Electrode for electric spark alloying

Abstract

FIELD: electrophysical; electrochemical processing methods.SUBSTANCE: invention relates to electrode materials for electrospark alloying of metal surfaces. The electrode for electric spark alloying is manufactured by spark plasma sintering of powders obtained by electrodispersion from metal waste of “12Х18Н10Т” steel at a temperature of T=1200 °C, pressure P=40 MPa and holding time t=10 min, and has an elemental composition, wt.%: C 1.58, O 2.73, Si 1.59, Ti 0.69, Cr 17.37, Ni 9.07, Fe 66.96.EFFECT: producing an electrode for electric spark alloying with a fine-grained, pore-free, defect-free structure.1 cl, 6 dwg, 3 ex

Description

[0001] The invention relates to electrophysical and electrochemical processing methods, in particular to electrode materials for electrospark alloying of metal surfaces.

[0002] An electrode is known for the electric spark alloying of overhead power line wires [see patent for utility model of the Russian Federation 115697, published 10.05.2012, bulletin No. 13], which consists in the fact that the electrode for the electric spark alloying of aluminum overhead power line wires is made from shungite from the Zazhoginsky deposit with a carbon content averaging 30% by weight and in an amorphous state in the form of fullerene.

[0003] The disadvantages of this utility model are the multi-operation nature of the electrode production process and its high cost.

[0004] The closest to the claimed technical solution is an electrode for electric spark alloying [see patent RF76594U1, published 09.27.2008, bulletin No. 24], in which the electrode for electric spark alloying, containing titanium carbide, cobalt and other chemical elements, additionally contains a boron-containing component in the form of ferroboron, the electrode is also made hollow and blown by a cooler from the inside and outside, in addition, it is made with a coating in the form of an electrocorundum coating with a thickness of 0.3-2.0 mm.

[0005] The disadvantages of this utility model are the porous structure of the electrode.

[0006] The technical problem of the invention is to manufacture an electrode for electric spark alloying with a fine-grained, pore-free, defect-free structure.

[0007] The technical task is achieved in that the electrode for electric spark alloying is manufactured by spark plasma sintering of powders obtained by electrodispersion from metal waste of steel grade 12X18H10T at a temperature of T=1200 °C, a pressure of P=40 MPa and a holding time of t=10 min, and has an elemental composition, wt. %: C 1.58, O 2.73, Si 1.59, Ti 0.69, Cr 17.37, Ni 9.07, Fe 66.96.

[0008] Fig. 1 – SEM image of powder; Fig. 2 – Size distribution of powder microparticles; Fig. 3 – Powder consolidation by spark plasma sintering; Fig. 4 – Spark plasma sintering technology: A – schematic diagram of SPS synthesis; B – general heating diagram by SPS method; Fig. 5 – Microstructure of electrode section, elemental composition; Fig. 6 – Microstructure of sample with ESA coating.

[0009] The process of producing powders from metal waste is based on the breakdown of molten metal by electrical discharges in a liquid dielectric medium. Passing a pulsed electric current through a metal electrode immersed in a dielectric (e.g., kerosene) causes localized heating, melting, and dispersion of the material, forming fine spherical particles. This process produces powders with specified particle sizes and minimal oxidation due to the protective action of the dielectric liquid.

[0010] Next comes the electrode sintering process, which is carried out using spark plasma sintering (SPS) on a ThermalTechnology SPS 25-10 system. The powder obtained by electrodispersion is placed in a graphite mold and subjected to the simultaneous action of high-intensity pulsed direct current (up to several thousand amperes) and pressure (20-100 MPa) at a temperature below the melting point of the main powder component. This results in rapid (5-20 minutes) compaction of the material due to the activation of diffusion processes in the contact zones of the particles under the influence of localized Joule heating and plasma discharges, ensuring the formation of a dense (up to 99% of the theoretical) fine-grained structure without significant grain growth and maintaining the chemical purity of the material.

[0011] Example 1

[0012] Dispersible metal waste – steel grade 12X18H10T.

[0013] Working fluid – kerosene.

[0014] Metal waste dispersion unit – experimental, patented (RU Patent No. 2449859).

[0015] Metal waste dispersion modes: capacity – 62.5 μF; voltage – 140 V; frequency – 150 Hz.

[0016] Powder fusion unit – SPS 25-10 “ThermalTechnology”.

[0017] Powder fusion modes: temperature T=1200 °C, pressure P=40 MPa and holding time t=5 min.

[0018] These modes are not recommended because the powder particles are not completely fused.

[0019] Example 2

[0020] Dispersible metal waste – steel grade 12X18H10T.

[0021] Working fluid – kerosene.

[0022] Metal waste dispersion unit – experimental, patented (RU Patent No. 2449859).

[0023] Metal waste dispersion modes: capacity – 62.5 μF; voltage – 140 V; frequency – 150 Hz.

[0024] Powder fusion unit – SPS 25-10 “ThermalTechnology”.

[0025] Powder fusion modes: temperature T=1200 °C, pressure P=40 MPa and holding time t=10 min.

[0026] Powder fusion unit – SPS 25-10 “ThermalTechnology”.

[0027] The following are the results of the research of the obtained electrode.

[0028] The SEM image of the powder obtained by electrodispersion of 12X18N10T steel waste is shown in Fig. 1.

[0029] From Fig. 1 it can be seen that the high-chromium powder obtained by electrodispersing the metal waste of 12X18N10T steel has a predominantly spherical shape and an average particle size of about 10 μm.

[0030] The particle size measurement results are shown in Fig. 2.

[0031] Powder sintering was carried out by spark plasma sintering using an SPS 25-10 spark plasma sintering system (ThermalTechnology, USA) according to the scheme shown in Fig. 3. The starting material was placed in a graphite matrix, which was placed under a press in a vacuum chamber. Electrodes integrated into the mechanical part of the press supply electric current to the matrix and create spark discharges between the sintered particles of the material, ensuring intense interaction. The powder consolidation process is shown schematically in Fig. 4. Advantages of the technology: uniform heat distribution over the sample; high density or controlled porosity; binders are NOT required; uniform sintering of homogeneous and dissimilar materials; short working cycle time; manufacturing of the part immediately in the final shape and obtaining a profile close to the specified one.

[0032] Scanning electron microscopy was used to study the sample's surface microstructure. The sample's surface (section) was ground and polished. Grinding was performed using coarse-grained (Nos. 60-70) and fine-grained (Nos. 220-240) metallographic paper. During grinding, the sample was periodically rotated 90°. The abrasive particles were washed off with water and polished on a polishing wheel using metal oxide suspensions (Fe3O4, Cr2O3, Al2O3). After achieving a mirror finish, the section surface was rinsed with water and alcohol and dried with filter paper. Using an EDAX energy-dispersive X-ray analyzer built into a Quanta 600 FEG scanning electron microscope, characteristic X-ray radiation spectra were obtained at various points on the sample surface and along a cross-section.

[0033] The microstructure of the electrode section sintered from the obtained high-chromium powders, as well as the elemental composition, are shown in Fig. 5.

[0034] From Fig. 6 it can be seen that spark plasma sintering at high pressure and short-term pulsed high-amperage current flow through the high-chromium powder contributed to the suppression of grain growth and the formation of a pore-free, defect-free structure of the sintered electrode material.

[0035] Example 3

[0036] Dispersible metal waste – steel grade 12X18H10T.

[0037] Working fluid – kerosene.

[0038] Metal waste dispersion unit – experimental, patented (RU Patent No. 2449859).

[0039] Metal waste dispersion modes: capacity – 62.5 μF; voltage – 140 V; frequency – 150 Hz.

[0040] Powder fusion unit – SPS 25-10 “ThermalTechnology”.

[0041] Powder fusion modes: temperature T=1200 °C, pressure P=40 MPa and holding time t=15 min.

[0042] These modes are not recommended because the powder particles are completely melted in the matrix volume.

Claims

An electrode for electric spark alloying, characterized in that it is manufactured by spark plasma sintering of powders obtained by electrodispersion from metal waste of grade 12X18N10T steel at a temperature of T=1200 °C, a pressure of P=40 MPa and a holding time of t=10 min, and has an elemental composition, wt. %: C 1.58, O 2.73, Si 1.59, Ti 0.69, Cr 17.37, Ni 9.07, Fe 66.96.

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