Wear Scar Diameter for Lubricating Fluids

Description

Evaluates the tribological effectiveness of anti-wear (AW) additives in oils using the four-ball tester (FBT) method to protect metal parts from abrasion.

Modern industrial and mobile equipment has become much more compact, while the load on each part has significantly increased. Base oils alone are incapable of preventing direct contact of metal surfaces under conditions of mixed and boundary lubrication. To save the equipment, anti-wear (AW) additives exist. Wear scar diameter analysis on the Four-Ball Tester (FBT) at the RENA laboratory is direct, objective, and visual proof of how well your oil protects metal from irreversible abrasion. This is an absolutely indispensable test for the development of new formulations of hydraulic and gear oils and for quality control of incoming batches of premium lubricants. The tribological test is conducted according to the globally recognized ASTM D4172 standard on a Four-Ball Tester (FBT). Three steel balls (made of special high-alloy AISI 52100 bearing steel with strictly regulated hardness and micro-roughness) are rigidly clamped in a steel cup in the form of a stationary triangle and completely covered with the test oil. The fourth ball (the top one) is fixed in the spindle of a powerful electric motor and pressed against the three lower balls with a strictly specified load (usually 40 kgf, or 392 N). The oil temperature is maintained by a thermostat at 75 °C. The top ball rotates at a speed of 1200 rpm for exactly 60 minutes. As a result of colossal point friction and high contact pressure, circular wear areas form on the three lower stationary balls. After the test is complete, the oil is drained, the balls are washed with a solvent, and a tribology engineer measures the diameters of these wear scars in two mutually perpendicular directions using a high-resolution optical microscope.