Patent ID: 8240923

Claim:
A bearing assembly for an x-ray tube rotating anode, the bearing assembly comprising: a housing having an axial bore at one end thereof defining a bore surface; the housing being made from a material selected from a set of materials including copper or a copper-containing metallic alloy; an axially moveable bearing outer ring being made of iron or an iron containing alloy; said axially moveable bearing outer ring being sized to be received in said axial bore to be axially moveable relative to said axial bore; said axially moveable bearing outer ring having an inner surface and an outer surface; said axially moveable bearing outer ring inner surface defining an outer raceway; a shaft received inside of said axially moveable bearing outer ring; a plurality of rolling elements positioned between said outer raceway of the axially moveable bearing outer ring and said shaft; a thermally stable, tribological coating covering substantially all of said axially moveable bearing outer ring outer surface and/or substantially all of a portion of the bore surface relative to which the axially movable bearing outer ring will slide; said tribological coating selected to be metallurgically incompatible with the material of the housing to prevent said axially moveable bearing outer ring from binding to said bore surface such that said axially moveable bearing outer ring will remain axially movable relative to said axial bore; and wherein the tribological coating is a chromium nitride coating which contains N and Cr in a sub-stoichiometric composition with N dissolved in Cr phases mixed with Cr2N.