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

Core Differences in TBC Application Methods

Thermal barrier coatings (TBCs) for superalloy components can be applied using two primary techniques: plasma spraying and electron beam physical vapor deposition (EB-PVD). Both methods protect critical parts in aerospace and aviation and power generation turbines, but they produce fundamentally distinct microstructures and performance characteristics. Plasma spraying builds a lamellar, slightly porous structure suitable for thermal insulation, whereas EB-PVD produces a columnar, strain-tolerant coating ideal for high-temperature cyclic environments.

Plasma Spraying Characteristics

Plasma spraying is cost-effective and widely used for large surface coverage. Molten ceramic particles are propelled toward the substrate, forming a layered structure with non-directional grain orientation. This method provides strong thermal insulation but lower strain accommodation under rapid heating and cooling. It is typically used on equiaxed castings produced through superalloy equiaxed crystal casting, where moderate thermal cycling is expected.

However, plasma-sprayed coatings may suffer from microcracking if prior densification steps like hot isostatic pressing (HIP) are not applied to stabilize the substrate and eliminate casting porosity.

EB-PVD Characteristics

EB-PVD generates a highly adherent, columnar microstructure that allows for elastic deformation under thermal gradients. This structure is ideal for components produced via single crystal casting and directional casting, where long-term creep resistance and thermal fatigue performance are crucial.

Although EB-PVD is more expensive and requires vacuum equipment, it delivers superior coating integrity, reduced spallation risk, and greater resistance to thermal shock. As such, it is preferred for aerospace high-pressure turbine blades where operating temperatures often exceed 1100 °C.

Integration with Post-Processes

Regardless of the coating method, surface preparation via superalloy CNC machining and stress-relief heat treatment is essential. After coating, non-destructive material testing and analysis validates coating thickness, adhesion quality, and porosity level before deployment in service.

Systems with extreme thermal gradients may also require thermal barrier coating repair cycles, which Neway supports through precision re-coating and post-weld treatment processes.

Summary

Plasma spraying is economical and widely applicable, while EB-PVD provides superior thermal fatigue resistance and strain tolerance for critical turbine components. Selection depends on temperature exposure, mechanical loading, and structural design constraints.