mo

In this research, Ni-Mo-Al2O3 composite coatings were electro-deposited on the mild carbon steel in a citrate bath containing micro- sized Al2O3 particles. Afterward, the effect of the particle concentration in the electrolyte bath (ranging from 0 g/L to 30 g/L) on the microstructure, microhardness, and corrosion performance was evaluated. To investigate the microstructural changes and the surface morphology of the coatings, as well as the particle distribution in the deposits, optical and scanning electron microscopy coupled with the energy dispersive X-ray spectroscopy was utilized. The corrosion behavior of the prepared coatings was investigated in a 3.5 wt. % NaCl solution. The results showed that the presence of the Al2O3 particles in the Ni-Mo coatings changed the microstructure and also, increased the microhardness and corrosion resistance of them. It was also found that the desirable structure of the protruding crystallite morphology with no detectable pores could be achieved at the medium concentrations of reinforcement (e.g. 20 g/L). Further the optimum concentration of the particles in the electrolyte bath to attain the composite coating with the desirable microstructure and consequently, the desirable corrosion resistance was found to be 20 g/L

In this research, the Ni-Mo-PCTFE nanocomposite coatings in the presence of various concentrations of PCTFE were prepared on copper sheets by electrodeposition from citrate bath. Effect of PCTFE concentration on the corrosion resistance was determined. Surface morphology and composition of the composite coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) measurements. Also, corrosion resistance of coatings was evaluated using open-circuit potential (EOCP) measurements, electrochemical impedance spectroscopy (EIS) and Tafel polarization techniques in 3.5 wt.% NaCl solution. The study reveals significant shift in corrosion potential towards the noble direction, decrease in corrosion current density and increase in charge transfer resistance with the incorporation of PCTFE particles in the Ni-Mo matrix. The highest value of charge transfer resistance was obtained for Ni-Mo-PCTFE coating deposited from solution with concentration of 8 g /L PCTFE.

In this study, Mo-14Si-10B and Mo-57Si-10B (at%) elemental powders were separately milled using an attritor mill.Mechanically alloyed powders were agglomerated and annealed. Then, powders of Mo-Si-B as alloyed (with composites) and agglomerated (without composites) were plasma sprayed onto plain carbon steels. The samples, both coated and noncoated,were subjected to isothermal oxidation tests. Metallurgical characteristics of powders and coatings were evaluated by SEM and XRD. Plasma-sprayed Mo-Si-B coatings (with phases of MoSi2, Mo5Si3, MoB and Mo5SiB2) greatly improved the oxidation resistance of the plain steel substrates, but plasma-sprayed Mo-Si-B coatings (without any phases) did notsignificantly improve the oxidation rate of substrates. Also, the kinetics and composition of the oxide-scale have been found to depend on the alloy composition.

In this study, an attempt was made to synthesize Mo-Si-B multiphase alloy coatings using a combination of mechanical alloying (MA) and air plasma spraying (APS). Mo-14Si-10B (at%) elemental powders were milled using an attritor mill. Mechanically alloyed (MAed) powders as compacted buttons were annealed in an atmosphere controlled furnace at 1100ºC for different times. The annealed Mo–Si–B buttons were crushed, sieved and prepared for coating. Then, powders of Mo-Si-B as alloyed and agglomerated, were plasma sprayed under different conditions onto plain carbon steel. Metallurgical characteristics of powders and coatings were evaluated by SEM, OM, XRD and AAS. The results did not show any related intermetallics after MA. However, Molybdenum silicides were identified when the MAed powders were subjected to high temperature annealing over 10 h. Also, the critical parameters in APS to maintain the starting stoichiometry were identified; this included thermal spraying in an inert environment to minimize the oxidation of coatings. No intermetallic compounds could be identified when alloyed powders were sprayed.