The dual role of metal sulfides as lubricant and abrasive: an interface study in friction composite

In automotive brake pad materials, the metal sulfides act as a solid lubricant at low and medium temperatures (80 °C–260 °C). The metal sulfides improve the fade resistance of brake pad material at elevated temperature cycles (above 260 °C). The purpose of this research work is to highlight the individual effect of the metal sulfides, namely Bismuth Sulfide (Bi 2 S 3 ), Tin (IV) Sulfide (SnS 2 ) and Antimony trisulfide (Sb 2 S 3 ) in the friction and wear behavior of the brake pad (BP) material formulation. The friction and wear performance of the developed brake pads were studied with the help of the chase friction tester using SAE J661a standard. The worn surface was characterized using Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscope (EDS). The thermal properties of metal sulfides were found out using differential scanning calorimetry (DSC). All the developed brake pads with different metal sulfides contributed to the friction stabilization at a particular temperature range. The sulfides influenced the formation of a tribo layer in all the brake pads. The friction performance of SnS 2 -BP has been found to be comparatively better than Bi 2 S 3 and Sb 2 S 3 -BPs. The wear performance of the Bi 2 S 3 -BP has been found to be moderately higher than other BPs.