Co-deposited Ni-Cr-B Nanocomposite Coatings for Protection Against Corrosion-Erosion

Electrodeposition is a low-cost and low-temperature method for producing metal matrix composite coatings. The electrodeposition of Ni matrix/Ni-Cr-B particles is considered as the co-deposition of Ni-Cr-B particles in a Ni matrix, resulting in nanocomposite coatings that can offer good wear and corrosion resistance between other applications. For comparison, the electrodeposition of Ni films and their wear and corrosion evaluation were also carried out under the same conditions. Some coatings usually contain oxide or carbide particles in micrometer size and are electrodeposited in a nickel matrix; however, the use of the mechanical alloying process offers the possibility to reduce the particle size in the order of nanometers obtaining solid solutions, amorphous phases, or intermetallic compounds during the development of new alloys to be co-deposited, improving the engineering materials properties. This kind of nanocomposite can be used in industrial components with an irregular geometry exposed in aggressive environments such as the energy generation and oil industry

Synthesis of TiB2-Ni3B Nanocomposite Powders by Mechanical Alloying

Combination of good oxidation resistance, thermal stability, hardness and high strength are great interest properties in engineering and, that are possible to obtain with the Ni-Ti-B ternary system. Mechanical alloying (MA) is an alternative method and cheapest for the synthesis of this kind of metal-ceramic materials with respect to the traditional melt and quench process. The transformation sequence of all the mixtures reported the formation of (ɣ Ni) phase with a nodular morphology and identified the additional presence of the TiB2 phase (needle morphology), which was more evident with the increase of titanium content (M2 and M3 mixtures) after 24 h of milling. Thermal activation of the milled powders showed the nucleation and growth of the Ni3B (O boride) and TiB2 (Hex) as the main phases after heat treatment, where the TiB2 phase (thin flakes morphology) was nucleated onto Ni3B matrix. Ternary alloy by MA took place under a metastable equilibrium, offering the possibility to form glassy alloys for compositions, which are not accessible by melting or quenching techniques

Corrosion behavior of boride diffusion layer on CoCrMo alloy surface

87-95In the present study, the corrosion behaviour of CoCrMo ASTM F75 alloy with boride diffusion layer and under simulated physiological conditions has been investigated using electrochemical methods. Corrosion has been analyzed using Tafel and electrochemical impedance spectroscopy (EIS) curves. The corrosion resistance optimization of boride diffusion layer on ASTM F-75 alloy using a central composite design (CCD) in response surface methodology (RSM) has been studied. A boronizing thermochemical treatment has been carried out at different temperatures, time periods and paste mass. The roughness for samples subjected to boride annealing has been higher than that of the unboride sample. X-ray diffraction (XRD) measurement has shown that the boride layer of the sample at least consists of a mixture of CoB and CrB phases. The EIS and Tafel curves results have suggested that boride ASTM F75 alloy has not been a suitable candidate for orthopedics applications

Preparation and Scintillating Properties of Sol-Gel Eu3+, Tb3+ Co-Doped Lu2O3 Nanopowders

Nanocrystalline Eu3+, Tb3+ co-doped Lu2O3 powders with a maximum size of 25.5 nm were prepared by the sol-gel process, using lutetium, europium and terbium nitrates as precursors, and ethanol as a solvent. Differential thermal analysis (DTA) and infrared spectroscopy (IR) were used to study the chemical changes during the xerogel annealing. After the sol evaporation at 100 °C, the formed gel was annealed from 300 to 900 °C for 30 min under a rich O2 atmosphere, and the yielded product was analyzed by X-ray diffraction (XRD) to characterize the microstructural behavior and confirm the crystalline structure. The results showed that Lu2O3 nanopowders start to crystallize at 400 °C and that the crystallite size increases along with the annealing temperature. A transmission electron microscopy (TEM) study of samples annealed at 700 and 900 °C was carried out in order to analyze the microstructure, as well as the size, of crystallites. Finally, in regard to scintillating properties, Eu3+ dopant (5 mol%), Tb3+ codoped Lu2O3 exhibited a typical red emission at 611 nm (D°→7F2), furthermore, the effect of Tb3+ molar content (0.01, 0.015 and 0.02% mol) on the Eu3+ radioluminiscence was analyzed and it was found that the higher emission intensity corresponds to the lower Tb3+ content

Corrosion behavior of boride diffusion layer on CoCrMo alloy surface

In the present study, the corrosion behaviour of CoCrMo ASTM F75 alloy with boride diffusion layer and undersimulated physiological conditions has been investigated using electrochemical methods. Corrosion has been analyzed usingTafel and electrochemical impedance spectroscopy (EIS) curves. The corrosion resistance optimization of boride diffusionlayer on ASTM F-75 alloy using a central composite design (CCD) in response surface methodology (RSM) has beenstudied. A boronizing thermochemical treatment has been carried out at different temperatures, time periods and paste mass.The roughness for samples subjected to boride annealing has been higher than that of the unboride sample. X-ray diffraction(XRD) measurement has shown that the boride layer of the sample at least consists of a mixture of CoB and CrB phases.The EIS and Tafel curves results have suggested that boride ASTM F75 alloy has not been a suitable candidate fororthopedics applications