Abstract:
NiCrW-Al
2O
3-SrCO
3-Ag composites with different contents of SrCO
3 and Ag were fabricated by powder metallurgical method (mechanical alloying and vacuum hot-pressing sintering). The friction and wear properties were tested by UMT-3 from room temperature to 1 000 ℃. The microstructures, phase compositions and wear mechanism of the composites were analyzed by scanning electron microscopy, energy dispersive spectrocopy and X-ray diffraction. The results show that the decomposition of SrCO
3 and the formation of SrAl
4O
7 during the hot-pressing. Meanwhile, the new phases such as Cr
2O
3 and NiCr
2O
4 were found. The composite with addition of 10% SrCO
3 and 10% Ag exhibited the best friction and wear properties in a wide temperature range and that was attributed to the formation of the tribolayers containing oxides (SrCrO
4 and NiO) by tribo-chemical reactions during the medium-high temperature process. Together with Ag and NiCr
2O
4 in composites, SrCrO
4 and NiO worked synergistically to improve the tribological properties of the composites in a wide range of temperatures (400~1 000 ℃).