The surface analysis of as-sprayed Al2O3 coatings (Fig. 1a–b) evidenced the continuous stacking of micrometrical splats typical of thermal sprayed coatings, indicating that these layers seal the pores of the silico-aluminous refractory. Additionally, on the surface coating sprayed from the agglomerated powder feedstock, sub-micrometrical particles were identified into some splats. (Fig. 1a). Furthermore, the cross-section analysis (Fig. 1c–d) allowed to establish that the thickness of both coatings was similar, 370 ± 20 μm for the coating sprayed from the agglomerated powder feedstock and 355 ± 20 μm for that made from the fused & crushed powder feedstock. Concerning the porosity (Table 1), it is possible to see that the values before and after the wear tests for all materials and all temperatures evaluated are statistically the same (all p-values are > 0.05), evidencing that there were no sintering processes.
Fig. 1. As-sprayed structures obtained: a–b) Surface of the Al2O3 coatings manufactured from the agglomerated and the fused & crushed feedstock powders respectively. c–d) Cross-section of the Al2O3 coatings manufactured from the agglomerated and the fused & crushed feedstock powders respectively.
Table 1 Porosity measured before and after the wear tests for all materials evaluated.
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