friction and wear behavior were tested respectively. The microhardness testing results indicated that the fabricated coatings could largely strengthen the substrate surface. And the friction and wear resistance were tested with a ball-on-block sliding configuration, with the testing results showing decrease in both friction coefficients and wear weight loss after mechanical alloying treatment. The analysis and testing results also showed that a proper increase in the applied milling time favored the improvement in the thickness, surface smoothness, densification level, microstructural and chemical homogeneity as well as amorphization degree of the deposited coating. On the basis of two significant action mechanisms associated with a planetary ball mill, a reasonable mechanism was presented for the formation of amorphous phase contained coatings on Ti–6Al–4V alloy substrate.