Microstructural, mechanical and tribological properties of nanostructured YSZ coatings produced with different APS process parameters

Microstructural characterisation of air plasma sprayed nanostructure ceramic coatings on Mg–1%Ca alloys (bonded by NiCoCrAlYTa alloy)

“…Moreover, the mechanism of crack arrest in the nanostructured ceramic zones is able to improve the bonding strength. It was reported that the bonding strength in the metallic bond layer could be probably reduced by the more presence of splat boundaries [23,39,41,42,43]. The relatively high value of bond strength of NiCoCrAlYTa/nano-Al 2 O 3 .13%TiO 2 /nano-TiO 2 coated Mg alloy (15.873.1 MPa) (Fig.…”

“…The aforementioned mechanism can be ascribed to the coatings with relatively low percentage of nano-zones [23,42,49], such as the nano-TiO 2 coating in this research. However, in coatings with higher percentages of nano-zones, the molten part of the semimolten agglomerates cannot fully diffuse into the capillaries of their non-molten cores during the plasma spraying process [23,42,[49][50][51].…”

“…However, in coatings with higher percentages of nano-zones, the molten part of the semimolten agglomerates cannot fully diffuse into the capillaries of their non-molten cores during the plasma spraying process [23,42,[49][50][51]. This phenomenon would lead to the formation of porous and brittle nano-zones, which were observed in the air plasma-sprayed nanostructure Al 2 O 3 -13 wt% TiO 2 coating.…”

“…In many studies, it has been proved that nanostructured ceramic coatings have superior wear performance compared to micro-structured coatings [22,23,42]. A combination of brittle fracture and abrasive wear (promoted by delamination and detachment of small fragments or particles from the surface) was considered to be a wear mechanism for this kind of coating.…”

“…However, the abrasive wear can be decreased by the wear scars of the nanostructured coating. These wear scars are finer and smoother than the wear scars of the micro-structured coatings and are able to form an adherent layer that can reduce the wear rate [42].…”