Fabrication and Tribological Properties of Nickel-Based Cellular Structure Self-Lubricating Composites by Selective Laser Melting and Metal Infiltration

The service life of Inconel 718 (IN718) nickel-based superalloys under extreme working conditions is limited due to their poor tribological properties. In this study, IN718 cellular structure self-lubricating composites were fabricated by selective laser melting (SLM) and multi-soft metal (Sn-Pb-Ag) infiltration. Different cellular structures were verified by means of numerical simulation and experiment. The effects of pore diameter and temperature on tribological properties of the selective-laser-melted (SLMed) IN718 with Sn-Pb-Ag (INSPA) infiltration self-lubricating composites were investigated. Results show that INSPA samples of cellular structure with a pore diameter of 1.4 mm (INSPA3) exhibited excellent tribological properties compared to the two other pore diameters of 1.2 mm (INSPA2) and 1.0 mm (INSPA1). The tribological properties test results at different temperatures indicate that the coefficient of friction (COF) of INSPA3 was decreased from 0.29 to 0.13 as the temperature of 25 °C rose to 350 °C. The reason is that more Sn-Pb-Ag lubricant was stored in the Ф1.4-mm holes, which were heated and expanded to the worn surface during the friction process to realize self-compensation lubrication. At 350 °C, the friction product of Pb2O was decomposed into PbO and other multicomponent friction oxides were generated, which improves the wear resistance of the SLMed INSPA self-lubricating composites. This study demonstrates a potential approach to enhance the tribological properties and service life of IN718 superalloys used in harsh friction conditions.