Scuffing Index by GOST

Description

A calculated indicator evaluating the ability of a lubricant to prevent scuffing on metal surfaces under gradually increasing loads.

For heavy industry enterprises, metallurgical plants, and mining and processing facilities, the key criterion for selecting gear oil is its ability to withstand extreme pressures in gear meshes. The Scuffing Index (Iz) analysis according to GOST 9490 at the RENA laboratory is uncompromising proof of the effectiveness of extreme pressure (EP) additives. This test is specially adapted to the strict requirements of technical passports of domestic and post-Soviet equipment, allowing for the justified replacement of expensive imported lubricants with proven local analogues without the risk of «welding» the gearbox or rolling mill. The Scuffing Index (Iz) is not just a single measurement, but a complex series of tests on a four-ball friction machine (FBT-3). Testing is conducted at room temperature (20 °C) and a spindle rotation speed of 1460 rpm. Unlike the wear scar diameter test, the duration of one cycle is only 10 seconds (dynamic shock load). The essence of the method consists of conducting a series of short runs with a gradual (stepwise) increase in the axial load on the four-ball pyramid. The lab technician starts with an initial load, measures the diameters of the resulting wear scars, and then proceeds to the next, higher load (using new sets of steel balls each time). This continues until the oil film breaks completely and the balls weld together (weld point). The scar sizes obtained at each step and their corresponding loads are substituted into a special mathematical GOST formula, which generates an averaged indicator — the Scuffing Index (Iz).