Authors: S. Abdi, B. Malki, S. Lebaili
Abstract: The object of the present work is to study the spraying of poly-powders nickel bases
containing Cr, Si, C and B elements addition with variable percentage of iron, deposited on a steel
substrate by oxy fuel thermal spraying. The substrate surface was previously treated by Al–Ni bond
coat and post–annealing at 650°C. The spraying powder and coating micro structure were
investigated by combination of X-ray diffraction, electron microprobe and scanning electron
microscope coupled to an analyzer energy dispersive x-ray. The adherence to substrate was
determined by using shear test for adhesion. The result of this study was to investigate to compare
potentials of HVOF sprayed NiCrBCSi and satellite 6 coating for a possible to replacement of hard
chromium plating. A good adherence of coating NiCrBCSi (Fe) on steel substrate is explained by
formation of large diffusion zone in interface after annealing and by the nature of the structure
deposit duplexes.
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Authors: Jin Zhang, Ren Yu Li, Qing Song Yu
Abstract: In this study, plasma treatment using Ar and H2 and plasma polymerization with trimethylsilane (TMS), were carried out to create the interface film systems with a structure of Mg/plasma interlayer/cathodic electrophoretic coating (E-coat) for a magnesium (Mg) alloy AZ31B. The interface adhesion of the coating system was evaluated using N-methylpyrrolidinone (NMP) paint removal test and ASTM tape test conducted under dry and wet conditions. Plasma TMS film could stick the Mg substrate more strongly than E-coat.The surface of samples with different interlayer treatment after NMP test has been observed by SEM. The potentiodynamic study performed on the E-coated samples showed a noticeable reduction of corrosion current, three orders of magnitude less than bare Mg. Salt spray test also was done to confirm the resistance corrosion of E-coat. It was found that plasma interface treatment has the ability of increasing the adhesion of E-coat on Mg alloy more or less, thus restrict access to damaging species that exist in Cl- aqueous environments.
984
Abstract: In this study, a comparison of appearance surface and fracture surface of mechanical plating was made, respectively formed by spherical Zn powders and Zn-Al compounding flake powders. It is found that the spherical particles are deposited and embedded on Zn plating. The deformation of granular Zn powders on coating superficial is relatively large, but there is little distortion of globe grain inside the coating, mainly with spheroidicity distorted. Besides, there are obvious gaps between the particles in Zn coating. In contrast, the flake structure granules of Zn-Al plating are densely and compactly laid out with small space. After contacting with air, the plating coat expands owing to aluminum oxidation, leading to the higher position of the plating coat on the cross section than the matrix metal. We then did salt mist test to verify the corrosion resistance of Zn-Al compounding flake coating. It was found that the Zn-Al compounding flake coating was superior to that formed by globe Zn powder. Results show that the addition of layers of flakes has a better shielding action resisting corrosive medium, leading to the decrease of the osmosis from corrosive medium to the coatings. And the coating can repair naturally after being damaged. We further passivate plating with molybdate to improve the anticorrosion of the coating.
811
Authors: Katarina Monkova, Peter Monka
Abstract: The article deals with the influence of the laser melting process on the surface roughness characteristics of the coat deposited on material by electrospark way granted by KEGA 035TUKE-4/2011 project of Ministry of education of Slovak republic. The aim of the article is research of material properties after coating by WC-Co and laser treatment. As the research method were used experiments and tools of statistics. Experiments were carried out on WC-Co coat (the anode), which was deposited on C45 carbon steel (the cathode) and molten by a laser beam. After surface treatment were analysed of changes in surface structure of the coat. Results of the research shows influence of parameters of this process to roughness, tribologic properties and morphology of the surface layer prepared by WC-Co coating and laser treatment.
370
Authors: Poonam Yadav, Muhammad Ali Abro, Dong Bok Lee
Abstract: The thermal barrier coating that consisted of ZrO2-8Y2O3 top-coat and Ni-22Cr-10Al-1Y bond-coat corroded in Ar-1%SO2 gas at 1000-1200°C for up to 300 h. The top-coat and bond-coat consisted primarily of β-ZrO2 and (γ-Ni, α-Al2O3), respectively. During corrosion, Al oxidized preferentially to α-Al2O3 to protect TBC, and sulfidation occurred to a small extent.
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