三维双连续铜/石墨自润滑复合材料的构筑及其摩擦磨损性能研究

以聚氨酯海绵为三维连续网络结构模板，采用浸渍法在聚氨酯海绵骨架表面均匀涂敷石墨浆料构筑具有三维连续网络结构的石墨骨架，然后在石墨骨架中填充铜合金粉，经排胶-热压烧结工艺制备石墨相和金属铜呈三维双连续复合型结构的铜/石墨自润滑复合材料. 研究考察了三维双连续复合结构对材料承载能力和抗冲击破坏能力的影响，并探究了材料在重载作用下的摩擦磨损行为. 结果表明:通过三维双连续结构设计，能够有效改变石墨相的富集状态和分布形式，并借助连续金属铜基体的高承载作用，显著提升材料在重载作用下的减摩抗磨性能. 在180 N载荷下与轴承钢相对摩擦时，块体663铜合金和均相铜/石墨复合材料均出现急剧磨损并与摩擦配副发生“卡咬”现象，其中块体663铜合金与配副由于“卡咬”严重而停止试验，均相铜/石墨复合材料的磨痕深度达1.38 mm. 然而，具有三维双连续结构的铜/石墨复合材料的摩擦系数可保持约在0.12左右，磨痕深度为0.16 mm，展现出优异的长时间耐磨损性能，磨损率约为5.3×10?6 mm3/(N?m). 同时，该结构设计能够大幅减少石墨相与金属铜间的弱界面数量，并有效利用连续石墨相对裂纹传播路径的“歧化”引导和金属铜对扩展裂纹的钝化作用，使复合材料在保持铜合金高承载的同时显著提升材料的抗冲击破坏能力. 具有三维双连续结构的铜/石墨复合材料的抗弯强度可与块体663铜合金比拟，高达372±38 MPa，是均相铜/石墨复合材料抗弯强度的2.0倍左右. 此外，具有三维双连续结构的铜/石墨复合材料还具有更加优异的抗外载冲击破坏能力，其冲击韧性高达32.8±3.1 J/cm2，比均相铜/石墨复合材料的冲击韧性提高了11.1倍，甚至比块体663铜合金的冲击韧性高出2.2倍. 

Fabrication and Tribological Performance of Copper/Graphite Self-Lubricating Composites with 3D Bi-Continuous Structure

In this paper, polyurethane sponge was used as a three-dimensional continuous network structure template, and graphite slurry was uniformly coated on the surface of the polyurethane sponge skeleton by dipping to construct a graphite skeleton with a three-dimensional continuous network structure, and then populate a quantity of copper alloy powder was filled in the graphite skeleton. Then, the copper/graphite self-lubricating composites with a bi-continuous three-dimensional structure of graphite phase and metallic copper were prepared by degumming-hot pressing sintering process. The study investigated the effect of the three-dimensional bi-continuous structure on the carrying capacity and impact resistance of the material, and explored friction and wear behavior of the material under heavy load. The results showed that the enrichment state and distribution form of graphite phase could be effectively changed by three-dimensional bi-continuous structure design, and the anti-wear properties of the material under heavy load were significantly improved by the high bearing capacity of copper matrix. When the experimental load was up to 180 N and the friction pair was bearing steel, the Cu663 block and the homogeneous copper/graphite composites both showed severe wear and ‘jamming’ against with the friction pair. The test stopped due to the serious ‘jamming’ of Cu663 block and the friction pair. Although the homogeneous copper/graphite composite did not stop experiment with the friction pair ‘jamming’, its grinding depth was as high as 1.38 mm. However, the friction coefficient of the copper/graphite composites with a three-dimensional bi-continuous structure could be maintained at about 0.12 over time, and the wear scar depth was 0.16 mm. Compared to the other two composites, this material exhibited excellent long-time wear stability, the wear rate was only about 5.3×10?6 mm3/(N?m). At the same time, the structure design greatly reduced the number of weak interfaces between graphite phase and copper matrix, and effectively utilized the ‘disproportionation’ guidance of continuous graphite on the crack propagation path and the passivation effect of metal copper on extended cracks, so that the composites maintained the high load capacity of the copper alloy and significantly improved impact resistance of the material. The bending strength of copper/graphite composites with three-dimensional bi-continuous structure was as high as 372±38 MPa (comparable to the Cu663 block), which was twice stronger than that of homogeneous copper/graphite composites. In addition, the copper/graphite composite material with a three-dimensional bi-continuous structure also had better resistance to external load impact damage, and its impact toughness was as high as 32.8±3.1 J/cm2, which was 11.1 times higher than that of the homogeneous copper/graphite composites, and even 2.2 times higher than that of the Cu663 block.