X-ray tube and X-ray generating apparatus

An X-ray tube, comprising:

• a cathode configured to produce electrons emitted towards a vacuum when energized;
• an anode comprising a rotatable anode target disk configured to emit X-rays after sustaining bombardment by the electrons,
• wherein the cathode and the anode are contained within a housing that provides a vacuum environment,
• a bearing assembly coupled to the rotatable anode target disk, the bearing assembly comprising:
• a rotatable shaft configured to rotate with the rotatable anode target disk;
• and
• a bearing part comprising multiple bearing bodies that are (i) disposed at an outer side of the rotatable shaft, (ii) in contact with the rotatable shaft, and (iii) in a rolling fit with the rotatable shaft, the multiple bearing bodies comprising at least one first rolling body configured to be located at a near-end position of the bearing assembly with respect to a position of the rotatable anode target disk, and at least one second rolling body configured to be located at a far-end position of the bearing assembly with respect to the position of the rotatable anode target disk,
• wherein a surface of the first rolling body is coated with a first lubrication layer,
• wherein a surface of the second rolling body is coated with a second lubrication layer having a different composition than the first lubrication layer, and
• wherein a temperature at which the first lubrication layer remains in a solid state is greater than a temperature at which the second lubrication layer remains in a solid state.