Tribological properties and self-compensating lubrication mechanisms of Ni3Al matrix bio-inspired shell-like composite structure

Abstract Composite surface structures inspired by biological characteristics have the potential to strengthen the synergistic effects of surface micro-textures and solid lubricants by improving their tribological properties. This investigation sought to discuss the lubrication mechanisms by designing bio-inspired shell-like Ni3Al matrix composite surface structure, in which an ordered patterning composite (OPC) structures contained Ni3Al matrix and solid lubricants Sn-3.0Ag-0.5Cu(SAC305) alloys. Reciprocating dry sliding tests of OPC structures with different surface texture densities against high-carbon steel balls were performed, and the results were compared to those for orderly pattern (OP) structures without the SAC305 alloy. The results showed that the appropriate volume fraction of the SAC305 alloy should further promote decreases in the friction coefficients and wear losses. This could be attributed to the self-compensating lubrication behaviors of the SAC305 alloy. It formed a lubricating film with a certain area and thickness, which should be controlled by the material properties and components of the bio-composite surface structures, as well as the surface texture density. Additionally, methods based on a combination of theoretical models and experimental measurements further confirmed that the soft and hard materials of the OPC structure played different roles. The soft material (SAC305 alloy), which had a high surface energy and low hardness, had a better material transfer tendency than the hard material (Ni3Al matrix), which had a low surface energy and high hardness. This resulted in the formation of a transfer film and the occurrence of self-compensating lubrication behaviors.