Although bearings and other precision components are generally made of hardened steel or metal alloys, those used in high load applications can still fail from excessive wear, surface fatigue, pitting, galling and corrosion.
This is exacerbated in applications with metal-to-metal interaction, repetitive friction at high speeds or where little to no lubrication is present.
Fortunately, there are several carbon-based coatings available that provide a unique combination of extreme surface hardness, low friction coefficient and anti-corrosion properties like those provided by global coating provider Oerlikon Balzers.
The company’s BALINIT C coating is a WC/C ductile carbide carbon coating that is highly resistant to adhesive wear (scuffing) in particular.
Bearings often suffer from severe and disproportionately distributed abrasive wear. A coating such as BALINIT C is particularly suitable for case-hardening as well as ball- and roller-bearing steels because it can be applied at temperatures under 200 °C.
The PVD coating can be applied not only to inner and outer races and cylinders but also to the balls in ball bearings in a uniform coating thickness of 0.5-1 μm. The slight increase in roughness is offset by the good burnishing qualities of the coating, which smoothes the raceway of the inner and outer rings, providing additional protection against scuffing and pitting.
Bearings in the soft calendar rolls of paper machines frequently experience smearing. Not only does PVD coating reduce the possibility of smearing, but by making the bearings harder with a coating, it has been shown that the life of these parts can be increased by a factor of three or four. As a result, paper mills are able to hold off on bearing replacement until the calendar roll needs regrinding, significantly reducing costly production downtime.
Similarly, cylindrical roller bearings in compressors are often exposed to low loads and vibrations, causing potential smearing. Applying PVD coating to the bearings removes any such possibility.