Reaction Mechanism and Synthesis of Ni3Al–MoS2 Matrix Self-Lubricating Composites Using Ni, Al, and MoS2 Powders

Abstract

The reactions between MoS2 and several metallic powders, including Ni, Al, and Ni3Al, were studied by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The DSC results revealed that MoS2 started to react with Ni and Al at 630 and 560 °C, respectively, but did not react with Ni3Al even at 1200 °C. The XRD results indicated that the reaction products of MoS2 and Ni were a series of new sulfides and molybdenum compounds, including Ni3S2, Ni7S6, and Ni4Mo, and those of MoS2 and Al were Al2S3 and various aluminides. Additionally, the compositions of the products varied with the reaction temperature. Because these new sulfides did not possess self-lubricating properties, the consumption of MoS2 should be avoided. According to these reactions, a synthetic route for the Ni3Al/MoS2 composite using Ni, Al, and MoS2 composite powders was proposed and demonstrated. During the synthesis process, the composite powders were first compressed under a pressure of 180 MPa. The resulting green compacts were heated to 500 °C with a heating rate of 20 °C/min, and then to 530 °C with a heating rate of 1 °C/min. The holding time at 530 °C was 4 h. The phase composition and microstructure of the as-synthesized composite were studied by XRD and SEM. The results showed that MoS2 remained stable during the synthesis process. Friction and wear tests demonstrated that the composite exhibited good self-lubricating properties with a low friction coefficient of about 0.2 and a small wear rate of 1.04 × 10− 5 mm3 N− 1 m− 1.