Effect of Graphene Enrichment on Solid Particle Erosion Performance of Electroless Ni-P Composite Coatings

Abstract

Abstract Solid particle erosion (SPE) and dents (from contact loads) are among numerous surface degradations in the hydrocarbon industry that can in turn compromise the longevity of protective coatings. Both these degradation mechanisms can induce cracks that allow the corrosive solutions to seep through those cracks and corrode the underlying metal, thereby defeating the purpose of surface protection. Nickel-phosphorus (Ni-P) coatings have been known for decades for their corrosion resistance, but their applications in hydrocarbon industries are impeded by their tribological limitations, namely low wear resistance. In the current research work, graphene nanoplatelets were introduced to an Ni-P electroless plating bath in various concentrations (30 mg/L, 60 mg/L, and 100 mg/L) to achieve three different compositions of ternary Ni-P–graphene coatings, namely Ni-P-30 mg G, Ni-P-60 mg G, and Ni-P-100 mg G, respectively. Surface roughness was characterized via topography employing a laser confocal microscope. Coating hardness was characterized using Vickers hardness and the composition analyses were carried out via energy dispersive spectroscopy. SPE was conducted via Tungsten carbide (WC) erodent ball at three different impact angles and two different particle velocities. Finally, Hertzian indentation was performed under two different loads to characterize the denting behavior of coatings. Eroded and dented coatings were further visualized via an optical microscope. The highest concentration of graphene (by 18 vol.%) in Ni-P-30 mg G coating improved the hardness, leading to the smallest size of indents during both SPE and Hertzian indentation. Also, Ni-P-30 mg G exhibited no evidence of cracking under normal impact angle and particle velocities of 35 ms−1 and 52 ms−1.