In this paper, the effect of hydrogen embrittlement in High-strength low-alloy steel (HSLA) material was studied. HSLA steels are known for their susceptibility to hydrogen induced failure especially when subjected to hydrogen rich environment. In this research, samples from HSLAS were surface-treated using chemical vapor deposition (CVD) techniques, followed by direct Zinc coating using physical vapor deposition (PVD). Other samples were additionally post-heat treated at a temperature of 260∘C for 4[Formula: see text]h to optimize the coating process. The hydrogen embrittlement test was performed by immersing the tensile samples in a solution containing H2SO4 diluted with water for 24[Formula: see text]h. Hardness, and mechanical properties were evaluated using tensile testing. XRD and SEM were used for microstructural and topographical features’ examination of the treated samples. The results indicate that the samples of combined [Formula: see text] coating that was backed at 260∘C show superior resistance to hydrogen embrittlement compared to other conditions. This could be attributed to the buildup of a strong outer layer that prevents hydrogen from diffusing towards the base HSLAS material. The greater mechanical properties are possibly due to the reduction of hydrogen amount generated by the surface reaction associated by the formation of Zn(N[Formula: see text] phase and the reduction of hydrogen amount passed through Zn and C3N4 layers.
Using the BNi-2 alloy nano layer improves corrosion resistance.• Applying DC sputtering as a coating method. • Predicting generated phases for the nanocoating from EDX analysis on equilibrium phase diagrams.This work studies the protection from corrosion in the inner surface of petroleum storage tanks by applying nano-coating on the AISI1018 steel type used in these tanks. BNi-2 alloy, used as coating layer, was deposited using the DC sputtering technique to obtain protection layers of nano-coating. The cyclic potential dynamic polarization technique is used to study and evaluate the resistant metal to localize corrosion, for example, pitting and crevice corrosion. The samples were evaluated in a 3.5% NaCl aqueous solution using the polarization method to determine the corrosion rate. The input parameters of deposition included ion current 16 mA, vacuum 10 -1 mbar, time of deposition was 60 minutes, and the distance between target and substrate was 2.5 cm. The surface roughness of the uncoated specimens was (0.1466 µm), and after coating, it decreased to (0.0933µm). The most important factor that affects the corrosion of the coated steel surface is the surface topography of steel before coating, as it is known that the spattering process coats the facing surface to target better than the inclined surface topography. Therefore, some micro scratches non-coated well worked as nucleation for corrosion as detected in stereo microscope images for coated and uncoated surfaces. By calculating the corrosion rate from cyclic potential dynamic polarization for coated and uncoated workpieces, pitting and crevice corrosion improved approximately ten times compared to the uncoated AISI1018 steel surface.
High strength low alloy steel (HSLAS) is quite sensitive to hydrogen embrittlement due to its different phases. This study investigated the hydrogen embrittlement (HE) behavior of uncoated, physically vapor deposition (PVD) coated, and chemically vapor deposition (CVD) coated HSLAS. The XRD indicates the formation of ZnO, Zn(N3)2, γN and C3N4 phases at the outer coating layer. The results show that combination of surface nitriding and zinc deposition are efficient method against hydrogen embrittlement. This could be attributed to the reduction of hydrogen that is generated by the reaction of surface Zn) N3)2 phase and the low rate of hydrogen transport through the γN phase. The coatings were tested by immersing the tensile samples in a diluted H2SO4 solution with water for 24 hours. Additionally, the result shows that combined coating resulting in higher tensile strength, yield stress, and tensile elongation compared to uncoated samples. Hardness results indicate that the combined coatings (PVD + CVD) has the higher value of about 258 HV, followed by the uncoated sample of about 218 HV, while the PVD only coated sample have the lower hardness value of about 175 HV.
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