Architecture and phases composition of suspension plasma sprayed alumina–titania sub-micrometer-sized coatings

Abstract

Sub-micrometer-sized Al2O3-TiO2 plasma-sprayed coatings exhibit superior performances compared to micrometer-sized ones. Two routes can be implemented to manufacture such finely structured coatings:i)spraying micrometer-sized agglomerates of nanometer-sized particles which results in a two-scale coating architecture and ii) spraying a suspension of sub-micrometer-sized particles (suspension plasma spraying, SPS). SPS was implemented in this study and Al 2 O 3-base coatings with 13 and 60 wt.% of titania, respectively, were manufactured by spraying a suspension made of a mixture of Al 2 O 3 and TiO 2 particles both of 300 nm, average diameter. Coating structural features and phase contents were studied. Results show that the coatings exhibit averyfine lamellar structure with a homogeneous repartition of Al and Ti. Complex phases, made of intermediate Al, Ti, and O oxides, have been also identified. Indeed, coatings formation results from rapid solid-ification rates and high transient thermal fluxes imparted by the plasma flow to the substrate due to the short spray distance encountered in SPS (in the order of 30 mm) requested by the small kinetics and thermal inertia of sub-micrometer-sized particles.

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

“…In each case, the dispersant is burned and disintegrated during the spraying procedure. Other technical details of the preparation and stabilization of suspensions can be found in our previous work [25].…”

“…The literature reports that low density coatings with low cohesion and high porosity [25] can be obtained.…”

Effect of the initial particle size distribution on the properties of suspension plasma sprayed Al2O3–TiO2 coatings

“…Moreover, the Al 2 O 3 -TiO 2 mixture with 13 wt% of TiO 2 displayed the best wear resistance among all the nanostructured Al 2 O 3 -TiO 2 coatings [19]. However, the research on Al 2 O 3 -TiO 2 coatings by SPS is still incipient and very few authors have studied such layers [20].…”

Effect of TiO 2 addition on the microstructure and nanomechanical properties of Al 2 O 3 Suspension Plasma Sprayed coatings

“…Indeed Al 2 O 3 -TiO 2 coatings obtained by APS from both conventional feedstocks and agglomerated powders has been extensively studied [38][39][40][41][42][43][44]. However, the research on SPS Al 2 O 3 -TiO 2 is still incipient and very few authors have studied such layers [45]. Consequently, it is still necessary to study the effect of the addition of TiO 2 on the characteristics of alumina SPS coatings.…”