Axial Suspension Plasma Sprayed Thermal Barrier Coatings

Suspension plasma spraying is gaining greater interest for emerging applications such as highly durable thermal barrier coatings (TBCs).  Mettech developed an axial suspension plasma spray technology (ASPS), and demonstrated its capability to overcome the complexities of the process and deliver quality coatings. The ASPS-TBCs have columnar structures with vertical cracks, similar to EB-PVD coatings.  Such structures allow the TBC to compensate for thermal expansion differences between it and the base material, resulting excellent durability. A 120-hour duration test indicated that the equipment and process are stable and reliable, and ready for industrial applications. This paper will present the ASPS development history, development challenges especially on automatic suspension feeder, and axial suspension injection. The process has significantly lower capital and operational cost compared to EB-PVD process. With many years of development, the technology is being adopted to replace EB-PVD for durable TBCs on aircraft turbines.