Enhanced Tribological Properties of Electrodeposited Fe-W Alloy Coatings through Carburization

Carburization is a promising surface-hardening approach to maximize the tribological and mechanical properties of metals and alloys by making thin-layer surface carbides. The current study investigates the effect of carburizing on the electrodeposited Fe-W alloy coating. This process involeves the thermal decomposition of ethanol in an argon (Ar) atmosphere at varying temperatures. The amorphous electrodeposits of Fe-W alloy coating formed at optimized current density (500 A/cm2) are transformed to the uniform W-rich reinforced bimetallic carbide (Fe3W3C) layers at a carburizing temperature of 850 °C. The sample Fe-50WC (850 °C) shows enhanced hardness and highest wear resistance with a lowest specific wear rate (10-7 mm3/Nm) as compared to the as-electrodeposited Fe-W alloy and other Fe-W, Co-W, and hard chromium coatings reported in the literature. The present strategy can be applied to develop alternative, low cost, and environmentally friendly W-based composite coatings to replace the toxic chromium coatings.

Composition and

Principles of three component Iron-Cobalt-Tungsten alloys electrodeposition from complex Fe (III) based citrate electrolytes are discussed. It is shown, that deposition of ternary alloys proceeds through competitive reduction of cobalt and tungsten with iron. With increasing ligand concentration coatings are enriched with a refractory component; however, increasing current density favors a reverse trend. The effect of both current density and pulse on/off time on the quality, content of alloying metals and surface topography of electrolytic coatings were determined. The application of pulsed electrolysis provides increasing tungsten content up to 13 at.%, at current efficiency of 70–75%. Globular relief of Fe-Co-W coatings is caused by refractory metals incorporation, and crystalline and amorphous parts of structure are visualized by X-ray spectroscopy, including inter-metallic phases Co7W6, Fe7W6 along with α-Fe and Fe3C. The crystallite size of the amorphous part is near 7–8 nm. Corrosion resistance of the coatings is 1.3–2.0 orders of magnitude higher than the substrate parameters as follows from data of polarization resistance method and electrode impedance spectroscopy.

Composition, Morphology, and Topography of Galvanic Coatings Fe-Co-W and Fe-Co-Mo

Ternary coatings Fe-Co-W with an iron content of 40-55 at.%, cobalt 39-44 at.%, and tungsten 4-12 at.% and Fe-Co-Mo with an iron content of 40-55 at.%, cobalt 39-44 at.%, and tungsten 4-12 at.% were obtained by galvanostatic and pulse electrolysis on the mild steel substrate from iron(III) citrate-based electrolyte. The influence of electrolysis mode and parameters on composition of deposited alloys was studied. The competing reduction of iron and tungsten in Fe-Co-W coatings as well as the competitive deposition of iron and cobalt in Fe-Co-Mo coatings at various current densities were defined. Simultaneously, the alloy enrichment with molybdenum is more marked at a pulse mode. Atomic force microscope analysis of the Fe-Co-W alloy coating morphology and surface topography indicates their globular structure with spherical grains in the range of 2.5-3.5 μm. The surface of Fe-Co-Mo is characterized by parts of a globular structure with an average conglomerate size of 0.3-0.5 μm and singly located cone-shaped hills with a base diameter of 3 μm. Sites with a developed surface were detected within the same scan area which topography is identical to the crystal lattice of cobalt with the crystalline conglomerate sizes in the range of 0.2-1.75 μm.

Tuning electronic states of catalytic sites enhances SCR activity of hexagonal WO3by Mo framework substitution

The electronic states of the catalytically active sites of HWO were tuned by Mo framework substitution.