Ceramic Coated Bearings Prevent Current Damage from Electrical Erosion

NINE STAR ceramic coated bearings help equipment such as traction motors to achieve a greatly extended lifetime, overcoming the problem of electrical erosion which occurs when electric current flows through the motor bearings to earth. The extent of the damage which this current flow can cause depends upon the magnitude of the current and the duration of the conditions.

Damage usually takes the form of parallel axial marks, known as "fluting" in the areas of contact between the raceways and the rolling elements. Other more damaging effects of the current are craters, that is sometimes accompanied by a dark brown discolouration, which occurs in the trackways and this leads to premature bearing failure.

NINE STAR's solution to this problem is to coat the external surfaces of the bearing outer ring with Aluminum Oxide, using a plasma spraying method. To enhance the adhesion of the ceramic material to the bearing steel a bond coat compound is first applied. The normal thickness of the ceramic coating is 200-250 micron, enabling the bearings to cope with direct voltages at least 1000v AC or DC.

The high quality coating is able to withstand press fitting forces without damage; and no dimensional modifications of the bearing housing are necessary, as the dimensions and tolerances of the insulated bearing are identical to those of the standard bearing. NINE STAR is capable of manufacturing insulated bearings with diameter of 50 to 500mm, making them suitable for applications across many industries.