Wearrate

Wearrate refers to the rate at which material is removed from a surface as a result of wear under relative motion between contacting surfaces. In tribology, it is commonly described as the volume of material worn away per unit sliding distance per unit normal load, giving a practical measure of how quickly a surface deteriorates under service conditions. A standard expression for wear in many metal-on-metal contacts is Archard's law, which relates wear volume V to load W, sliding distance L, and the hardness H of the softer material: V = k · W · L / H, where k is a dimensionless wear coefficient. From this, the wear coefficient can be determined as k = V · H / (W · L). A smaller k indicates better wear resistance under the same conditions.

Wear rate is typically measured in laboratory tests such as pin-on-disk, pin-on-flat, or block-on-ring configurations. These tests record wear volume or mass loss as a function of sliding distance and load, often using profilometry, 3D microscopy, or precise mass measurements to estimate V. Wear rate can also be defined as V/(F·s) or expressed through the specific wear rate k, depending on the geometry and reporting convention.

Factors influencing wear rate include material properties (hardness, microstructure, and the presence of interlayers or coatings), counterpart material, surface roughness, temperature, lubrication, and environmental conditions. The concept of wear rate aids in material selection and component design, particularly for bearings, gears, seals, and cutting tools, but it is an empirical parameter that depends on test conditions and may not universally predict performance across all regimes of wear.