Iranian Journal of Oil and Gas Science and Technology

Abstract In this study, nanostructured homogeneous and functionally graded (FG) Ni-Co/SiC coatings were fabricated on aluminum substrates via electrodeposition using a square pulse current. The FG coating was produced by continuously varying the concentration of SiC particles (0–40 g/L) in the electrolyte, resulting in a graded particle distribution across the coating thickness. The microstructure and morphology of the coatings were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical and electrochemical properties were evaluated through microhardness testing, T-peel adhesion testing, pin-on-disk wear testing, erosion testing, and potentiodynamic polarization and impedance spectroscopy. The results revealed that the SiC content in the FG coating gradually increased from 0 wt.% at the substrate interface to 6 wt.% at the surface. Compared to the homogeneous Ni-Co/SiC coatings, the FG coating demonstrated 40% higher adhesion strength and twice the wear resistance. Additionally, the FG coating exhibited improved corrosion resistance and overall mechanical performance, highlighting its potential for demanding industrial applications.

Abstract In some engineering fields, wear resistance and a low friction coefficient are required at the same
time. In this research, PTFE nanoparticles and carbon nanotubes were co-deposited within Ni-P
matrix to obtain an Ni-P-PTFE-CNT hybrid coating for wear resistance and a low friction coefficient.
The tribological properties of the deposits were evaluated by pin on disc tribometer. The morphology
of the coatings and worn surface was evaluated by scanning electron microscopy. However, the
results showed that the addition of PTFE nanoparticles to the Ni-P electroless coating caused the
friction coefficient to decrease to values lower than 0.2, which led to an improvement in friction
behavior because of its self-lubricity properties; it, however, decreased the strength of coating due to
polymeric and soft structure of the molecules. The simultaneous incorporation of PTFE nanoparticles
and carbon nanotubes can provide the properties of both molecules and increased the strength of
coating with a low friction coefficient and self-lubricity properties. Therefore, the wear rate and the
degradation of surface were decreased during the wear process.

Abstract In the past 30 years, electroless nickel (EN) plating has grown to such proportions that these coatings and their applications are now found underground, in outer space, and in a myriad of areas in between. Moreover, in order to further improve the mechanical and tribological properties of the nickel-phosphorous (Ni-P) coatings, Ni-P/PTFE composite coatings can be obtained, which provides even greater friction behavior and lubricity than the one naturally occurring in the nickel-phosphorous alloy deposit. In this paper, The Ni-P-PTFE coating was deposited on mild carbon steel surface via electroless deposition process. The friction behavior and wear mechanisms of Ni-P-PTFE nanocomposite coating were studied at different concentrations of PTFE. Frictional behavior was examined using a pin on disk wear test method. Surface morphology and worn surface was evaluated using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS) analysis. The results showed that the incorporation of PTFE nanoparticles can reduce the wear rate of Ni-P coating from 33.07×10-6 mm3/Nm to 12.46×10-6 mm3/Nm for the Ni-P PTFE containing 10 g/l PTFE and decrease the friction coefficient from 0.64 to 0.2. Thus the tribological behavior of Ni-P coating is much improved in the presence of PTFE nanoparticles and 10 g/l is the optimized concentration of PTFE in the electroless bath.