How do plasma spraying and EB-PVD differ in applying TBC coatings?

Fundamental Differences in Application

Plasma spraying and electron beam physical vapor deposition (EB-PVD) are the two primary methods for applying thermal barrier coatings (TBCs) to high-temperature superalloy components. While both are used to protect parts in aerospace and aviation and power generation turbines, they produce different coating structures and performance characteristics. Plasma spraying builds a layered, more insulating structure, whereas EB-PVD creates a columnar, strain-tolerant coating that better withstands thermal cycling.

Plasma Spraying – Advantages and Limitations

Plasma spraying uses a high-temperature plasma jet to propel molten ceramic particles onto the substrate. It is cost-efficient and suitable for large surfaces or moderate-temperature applications. The resulting coating structure is lamellar with limited strain tolerance, making it prone to microcracking under severe operating conditions. For castings produced via superalloy equiaxed crystal casting, plasma spraying provides effective insulation but may require post-treatment such as hot isostatic pressing (HIP) to stabilize the substrate and enhance adhesion.

EB-PVD – Performance Benefits

EB-PVD is performed under vacuum using an electron beam to vaporize coating material that condenses onto the component, forming a columnar microstructure. This structure allows elastic deformation during thermal expansion, reducing spallation risk. EB-PVD is ideal for high-speed rotating parts produced via single crystal casting and directional casting, where thermal fatigue resistance and long-term creep performance are critical.

Although EB-PVD is more expensive and slower to apply, it provides superior durability and heat resistance for turbine blades and combustor components operating above 1100 °C.

Integration with Post-Processing

Both coating methods require high-quality surface preparation using precision superalloy CNC machining to ensure coating uniformity. After application, non-destructive material testing and analysis verifies thickness, pore distribution, and adhesion strength. In high-pressure environments, EB-PVD coatings may be paired with thermal barrier coating repair procedures to extend service life.

Summary

Plasma spraying is economical and suitable for moderate thermal environments, while EB-PVD delivers superior strain tolerance, adhesion, and fatigue resistance. Selection depends on component geometry, temperature exposure, and operational stress.