Relationship Between Wear Performance and Solid Lubricants in Sintered Friction Materials

Cast iron (FC and NCM) and forged steel (ST) discs, and four types of sintered friction material pads have been employed in the braking systems of Japanese high-speed trains. These sintered friction materials have complex microstructures. This paper reports result of an investigation to establish correlations between friction, wear and temperature characateristics of the disc–pad friction pairs and pad microstructure. A scale friction rig was used to examine friction, wear and temperature performance of the selected brake friction pairs. Area fraction of lubricants in the sintered friction materials was, depending on formulation, in the range 30–47%. It was found that increasing the lubricant area fraction up to 40%, was effective in reducing pad wear. Above 40% lubricant, wear rate either remained constant or increased slightly to decrease pad wear. For FC discs wear was a minimum at 40% lubricant whilst wear drecreased with increasing overall lubricant content for NCM discs and wear was unaffected by variation in lubricant content for the ST discs. The harder ST forged steel discs exhibited less wear than the softer FC and NCM cast irons.