The Tribological Properties of NiCr-Al2O3-TiO2 Composites at Elevated Temperatures

Ni-based composite that contains TiO2 and Al2O3 was prepared by powder metallurgical hot pressing method. TiO2 and Al2O3 being added to Ni-based composite at the same mass fraction and the effects on some mechanical and tribological properties of the composites when rubbing against alumina ball were investigated from room temperature to 700 degrees C. The results show that the tribological properties of the composites were improved by adding TiO2 and Al2O3 simultaneously. The best comprehensive properties of mechanics and tribology were obtained when TiO2 and Al2O3 in the alloy have the same content of 10 wt%. The friction coefficient and wear rate of the composites decrease with the increasing of temperature and TiO2 and Al2O3 contents, and the composites with addition of 10 wt% TiO2 and 10 wt% Al2O3 exhibit the lowest friction coefficient (0.32) and wear rate (1.71 x 10(-5) mm(3)/N m) at 700 degrees C. XRD and SEM equipped with EDS analysis shows that the lubrication films consist of aluminum titanate and several kinds of titanium oxide formed on rubbing surface with the temperatures elevated. The synergistic action of titanium oxide and aluminum titanate and NiTiO3 in the wear surface at high temperature is responsible for the improving of tribological properties of the composites.