NoWear coated bearings

NoWear

NoWear is a wear-resistant carbon coating that can be applied to the rolling elements and inner ring raceway(s) of a bearing (designation suffix L7DA) or only the rolling elements (designation suffix L5DA) (fig. 1).

A physical vapour deposition process applies the wear-resistant carbon coating. Thickness of the coating ranges from 1 to 3 μm, depending on the size of the bearing. The hardness of the coating is 1 200 HV10.

NoWear coated bearing surfaces retain the toughness of the underlying material while adopting the hardness, improved friction properties and wear-resistance of the coating.

During the running-in period, minute amounts of the coating material are transferred to the counter-surfaces. This coating reduces friction and improves resistance against wear and smearing, even in bearings where only the rolling elements are coated.

fig. 1

Bearing features

Long service life

Withstand severe operating conditions

increased risk of smearing

insufficient lubricating film

sudden load variations

light loads

rapid speed changes

vibration and oscillations

Applications

NoWear coated bearings may provide new possibilities for existing applications operating under severe conditions. They can provide new design possibilities while requiring no major design changes. Typical applications where NoWear coated bearings are used include:

paper machines

marine and offshore applications

fans

compressors

hydraulic pumps

gearboxes

hydraulic motors

NoWear coated bearings are not intended for vacuum or other completely dry running applications. The coating does not act as a barrier against oxygen, and is therefore not recommended as a corrosion inhibitor.

Designs and variants

The most commonly used NoWear coated bearings have a coating on only the rolling elements (designation suffix L5DA). They are recommended for applications where the bearing load is light to normal, or where vibration and oscillating movements occur.

NoWear coated bearings that have the inner ring raceway(s) and rolling elements coated (designation suffix L7DA) are recommended for any of the following operating conditions:

abrasive contaminants that can cause premature wear

heavy loads

unusual lubrication conditions such as bearings lubricated by the process media

Most SKF rolling bearings can be supplied as NoWear coated bearings. For variants not listed in table 1, contact SKF.

Cages

Refer to Cages in the relevant product section of the standard bearing.

Bearing data

Dimension standards, tolerances, internal clearance, permissible misalignment

Refer to Bearing data in the relevant product section of the standard bearing.

Bearing service life

The extended bearing service life that NoWear can provide in high-speed, lightly loaded applications is difficult to calculate and depends on a variety of factors. However, experience has shown a multifold improvement in bearing service life.

For greased bearings that operate at speeds near or above the permissible speed, or at high temperatures that shorten the grease life, using NoWear potentially extends relubrication intervals.

When operating under marginal lubrication conditions, NoWear can extend bearing service life.

Loads

Minimum load

Owing to the material combination of NoWear/steel in the contact area, the risk of smearing damage is reduced. NoWear coated bearings are recommended for applications with light loads in combination with high speeds, where smearing damage is an issue.

Load carrying capacity, equivalent bearing loads

Refer to Loads in the relevant product section of the standard bearing.

Temperature limits

For temperature limits of the bearing, refer to Temperature limits in the relevant product section of the standard bearing.

The NoWear coating withstands temperatures up to 350 °C (660 °F).

Permissible speed

Refer to Permissible speed in the relevant product section of the standard bearing.

Lubrication

In general, the same lubrication guidelines are valid for NoWear coated bearings as for standard bearings (→ Lubrication). However, NoWear coated bearings can operate reliably even where adequate surface separation cannot be achieved. NoWear acts as a protective layer and may reduce the need for EP and AW additives in the lubricant.

Designation system

Refer to Designation system in the relevant product section of the standard bearing.

The designation suffixes used to identify NoWear coated bearings are:

L5DA	Coated rolling elements
L7DA	Coated rolling elements and inner ring raceway(s)