Studies on Friction Mechanism of NAO Brake-Pads Containing Potassium Titanate Powder as a Theme Ingredient

摘要

Potassium titanate (KT) fibers/whiskers are used as a functional filler for partial replacement of asbestos in NAO friction materials (FMs). Based on little information reported in open literature; its exact role is not well defined since some papers claim it as the booster for resistance to fade (F_R), or wear (W_R) and sometimes as damper for friction fluctuations. Interestingly, KT fibers and whiskers (but not powder) are proved as carcinogens by the International Agency for Research on Cancer (IARC). However, hardly any efforts are reported on exploration of influence of KT powder and its optimum amount in NAO FMs (realistic composites) in the literature. Hence a series of five realistic multi-ingredient compositions in the form of brake-pads with similar parent composition but varying in the content of KT powder from 0 to 15 wt% (in the steps of 3) were developed. These composites were characterized for physical, mechanical, chemical and tribological performance. Composites were tribo-evaluated on reduced scale prototype (RSP) as well as on full scale brake inertia dynamometer by following ECE R90 and Japanese Automobile Standards (JASO C 406) testing procedure respectively. Optimum content of KT powder was evaluated by multiple objective optimization on the basis of ratio analysis (MOORA) method on the basis of several performance parameters such as performance μ, fade μ, recovery μ, % fade ratio, % recovery ratio, wear resistance etc. The friction and wear mechanisms were studies in details based on worn surface analysis. It was concluded that increase in KT amount played important role in improving wear and fade performance. With increase in amount of KT powder, most of the properties improved. Overall 12% KT powder shows best performance.