.bn / Ni (cr), The Preparation Process And Its Organization And Performance Of Self-lubricating Composite Materials Research

In order to develop advanced high performance thermodynamic technology, new style solid self-lubricating composites are needed, which can work at high temperature to prevent wearing and failure of parts. Ni-Cr alloys have splendid high-temperature mechanical properties, oxidation resistance and corrosion resistance suffered from 500 to 1000℃, making them promising high-temperature self-lubricating composites. The solid lubricant BN, whose heat endurance is better than graphite and M0S2, exhibiting perfectly abradable and lubricated properties under 900℃, is a good addition to the high-temperature self-lubricating composites..In this article, BN/Ni(Cr) self-lubricating composites were fabricated by powder metallurgy, during which the Ni-Cr powder was used as original materials, and a hexagonal BN powder was added as solid lubricant. The density, strength, hardness, frictional wear properties of the composites were tested, meanwhile, the microstructure of BN/Ni(Cr) was analyzed by X-ray diffraction(XRD) and Scanning Electron Microscopy(SEM). Effects of sintering temperature and BN content on the microstructure evolution and tribological property of Ni-based self-lubricating composites were studied. Furthermore, the effects of BN prilling on the microstructure evolution and property of BN/Ni(Cr) BN composites were studied. The study shows:With increasing BN content, the capacity of BN increased and the formation, growth of the sintered necks and the densification process become more difficult, which led to the reduction of density, strength and hardness and the increase of porosity. With increasing BN content, friction coefficient tended to decrease, while wear rate decreased firstly, and then increased. The material with 11 % BN content has the minimal wear rate, possessing high hardness, high strength and perfect frictional wear property. This is a new style self-lubricating composites.The reasonable sintering temperature of normal pressed sintering process is between 1100-1180℃, with increasing temperature no higher than 1180℃, the porosity of BN/Ni(Cr) composites decreased, while the hardness and three-point bending strength of them increased. The specimens sintered under 1180℃has the best comprehensive properties, while the specimens sintered higher than 1200℃were over-burned.BN/Ni(Cr) composites with prilling BN had higher green density, less porosity, bigger sintered necks, so the densification process become more perfect and the matrix associated closer; Compared to BN/Ni(Cr) composites without prilling BN, the density of the BN/Ni(Cr) composites with prilling BN had increased, meanwhile the strength, hardness, frictional wear properties also had obvious increased.