NAO friction materials with various metal powders: Tribological evaluation on full-scale inertia dynamometer

A right selection of filler, its type, shape, size, amount and its compatibility with other co-fillers contribute to the performance of a friction material. Among various types of fillers, metallic fillers are very important and multifunctional. In spite of well-accepted fact that these affect all performance properties of friction materials, in depth studies and systematic evaluation as per standard procedure are not documented. Hence, in this work three friction composites were developed in the laboratory with identical parent composition (90 wt.%) except metallic filler (10 wt.%) viz. brass, copper and iron powders while one more composite was developed without any metal contents for comparison's sake. These were characterized for physical, thermo-physical, chemical and mechanical properties. For tribo-evaluation inertia brake-dynamometer testing which reflects the most realistic performance was selected. The various performance properties like friction, μ sensitivity to load, speed and temperature were studied as per industrial schedule.It was concluded that inclusion of metal contents, improved almost all the performance properties and copper containing composite showed best tribo-behavior followed by brass and then iron powder containing composite. Composite without metal powder proved poorest. Worn surface analysis and wear mechanism are also discussed in detail.

Research highlights▶ This article emphasizes on wear-property correlations of laboratory developed FMs varying in type of metallic fillers when evaluated on dynamometer. ▶ Use of metallic ingredients affected most of the performance properties in a beneficial way. Cu was most effective in boosting TC significantly followed by brass and iron. ▶ Inclusion of metallic fillers led to appreciable increase in magnitude of μ, decrease in μ sensitivity towards pressure–speed, temperature and wear resistance also. ▶ Thermal conductivity of the composites played an important role in enhancement of the performance properties of composites (fade resistance, recovery performance and counterface friendliness). ▶ Copper proved best performing metallic filler in all the three major performance properties viz. performance μ (friction), sensitivity studies (pressure-speed and F & R) and wear behavior, followed by brass. Iron powder proved moderate in these aspects.