Tribofilms generated from bulk polyphosphate glasses at elevated temperatures

In this study polyphosphate lubricant was introduced into steel rolling process. The friction coefficient reduced from 0.463 to 0.238 by the presence of polyphosphate lubricant as compared with unlubricated condition, calculated from 2-high Hille 100 rolling mill tests. A tribofilm of ~100 nm can be observed on the strip surface, greatly improving the surface finish. This tribofilm well adhered on the oxide layer/steel base by the interfacial reactions. Laser-scanning confocal microscope well confirmed the reactions of polyphosphate lubricant with the oxide scales occurring. Furthermore, a feasible mechanism the composition and structure of this lubricant during thermal reaction was proposed when exposed to different temperatures.