Electrodeposition kinetics and surface morphology of Ni-B-UDD composite coating

The article presents the results of kinetic investigates of electrodeposition of a composite electrochemical coating based on a nickel-boron alloy. Current efficiency, polarization potentiodynamic researches had shown the joint participation in the electrodeposition process of finely dispersed compounds of nickel hydroxides, poorly soluble nickel and boron compounds present in the electrolyte or formed during electrolysis, and ultradispersed diamond introduced into the electrolyte. Comparison of 2D and 3D scans of the surfaces of the formed coatings confirmed the leveling effect of additives, as well as sparingly soluble nickel and boron compounds on the structure of coatings. The proposed composite electrochemical coatings can be used instead of chrome coatings when restoring parts and units of agricultural machinery.

THE SUPPORT BONDS RIGIDITY INFLUENCES ON THE CARRYING CAPACITY REDUCTION OF THE SHALLOW SHELLS ON A RECTANGULAR PLAN

The coatings construction of buildings and structures in the form of wooden shallow shells on a rectangular plan are considered. The orthotropic of the material and the geometric nonlinearity of the thin-walled structure taken into account in the equations. The Bubnov-Galerkin method is used to solve differential equations of wooden shallow shells with different supports. The influences of the ratio of elasticity in mutually perpendicular directions, shape and thickness of a structure on the value of stresses, critical load and low frequencies of small values of vibrations are investigated. The investigations results are given in dimensionless form and graphs are shown. This makes them useful in engineering calculations. Recommendations for adjusting the shape and thickness of the structure of coatings in the form of shallow shells to increase their bearing capacity or reduce material consumption are given.

OBTAINING COATINGS FROM HARD ALLOYS BY EXPLOSIVE LOADING OF MIXTURES OF CHROME CARBIDE AND TITANIUM CARBIDE POWDERS ON METAL BASES

The principal features of the mechanism of formation of coatings from hard alloys during their production by explosive pressing of mixtures of CrC and Ti powders on metal substrates are described. The phase composition and structure of coatings deposited using loading by a plane normally incident detonation wave and sliding loading are considered.

Influence of Diameter of Electrode Powder-like Wires is on Mechanical Descriptions of Elektrodugovikh Coverages

The influence of the diameter of the electrode flux-cored wires on the mechanical characteristics of the electric arc coatings is carried out in the work. Electric arc coatings were obtained on the original equipment, developed and manufactured at the Institute of Physics and Mechanics. GV Karpenko NAS of Ukraine. For spraying, model flux-cored wires of basic doping systems Fe – Cr – C and Fe – Cr – B with a diameter of 1.6 and 2.4 mm were used. The influence of the diameter of flux - cored wires on the structure, electric arc coatings from model flux - cored wires of different diameters is investigated. The dependence of porosity, microhardness, adhesion to the steel base, abrasive wear resistance of electric arc coatings sprayed from flux-cored wires with different amounts of charge on the thickness of the lamellae in the coating structure has been established. The influence of the thickness of the lamellae in the structure of coatings sprayed from flux-cored wires with different amounts of charge (depending on their diameter 1.6 and 2.4 mm) on their abrasive wear resistance was determined. It was found that the thickness of the lamellae in the coatings of all analyzed alloying systems increased with increasing volume of molten metal at the ends of flux-cored wires with the corresponding formation of droplets of larger diameter during its dispersion by air jet. shell charge and high arc current. It is shown that the amount of oxide phase in the structure of coatings doubles with increasing spray distance of flux-cored wires from 80 to 120 mm. More oxide phase (40… 100%) was found in coatings formed of flux-cored wires with a diameter of 2.4 mm with a higher filling factor of its shell charge compared to coatings formed of flux-cored wires with a diameter of 1.6 mm with lower filling. This is due to the larger volume of the charge in the powder wires of larger diameter, the cavities between the powders in which are filled with air, which intensively oxidizes the melt droplets inside the powder wires and at their ends during spraying. It is established that the porosity and microhardness of coatings from the developed flux-cored wires increase with the increase of the thickness of the lamellae in their structure and, accordingly, the diameter of the flux-cored wires. The increase in micro hardness is due to less evaporation and burnout of alloying elements from the droplets forming the coating, and the increase in porosity is caused by intensive spraying of droplets when hitting the sprayed surface, which contributes to micro cavities between the lamellae of the coating. It was found that with increasing the thickness of the lamellae in the structure of coatings of flux-cored wires 250H21VFGS and flux-cored wires 50HN2R5GS their adhesion to the steel base decreased slightly due to the occurrence of tensile stresses in coatings, which cause micro cracks or cracks. At the same time, the adhesion of 50X6MG2C flux-cored wire coatings to steel increased due to the higher carbon content of large lamellae and favorable conditions for the formation of high-carbon martensite, which has the lowest coefficient of thermal expansion and causes the lowest residual tensile stresses. It was found that the abrasive and gas-abrasive wear resistance of coatings from flux-cored wires 250Х21ВФГС decreased, and from flux-cored wires 50ХН2Р5ГС increased due to the increase in the thickness of the lamellae in their structure using a larger diameter.

The corrosion-resistant Ni-based coatings and their tribological properties

Ni-based coatings can be successfully applied under abrasive and adhesive conditions as a substitute for environmentally harmful chrome coatings. The research has been carried out for thermally flame sprayed Ni-based coatings with remelting (so-called the two-step process) with the different chemical composition of starting powders. The structure of coatings was evaluated by optical and scanning electron microscopy. Both the three-body abrasive wear test, according to ASTM G65-4 (Dry-Sand Rubber Wheel Test) and dry sliding wear test by the Falex tester, were performed. The results show the influence of the effective chemical composition of the metal powders on improving the properties of the coating. The higher hardness of the coatings leads to a lower tendency for the creation of adhesive bonds, and as a result, leads to a lower tendency to scuffing. A similar trend shows the influence of higher coating hardness on the increasing of abrasive wear resistance.

Comparison of tribological properties and structure of coatings produced in powder flame spraying process on grey cast iron

In this article results of tribological and structural properties comparison of flame sprayed, by SupJet-S-Eutalloy® multipurpose system, two self-fluxing alloys of Ni-B-Si type in the form of powder for spraying with remelting are presented. Layers were produced on EN-GJL-250 grade grey cast iron with flake graphite in an austenitic matrix. Abrasive wear resistance examination acc. to ASTM G65-00 and erosive wear resistance examination acc. to ASTM G76-2 were performed. Obtained results were compared with abrasion-resistant steel Hardox® 400. Macro- and microscopic examination were carried enabling layer quality evaluation and structure of examined layer and base material determination. X-ray microanalysis was performed to obtain qualitative and quantitative data about microareas chemical composition. The Eutalloy® BronzoChrom 10185 powder flame sprayed layer with higher Boron and Silicon content was characterized by 13% lower wear intensity under mineral abrasive conditions and about 30% higher erosion wear resistance than Eutalloy® NiTec 10224 powder flame sprayed layer.

Application of Complex Concentrate of Rare-Earth Elements for Obtaining Electrometallic Coatings

The unique physical and chemical characteristics of rare earth elements make them attractive for use in a number of existing and innovative production lines. The use of complex concentrates of various deposits to obtain new materials is a promising area of modern materials science. The article presents the results of studies of electroarc metallization coatings of flux-cored wires with modifying additives. As additives, a complex concentrate of rare-earth metals from the deposits of the Republic of Sakha (Yakutia) and other modifying powders were used to obtain hardening phases. To determine the optimal composition of the modifying additives, various compositions of cored wires were made. An analysis of the structure of coatings showed a uniform distribution of the main elements of the cored wire, as well as a local distribution of unmelted particles of the modifying additives. The levels of open porosity and microhardness of the phase components of the coatings are determined. The prospects of using complex concentrate with rare-earth elements from deposits of the Republic of Sakha (Yakutia) as modifying additives for coatings with enhanced performance properties is shown.

Improving the Characteristics of Wear-Resistant Coatings Obtained by HDTV-Boration, their Modification by Intermetallic Compounds of Fe-Al and Ni-Al Systems

Innovative technology of HDTV-borating, that is distinguished by high hardness, strength, wear resistance and corrosion resistance occupies a special place among the hardening processes for steels and construction materials. During the new technology process HDTV-boration of structural steel 65Mn (65Г in Russian) under a mix layer of charge mixture based on fused borate fluxing agent P-0.66, boron carbide and intermetallic compounds FexAly, NixAly. Using the methods of X-ray phase analysis, spectrography and metallography, the composition and structure of coatings were determined, the microhardness distribution over the coating thickness was studied. In the coatings, new phases of intermetallic compounds, the double superhard boride Fe2AlB2, were found; in the coatings, the base iron boride is FeB, what leads to an increase in their hardness and wear resistance. Modification of boride coatings formed by intermetallic compounds with melting temperatures close to the process temperature of HFC surfacing leads to a decrease in the cracks number and the appearance of new consumer qualities of the material.