Effects of lignite bottom ash content and particle size on the properties of a bronze-based friction material

Abstract

This research studied the effects of content and particle size of lignite bottom ash (LBA) on the density of a bronze-based friction material. LBA from the Mae Moh power plant, Lampang province, Thailand, was pulverized and screened into three particle size ranges (< 38 µm, 38-75 µm and 75-150 µm). A particle size analysis, chemical analysis, and phase analysis on the LBA powder were performed. The amount of LBA in the friction material was varied from 5 to 20 percent by weight. Samples were prepared by powder metallurgy, which is common for bronze-based friction materials. Copper powder, tin powder, LBA powder and graphite powder were mixed and compacted in a cylindrical die using a single action press under a pressure of 277 MPa. The compacted samples were sintered at 600 °C for 30 minutes in a tube furnace with a flowing gas mixture of N2 with H2 (90:10). It was found that the densities of the sintered samples were lower than the corresponding green densities. This is likely due to sample expansion from the use of pre-mixed bronze powder. The sintered densities of the samples were decreased with an increase of LBA content due to the lower density of the LBA. The sintered density also increased with an increase of LBA particle size due to increased packing efficiency.