SEAL-FRIENDLY WEAR- AND CORROSION-RESISTANT CVD COATING for COMPLEX SHAPED AIRCRAFT PARTS

Leak-tightness of aircraft hydraulic actuators and rotating shafts depends on seals. In abrasive and corrosive environments, metal shaft seal track or piston rod surface finish degradation can accelerate the seal wear rate by an order of magnitude. Hardide nano-structured CVD Tungsten Carbide coating can protect metal surfaces and thus reduce the seal wear. The coating can be polished to better than 0.2 micron Ra and super-finished to 0.05 micron Ra and 0.1 micron Rz. Thanks to the coating’s enhanced resistance to wear, erosion and corrosion the coated metal part’s finish will be maintained, and often improve, during  operation for longer and thus will remain less abrasive for the seal.

The Hardide CVD coating is crystallised atom-by-atom from low pressure gas media, this enables the uniform conformal coating of internal and external surfaces, and complex shapes.

The CVD coating has excellent anti-galling properties and can be used on metal/metal seals and load-bearing parts under high loads and at temperatures up to 400^oC (750^oF).

The coating has been used continuously on Eurofighter Typhoon aircraft components since 2005. It is at the final stage of qualification by a major international civil aircraft manufacturer and by several EU aircraft component producers as an environmentally sound alternative to Hard Chrome plating (HCP). Hardide-A matches HCP in thickness (50…100 microns) and hardness (800…1200 Hv). This simplifies the switching from HCP to Hardide-A with only minimal design changes. The CVD coating is free from micro-cracks typical of HCP and, as a result, has reduced fatigue debit and provides much better protection against corrosion. 

Other applications of Hardide coatings include oil drilling tools, pumps and valves operating in an abrasive, erosive and corrosive environment, where the coating typically triples the life of critical parts.