Microstructure and tribological property of Ni–MoS₂ composite coatings prepared by ultrasonic and mechanical stirring electrodeposition

To optimize the deteriorated mechanical properties of the loose MoS₂ coatings, ultrasonic oscillation was employed to change the deposition mode of MoS₂ particles, hence their structure and mechanical properties. The electrodeposition of Ni–MoS₂ self-lubricating composite coating was assisted by magnetic stirring (Mag-NM) or ultrasonic oscillation (US-NM), respectively. A comparison of coating structure, depositing mechanism, and friction performance was investigated by means of XRD and SEM. Moreover, the influence of MoS₂ concentration on the coating morphology and the friction performance was explored. The results demonstrated that the Ni–MoS₂ composite coatings have superior antifriction performance compared to pure Ni coating. Comparing to the porous structure of Mag-NM coatings, the US-NM coatings obtained compact structures with well-dispersive MoS₂ particles. There is 80.4% hardness reduction occurred on the Mag-NM coatings, but only 8.8% reduction of the US-NM coatings. With the increase of MoS₂ concentration, a clear and continuous wear trace was formed on the Mag-NM coatings. The protrusion grinding indicates the excellent wear resistance of the US-NM coatings. (paper)