A I Abduljaleel Al Rabeeah - Department of Materials Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran
M Razazi Boroujeni - Department of Materials Engineering, Lenjan Branch, Islamic Azad University, Isfahan, Iran

Due to their morphology, chemical composition, and phase structure, electroless nickel-phosphorus coatings are used onvarious substrates, including st۳۷ steel, with the aim of improving working life in various industries. The latest generation ofthese coatings is the multilayer or hybrid type of nickel-phosphorus electroless coatings. In this research, for the first time, athree-layer Ni-P/Ni-P-Al۲O۳/Ni-P-SiC coating was produced and its tribological properties were investigated. X-raydiffraction test, energy beam spectrometer, optical and electron microscope images, hardness measurement, roughnessmeasurement, adhesion test (according to ASTM B۵۷۱ standard), and pin-on-disk wear (according to ASTM-G۹۹ standard)were used for characterization. In the X-ray diffraction pattern related to the multilayer coating, in addition to the amorphousnickel-phosphorus phase, SiC and Al۲O۳ phases were also seen. The hardness of multilayer coating was ۱۲۶ Vickers morethan that of single-layer coating. The adhesion of all the coatings was very good, so after performing the bending test, nogalling was observed in the coatings. In general, it was found that the use of multi-layer coating compared to single-layercoating (with the same thickness) leads to increased hardness, better adhesion, and superior wear behavior. The wearmechanism of the coatings was also evaluated with the help of electron microscope images and energy-dispersive X-rayspectroscopy. The wear mechanism of the electroless nickel-phosphorus coating was delamination and Abrasive, while thehybrid coating changed the mechanism to adhesive by creating a gradient of mechanical properties and lubrication.

Multilayer Coating, Wear Mechanism, Adhesion, Nickel-Phosphorus