Complex geometry components with high aspect ratio bores, blind holes and non-line-of-sight areas pose a significant challenge when it comes to applying protective coatings uniformly.
Traditional coating methods often fall short, especially with components like gate
valves, pumps and actuators where internal channels and intricate designs require
consistent protection. Here, Chemical Vapour Deposition (CVD) technology stands out as an
alternative solution, enabling precise and uniform coating on complex shapes and internal
surfaces.
Applying protective coatings to complex geometry components using traditional methods like
High-Velocity Oxygen Fuel (HVOF) and Physical Vapour Deposition (PVD) presents
significant engineering challenges.
Coating consistency: Achieving uniform coating thickness is difficult, as traditional line-of-sight processes often result in uneven distribution, particularly in recessed or intricate areas. Inconsistent thickness can lead to performance issues and require post-application adjustments.
Masking complex areas: Masking during the coating process is often necessary to prevent coverage in unintended areas. However, intricate geometries increase the complexity of masking, risking imprecise boundaries and potential coating in critical non-coated zones.
Achieving sufficient bond strength: Effective bonding on internal surfaces or high aspect ratio areas can be compromised, as traditional methods rely on mechanical adhesion rather than a strong metallurgical bond, leading to potential delamination under stress.
Corrosion protection in enclosed spaces: Porosity in traditional coatings can allow moisture or chemicals to penetrate in enclosed areas, making it difficult to ensure long-term corrosion protection across all areas of a complex geometry.
CVD is distinct in that it does not rely on particle projection and instead forms coatings atom-by-atom from a gas phase. This atomised application ensures a consistent deposition on intricate shapes, including internal channels and recessed areas. By ensuring uniform
coverage across the entire component, CVD technology provides exceptional protection for
even the most complex geometries.
The process is particularly well-suited for coating parts that require precise thickness control, typically between 25 and 75 microns. This capability is essential for applications such as hydraulic actuators, gearbox shafts and pump internals where uneven coatings could lead to performance issues or premature wear. Additionally, the CVD process requires minimal post-coating finishing, further reinforcing its suitability for parts with tight tolerances and intricate designs.
Gate valves and pumps used in harsh operating environments require consistent protection
against erosion, wear, corrosion as well as heat, fatigue and stress resistance due to the
materials and gases they are exposed to. Uniform coatings are vital to ensure seating
surfaces achieve effective sealing in critical areas which eliminates the risk of leakage as
well as ensuring optimum operating performance without losses or equipment failure when
exposed to fluctuating loads and pressures.
Aerospace hydraulic actuators and gearbox shafts often experience wear, fatigue and
corrosion. CVD coatings enhance these components’ durability, reduce friction and leakage,
and offer a high level of fatigue resistance as an effective alternative to hard chrome plating.
The coating’s ability to coat internal channels and complex mating surfaces contributes to
longer-lasting, more reliable actuators and shafts.
In the oil and gas sector, valves and downhole tools encounter abrasive and corrosive
environments. CVD coatings ensure that internal surfaces of valves and pumps are
protected from wear, corrosion and galling. Their pore-free, uniform structure enhances
resistance to chemical attacks, increasing operational life and minimising equipment
downtime.
The adoption of CVD technology for coating complex geometries and internal surfaces has
revolutionised protective coatings, overcoming limitations that have long restricted traditional
methods. With its ability to deliver uniform, non-line-of-sight coverage, CVD technology sets
a new standard for applications requiring enhanced durability, wear resistance, and
corrosion protection in challenging environments.
Hardide’s advanced tungsten carbide/tungsten metal matrix composite CVD coatings stand
out for their unique combination of high hardness, toughness and pore-free structure.
Together, these features provide unparalleled resilience in components exposed to severe
wear, erosion and corrosive conditions.