High Temperature Tribological Properties of NiCrWAl₂O₃- SrCO₃-Ag Cement Composites

NiCrW-Al₂O₃-SrCO₃-Ag composites with different contents of SrCO₃ 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 SrCO₃ and the formation of SrAl₄O₇ during the hot-pressing. Meanwhile, the new phases such as Cr₂O₃ and NiCr₂O₄ were found. The composite with addition of 10% SrCO₃ 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 (SrCrO₄ and NiO) by tribo-chemical reactions during the medium-high temperature process. Together with Ag and NiCr₂O₄ in composites, SrCrO₄ and NiO worked synergistically to improve the tribological properties of the composites in a wide range of temperatures (400~1 000 ℃).