A macrograph of the thick cold-sprayed Ni–Al–CuO coating is shown in Fig. 1(a). The density of the Ni–Al–CuO coating was determined to be 5.04 g/cm3 by the Archimedes method, similar to that (5.17 g/cm3) of the Ni–Al binary coating. The BSE morphologies of the Ni–Al and Ni–Al–CuO coatings are shown in Fig. 1(b) and (c). Both Ni–Al and Ni–Al–CuO exhibited a quite dense structure without obvious cracks or pores. Ni particles (bright areas) were located in a matrix of Al (dark area) in the Ni–Al coating, while CuO particles with medium brightness could be seen in the Ni–Al–CuO coating, as marked in Fig. 1(c). The statistical atomic ratio between Ni and Al as analyzed using Image-Pro Plus 6.0 software was about 1:1 for both the Ni–Al and Ni–Al–CuO coatings. Moreover, the Ni–Al–CuO coating contained about 10 wt.% CuO, which is lower than its content (16 wt.%) in the feed-stock powder. This difference in the composition between the coating and feedstock powder can be attributed to the entrapment deposition mechanism of CuO particles during cold spraying . The mechanical behavior of the cold-sprayed Ni–Al and Ni–Al–CuO coatings under quasi-static-state and dynamic compression conditions is shown in Fig. 1(d). These results reveal that the yield stress of Ni–Al–CuO was approximately 50 MPa higher than that of Ni–Al in both conditions, which may occur due to the dispersion strengthening effect of the CuO particles.
Fig. 1 (a) Cold-sprayed bulk energetic structural material; microstructure of cold-sprayed coatings (b) Ni–Al, and (c) Ni–Al-CuO; (d) stress–strain curves of different materials analyzed under quasi-static-state and dynamic conditions
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