lubricated

Lubricated refers to surfaces that are covered with or treated by a lubricant to reduce friction, wear, and heat generation during relative motion. Proper lubrication forms a protective film between surfaces, enabling smoother movement and extending component life. The term can describe the state of machinery parts, joints, or other interfaces, as well as the action of applying lubricant.

Lubricants come in several categories: liquids such as mineral, synthetic, or vegetable oils and water-based fluids; semi-solid greases that combine oil with thickeners; and solid lubricants like graphite or molybdenum disulfide that can form protective films. Dry or solid-film lubricants are used under high temperature, vacuum, or contamination-sensitive conditions. Lubricants may be petroleum-based, synthetic, bio-based, or food-grade, depending on application and compatibility.

Common applications include mechanical engineering and industry (bearings, gears, piston-cylinder devices, turbines, conveyors); automotive and aerospace; energy and manufacturing; biomedical contexts (synovial fluid in healthy joints; lubricants for implants and surgical tools); and everyday uses such as door hinges and bicycle chains.

Performance depends on properties like viscosity and viscosity index, lubricity, film thickness, and temperature and pressure. Lubricants may include additives for anti-wear, corrosion inhibition, oxidation stability, and detergency. The lubrication regime—hydrodynamic, elastohydrodynamic, boundary, or mixed—determines how the film is formed and sustained.

Safety and environmental considerations include flammability, toxicity, and disposal; contamination risks; material compatibility; and the need for proper selection to avoid residue, contamination, or ecological impact.