Figure 1 shows the DSC curves of the cold-sprayed Ni–Al and Ni–Al–CuO coatings. For comparison, the DSC curve of the cold-sprayed Al–CuO coating is also plotted in Fig. 1. Three separate peaks in the temperature range of 450–700 ℃ can be observed for both the Ni–Al and Ni–Al–CuO coatings. For the Ni–Al–CuO coating, a fourth peak marked D in Fig. 1(b) appeared at 740–780 ℃. The two broad peaks A and B lie below the eutectic temperature of 640 ℃ based on the Ni–Al phase diagram , indicating that these reactions are controlled by solid-state diffusion. The third peak C identified for the Ni–Al coating is a sharp exothermic solid–liquid reaction peak at 640 ℃, also being observed for the Ni–Al–CuO coating. Peak D in the DSC curve of the Ni–Al–CuO coating indicates that CuO took part in the reaction at 740 ℃. As for the cold- sprayed Al–CuO coating, only one endothermic peak appeared, at 660 ℃, corresponding to the melting point of Al.
| 