Ni3Al matrix composite with 20wt% Cr exhibited low friction coefficient of 0.24–0.37and a wear rate of 0.52–2.32×10-4mm3N-1m-1, found by researchers at the State key Laboratory of Solid Lubrication of the Lanzhou Institute of Chemical Physics of the CAS in a recent study.
Especially at 800℃ it showed the lowest friction coefficient of 0.24 and a favorable wear rate of 0.71×10-4 mm3 N-1 m-1. This implied that 20wt% Cr was the optimal Cr content and its excellent tribological performance could be attributed to the balance between strength and lubricity.
The development of a class of high temperature self-lubricating composites known as PM/PS212 and 304 has attracted much attention. PM212 is comprised of a matrix of metal bonded chromium carbide with silver and fluoride additions, which act as low and high temperature lubricants.PM212 provides low friction and wear from room temperature (RT) to 900℃. PM212 as well as PS304 has been successfully applied on steam turbine components at 650℃. In addition, ceramic matrix self-lubricating composites based on Al2O3, Si3N4 and ZrO2–Y2O3 exhibit excellent friction and wear behavior within 800℃ and may achieve higher working temperature. However, their inherent brittleness restricts the manufacture of complex shapes and the reliability of applications. There is an ongoing need to develop high temperature self-lubricating composites capable of use over a wide temperature range, between RT and 1000℃, to meet the requirements for industrial applications such as the sliding bearing, seal, etc.
The work has received support from the National Natural Science Foundation of China (NSFC), the Innovation Group Foundation from NSFC and the National Program on Key Basic Research Project of China (973 Program).
Tribology International(Tribology International44 (2011) 1182–1187)
Variations of friction coefficients (a) and wear rates (b) of samples with different Cr content at different temperatures.