Assessing HVOF as a novel deposition approach for AlSi-polyester abradable coatings
Assessing HVOF as a novel deposition approach for AlSi-polyester abradable coatings
Tuesday, September 29, 2026
Exhibit Hall 400ABC - Poster Area (Québec City Convention Centre)
In aircraft turbine engines, maintaining appropriate tip clearance is essential for reliable and
efficient operation, as variations in the gap between blades and the casing can cause
performance losses and undesirable blade-casing contact. Thermally sprayed abradable
coatings are commonly applied to casing surfaces to accommodate these interactions. These
materials are designed to wear preferentially during blade contact, limiting component damage
while providing thermal protection and facilitating surface repair. They can also suffer from
erosion, which is related to airborne particles such as sand and fly ash, that can degrade the
surface and impair engine performance. Consequently, abradable coatings must combine
abradability (ability to be abraded off) with erosion resistance. However, these features often
compete, such that improving one may compromise the other. Different approaches can be
adopted to optimize this balance, including the deposition process. AlSi-polyester coatings are
commonly used in low-pressure turbine sections, consisting of polyester dispersed within an
AlSi alloy matrix. These coatings are typically deposited by Atmospheric Plasma Spraying
(APS), a well-established, versatile, and reproducible process. However, their deposition by
High-Velocity Oxy-Fuel (HVOF) remains scarcely investigated. HVOF could promote greater
coating densification while requiring lower energy input, potentially benefiting coating
properties, although maintaining adequate abradability remains a concern. Accordingly, AlSipolyester coatings were deposited by APS and HVOF. The as-sprayed coatings were
characterized in terms of microstructure, material and mechanical properties, followed by
abradability testing using a laboratory-scale rig. HVOF coatings exhibited higher hardness and
lower porosity than APS coatings. APS coatings showed distinct particle boundaries,
particularly around the polyester phase, whereas HVOF produced a denser, lamellar-like
structure. Despite these differences, both coatings exhibited comparable abradability forces in
rub testing. These results demonstrate that HVOF can produce AlSi-polyester coatings for lowpressure turbine applications while retaining the required abradability performance.
Keywords: Abradable coatings; Atmospheric Plasma Spray; High Velocity Oxy-Fuel; Gas
turbine engine
efficient operation, as variations in the gap between blades and the casing can cause
performance losses and undesirable blade-casing contact. Thermally sprayed abradable
coatings are commonly applied to casing surfaces to accommodate these interactions. These
materials are designed to wear preferentially during blade contact, limiting component damage
while providing thermal protection and facilitating surface repair. They can also suffer from
erosion, which is related to airborne particles such as sand and fly ash, that can degrade the
surface and impair engine performance. Consequently, abradable coatings must combine
abradability (ability to be abraded off) with erosion resistance. However, these features often
compete, such that improving one may compromise the other. Different approaches can be
adopted to optimize this balance, including the deposition process. AlSi-polyester coatings are
commonly used in low-pressure turbine sections, consisting of polyester dispersed within an
AlSi alloy matrix. These coatings are typically deposited by Atmospheric Plasma Spraying
(APS), a well-established, versatile, and reproducible process. However, their deposition by
High-Velocity Oxy-Fuel (HVOF) remains scarcely investigated. HVOF could promote greater
coating densification while requiring lower energy input, potentially benefiting coating
properties, although maintaining adequate abradability remains a concern. Accordingly, AlSipolyester coatings were deposited by APS and HVOF. The as-sprayed coatings were
characterized in terms of microstructure, material and mechanical properties, followed by
abradability testing using a laboratory-scale rig. HVOF coatings exhibited higher hardness and
lower porosity than APS coatings. APS coatings showed distinct particle boundaries,
particularly around the polyester phase, whereas HVOF produced a denser, lamellar-like
structure. Despite these differences, both coatings exhibited comparable abradability forces in
rub testing. These results demonstrate that HVOF can produce AlSi-polyester coatings for lowpressure turbine applications while retaining the required abradability performance.
Keywords: Abradable coatings; Atmospheric Plasma Spray; High Velocity Oxy-Fuel; Gas
turbine engine