Fabrication and properties of plasma-sprayed Al2O3/TiO2 composite coatings: A role of nano-sized TiO2 addition

Atmospheric plasma spraying coatings from alumina–titania feedstock comprising bimodal particle size distributions

“…Such results are apparently in contradiction with the common hypothesis of a crack deviation effect of the unmelted nanozones present throughout the bimodal microstructure [18,19,21] suggesting poor cohesion of these nanozones due to the low density of the granules found in the corresponding feedstock together with the plasma spraying conditions used in this work. More interestingly, significant differences were observed in the microhardness of the coatings, which varied from 2.2 GPa, for the conventional layer, up to 9.5 GPa, for AsTn30-1200 ºC coating.…”

“…Firstly, it can be seen that the coatings obtained from both thermally untreated powders mainly consist of α-Al 2 O 3 , γ-Al 2 O 3 and rutile. These findings are consistent with the phases observed in most of the works related to this Al 2 O 3 -TiO 2 system which employ submicron or nanostructured feedstocks [18,21].…”

“…The increased wear resistance of coatings obtained from nanostructured feedstocks in comparison with conventional (obtained from micrometric powders) coatings has been extensively reported in the recent literature [10,16,18,21]. The reasons showed in the literature for explaining this behaviour are as follows: the toughening contribution of the partially molten nanostructured zones [18,23,24] (not seen in this work), a more homogeneous TiO 2 distribution inside the splats leading to higher splat bonding strength [5,16] and the role of different additives such as CeO 2 and ZrO 2 added to the composition [25].…”

A study of the influence of TiO2 addition in Al2O3 coatings sprayed by suspension plasma spray

“…Improving the quality of Al 2 O 3 coatings is of special interest because of its exceptional wear resistance properties [26][27][28]. In this sense, researchers are focusing their attention to find the experimental SPS conditions to obtain denser alumina coatings while maintaining the nanostructure.…”

“…The best result achieved in alumina coatings obtained by SPS involves the addition of low quantities of titania, e.g. Al 2 O 3 with 13 %wt TiO 2 [28]. It was found that titania acts as a flux agent and its presence improves the resultant mechanical features of coatings.…”