Figure 1 shows the surface morphology of MoSi2-ZrB2 coatings. The surfaces of all spraying samples are rough. In addition, the molten zone is interwoven with the incompletely molten particles, which is a typical structure feature of plasma sprayed coatings. In the process of coating preparation, high-speed particles are heated by plasma flame, and then the molten particles impinge on the substrate to form a flat structure. The temperature of the plasma arc elevates as the spraying power increases.Therefore, the full molten area of the mz43 sample is larger than that of the mz40 sample, leading to a much smoother surface of the mz43 sample. As for the mz45 sample, the completely molten area of themz45 sample is the largest (as shown in Figure 1c). Therefore, the mz45 sample shows a more compact surface as compared with that of the mz40 and mz43 samples.
Figure 1. Surface morphology of MoSi2-ZrB2 coatings:(a) mz40,(b) mz43 and(c) mz45.
Figure 2 shows cross-sectional morphologies of MoSi2-ZrB2 coatings. The mean thickness of the coatings of the mz40, mz43 and mz45 samples are about 122,138 and 158 um, respectively. As shown in Figure 2, the interface between the coating and the substrate becomes denser and more uniform as the power increases. For the mz45 sample, the interface is more compact, indicating that the mz45sample has a better combination of the coating and substrate as compared to that of the mz40 and mz43 samples. As shown in Table 1, the main constituent phase of the mz45 sample is confirmed tobe MoSiz. The elements mapping, as shown in Figure 4, reveals that the coating mainly consists of Mo, Si and O. The existence of O element may be induced from the spraying in oxygen atmosphere.Furthermore, the Vickers hardness of the coating prepared by 40,43 and 45 Kw are measured to be 850,924 and 979, respectively. This may be due to the better combination of the substrate and coating as the increase of the spraying power.
Figure 2. Cross-section morphology of MoSiz-ZrB2 coatings:(a) mz40,(b) mz43 and(c) mz45.
Table 1. The EDS results of constituent phase of mz45 sample(at.%).
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