“Thermal Barrier Coatings:
The pursuit of ever-increasing efficiency & performance, the operating temperatures of aeroengines and gas turbines, have increased significantly. To the point that without protection, critical metal components like turbine vanes & nozzle guide vanes would literally melt. For example, the Pratt & Whitney F135 engine used in the F-35 (JSF), has a reported turbine-inlet temperature of up to 1982 °C (3600 °F). Thermal barrier coatings provide the vital protection from the extreme operating temperatures and extend the operational life of the exposed components considerably. The thermal barrier coatings are composed of an insulating ceramic top coating, and a bond coating composed of M-CrAlY alloy.
The base element (M) of the M-CrAlY alloy is comprised of nickel, cobalt or iron, and enhances the adhesion between the ceramic topcoat, typically made of yttria stabilised zirconia (YSZ) and the metallic substrate, which is normally a nickel based super-alloy. M-CrAlY alloys provide resistance to oxidation and corrosion resistance due to the yttria stabilised aluminium & chromium oxide and prevent spalling of the ceramic topcoat. Spallation is the primary failure mode of the thermal barrier coating, due to high thermal and mechanical stress experienced during operation.
The M-CrAlY alloy bond coating is applied to the surface of the critical components by a number of different coating processes; including Physical Vapour Deposition (PVD) and Low-Pressure Plasma Spray, Vacuum or Air plasma spraying , as well as High Velocity Oxy-Fuel (HVOF), which use M-CrAlY powders as the principle raw material. Therefore, producing high quality M-CrAlY powders, to rigorous OEM specifications and following the required international standards, such as AS9100D, is vital to the on-going operation & refurbishment of aeroengines and gas turbines. The hollow sections and strategically position cooling holes of turbine blades, typically manufactured by investment casting, also play a critical role and with the increasing complexity open opportunities for production of the blades by Additive Manufacturing processes, like Powder Bed Fusion – Laser (PBF-LB) or Electron Beam. As well as sinter-based processes like metal binder jetting, which can process nickel super alloys like CM247LC that are extremely challenging to weld and therefore difficult print by PBF-LB.”
CoNiCr Alloy Coated sample- by Plasma Spray
Coating Process: Plasma Spray
Plasma Equipment make: Metco
Plasma Spray Equipment Model: 3MB
Coating Thickness: Avg 274μm
Coating Hardness: Avg 97 HRB
Coating Porosity: Avg 1.57%
