Corrosion performance and tribological behavior of diamond-like carbon based coating applied on Ni−Al−bronze alloy

The effect of diamond-like carbon(DLC)coating(fabricated by cathodic arc deposition)on mechanical properties,tribological behavior and corrosion performance of the Ni−Al−bronze(NAB)alloy was investigated.Nano-hardness and pin-on-plate test showed that DLC coating had a greater hardness compared with NAB alloy.Besides,the decrease in friction coefficient from 0.2 for NAB substrate to 0.13 for the DLC-coated sample was observed.Potentiodynamic polarization and EIS results showed that the corrosion current density decreased from 2.5μA/cm2 for bare NAB alloy to 0.14μA/cm2 for DLC-coated sample in 3.5 wt.%NaCl solution.Moreover,the charge transfer resistance at the substrate−electrolyte interface increased from 3.3 kΩ·cm2 for NAB alloy to 120.8 kΩ·cm2 for DLC-coated alloy,which indicated an increase in corrosion resistance due to the DLC coating.

Effect of Mg and Si on intermetallic formation and fracture behavior of pure aluminum-galvanized carbon-steel joints made by weld-brazing

Commercial pure aluminum and galvanized carbon steel were lap-welded using the weld-brazing(WB)technique.Three types of aluminum filler materials(4043,4047,and 5356) were used for WB.The joint strength and intermetallic compounds at the interface of three series of samples were analyzed and compared.Depending on the Si content,a variety of ternary Al-Fe-Si intermetallic compounds(IMCs) such as Fe_(4)(Al,Si)_(13),Fe_(2) Al_(8) Si(τ_(5)),and Fe_(2) Al_(9) Si_(2)(τ_(6)) were formed at the interface.Mg element in 5356 filler material cannot contribute to the formation of Al-Fe intermetallic phases due to the positive mixing enthalpy of Mg-Fe.The presence of Mg enhances the hot cracking phenomenon near the Al-Fe intermetallic compound at the interface.Zn coating does not participate in intermetallic formation due to its evaporation during WB.It was concluded that the softening of the base metal in the heat-affected zone rather than the IMCs determines the joint efficiency.

Synthesis of a NiTi_(2)–AlNi–Al_(2)O_(3) nanocomposite by mechanical alloying and heat treatment of Al–TiO_(2)–NiO

The aim of the present study was to investigate the phases formed during ball milling of Al–TiO_2–NiO. For this purpose, a mixture of Al–TiO_2–NiO with a molar ratio of 6:1:1 was used. Characterization of the milled powders by X-ray diffraction, differential thermal analysis, field-emission scanning electron microscopy, and transmission electron microscopy showed the formation of nanocrystalline NiTi_2 along with AlNi. A thermodynamical investigation confirmed that NiO was reduced by Al during ball milling, which consequently promoted TiO_2 reduction and the formation of NiTi_2. Al is capable of reducing NiO either during ball milling or at temperatures above the melting point of Al; by contrast, TiO_2 can be reduced by Al only by milling.

Applying the Protective Mn-Co-La_(2)O_(3)Coating on Crofer 22 APU Ferritic Stainless Steel Used as Solid Oxide Fuel Cell Interconnects

This research studies the effect of Mn-Co-La_(2)O_(3) coating synthesized by the electrodeposition method on the oxidation resistance and electrical conductivity of the Crofer 22 APU stainless steel interconnect plates in solid oxide fuel cells.The test samples were characterized by a field emission scanning electron microscope(FESEM)equipped with energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The oxidation kinetics of the coated and uncoated samples were studied by tracking their weight changes over time at 800°C,showing that the oxidation mechanism for all samples follows the parabolic law.Lower oxidation rate constant(k_(p))values of the coated sample compared with that of the uncoated one indicated a reduction in the oxidation rate of the steel substrate in the presence of the Mn-Co-La_(2)O_(3) coating.The examination of the cross-section of different samples after the isothermal oxidation for 500 h at 800°C exhibited that applying the composite coating leads to a decrease in the thickness of the chromia layer formed on the steel surface.Furthermore,under these conditions,the area-specific resistance(ASR)of the coated sample(13.11 mΩcm^(2))is significantly lower than that of the uncoated one(41.45 mΩcm^(2)).