Severe scuffing and cold flow

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Tooth Wear Modes

Scuffing
• rough torn furrows in the direction of sliding
• adhesion is due to micro-welding and tearing of asperities under high loads.
• affects addendum or dedendum of the tooth or both.
• not present at pitchline (no relative sliding)
• not a fatigue phenomenon

Plastic deformation/cold flow
• through hardened gears
• insufficient hardness
• high sliding and high loads (under adequate lubrication) - material yields
• tooth profile is destroyed

Polishing
• fine scale abrasion promoted by lubricants with aggressive anti-scuffing additives
• it degrades gear tooth profile.
• wear steps at ends of contact and along the tip.

Prevent Scuffing, Polishing and Wear

• Clean, dry lube
• For low speed applications use nitride or carburized gears and high viscosity lube
• Optimize gear geometry and accuracy
• Grind gear teeth
• Use phosphate coating
• Use high-viscosity lube with borate anti-scuff additives
• Adequate tooth mesh lubrication – calculate specific film thickness
• Remove abrasive from lube.
• If through-hardened, use material of higher hardness