Microstructure and Tribological Properties of Self-Lubricating FeS Coating Prepared by Chemical Bath Deposition Coating Technique

The FeS solid lubricating coatings were prepared on the AISI 5140 steel by chemical bath deposition (CBD) coating technique at various temperatures from 30 to 90 °C. The influence of temperature on microstructure, microcracks, and tribological properties was characterized and studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometry (EDS). The results show that the coating mainly consists of FexSy (FeS, FeS2, and Fe1−xS), and has a chrysanthemum-shaped (CS) morphology composed of the FeS crystal petals. The CS particles nucleate at about 30 °C, rapidly grow and reach a peak thickness at about 50–70 °C, and finally disappear and are replaced by disordered thick petals at 90 °C. The wear resistance of the steel was improved obviously after introducing of FeS coatings, owing to that the coatings can provide better lubrication and improve the wear resistance.