Plasma Spray Coatings for Heat Shielding – Engineering Guidelines for Designers and Purchasing Agents.
Choose the Right Ceramic Material
The most commonly used ceramic material for thermal barrier coatings is Yttria-stabilised zirconia (YSZ) which can operate continuously at temperatures up to around 1100°C. Alumina is used where high hardness and good wear resistance are required in addition to high temperature resistance. The main limitation of alumina is its poor thermal cycling performance and therefore is generally not recommended for such applications.
Always Include a Bond Coat
As already noted, the ceramic top coat must be bonded to the substrate with a suitable bond coat. The bond coat is typically a MCrAlY type alloy of nickel or cobalt base. This forms a strong adhesive bond with the substrate and also acts as an oxidation barrier to prevent the ceramic from reacting with the substrate during thermal cycling.
Understand What Substrates Are Suitable
(INCONEL 718, INCONEL X 750, Waspaloy), Stainless Steels and Titanium Alloys are state of the art. Also materials made of Aluminium and Magnesium are possible, but have to be checked prior application with the supplier of the coating. For more on this, take a look at https://www.poeton.co.uk/surface-treatments/thermal-metal-sprays/plasma-coatings/.
Know Where It Gets Specified
Examples of parts that are coated with plasma spray coatings for heat shielding are: turbine blades, combustion chambers, exhaust components, and industrial burner nozzles. Plasma spray coatings are commonly used in the aerospace industry as well as in power generation and in the high-performance section of the automotive industry. Thermal Plasma Spray is worth getting right.
Check Thickness and Dimensional Allowance
Coatings are typically applied in thicknesses from 100µm up to 500µm and therefore must be taken into account when designing components for thermal barrier coatings prior to application. The finished dimensions of parts coated with thermal barrier coatings can be outside of specified limits.
Getting the material, the bond coat and the substrate right from the start is crucial in avoiding rework.
