Mechanical and tribological properties of NiAl-NbC-Ag composites prepared by hot-pressing sintering

NiAl-based nanocomposites were successfully fabricated by mechanical alloying proceeded vacuum-hot-pressing sintering, and the mechanical and tribological properties of the NiA-NbC composite were investigated. The results show that the nanostructured powder particles with the average size around 5 nm were successfully obtained by a high-energy-ball mill. After sintering, the composites were consisted of B2-ordered NiAl and NbC second phase, and the crystalline size of the NiAl phase was about 20 nm. The relative density, hardness, and compressive strength of nanostructured NiAl materials increased with increasing the Nb content, which can be attributed to the second phase hardening effect of in situ formed NbC particulates and fine grain strengthening of nanocrystalline NiAl phase. Thereafter, the friction coefficient of the NiAl-3NbC composite was lowered by the addition of silver and that is significantly lower than the NiAl intermetallic compound and NiAl-3NbC composite at elevated temperatures, which was attributed to the lubricating films formed in sliding process at elevated temperatures. While the wear rates of NiAl-3NbC-10Ag composites are higher than that of the NiAl-3NbC composites at each test temperature, especially at 500 degrees C and 700 degrees C, which might be attributed to the phase variations on the worn surfaces of the composites.