Adhesive wear (smearing & skidding)

Metal dragged across metal: surfaces tear and weld on a tiny scale. Urgency

Material rubbed away: by grit, or by surfaces dragging instead of rolling.

What adhesive wear (smearing & skidding) looks like

• Smeared, smudged or scuffed areas where metal has transferred from one surface to the other
• Often a glazed or frosted look, sometimes with heat tint nearby
• Typical spots: roller ends and guide flanges, and the tracks of rolling elements that slide instead of roll

Rotec AI schematic illustration. It shows the typical pattern and is not a photograph of a real bearing.

How adhesive wear (smearing & skidding) develops

Rolling elements need traction to roll. With too little load, a sudden change in speed, or a film that is thick, starved or wrong, they slide instead. Sliding under load heats and tears the surfaces, and the torn metal sticks to its neighbour.

How fast it progresses: Can escalate fast: smearing generates heat, heat breaks down lubricant, and the end point can be seizure.

Causes of adhesive wear (smearing & skidding)

Operating conditions

• Load below the bearing's minimum, fast acceleration or deceleration, rapid reversals

Lubrication

• Wrong viscosity or additives, too little lubricant, or a stiff grease at low temperature

Bearing selection

• Bearing oversized for a light-duty job

Environment & sealing

• Contamination that roughens the contact

How to confirm it is adhesive wear (smearing & skidding)

• Compare the actual load with the bearing's minimum load (your Verify result shows it)
• Look at the pattern: smears in the loaded zone, dull rolling elements and shiny skid marks point at sliding
• Check operating history for abrupt speed changes

How to fix and prevent adhesive wear (smearing & skidding)

• Make sure the bearing is loaded enough: spring preload, or a smaller bearing for light duty
• Tune the lubricant (viscosity, anti-wear and EP additives) to the real conditions
• Soften starts and stops where the process allows
• In skid-prone service consider coatings or hybrid ceramic-ball bearings

Easily confused with

• Thermal cracking: Thermal cracks are fine cracks across the sliding direction; smearing is smudged, torn metal.
• Overheating & lubricant breakdown: Overheating is mainly about colour and lubricant; smearing shows transferred metal.

Worth knowing

Smearing can be made in the lab

Test work on a large cylindrical roller bearing produced smearing only when the load direction was reversed repeatedly, then dropped to near zero. The rollers lost their traction, the cage slowed, and the rollers smeared when the load returned. Even a very light load, about 1.5 percent of the dynamic rating, was enough. Special roller coatings stopped it. Ordinary ground finishes did not.

Slippage tracks

Spotted smear marks or roughening of the rolling elements or raceways are the signature. They appear when load is low and lubrication is poor, when the load zone is so short that elements brake in the unloaded zone and speed up again entering it, or with fast changes in speed. Choose a bearing with lower capacity, preload it, reduce clearance and improve lubrication.

Screw compressors: when speed outruns the load

In a twin screw compressor the thrust bearings can skid or let the rotor rub if the axial load is too light for the speed. Above an ndm of about 450,000 centrifugal force on the balls pushes the bearing rings apart and a back-up or reverse thrust bearing is advised. Also keep the lubrication parameter above 1.0 and preferably above 1.5.

Catching adhesive wear (smearing & skidding) early

Damage to a rolling element shows up at BSF (ball spin frequency, typically 1.5–3× shaft speed), often with sidebands spaced at FTF (cage frequency) since the damaged element passes the load zone once per cage revolution. Envelope analysis usually beats a plain FFT here.

Other wear modes

Questions about adhesive wear (smearing & skidding)