The Utility of Nanographite Materials as Solid Phase, Integral Die Wall Lubricants in PM

摘要

The use of fine particle size graphite materials in powder metallurgy is generally restricted to use as "carbon raiser". Although graphite is considered a very effective solid phase lubricant, at the addition rates needed for most PM parts there is not enough graphite at the die wall-part interface to provide the degree of lubricity needed for proper part ejection. These same PM mixtures contain wax-based lubricants to provide the die wall lubricity necessary for efficient PM compact ejection. A study was performed to determine the utility of nanographite materials to provide effective die wall lubrication, reducing or eliminating the need for added wax, while also providing metallurgically reactive carbon in place of or in conjunction with conventional graphite powders. Test results indicate that nanographite powders provide significant die wall lubricity, have lubrication synergy with PM mixtures containing reduced levels of wax lubricant, and provide metallurgically active carbon during the sintering process.