Transfer film formation and dissipation and its effect on friction coefficient in NAO friction materials containing FeS₂ lubricant

Abstract

Purpose The purpose of this study is to investigate the accumulation process of transfer film formation and dissipation and its effect on friction coefficients in non asbestos organic friction materials with various lubricant FeS2 contents. Design/methodology/approach In total, 2.5%, 5% and 10% FeS2 were added as lubricating components to the friction materials. Friction tests composed of two stages were conducted for these friction materials, and the friction surfaces of the counterpart discs were examined using scanning electron microscopy. Findings The transfer film formation reduced the friction coefficients, and the transfer film dissipation influenced the recovery of the friction coefficients. The effect of a high content of FeS2 was to promote the transfer film formation at high temperatures and to hinder the transfer film dissipation at low temperatures, thus resulting in a decrease in the friction coefficients at high temperatures together with recovery retardation at low temperatures. Originality/value FeS2 contributed to the transfer film formation at high temperatures in the fade test but hindered the transfer film removal in the recovery test, resulting in the retardation of friction coefficient recovery. The mechanism by which the FeS2 lubricant component affected the transfer film formation and dissipation was analyzed and attributed to the different levels of FeS2 pyrolysis at different temperature levels.