Electrospark Treatment Research Articles

Осаждение покрытий из металлического стекла электроискровой обработкой в среде гранул состава Fe39Ni8Cr7W7Mo7Co2C16B14

The article is devoted to the deposition of FeNiCrWMoCoCB coatings on the basis of metallic glasses on a steel 35 substrate by an electrospark treatment in a medium of granules of pure metals and alloys used as electrode materials. X-ray diffraction studies have shown the predominance of the amorphous phase in the coating composition. It is shown that its fraction increases with an increase in the run-in time of the granules mixture used up to 300 min. According to the X-ray data, during annealing, the amorphous phase persists up to the temperature of 600°C and then crystallizes into the phase of a complex iron-based carbide (Cr,Fe,W,Mo)23Fe12(W,Mo)2C12 . The corrosion properties, microhardness and wear resistance of the coatings obtained are studied. Polarization tests in a 3.5 % aqueous NaCl solution showed an increase in the corrosion potential of the coatings with an increase in the run-in time of the granules used. A completely metallic glass coating showed a lower corrosion current and a higher polarization resistance as compared to steel 35. The study of oxidation kinetics has shown that the use of the FeNiCrWMoCoCB coating on steel 35 increases the resistance of its surface to high-temperature gas corrosion by 16 times in 100 hours of testing at a temperature of 700°C. The microhardness of the deposited layers was about 8 GPa that is 4 times higher than that of non-coated steel 35. The wear resistance of the deposited FeNiCrWMoCoCB coatings to dry sliding friction relative to P6M5 steel showed that its wear for 30 km of the test was almost 2 times lower than that of steel 35. The proposed approach opens the possibility for a one-stage synthesis of metallic glasses in the form of coatings in an automatic mode from individual crystalline components.

Analysis of electric pulsed processes in electrospark treatment of metallic surfaces in a gas medium

Results of investigations of electric pulsed processes investigated in BIG-5 universal electrospark equipment, including determination of the energy parameters and efficiency of the process using a new procedure, are presented. The procedure is based on the automatic recording of the parameters of the pulsed process and analysing the process using computer programs producing the data for the number of pulses, energy of the pulses, duration of the pulses and current. The method can also be recommended for investigating pulsed processes for developing new methods for electrophysical or electrochemical processing of materials and diagnostics of equipment in production conditions.

Improving the efficiency of electrospark treatment of metallic surfaces by combining the method with other methods

One of the methods of increasing the efficiency of the electrospark treatment (EST) of metallic surfaces is investigated. On the basis of the experimental results, it is shown that combining the EST with other methods produces the surface layers on components with new, improved high-quality and strength characteristics and widens the range of application of the EST.

Investigation into the performance of the friction surfaces developed by electrospark treatment

A probabilistic and statistical method is used to obtain data that are the starting point for forecasting and construction of models of reference curves of rough surfaces formed by electric discharge machining. Links are established between roughness parameters and performance of reconditioned friction pairs.

Sintered Ti–Ti3P–CaO electrodes and their application for pulsed electrospark treatment of titanium

In this study, the effect of mechanical treatment on the structure and phase composition of Ti+10% Ca3(PO4)2 powder mixtures was investigated. Ceramic Ti–Ti3P–CaO electrode materials with a high component homogeneity and a residual porosity of 5–7% were obtained in a process involving cold pressing and vacuum sintering. The erosive power of the sintered ceramic-metal Ti–Ti3P–CaO electrode during the electrospark treatment of titanium substrates was examined, and a comparison with the SHS TiC0.5–Ti3POx–CaO electrodes was performed. Both the Ti–Ti3P–CaO and TiC0.5–Ti3POx–CaO coatings exhibited high denseness with a width of approximately 20μm, a hardness of 3.6GPa, a roughness of 3.3–4.6μm and a uniform distribution of bioactive calcium and phosphorus elements.

Formation of the surface layer on a low-carbon steel in electrospark treatment

Results of investigations into the morphology and elemental and phase composition of surface layers produced by electrospark treatment of St10 steel in a gas medium using a VK8 hard cermet alloy are presented.

Nanostructuring a steel surface by electrospark treatment with new electrode materials based on tungsten carbide

The effect of the physical and chemical properties of the material of a carbide VK8 alloying electrode with 1–5 wt % Al2O3 nanopowder was studied based on the composition, structure, and properties in the modified surface layer upon the electromechanized hardening of steel 35 with varying the frequency and duration of the electrical pulse repetition. The data obtained can serve as a basis for creating devices of a new generation, special electrode materials, and for developing the technologies for nanostructuring the surface layers of metal materials.

Effect of secondary electrospark treatment with carbon-bearing materials on the properties of titanium alloys

The Scientific Training Center for Self-Sustaining High-Temperature Synthesis at the Moscow Institute of Steel and Alloys has conducted a study of the structure and properties of two-layer electrospark coatings on titanium alloy OT4-1. The coatings were applied by the successive use of STS electrode material STIM-2 (TiC - 20% Ni) (primary treatment) and several different carbon-bearing materials (secondary treatment). It was established that treatment of the surface with carbon-bearing materials decreases the friction coefficient and increases the resistance of specimens of the titanium alloy to heat and wear.

Structure, mechanical and erosive properties of AlN-MoSi2 composite materials and their electrospark-deposited coatings

The paper examines the phase composition, structure, and properties of AlN-MoSi2 alloys and associated electrospark-deposited coatings on titanium. It is shown that the most intensive erosion and mass transfer are characteristic of alloys containing 60–80 wt.% MoSi2 and that the erosive characteristics essentially depend on the electrospark treatment parameters. A protective coating with a thickness of 30–40 µm and hardness to 1 GPa is formed on the substrate. There is a thermal impact area up to 300 µm deep and 1.4 GPa hard under the coating. The high-temperature holding of coated samples promotes the rapid formation of heat-resistance phases in the coating and the formation of a secondary structure in the thermal impact area. As a result, this area becomes thicker and the hardness of its material increases up to 1.9 GPa.

Epitaxial MCrAlY coating on a Ni-base superalloy produced by electrospark deposition

A novel electrospark deposition technique has been successfully developed to deposit epitaxially MCrAlY coating onto a directionally solidified nickel base superalloy. The coating is featured by cellular directionally solidified microstructure with primary γ phase. Its formation mechanism may be attributed to the facts that the alloy solidifies primarily with γ phase and solidification conditions of the tiny thin melt close to the limit of constitutional undercooling under the electrospark treatment condition.

Formation of residual stresses in coatings during high-energy treatment: A survey

The appearance of residual stresses in metals is one of the effects accompanying the action of high-energy treatment. Under both electrospark and laser treatments, temperature is a prevailing factor affecting the formation of residual stresses. High rates of heating and cooling of a metal in the melting zone result in the appearance of thermal stresses determined by the difference between the coefficients of thermal expansion of the metal. A combined electrospark and laser treatment creates a stressed state in the surface layer with better characteristics than each treatment does separately. The value, sign, and distribution of the residual stresses substantially influence the service properties of machine parts.

Stress state in the surface layers of steel R6M5 after electrospark and laser treatment

Laser irradiation of the electrospark alloyed surface of high-speed steel produced remelting of the surface layer and formation of a broad structure transition zone. This optimized the gradient of properties at the surface. Laser treatment of the electrospark coatings produced tensile stresses in the surface layers, whose magnitude and distribution were dependent on the treatment conditions, as well as the physico-chemical interaction of the refractory compound with molten steel in the liquid pool formed by irradiation.

Electric erosion of the composite W(Mo)-Cu in electroerosion treatment of hard alloy in a carbon-containing liquid. I. Mechanism of wear of pseudoalloys W-Cu

The discovered mechanism of erosion of tungsten-copper pseudoalloys in electrospark treatment of the hard alloy VK20 in a carbon containing liquid Is characterized by the formation of sections of high melting phase on the working surface, the phase consisting of a mixture of tungsten and its carbides, and by the predominant action of the electric discharges on these sections. As a rule, copper is removed along the perimeter of the sections of high melting phase. The amount of removed phase is determined (with constant pulse parameters) by the ratio between the components of the pseudoalloy. The concept was advanced of a dynamic surface layer of pseudoalloys during mass effect on them of electrlc discharges in a carbon containing liquid.

Special features of the formation of the surface layer during electrospark treatment of alloy 45NKhT

Special features of the formation of the surface layer during electrospark treatment of alloy 45NKhT

Changes in the superficial layer of a metal caused by electrospark treatment

1. A diffusion of the electrode material into the processed part as well as an “inverse” diffusion of the material of the workpiece into the electrode-tool was observed during electrospark erosion “drilling”. In addition, small particles of metal suspended in the liquid used in spark machining diffused into the metal being processed. 2. The amount of metal which diffused from the electrode into the processed surface was roughly proportional to the circuit capacitance used in the electrospark procedure. 3. The depth of the white layer being formed generally increased with the capacitance. 4. The initial structure of the steel had a profound effect on the structure formed near the processing point. The white peripheral band formed irrespective of the structure of the matrix but its microhardness varied. A structure of high hardness and a tempered layer could be clearly distinguished in quenched specimens. With other types of matrix structure, these layers were not clearly defined, especially when a weaker current was used.