Compared with the uncorroded coatings, the corroded ones were significantly rougher and had severe erosion scars, as shown in Fig. 1. The mass loss of the uncorroded and corroded Cr3C2-NiCr coatings are shown in Fig. 2. The slope of the curves represents the cumulative mass erosion rate. The erosion wear process consisted of the running-in (initial 20 g erosion particles) and steady wear (succeeding 80 g erosion particles) stages. The erosion rate in the running-in stage was higher than that in the steady wear stage for the uncorroded and corroded coatings as a result of removal of surface oxide. The erosion rate was higher when the porosity was higher for both uncorroded and corroded coatings because porosity was related to hardness. The erosion rate of corroded coatings was significantly higher than that of the uncorroded ones in both erosion stages due to the “softening” effect of corrosion. Overall, the salt spray corrosion remarkably accelerated the deterioration of erosion wear resistance, and the erosion wear resistance of the corroded and uncorroded coatings deteriorated with increasing porosity.
Fig. 1. Erosion scar of coatings before and after 7 days corrosion.
Fig. 2. Mass loss of (a)uncorroded coatings, and (b) 7 days corroded coatings.
Erosion was significantly affected by corrosion. In the uncorroded coatings, microcutting dominated at the low impact angle (30°). Hardness was the key factor affecting the microcutting performance. On the one hand, hardness decreased with increasing porosity. On the other hand, the galvanic corrosion worsened with increasing porosity, which further increased the difference in hardness. In the corroded coatings, microcutting dominated at the low impact angle (30°), and deformation wear was remarkable. The loosened structure produced by corrosion led to typical deformation wear. Therefore, the reduction of porosity and proper sealing is crucial in the improvement of the antierosion performance under corrosive environment.
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