Aqueous suspension processing of multicomponent submicronic Y-TZP/Al 2 O 3 /SiC particles for suspension plasma spraying

Abstract

In order to obtain thermal barrier coatings by Suspension Plasma Spraying (SPS) process with potential new self-healing ability multicomponent submicronic Y-TZP/Al2O3/SiC suspensions were prepared. For this purpose, concentrated aqueous suspensions of individual components as well as the multicomponent mixture were studied and characterised in terms of colloidal stability and rheological behaviour to determine the best conditions for processing and preparation of the coatings. In the study, different dispersant contents and sonication times were tested. Subsequently, low concentrated suspensions were prepared to obtain preliminary thermal barrier coatings with the optimised feedstock. Thus, ceramic coatings were deposited by SPS and then characterised in order to assess the microstructure and phase distribution, in particular, the degree of preservation of the sealing agent, SiC, in the final coating as a previous indicator of its self-healing ability.

Effect of fructose-containing feedstocks on the microstructure of multicomponent coatings deposited by suspension plasma spraying

“…The flow curves show the evolution of shear stress with shear rate for different sonication times and the enlargement of the curves is represented for a better evaluation in the high shear rate range. InFigure 2a, the flow curves are very similar to those reported in other previous research[28,32], i.e. suspensions show a practically Newtonian behaviour with a little trend of dilatant fluid at high shear rates.…”

“…Starck, Germany), as disperse phase in a concentration of 15 wt%. More details of raw materials are described in previous works [6,28]. Al2O3, and 1.5 wt% synthetic polyelectrolyte (PKV, Produkt KV5088, Zschimmer-Schwarz, Germany with polycarboxylic nature) for SiC), which has been studied in a previous work [28].…”

“…More details of raw materials are described in previous works [6,28]. Al2O3, and 1.5 wt% synthetic polyelectrolyte (PKV, Produkt KV5088, Zschimmer-Schwarz, Germany with polycarboxylic nature) for SiC), which has been studied in a previous work [28]. Rheological behaviour was analysed using a rheometer (Haake RS50; Thermo, Karlsruhe, Germany) which operated in controlled shear rate mode.…”

“…Before spraying, the metallic substrates with dimensions of Ø 25 mm x 10 mm were grit blasted with black corundum at a constant pressure of 4.2 bars and cleaned in ethanol and ultrasonic bath to remove surface residues. Bond coats (Amdry 997, Sulzer-Oerlikon, Germany) were sprayed by atmospheric plasma spraying under standard conditions set out in a previous research [28] in order to enhance the adhesion between layers. The suspensions feeding was carried out using an injection system developed by the Institute for Ceramic Technology (ITC, Castellón, Spain), which consists in a peristaltic pump to inject the suspensions from the vessels to the plasma gun through a pressure nozzle with a hole size of 150 µm diameter.…”

Deposition of hydroxyapatite and tricalcium phosphate coatings by suspension plasma spraying: Effects of torch speed

“…In particular, the formation of CaO, which reacts with water molecules to produce Ca(OH)2 connected with considerable increase of volume, is one of the most problematic issues because it causes cracking and delamination of the coating [7][8]. Recently, a modification of APS was introduced known as suspension plasma spraying (SPS) that allows the injection of submicrometer sized powder particles and the preparation of new and unique types of structures [9]. In this method, the powder is injected into the plasma as a suspension, thus avoiding problems associated with powder flowability.…”