Study On Novel Wide Temperature Self-lubricating Metal Based Composite Material

Space technology are increasingly stringent requirements for materials.As a result many extreme conditions are beyond the scope of the liquid lubricating oil, so the solid lubricant has emerged.Three layered compound Cr2 AlC with MAX structure was prepared by solid-state reaction method and added to the Ni- Cr alloy matrix. SEM, TEM, EDS, XPS, Vicker hardness tester, high temperature friction and wear tester were used to investigate the composition, microstructure, surface morphology, composition, hardness and tribological properties of the composites. The effects of solid lubricant content and temperature on the microstructure, mechanical properties and high temperature tribological properties of the composites were investigated.Due to the melting point of raw materials and saturated vapor pressure, the appropriate proportion was calculated and selected. XRD phase analysis was used to determine the Cr:Al:C=2:1.2:1 of raw material and Cr2 AlC with high purity and small particle size was synthesized. The mechanism of the effect of Cr2 AlC on the composition of the materials was analyzed.Cr₂AlC can keep the layered structure in the composite materials which is obtained by spark plasma sintering. The density of composite materials decreases with the increase of the content of Cr2 AlC content, and Vicker hardness increases with the increase of Cr2 AlC content. When the content of solid lubricant was 20 wt.%, the tribological propertie of composites was the best: wear rate of composite was lower than 5.0×10-5mm3/Nm; the friction coefficient was only 0.3 at 400℃ and 600℃.At room temperature and 200℃ the composite material has a slight oxidation, the products is NiO、Cr2O3、Al2O3.The friction coefficient is higher and the friction process fluctuates greatly. The wear mechanism is brittle fracture and delamination wear. When the temperature were 400℃ and 600℃,the surface of the composite material was seriously oxidized. The oxide film is NiO, Cr2O3, Al2O3 and the NiCr2O4 which has good lubricating property. With the softening of high temperature, wear debris "glaze" to form a good coverage, continuous lubrication film, which can significantly reduce the friction coefficient and reduce the friction of the process. The surface of the grinding ball is smooth and flat. When the Cr2 AlC content is too high, it will introduce too many CrxCy hard phase, which will lead to a lot of fluctuations in the early run, so it is reasonable to control the content of Cr2 AlC.