Method of manufacturing a brinelling-resistant hub bearing unit

A method of manufacturing a wheel hub bearing unit, the method comprising the steps of:

• providing a bearing ring having at least one raceway surface, the bearing ring being formed of a steel having a carbon content of between about 0.55% by weight and 0.60% by weight;
• carbonitriding the bearing ring within a furnace having an enclosed atmosphere containing ammonia gas;
• tempering the bearing ring by heating the bearing ring to at least four hundred twenty-five degrees Celsius (425° C.);
• induction hardening the at least one raceway surface of the bearing ring;
• tempering the bearing ring after induction hardening the at least one raceway surface by heating the bearing ring to a temperature no greater than three hundred degrees Celsius (300° C.) so as to retain residual compressive stresses within the bearing ring;
• and
• machining the at least one raceway surface of the bearing ring to desired final dimensions and surface finish.

A wheel hub bearing unit comprising:

• a bearing inner ring;
• a bearing outer ring, at least one of the inner ring and the outer ring being formed of a medium carbon steel, the medium carbon steel having a carbon content of between about 0.55% by weight and 0.60% by weight, and having at least one raceway, the at least one ring being carbonitrided and the at least one raceway surface being induction hardened after carbonitriding the at least one ring;
• and
• a plurality of rolling elements rotatably coupling the bearing inner ring and the bearing outer ring.