BN-plated Nickel On Ni-Cr/BN Self-lubricating Material Organization And Performance

In order to improve the sintering property and the strength of Ni-Cr/BN composite material, the surface of BN powder was plated nickel layer by electroless plating method in this research, and farther enhance the wettability between BN power and Ni-Cr particles. Ni-Cr/(Ni/BN) composites were produced by powder metallurgy. The microstructure mechanical properties and friction wear properties of Ni-Cr/(Ni/BN) composite were determined by scanning electron microscopy (SEM), optical microscope (OM) experimental means, X-ray diffraction (XRD), three-point bending test and hardness (HB) tests, The results show that:(1) In alkaline conditions, using sulfate nickel as mainly salt and hydrazine hydrate as reducing agent, the optimum processing parameter of plating nickel layer to the surface of BN powder are: 45g/L NiSO₄·6H₂O solution, 18g/L N₂H₄·H₂O solution, 10 of pH value, temperature of 90℃and time of 30min.(2) The surface of the BN powder plating with nickel can improve the sintering property of Ni-Cr/BN composite material.With the increasing of sintering temperature, the strength, density and hardness of the Ni-Cr/BN composite increase. However, when the sintering temperature reaches 1100℃and more, the plated nickel layer on the surface of BN powder globurize and migrate to surface of the composites under the pressure of the vapor tension in the composite material. The BN relocate and gathere in the center of the Ni-Cr/(Ni/BN) composite, so the composite occure segregation of the element. The optimum sintering temperature is about 1000℃.(3) The friction and wear mechanism of Ni-Cr/BN self-lubricating are concluded. In the interaction course of dual cases, the BN in Ni-Cr/BN self-lubricating composite material was extrused by the combined effect of hot extrusion deformation and friction, stretched and gradually became a perfect integrity and continuous solid lubricating film. However, the complexity contact stress lead to the membrane rupture and falling of the local self-lubricating, weakening the performance of the self-lubricating composite material. The forming of the BN nickel plated with nickel can improve interfacial bonding of the solid lubricant BN and Ni-Cr alloy matrix, benefite integrite BN bricating film the friction pair and enhance the anti-friction properties. Lead to the lubricating film more adhesion strength and uniformanity. Decreased the friction coefficient and wear rate of the Ni-Cr/BN composite.