Preparation of Ni-Cr/BN self-lubricating composites by active sintering process
(School of Materials Science and Engineering, Central South University, Changsha 410086, China)
Abstract: A Ni-Cr/BN composite was produced by a active sintering process. The powder of nickel carbonyl，Cr2O3 and C were used as the original materials，and a hexagonal BN(h-BN) powder was added as a solid lubricant. The influence of sintering temperature，heating rate and holding time on the properties of Ni-Cr/BN were studied. The composition and microstructure of Ni-Cr/BN were analysed by X-ray diffraction(XRD) and the optical microscopy(OM). The frictional behavior and hardness were measured with ring-block friction testing machine and Brinell hardness tester respectively. The results show that Ni-Cr is the matrix and a low-melting eutectic compound is the bonding phase in the composite. The porosity reaches 48% and the value of hardness reaches HB18 when the composite is fabricated at 1 100 ℃ for 1 h. Its wear rate is 7.44×10−5 g/min, and the average friction coefficient is 0.266. These properties make such composite suitable for use as self-lubricating material.
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