COATING TECHNOLOGY
CVD coatings can coat complex shaped parts and internal surfaces
this important characteristic. Te coating has enhanced ductility and toughness, minimum fatigue debit – much better high cycle fatigue performance than HCP or HVOF, and provides enhanced protection against galling.
After a lengthy and extensive test The pre-treatment line
expansion the coating as deposited is normally under compressive residual stress and is free from the micro-cracks typical of HCP. As a result, the CVD tungsten carbide coating is an excellent barrier against corrosion, outperforming HCP in
programme, Hardide Coatings, was selected by Airbus to provide its Hardide-A coating as a replacement for HCP and is now coating wing components for the Airbus A320, A330, A380 and A400M aircraft. One of the parts made from thin steel plate had HVOF coating specified, but in production most parts buckled after HVOF coating when the thermal spray layer cooled. Te Hardide CVD coating proved to be a better alternative with no distortion of the parts. A European helicopter manufacturer approved the Hardide CVD coating on a gearbox shaft replacing HVOF coating, as the smooth
Loading Hardide CVD coating reactor
The CVD coating can be applied to internal and or external surfaces and complex geometries
Hardide coating was shown to be far less abrasive for seals, reducing the risk of oil leakage and cutting maintenance. A major US-based producer of positive displacement pumps is increasingly using the CVD coating to replace HCP on both pistons and cylinders and has reported 3x increase in pump life when handling abrasive fluids. Every alternative to hard chrome and
HVOF has different characteristics and none will be an exact replacement, so evaluation of the application and its performance requirements is essential to determine the best solution. Tat approach followed up by extensive testing and evidence-based evaluation to ensure that performance criteria are met, will identify the most suitable alternative for hard chrome and HVOF replacement on a component-by-component basis.
Dr Yuri Zhuk is the Technical Director at Hardide Coatings.
www.hardide.com
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