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

Abstract 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

Research Into Composition and Properties of the Ni–Fe Electrolytic Alloy

Promising yet insufficiently studied is the new electrolyte based on methanesulfonate salts of the alloy-forming metals. Examining the laws that govern the electrodeposition of the Ni–Fe alloy with assigned physical-chemiсal properties from the methanesulfonate electrolyte is a relevant task. In the present work we established influence of the concentration of iron(ІІ) ions in the electrolyte and of current density on the composition of alloy. The content of iron in the Ni–Fe alloy grows with an increase in the concentration of iron(ІІ) ions in the methanesulfonate electrolyte. Dependence of the content of iron in the alloy on current density is of extreme character. The maximum corresponds to the current density of 1 A/dm2. It is shown that the organic additive applied in the present work, sodium saccharinate, does not exert any substantial influence on the composition of alloy at current density exceeding 2 A/dm2. Sodium saccharinate increases microhardness of the coating with the Ni–Fe alloy whose values reach 500 kg/cm2. When introducing into the methanesulfonate deposition electrolyte of the Ni–Fe alloy of 6 mmol/l of sodium saccharinate, practically unstressed precipitations precipitate. A reduction in the internal stresses leads to a decrease in the values of coercive force of the alloy. It is demonstrated that the investigated properties of the Ni–Fe precipitations are determined by the structure of coatings. Sodium saccharinate, being a surface-active compound under the conditions of electrolysis, changes the structure of the cathodic Ni–Fe alloy and improves functional characteristics of coatings. The established dependences represent a rather valuable basis for designing new technologies of the electrodeposition of polyfunctional coatings with the Ni–Fe alloy with enhanced mechanical and magnetic characteristic

Determining Features of Application of Functional Electrochemical Coatings in Technologies of Surface Treatment

Approaches to the use of electrochemical coatings in surface treatment technologies are analyzed. It is shown that directed surface modification allows expanding the functional properties of the treated material, in particular, increasing the strength, wear resistance, corrosion resistance, catalytic activity.The method for treating non-alloy steel and cast irons by forming thin-film coatings of ternary alloys of iron and cobalt with molybdenum and tungsten is proposed. It is shown that the incorporation of refractory metals up to 37 at. % into the surface layer leads to a change in the phase structure of the coating. This is found to provide an increase in wear resistance by 40 %, microhardness by 2.5–3.5 times, as well as a decrease in friction coefficient by 3–4 times in comparison with the substrate material. The resulting materials can be used for hardening and protection of surfaces in various industries.To modify the surface of piston silumins, it is proposed to use the method of plasma electrolytic oxidizing with the formation of ceramic-like coatings. It is shown that in the galvanostatic mode, from alkaline electrolyte solutions containing manganese and cobalt salts, it is possible to obtain uniform, dense, highly adhesive to the base metal, oxide coatings, doped with catalytic components whose content varies within 25–35 at. %. It is shown that the morphology and phase structure of the surface layers changes with the incorporation of dopant metals. The formed coatings have a high degree of surface development, which is a prerequisite for enhancing their functional properties. The proposed approach is used to modify the surface of the KamAZ-740 piston. It is found that the use of ceramic-like coatings of the engine piston leads to a decrease in hourly fuel consumption and amount of toxic substances with exhaust gases, which makes them promising for use in in-cylinder catalysis