Spalling

Damage condition: When the bearing rotates under load, the raceway surfaces or rolling element surfaces of the inner and outer rings exhibit fish-scale-like spalling due to rolling fatigue. Causes: Excessive load. Improper installation (misalignment). Torque loading. Foreign object ingress, water ingress. Inadequate lubrication, unsuitable lubricant. Inappropriate bearing clearance. Poor housing accuracy, uneven housing rigidity, excessive shaft deflection, rust, corrosion pits, scuffing, and indentations (surface deformation phenomena) contribute to development.

Countermeasures: Verify load magnitude and re-evaluate bearing selection. Improve installation methods. Enhance sealing arrangements and implement rust prevention during shutdowns. Employ lubricants of appropriate viscosity and refine lubrication practices. Inspect shaft and housing accuracy. Verify clearance.

Skinning

Damage condition: Displays a darkened surface with slight wear, featuring multiple micro-cracks extending 5-10μm deep beneath the surface, accompanied by extensive micro-flaking (minor delamination).

Causes: Inappropriate lubricant. Foreign matter ingress into lubricant. Poor lubricant quality causing surface roughness. Inadequate surface finish of mating rolling elements.

Remedial Action: Select suitable lubricant. Improve sealing arrangement. Enhance surface finish of mating rolling elements.

Burn Marks

Damage Condition: Burn marks constitute surface damage arising from the accumulation of minute scorch marks on sliding surfaces. Linear scars appear circumferentially on raceways and rolling surfaces. Cycloidal scars manifest on roller end faces, with corresponding scuffing on the inner ring surface adjacent to the roller ends.

Causes: Excessive load, excessive preload. Inadequate lubrication. Foreign object ingress. Misalignment between inner and outer rings, shaft deflection. Poor precision of shaft or bearing housing.

Countermeasures: Verify load magnitude. Apply appropriate preload. Enhance lubricant quality and lubrication methods. Inspect shaft and bearing housing precision.

Fracture

Damage condition: Fracture denotes localized breakage occurring at the flange of the raceway or the corner of the roller due to impact or excessive load.

Causes: Impact during installation. Excessive load. Improper use such as dropping.

Countermeasures: Improve installation methods (use hot mounting, appropriate tooling). Correct load conditions. Ensure bearing is seated correctly with flange supported.

Cracks, Fractures

Damage Condition: Cracks refer to fissures forming in raceways or rolling elements. Continued use may lead to fracture propagation.

Causes: Excessive interference fit. Overloading, impact loads. Progressive spalling. Friction heat and micro-vibration wear from contact between raceway and mounting components. Creep-induced heating. Inadequate taper angle on tapered shafts. Poor shaft cylindricity. Interference between bearing chamfers and shaft shoulder radii exceeding bearing chamfer dimensions.

Remedial actions: Ensure appropriate interference fit. Review load conditions. Improve installation methods. Ensure appropriate shaft geometry.

Indentations

Damage condition: Indentations formed on raceways or rolling surfaces when embedded with fine metallic particles, foreign matter, etc. Concave depressions (Brinell hardness indentations) develop between rolling elements due to impact during installation or similar operations.

Causes: Embedded foreign matter (e.g., metal powder). Excessive impact loads during assembly or transportation.

Countermeasures: Impact the bearing housing. Improve sealing arrangements. Filter lubricating oil. Optimise assembly and operating procedures.

Installation Scratches

Damage Condition: Axial linear scratches inflicted upon raceways and rolling surfaces during installation, removal, or operation.

Causes: Misalignment of inner/outer rings during mounting/dismounting; impact loads during disassembly.

Countermeasures: Employ appropriate tools and utilise a press to prevent impact loads. Ensure mutual centring during installation.

Discolouration

Damage Condition: Colour change in raceways, rolling elements, and cages due to temperature rise and lubricant reactions.

Causes: Inadequate lubrication. Thermal oil immersion caused by lubricant reactions. Significant temperature increase.

Countermeasures: Improve lubrication methods.