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 The corrosion inhibition effects of two antibiotic compounds, tetracycline (TE) and streptomycin (ST), on the corrosion of copper sheets in 1 M hydrochloric acid were investigated using weight loss measurements, Tafel polarization, electrochemical impedance spectroscopy, scanning electron microscopy, molecular dynamics simulations, and quantum chemical calculations. The Tafel polarization results indicated that both inhibitors act as mixed-type inhibitors and showed that the inhibition efficiency of streptomycin is higher than that of tetracycline. In addition, the adsorption behavior of the inhibitors was found to be consistent with the Temkin adsorption isotherm. As a complementary approach, computational chemical studies were performed. Molecular dynamics simulations were used to evaluate the most stable configurations and adsorption energies of the two compounds on the Cu 100, Cu 110, and Cu 111 surfaces. The theoretical results provide substantial support for understanding the inhibition mechanism of the two antibiotic compounds and show good agreement with the experimental findings.

Abstract In steel production plants, such as those manufacturing sheets, pipes, and round bars, raw materials are annealed in preheating furnaces at approximately 1200 °C before undergoing hot deformation. Substantial oxidation and loss of raw steel materials occur in preheating furnaces, resulting in significant economic losses. A potential solution to reduce losses in this scenario is the application of protective ceramic coatings. This research investigates the effect of a ceramic coating based on Al₂O₃–SiO₂ on the oxidation behavior of steel sheets. The industrial-scale impact of the coating on the oxidation of steel slabs is also examined. The coating was applied using a spray method with slurry ceramic materials dispersed through a compressed air flow. Thickness measurement tests, scanning electron microscopy, and energy dispersive X-ray spectroscopy (EDS) analysis were conducted to evaluate the kinetics, microstructure, and oxidation behavior of the coatings. The findings indicated that the oxidation kinetics for uncoated steel sheets followed a parabolic trend, while the kinetics for ceramic-coated samples exhibited a slower logarithmic behavior. The application of the coating resulted in a reduction of the oxide layer thickness by less than 30% compared to the uncoated samples, attributed to a lower diffusion coefficient in the coated samples. Applying the ceramic coating on ST52 slabs in industrial tests led to a significant reduction in the oxide layer thickness and a more straightforward peel of the oxide layers. This showed that using such ceramic coating for materials in preheating furnaces could effectively reduce oxidation losses and enhance the mechanical quality of final products.

Abstract Fin-pass rolls are the latest series of rolls in electric resistance welding (ERW) pipe production lines that form the sheets to tubular shape and adjust the edges of the sheet for welding. The rolls (made of AISI 8622 steel) lose their proper function after about 10 years of operation due to severe wear and change of their original surface profile. The worn portions were removed by grinding and replaced by an AISI D2 high carbon steel ring to repair these rolls. After a short time of service (about one year), the edge of the repair ring was exposed to severe spalling and fracture. The present study investigated the causes of the rapid failure of the AISI D2 repair ring and proposed a solution to the problem. The surface morphology, hardness, and wear resistance were studied. Moreover, the stress analysis of fin-pass rolls was studied using ABAQUS 6.14 finite element software for the closer investigation of the failure mechanism. The leading cause of spalling was the inherent brittleness of the AISI D2 steel and the presence of a high-stress concentration at the edges of the repair ring. To overcome this problem, carburized AISI P20 steel, case hardened AISI 4140 steel, and hard chromium electroplated AISI 4140 steel were replaced, and the resulting properties were studied. The highest resistance to spalling and wear occurred with carburized AISI P20 steel because of the high surface hardness and the gradual increase of toughness from the surface to the depth in the carburizing process, increasing the wear resistance and retarding the growth of fatigue cracks.