SECTION TITLE
COATING TECHNOLOGY
Oerlikon ta-C coatings are an excellent choice for components that are exposed to extreme operating forces over the long-term
FRICTION-FREE COMPONENTS
Advanced coating reduces friction of sliding ceramic, metallic and polymer components
C
omponents used in water, lubricated or in submersed environments face considerable tribological challenges that can ultimately affect
performance and reduce the life of the larger system – particularly those that come in contact or slide against other parts. Tis process includes pump parts, mechanical seals and high-pressure valves manufactured often using ceramic substrates designed to survive wet, corrosive environments. Unfortunately, these substrates are also easily damaged due to high friction of sliding/mated parts due to a consistently high coefficient of friction (COF) when uncoated. With that in mind, the goal is to keep the coefficient of friction of sliding parts as close to zero as possible. Te COF is the measure of the amount of friction existing between two surfaces. A low value of COF indicates that the force required for sliding to occur is less than the force required when the COF is high. Typical values for the COF when sliding is occurring between polished oiled metal surfaces, for example, is 0.1. Fortunately, there are industrial thin film coatings available that can reduce
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friction to dramatically improve the life and performance of critical components. Known as diamond-like carbon (DLC) coatings, they can increase the surface hardness of even hard, ceramic substrates while considerably decreasing their COF. One coating in the DLC family, tetrahedral amorphous carbon (ta-C), has unique tribological properties for water
environments that testing demonstrates can reduce the COF to levels that consistently approach 0.1-0.2, even in wet or dry running conditions. Best of all, the coating can be applied through experienced toll processors at a very low cost per part, increasing the performance and life of critical parts. Within the universe of wear resistant thin films, DLC coatings have emerged as the ideal solution for demanding physical applications where components are under high loads or subject to extreme friction, wear and contact with other parts. In these types of environments, the high hardness of a DLC coating – along with a corresponding low COF – can prevent parts from pitting, galling, seizing and ultimately failing in the field. For many, DLC coatings are
hydrogenated amorphous carbon (a-C:H) coatings, but this is a misconception. Coatings within the DLC family can be highly engineered based on factors such as hydrogen content (hydrogenated or hydrogen-free), the selection of additional metallic and non-metallic doping elements, the presence of sub-layers, and the choice of deposition and bonding methods. Together, these factors can be precisely
controlled to create a broad range of thinly applied (typically 1 to 5 μm) DLC coatings with a hardness of 8-80 GPa. Within the DLC coating category, the
For manufacturers of components often in contact with other parts and/or submersed in water, innovative coatings are changing what is possible
hydrogen-free formulations do not only provide very high hardness, but also an extremely low COF in water environments. Reducing friction when components are sliding against each other is critical, particularly in boundary lubrication. According to Dr Oliver Jarry of Oerlikon Balzers, a company that produces specialised
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