S. Yazdani, S. Javadpour, Sh. Mehdizadeh Naderi, M. Javidi,
Volume 13, Issue 2 (June 2016)
Abstract
The inherent reactivity of the Al–Cu alloys is such that their use for structural, marine, and aerospace components and structures would not be possible without prior application of a corrosion resistance system. Historically these corrosion resistance coatings were based on the use of chemicals containing Cr (VI) compounds. Silane coatings are of increasing interest in industry due to their potential application for the replacement of current toxic hexavalent chromate based treatments. In this study, hydrophobic coating sol was prepared with methyltriethoxysilane (MTES), methanol (MeOH), and water (as 7M NH4OH) at a molar ratio of 1:25:4.31 respectively. The coatings were applied by a dip-technique to 2024-T3 Al alloy, and subsequently cured at room temperature and there after heat treated in an oven at 150°C. The anticorrosion properties of the coatings within 3.5 wt% NaCl solution were studied by Tafel polarization technique. The sol–gel coating exhibited good anticorrosion properties providing an adherent protection film on the Al 2024-T3 substrate. The surface properties were characterized by water contact angle measurement, scanning electron microscopy (SEM), and the composition was studied by Fourier transform infrared spectroscopy (FTIR).
A. Jafari Tadi, S.r. Hosseini, M. Naderi Semiromi,
Volume 14, Issue 3 (September 2017)
Abstract
Influence of formation of surface nano/ultrafine structure using deep rolling on plasma nitriding and tribological properties of the AISI 316L stainless steel was investigated. Initially, the deep rolling process was carried out on the bar-shaped specimens at 15 cycles with 0.2 mm/s longitudinal rate and 22.4 rpm bar rotation. Then, plasma nitriding treatment was applied on the as-received and deep rolled kinds at 450 °C and H2-25% Vol. N2 gas mixture for 5 h. Surface micro-hardness and un-lubricated pin-on-ring sliding wear tests were carried out on the as-received, deep rolled, plasma nitrided and deep rolled-plasma nitrided kinds. Results revealed that deep rolled-plasma nitrided kind is shown the highest wear resistance than the others, due to the further increased surface hardness achieved via the combined process.
Amin Rezaei Chekani, Malek Naderi, Reza Aliasgarian, Yousef Safaei-Naeini,
Volume 21, Issue 0 (IN PRESS 2024)
Abstract
This paper presents the novel fabrication method of a three-dimensional orthogonally woven (3DW) C/C-SiC-ZrB2 composite and the effects of ZrB2 and SiC particles on microstructure and the ablation behavior of the C/C–SiC–ZrB2 composite are studied. C/C–SiC–ZrB2 composite was prepared by isothermal-chemical vapor infiltration (I-CVI), slurry infiltration (SI), and liquid silicon infiltration (LSI) combined process. Pyrolytic carbon (PyC) was first infused into the 3DW preform by I-CVI at 1050°C using CH4 as a precursor in order to form a C/C preform with porous media. The next step was graphitization at 2400°C for 1hr. Then ZrB2 was introduced into 3DW C/C preform with a void percentage of 48 by impregnating the mixture of ZrB2 and phenolic resin, followed by a pyrolysis step at 1050°C. A liquid Si alloy was infiltrated, at 1650 °C, into the 3DW C/C composites porous media containing the ZrB2 particles to form a SiC–ZrB2 matrix. An oxyacetylene torch flame was utilized to investigate The ablation behavior. ZrB2 particles, along with the SiC matrix situated between carbon fiber bundles, form a compact ZrO2-SiO2 layer. This layer acts as a barrier, restricting oxygen infiltration into the composite and reducing the erosion of carbon fibers. The findings were supported by FESEM imaging and further confirmed through x-ray diffraction and EDS analysis. The addition of ZrB2 to the C/C-SiC composite resulted in a lower mass and linear ablation rate; 2.20 mg/s and 1.4 µm/s respectively while those for C/C-SiC composite were 4.8 mg/s and 6.75 µm/s after ablation under an oxyacetylene flame (2500°C) for 120 s.
