Bearing component and method

Abstract

Bearing component providing unaffected material that has a surface, which has been subjected to a hard machining process during where the temperature of the surface did not exceed the austenitizing temperature of the unaffected material. The surface of the bearing component includes a white layer formed during the hard machining process. The white layer has a nano-crystalline microstructure that includes grains having a maximum grain size up to 500 nm. The white layer is located directly adjacent to the unaffected material of the bearing component, where no dark layer is formed during the hard machining process.

The invention claimed is: 
     
       1. A bearing component comprising:
 unaffected material having a surface that has been subjected to a hard machining process during which the temperature of the surface did not exceed the austenitizing temperature ( 24 ) of the unaffected material ( 14 ), the surface of the bearing component includes a white layer formed during the hard machining process, wherein 
 the white layer includes a nano-crystalline microstructure having grains having a maximum grain size up to 500 nm and the white layer is located on the unaffected material of the bearing component, wherein 
 no dark layer having a hardness less than the hardness of the unaffected material is formed during the hard machining process. 
 
     
     
       2. The bearing component according to  claim 1 , wherein the white layer comprises the same amount of retained austenite as the unaffected material of the bearing component. 
     
     
       3. The bearing component according to  claim 1 , wherein the layer comprises less retained austenite than the unaffected material of the bearing component. 
     
     
       4. The bearing component according to  claim 1 , wherein the bearing component exhibits a hardness profile, wherein the hardness of bearing component is greatest at an as-machined surface of the white layer, and decreases with depth below the as-machined surface, and wherein the hardness of the white layer is greater than the hardness of the unaffected material of bearing component. 
     
     
       5. The bearing component according to  claim 1 , wherein the layer extends up to 15 μm below the as-machined surface of the bearing component. 
     
     
       6. The bearing component according to  claim 1 , wherein the white layer has a Vickers hardness of 450-1500 HV1 and the unaffected material ( 14 ) of the bearing component has a Vickers hardness of 450 HV1 or more. 
     
     
       7. The bearing component according to the  claim 1 , wherein the unaffected material has a hardness greater than or equal to 450 HV1. 
     
     
       8. The bearing component according to  claim 1 , further comprising that it constitutes at least a part of one of the following: a ball bearing, a roller bearing, a needle bearing, a tapered roller bearing, a spherical roller bearing, a toroidal roller bearing, a ball thrust bearing, a roller thrust bearing, a tapered roller thrust bearing, a wheel bearing, a hub bearing unit, a slewing bearing, a ball screw, cylindrical roller bearing, cylindrical axial roller bearing, spherical roller thrust bearing, spherical plane bearing, or a component for an application in which it is subjected to alternating Hertzian stresses, such as rolling contact or combined rolling and sliding and/or an application that requires high wear resistance and/or increased fatigue and tensile strength. 
     
     
       9. A method for manufacturing a bearing component including an unaffected material, the method comprising the step of:
 subjecting a surface of a workpiece of the unaffected material to a hard machining process, wherein a white layer is formed during the hard machining process, and 
 controlling at least one process parameter of the hard machining process to ensure that the temperature of the surface of the bearing component does not exceed the austenitizing temperature of the unaffected material during the hard machining process. 
 
     
     
       10. The method according to  claim 9 , wherein at least one process parameter of the hard machining process is one or more of the following: cutting speed, cutting force, cooling of cutting tool, cooling of the at least one part of the surface of the bearing component, cutting tool material, cutting tool condition, cutting direction, feed rate, depth.