Lubricant
Lubricants are substances applied between two surfaces in relative motion to reduce friction and wear. They also serve for heat dissipation, corrosion protection, cleaning and can be used for power transmission.
Types:
- Liquid lubricants: oils (mineral oils, synthetic oils), emulsions.
- Semi-solid lubricants: greases, pastes.
- Solid lubricants: graphite, molybdenum disulfide (MoS₂).
Practical example:
When tapping in steel, a suitable lubricant is used to prevent the tool from overheating and to protect the cutting edge from wear. Lubricants are also used in engines and gearboxes to protect moving parts and improve efficiency.