RU2078847C1 - Method and apparatus for ionic treatment of machines pieces and tools - Google Patents

Abstract

FIELD: methods and apparatuses of ionic treatment of machines pieces and tools by beams of ions. SUBSTANCE: piece surface is subjected to ionic clearance by beam of argon ions, produced from gas discharge plasma with ions high concentration of ((10¹⁰-10¹³cm^-3)) in gas discharge chamber under argon pressure of 0,7 - 4,7 Pa and on treated piece surface pressure of working gas pressure P_wg and partial pressure of surface polluting gasses P_pf is kept from conditions: P_pg= 10^-2-10^-3Pa, P_pg≪(2,2•10^-2•j₂+S_wg•M $\genfrac{}{}{0ex}{}{\text{1/2}}{\text{pg}}$ /f, with j₊ - argon ions current density A/A/cm², S_f - polluting film spraying factor, atom/ion, M_pg - molar weight of polluting gas, T - temperature of the gas, K. f - factor of molecules or atoms of polluting gas adhesion to piece surface. After clearance protective layer is applied on working surface and implantation of nitrogen ions is exercised till metal nitride is formed on piece surface. Apparatus has cylindrical gas discharge chamber and located in it along circumference and in height of outer wall cathodes of direct filament voltage, ionic-optical system made in the form of mounted in gas discharge chamber three coaxial electrodes with slots for focusing and acceleration of nitrogen or argon or mixed beams in radial planes directed to axis of apparatus, evaporator, anode made as two rings, power supply system and system of vacuum pumping. Quoter electrode is inner wall of gas discharge chamber. Anode and evaporator are located in gas discharge chamber. As a version apparatus has located on gas discharge chamber outer surface permanent magnets. Cathodes of filament direct voltage are made of tungsten or its alloys, or of hexaboride of lanthanum as small wires or bifilar winding. EFFECT: improved quality of machines pieces and tools treatment by ions beams. 7 cl, 7 dwg, 2 tbl

Description

 The invention relates to methods and devices for ion processing of machine parts, tools and endoprostheses with ion beams and can find application in the automotive, tractor, tool, instrument-making, electronic and other industries, as well as in medicine and biology.

 Known methods and devices for ionic nitriding of the surface layers of metals, steels and alloys using axially and plane-symmetric beams of nitrogen ions accelerated to an energy of 40-3000 keV with currents from fractions of a microampere to several milliamperes created by plasma ion sources / 1 /.

 The disadvantages of ion processing methods for relatively low-intensity ion beams are the small thickness of the modified layer equal to the range of the nitrogen ion in metals and alloys / 0.01-1 μm /, the large heterogeneity of the ion current density distribution over the beam radius / it decreases 2.7 times at a distance a few millimeters from the beam axis /, low processing productivity and long exposure time of the part.

 The closest technical solution is a method and device for ionic processing of cylindrical parts, which consists in ionically cleaning the surface from contaminants, applying a protective titanium layer to the working surface and implanting nitrogen ions to form titanium nitride in the surface layer / 2 /.

This device is a cylindrical ion gun - contains a mask for applying to a cylindrical part by evaporation of titanium, two grids, six tungsten cathodes, a titanium evaporator with diaphragms. A voltage of positive polarity of 30–40 kV is applied to the part; a vacuum in the source of 2 • 10 ^-6 - 7 • 10 ^-5 Pa creates turbomolecular and cryogenic pumps. When inflowing a nitrogen source to a pressure of 1 • 10 ^-1 Pa and applying 30 kV to the part, the current of nitrogen ions reaches 3 mA. On a part with a diameter of 3 cm and a length of 7 cm, the average current density of nitrogen ions is 0.091 mA / cm ² and the power density is 2.7 W / cm ² .

The disadvantages of the known technical solutions are: firstly, the relatively small values of the current and ion current density, therefore, the low productivity of the ion processing processes and the long duration of ion cleaning / 6-13 min / and the production of titanium nitride films / 15-42 min /. Secondly, despite the initial high cryogenic quality, vacuum, the surface of the part is contaminated by impurity gas atoms, since the working pressure of nitrogen is 5 • 10 ^-2 -8 • 10 ^-3 Pa. Thirdly, the current of nitrogen ions strongly depends on the gas pressure near the part. Finally, even without taking into account the power emitted by the tungsten cathodes, ion bombardment heats the part to 440 ^o C, which is often unacceptable.

 The technical result is an increase in the current strength and current density of nitrogen ions, the use of argon ions for ion surface cleaning, increasing the speed of cleaning the surface from contamination, increasing the thickness of the modified layer, increasing the uniformity of the distribution of current density and radiation dose on the surface of the part, reducing the pressure of the working and impurity gases near the surface to be treated, increasing the adhesion of the protective coating to the surface, increasing the adhesion of the protective coating to the surface of the part, reduced f accelerating the ions and secondary electrons of the voltage, as well as the wavelength of the x-ray radiation generated by them, increasing the radiation safety and energy and gas efficiency of the ion source, reducing the processing time, increasing the productivity of the ion processing of parts, especially those with an axis of symmetry, processing of the surface layer and the entire part in a wide range of temperatures.

где J₊ плотность тока ионов аргона, А/см², S_пл - коэффициент распыления загрязняющей пленки, ат/ион, M_зг молекулярная масса загрязняющего газа, T температура этого газа, K, f коэффициент прилипания молекул или атомов загрязняющего газа к поверхности детали, после ионной очистки проводят нанесение металлического слоя и имплантацию ионов азота в поверхность защитного слоя до образования износостойкого нитрида металла, например Cr₂N или Fe₄N, при имплантации ионы азота смешивают с ионами водорода или гелия, или меди, на плазму воздействуют магнитным полем остроугольной геометрии напряженностью 500-2000 Э, ионную обработку ведут в импульсном или частотно-импульсном режимах электрического питания источника ионов, устройство для ионной обработки деталей машин и инструментов, содержащее испаритель, деталь мишень, катоды прямого канала, анод, систему электрического питания и систему вакуумной откачки, снабжено газоразрядной камерой и ионно-оптической системой, выполненной в виде трех коаксиально расположенных электродов: эмиссионного, являющегося внутренней стенкой газоразрядной камеры, ускоряющего и заземленного с щелями для вытягивания, фокусировки и ускорения нескольких (3-76) радиальных плоскостях, направленных к оси устройства пучков ионов аргона или азота или смешанных пучков ионов газов и металлов, два цилиндрических анода и испарители установлены в газоразрядной камере, в которой помещены катоды прямого накала равномерно по окружности и по длине наружной поверхности стенки цилиндрической камеры, наружная поверхность газоразрядной камеры равномерно окружена постоянными магнитами, площадь поверхности эмиссии электронов катодов составляет 4-6,5% от площади внутренних стенок газоразрядной камеры, расстояние d₂ между заземленным и ускоряющим электродами выбрано из условия d₂=(0,3-0,8)d₃, а расстояние d₃ между ускоряющим и эмиссионным электродами выбирают из условия электрической прочности U= 80 d $\genfrac{}{}{0ex}{}{\text{0,8}}{\text{3}}$ где U ускоряющая разность потенциалов, равная 10-40 кВ для оптимальных условий имплантации, длина щелевых отверстий эмиссии L_щ определяется длиной рабочего участка обрабатываемой детали L_уд L_щ=(1,1-1,2) L_уд, число щелей рассчитано из соотношений: N_щ= πD/b_пд, b_пд= Δ_щ+2d_сtgθ_⊥ где D диаметр детали, b_пд ширина пучка на поверхности детали, Δ_щ ширина щели эмиссии, θ_⊥ угол расхождения пучка перпендикулярно щели эмиссии, d_c=D₁ + d₂ + d₃, где d₁ расстояние между поверхностью детали и заземленным электродом, система электрического питания выполнена в виде источников постоянного напряжения и тока накала катода, дугового разряда, высоковольтного источника электрического питания ионного источника, источника электрического питания ускоряющего электрода, причем корпус газоразрядной камеры соединен с положительной клеммой высоковольтного источника электрического питания ионного источника, ускоряющий электрод соединен с отрицательной клеммой этого же источника и такой же клеммой источника электрического питания ускоряющего электрода, заземленный электрод и обрабатываемая деталь заземлены, прямонакальные катоды выполнены из вольфрама или его сплавов, или гексаборида лантана в виде двух близко расположенных прямолинейных проволок или стержней, или бифилярной намотки, другая система электрического питания выполнена в виде импульсионных или частотно-импульсных источников напряжения и тока накала катодов, дугового разряда, высоковольтного источника электрического питания ионного источника, источника электрического питания ускоряющего электрода, причем длительность импульсов изменяют от одной миллисекунды до одной секунды, а частоту их следования от 0,1 до 100 Гц.Technical results are achieved by the fact that in the method of ion processing of machine parts and tools, which consists in ion cleaning of contaminants, applying a protective layer to the working surface and implanting nitrogen ions to form metal nitride on the surface of the part, the surface is cleaned with an intense argon ion beam obtained from gas discharge plasma with a high concentration of ions (10 ¹⁰ -10 ¹³ cm ^-3 ) in the gas discharge chamber at an argon pressure of 0.7-4.7 Pa, and on the surface of the workpiece the working gas pressure is p _rg and the partial pressure of polluting the surface of the gases p _zg support from the conditions:

where J ₊ is the argon ion current density, A / cm ² , S _PL is the sputtering coefficient of the polluting film, at / ion, M _{sg is the} molecular weight of the polluting gas, T is the temperature of this gas, K, f is the coefficient of adhesion of molecules or atoms of the polluting gas to the surface of the part , after ion cleaning, the metal layer is applied and the nitrogen ions are implanted into the surface of the protective layer until a wear-resistant metal nitride is formed, for example Cr ₂ N or Fe ₄ N; during implantation, the nitrogen ions are mixed with hydrogen or helium or copper ions, magnesia act on the plasma 500-2000 Oe of acute-angled geometry, the ion treatment is carried out in pulsed or pulse-frequency modes of electric power supply to an ion source, a device for ion processing of machine parts and tools containing an evaporator, a target part, direct channel cathodes, an anode, an electric power system and vacuum pumping system, equipped with a gas discharge chamber and an ion-optical system made in the form of three coaxially arranged electrodes: emission, which is the internal wall of the gas discharge amers, accelerating and grounded with slots for drawing, focusing and accelerating several (3-76) radial planes directed to the axis of the device of argon or nitrogen ion beams or mixed beams of gas and metal ions, two cylindrical anodes and evaporators are installed in the gas discharge chamber, which placed direct-heating cathodes uniformly around the circumference and along the length of the outer surface of the wall of the cylindrical chamber, the outer surface of the gas discharge chamber is uniformly surrounded by permanent magnets, the surface area of the em SMAI electron cathodes is 4-6.5% of the area of the inner walls of the gas discharge chamber, the distance d ₂ between the grounded and accelerating electrodes is selected from the condition d ₂ = (0,3-0,8) d _3, and the distance d ₃ between the accelerating and emission electrodes are selected from the condition of electric strength U = 80 d $\genfrac{}{}{0ex}{}{\text{0.8}}{\text{3}}$ where U is the accelerating potential difference equal to 10-40 kV for optimal implantation conditions, the length of the emission slot holes L _Щ is determined by the length of the working section of the workpiece L _beats L _щ = (1,1-1,2) L _beats , the number of slots is calculated from the relations : N _u = πD / b _nq, b _nq = Δ _u + 2d _with tgθ _⊥ wherein d diameter parts, b _nq width of the beam on the workpiece surface, Δ _u slit width of emission, θ _⊥ divergence angle of the beam perpendicular to the gap emission, d _c = d ₁ + d ₂ + d ₃ d ₁ where the distance between the workpiece surface and the ground electrode, the electric power system is in the form sources of constant voltage and glow current of the cathode, an arc discharge, a high-voltage source of electrical power for an ion source, an electric power source of an accelerating electrode, the gas discharge chamber housing being connected to the positive terminal of a high-voltage electric power source of an ion source, an accelerating electrode connected to a negative terminal of the same source and such the same terminal of the electric power source of the accelerating electrode, the grounded electrode and the workpiece They are straight filament cathodes made of tungsten or its alloys, or lanthanum hexaboride in the form of two closely spaced rectilinear wires or rods, or bifilar winding, the other electric power system is made in the form of pulsed or pulse-frequency voltage and cathode filament current sources, an arc discharge, a high voltage source of electrical power for an ion source, a source of electrical power for an accelerating electrode, the pulse duration being varied from one millisecond to one ekundy and their repetition frequency of 0.1 Hz to 100 Hz.

In FIG. Fig. 1 shows a cross section of an ion source and a workpiece, as well as an electrical power supply system for cathodes, gas discharge, high voltage source and accelerating electrode; 2 is a longitudinal section through an ABCDE source; FIG. 3 addition of Gaussian distributions of ion current density on the surface of the part from four wide tape beams; in FIG. 4 for three such bundles; in FIG. 5 for 36 narrow beams having a divergence angle perpendicular to the emission gap of 1 ^o ; in FIG. 6 similarly to FIG. 5, but with said angle of 4 ^° ; FIG. 7 when using 76 tape bundles with a divergence angle of 4 ^o .

 In FIG. 1 and 2 show: cathodes 1, two anodes 2, gas discharge chamber 3, emission electrode 4, accelerating electrode 5, grounded electrode 6, inputs for supplying a gas or gas mixture 7, wires 8 for protective layers, permanent magnets 9, connector 10 of the source into two parts for installing the part, ion beam bundles 11, workpiece 12, cathode electrical power supply 13, arc discharge electrical power supply 14, high voltage ion power electrical source 15, accelerating electrode 1 electrical power source 6 and procrastination 8.17.

In FIG. Figure 3 shows the addition of Gaussian distributions, the number of which can be 3-76, the ion current density from four wide ribbon beams 11 with a half-width of a 2 cm and θ _⊥ = 1 ^q along the circumference of a part with a diameter of 25 mm, which create a non-uniform current density distribution in the total distribution 18 ions ± 1.2% of its average value.

In FIG. 4, the addition of three such beams creates a nonuniform current density distribution of ± 3.7%
In FIG. Figure 5 shows the total distribution of the ion current density from the addition of distributions from 36 narrow ribbon beams with a slit width of 0.4 mm in the emission electrode with a radius of 225 mm on a part with a diameter of 50 mm with an inhomogeneity of ion current density of ± 43%
In FIG. 6 shows a similar distribution, but the emission electrode radius 62.5 mm, diameter 25 mm and details θ _⊥ = 4 ^q, creating a heterogeneous distribution of ion current density ± 27%
In FIG. 7 the use of 76 similar ribbon beams and the above dimensions of the emission electrode and the diameter of the part reduces the heterogeneity of the distribution of ion current density on the surface of the part to ± 7.5%
In FIG. 3-7 it is clear that the main factors that significantly affect the total distribution of the ion current density from the addition of radially converging beams are the divergence angle of the tape beam perpendicular to the emission gap, the beam width in the emission hole, as well as the number of beams, the geometric dimensions of the part and the emission radius electrode. You can increase the divergence angle in the range of 1-15 ^{o in} various ways, for example, by increasing the radius of the edges of the jumpers forming the slots, and / or the width of the emission gap, and / or reducing the length of the accelerating gap.

 From the theory and practice of the ionic (cathodic) method of cleaning the surfaces of various materials from all kinds of contaminants, including oxides, metal carbides and polymer compounds, it is known that in order to obtain sufficiently clean surfaces, it is necessary to have an ion flux with a sufficiently high current density and ion energy, providing a spray rate significantly exceeding the rate of condensation of molecules and / or atoms of polluting gases or vapors coming together with the working gas from the walls of the vacuum chamber and the workpiece and vacuum pumps to the surface of the part.

This condition is written as inequality:
p _zg ≪ (2.2 • 10 ^-2 • j ₊ S _pl M $\genfrac{}{}{0ex}{}{\text{1/2}}{\text{sg}}$ T ^1/2 / f (I)
where p _{zg is the} pressure of the polluting gas, Pa, J ₊ is the ion current density, preferably argon, A / cm ² , S _{pl is} the atomization coefficient of the pollutant film, at / ion, M _zg and T is the molecular weight and temperature of the polluting gas, t is the adhesion coefficient (sorption ) molecules or atoms of a polluting gas to the surface of the ion-treated part. These gases include hydrocarbons, carbon oxides, nitrogen oxides.

Providing on the surface of the part 12 the pressure of the working gas, for example nitrogen, 10 ^-2 -10 ^-3 Pa, the pressure of all polluting gases 10 ^-3 -10 ^-4 Pa, M _sr 12 55, T 300 400 K, S _pl 0.2 3 at / ion, t 0.1 1, at a current density of argon ions of 0.2 to 100 mA / cm ² with an energy of 10-20 keV, the condition expressed by formula (I) will be satisfied.

To obtain the above values of the ion current density, a plasma with a high ion concentration (10 ¹⁰ -10 ¹³ cm ^-3 ) is needed, and to create ion beams with a current of 1-20 A, the plasma emission surface must be equal to 10 1000 cm ² . To obtain the indicated plasma parameters with sufficient uniformity in the distribution of the concentration and temperature of ions and electrons (5-10%), an arc discharge with incandescent cathodes 1 and two anodes 2 can be used at a working gas pressure of 3 0.7-4.7 Pa in the gas discharge chamber . It is possible to obtain a dense plasma using a microwave discharge.

 After ionic cleaning of the surface of the part, a film of the material of the protective layer, for example titanium or chromium, or ytterbium, or copper, is applied by cathodic sputtering or evaporation.

After ion cleaning and applying a protective coating, nitrogen is fed into the ion source instead of argon, nitrogen ion beams are obtained at approximately the same pressure values as argon, and nitrogen ions are implanted in a dose that ensures the formation of wear-resistant metal nitride of the part and / or protective coating, for example, Cr ₂ N or Fe ₄ N. With a sufficient current density of the ions of the working gas or a mixture of gases, such as nitrogen and argon, nitrogen and helium, the operations of ion cleaning and implantation are combined in one process.

The current density of the ions extracted from the plasma in the plane of the emission gaps is determined from the equation:
j ₊ = 8 • 10 ^-6 n ₊ T $\genfrac{}{}{0ex}{}{\text{1/2}}{\text{e}}$ M ^-1/2 (2)
where n _{+ is} the ion concentration, cm ^-3 , T _e is the electron temperature, K, M is the molecular mass of the ions, J ₊ is the ion current density, A / cm ² .

Table 1 for T _e 10 ⁵ K shows the values of the concentration of nitrogen ions n _{N +} and argon n _Ar + calculated by formula (2), which are necessary to obtain the ion diffusion current density of 0.0025 2.5 A / cm ² .

In the table. 1 also gives the minimum gas pressures necessary to obtain the required ion concentration with full ionization of the gases. In ionic sources of this type, the degree of ionization of gases is 30-60%
The distribution of the density and temperature of electrons in a gas discharge chamber, for example, of a cylindrical shape along the radius in a hydrogen plasma, substantially depends on the gas pressure. At a gas pressure of 0.65 and 1.3 Pa, the ion current density in the central part near the axis of the chamber is maximum and equal to 0.28 0.31 A / cm ² and 0.24 0.25 A / cm ² for a radius of 4 cm. Whereas at a pressure of 4.65 Pa in the central part of the chamber, the current density becomes minimal, 0.16 A / cm ² , and at a radius of 4 cm it increases to 0.25-A / cm ² . At an optimal gas pressure of about 1 Pa, the ion concentration and electron temperature are quite uniform. The ion concentration along the radius varies within 4–8% and the electron temperature is 4–5% of their average values.

With a flat plasma boundary, the current density of ions drawn from the plasma by an electric field is calculated according to the "three second" law
j ₊ = 5.4 • 10 ^{- 8} U ^3/2 d ^-2 M ^-1/2 ,
where j ₊ is the ion current density, A / cm ² , d is the distance between the emission and ion-accelerating electrodes, cm, M is the molecular mass of the ion.

 The ion source for ion processing of axially symmetric parts of machines and tools consists of cathodes 1 made of tungsten wires or wires deposited on them, for example, by plasma deposition, a layer of lanthanum hexaboride, and two anodes 2 made in the form of two cooled rings, insulated from the cathodes and gas discharge chamber 3. The cathodes are placed in pairs in the chamber 3 evenly around the circumference of its outer wall. The emission electrode 4 is made of a refractory material, for example, of a molybdenum alloy containing vanadium (0.5 to 1.0 wt.). Along the generatrix of this water-cooled electrode, there are linear slits in an amount of 3 to 76 depending on the size of the workpiece 12. When processing some parts with annular working surfaces, for example, broaches, in the emission electrode 4, accelerating electrode 5 and grounded the electrode 6 make a gap of a ring shape. Inputs for supplying argon, nitrogen or gas mixture are arranged uniformly in azimuth of the upper and lower parts of the gas discharge chamber 3. Evaporators 8 are made of a protective coating material, which must be applied to the part, for example, from titanium, copper, yttrium or other wires. Permanent magnets 9 are made of ferrite or a neodymium-iron-boron alloy, which provide a magnetic field of acute-angled geometry of 500 1000 Oe on the inner surface of the external cylinder of the chamber 3. Connectors 10 provide installation of parts of complex configuration in the ion source that exceed the internal diameter of the grounded electrode 6 or the overall dimensions of the ion source, for example, the crankshaft of a car, marine engine, endoprosthesis. The electric power supply system of the ion source includes sources of constant voltage and current for heating the cathodes 13, arc discharge 14, high voltage 15, accelerating electrode 16 and evaporators 17.

The method of use and operation of the ion source for ion processing of axially symmetric parts and tools are as follows. The workpiece 12 is placed along the axis of the ion source so that the surface to be treated is in the area of impact of the tape or concentric or segmented or other necessary shape of elementary (single) or continuous ion beams consisting of single beams converging to the axis. The direct-channel cathodes 1 are supplied with electric voltage from a power source 13, which causes an electric current to pass through them, the current density of which is sufficient to heat their surface to a temperature that provides emission of thermoelectrons with a current density of about 30 A / cm ² . When using tungsten cathodes, the temperature of their electron emission surface should be equal to 3150 K. If cathodes made of lanthanum hexaboride are used, then the temperature of the electron emission surface is lowered to 1500 K.

Оптимальное значение первеанса пучка равно (1,2 1,4)• 10^-7 A•B^-3/2)•см^-2. Распределение плотности тока ионов аргона или азота перед началом ионной очистки или ионной очистки и имплантации одновременно измеряют по длине и азимуту суммарного сходящегося к оси ионного источника пучка ионов при помощи системы электрических зондов. Результаты этих измерений фиксируются в памяти компьютера. Зонды раздвигаются на длину обрабатываемого участка и во время обработки детали 12 с двух сторон регистрируют распределение плотности тока по окружности в начале и конце обрабатываемого участка.Argon is supplied to gas discharge chamber 3 by means of inlets 9. An electric voltage of about 100 V is supplied between the cathodes 1 and the anodes 2. At an argon pressure of 0.7 4.7 Pa, an arc discharge is ignited between the cathodes 1 and the anodes 2. After that, or until the discharge is ignited, a positive polarity voltage of 15 20 kV is supplied to the gas discharge chamber 3 from the source 14, and a negative polarity voltage is supplied to the accelerating electrode 5 from the power source 16. In the region of emission gaps, the plasma boundary under the action of an extracting ion of an electric field is shaped like a meniscus, concave toward the accelerating electrode 5. From the emission gaps, elementary ribbon ion beams 11 are pulled, focused and accelerated. Under optimal conditions for the generation and stretching of ions, laminar beams with small angles are obtained discrepancies perpendicular to the gap θ _⊥ = 1-2 ^° and along the gap

The optimal value of the beam perveance is (1.2 1.4) • 10 ^-7 A • B ^-3/2) • cm ^-2 . The distribution of the current density of argon or nitrogen ions before ion cleaning or ion cleaning and implantation is simultaneously measured by the length and azimuth of the total ion beam converging to the axis of the ion source using an electric probe system. The results of these measurements are recorded in the computer memory. The probes are extended to the length of the treated section and during processing of the part 12, the distribution of the current density around the circumference at the beginning and end of the treated section is recorded on both sides.

 Cleaning the surface of the part from contamination is monitored and recorded using a mass spectrometer or a device that measures the energy spectra of reflected electrons with an energy of 1 20 keV. When reducing the current signals characterizing the level of polluting atoms and molecules to a predetermined value, turn off the flow of argon into the ion source through the inlets 7 and turn on the valve for introducing nitrogen into it. The process of implanting ions into the material of the part begins before the formation of iron or chromium nitrides, which have increased wear resistance. Then, evaporators 8 are turned on and a protective coating is applied while it is bombarded with nitrogen ions to form nitride of the coating material, which has increased wear and corrosion resistance. After performing the above ion processing operations, the part is removed from the treatment zone and a new part is installed in its place. All ion processing operations are repeated.

Ion-treated parts are sent for post-implantation annealing and, after cooling to 50 ^° -70 ^° C, they are sent to the storage of finished parts or, through a lock chamber, they are taken out of the vacuum chamber to the atmosphere.

The distribution of current density J ₊ (x) of nitrogen ions or mixtures of gases with an energy of 15 25 keV perpendicular to the emission gap is written in the form of a Gaussian formula:
J ₊ (x) J ₊₀ exp (-x ² / a ² ) (4)
where J ₊₀ is the ion current density at the distribution maximum equal to 1 100 mA / cm ² , x is the distance from the center of the slit, and the half-width of the current density distribution at the height of maximum 1 / е is equal to 1 4 cm. Consider the current density distribution around the part circumference, equal to 78.5 mm when using four tape bundles with J + ₀ 1 mA / cm ² and a 2 cm, converging to the axis of the part in planes located 90 ^o in azimuth.

 The results of calculations by the formula (4) are given in table 2.

In FIG. Figure 3 shows the distribution of ion current density for four tape beams 11 and the total distribution 18 on the surface of the part 12 with a diameter of 25 mm. From FIG. 3 it can be seen that for these conditions, the heterogeneity of the ion current density around the circumference of the part is ± 1.2% of the average ion current density of 1.76 mA / cm ² .

When using three ribbon ion beams irradiating part 12 under the same conditions as above, but the beams fall to the surface in planes located at 120 ^° in azimuth, as can be seen from FIG. 4, the azimuthal heterogeneity of the current density distribution 18 from the addition of the three beam distributions 11 is ± 3.7% and the average value is 1.35 mA / cm ² . This version of the cylindrical ion source is somewhat worse than the first, but is quite suitable for use.

 In the examples given, wide ribbon bundles are obtained from elementary ribbon bundles with a slit width of 2 mm in the emission electrode and a 4 mm pitch between adjacent slots. Under these conditions, high vacuum pumps with high pumping speeds are required. To reduce it, it is necessary to reduce the gas flow from the gas discharge chamber 3 by reducing the width of the slots in the emission electrode 4.

In FIG. Figure 5 shows an example of irradiation of a part with a diameter of 50 mm by 36 tape beams with an emission slit width of 1 mm at θ _⊥ = 1 ^° with a radius of emission electrode 4 equal to 225 mm. It is seen that the heterogeneity of the distribution of the ion current density on the surface of part 12 in azimuth is ± 43%. Such a large heterogeneity of irradiation of the surface of the part is sometimes necessary.

When irradiated with elementary tape beams, when the width of the emission gap is 0.4 mm and the divergence angle is θ _⊥ = 2 ^q on the surface of a part with a diameter of 25 mm, the azimuthal inhomogeneity of the current density distribution is seen from FIG. 6, is equal to 51.5%. If the same 36 elementary beams are used, but the angle θ _{⊥ is} increased to 4 ^o , then the heterogeneity of the distribution decreases to 27%. Increasing the number of elementary beams to 72, as can be seen from FIG. 7, the inhomogeneity value is obtained. azimuth current density distribution of the total beam ± 7.5%
The above examples show the wide possibilities of using elementary ribbon beams to change the azimuthal distribution of the ion current density over the machined surface of a cylindrical part.

The distance d ₁ between the surface of the workpiece and the grounded electrode is selected from the condition of ensuring sufficient conductivity of the pipeline to the flange of the high vacuum pump. The gas flow Q Pa • m ³ / s supplied to the ion source to obtain an ion beam with a current I A is determined by the formula:
Q = 0.023 I / η _g (5)
where η _{g is the} gas efficiency of the ion source, equal to 30-50% for arc sources.

If the ion current varies between 0.2-25 A, and η _g = 0.5, then Q is 0.0092-1.15 Pa • m ³ / s. For η _g = 0.3 in the indicated range of ion currents, Q is 0.0154-1.925 Pa • m ³ / s.

The conductivity G of the short pipeline is determined by the Clausing formula
G 116 K • F (6)
where K is the Clausing coefficient, Ф is the area of the inlet section of the pipeline.

For the ratio of the length of the pipeline to its diameter 400: 100 = 4, the value K = 0.23, and F = 0.0785 m ² G _n = 0.21 m ³ / s. With a constant gas flow to obtain a nitrogen ion current of 0.2 A, Q = 0.0092 Pa • m ³ / s, for the speed of pumping S _n diffusion steam-oil pump 4.9 m ³ / s, the speed of pumping of the ion source S ₀ is determined from the formula:
S ₀ S _n G / (S _n + G), (7)
which gives a value of 1.5 m ³ / s.

The gas pressure in the area of placement of the workpiece will be equal to p _d Q / S _o = 9.2 • 10 ^-3 / 1.5 = 6.1 • 10 ^-3 Pa. The maximum residual pressure created, for example, by a pump of the brand N-400/7000, has a value of 6.5 • 10 ^-3 Pa. This vacuum pump will provide the operation of the considered example of a cylindrical ion source.

In order for the gas discharge with incandescent cathodes to burn stably, and the plasma to be homogeneous and provide a calculated current density of ion emission, the electron current density in the discharge must meet the Langmuir criterion: the latter must exceed the first with respect to M $\genfrac{}{}{0ex}{}{\text{1/2}}{\text{+}}$ / M $\genfrac{}{}{0ex}{}{\text{1/2}}{\text{e}}$ . For ions, this ratio is 180, and for argon ion 272. Similar requirements are placed on the ratio of the discharge current to the ion emission current [3]
To obtain a uniform discharge with a small burning voltage of the order of 30-55 V, it is necessary that the cathode emission surface is 4-7% of the surface area of the gas discharge chamber. For example, to obtain hydrogen ion beams with a current of 35, 75, and 110 A, the optimal values of the discharge current are respectively 1300, 3500, and 3000 A. The ratio of the discharge current to the ion emission current is in the range 27-47, and according to the Langmuir criterion for a purely flowing beam it should be equal to 43. The optimal ion current density is 0.35-0.5 A / cm at a current emission density of thermoelectrons of 30 A / cm ^{2 of} tungsten cathodes heated to a temperature of 3150 K. The ratio of the current density of electrons and hydrogen ions in the discharge is within 60-86. In the gas discharge chamber and in the beam there is a significant amount of hydrogen ions with a mass of M = 2 and M = 3. In cases of a predominant content of these components, the Langmuir criterion value for them is 61 and 75, respectively. In connection with the foregoing, to obtain beams of nitrogen ions with an emission current density of 1 and 100 mA / cm ^{2, the} required values of the electron emission current density are 0.18 and 18, respectively A / cm ² . When receiving beams of argon ions with the same current density, ions, current density of electron emission increase, respectively, to 0.27 and 27 A / cm ² . In addition to tungsten, lanthanum hexaboride can provide such high current densities of thermoelectrons, moreover, at a temperature of only 1,500 and 2,000 K.

When stretching and electrostatically focusing laminar weakly diverging beams of hydrogen ions with currents of tens of amperes designed to heat the plasma to thermonuclear temperatures (100 million K), based on theoretical calculations of the ion trajectory and experiments, the optimal geometric shapes and sizes of unit cells with gaps in electrodes: emission, accelerating and grounded and the distance between them. The width of the gap in the emission electrode is selected from the condition: Δ _u = 0.5 d and in the accelerating electrode Δ _y = 0.6 d where d = 1.43 (t ₁ + d ₃ ), where t _{1 is the} thickness of the emission electrode in the region of the emission gaps . The width of the gap in the grounded electrode is determined from the ratio Δ _ze = 1,5d. The distance d ₂ between the grounded and accelerating electrodes is selected from the condition of giving the necessary geometry of the boundary of the secondary plasma of the ion beam: d ₂ (0.29-0.8) d ₃ , and the distance d ₃ between the accelerating and emission electrodes is selected from the condition of the electric strength of the accelerating gap : U = 80 d $\genfrac{}{}{0ex}{}{\text{0.8}}{\text{3}}$ , where U is the accelerating potential difference equal to 10-40 kV, selected from the optimal conditions of ion implantation. The thickness of the electrodes t ₁ 1-2 mm is selected from the condition of mechanical rigidity of the design of the electrodes.

The length of the slits in the electrodes is selected depending on the length of the working portion of the workpiece _w L (1,1-1,2) l _sp. The number of slots N _u is calculated from the relations: L _u = πD / b _nq, b _nq = Δ _u + 2d _with tgθ _⊥, where D diameter parts, b _nq width of the beam on the workpiece surface, Δ _u slit width of emission, θ _⊥ arrangement angle the beam perpendicular to the gap, d _c d ₁ + d ₂ + d ₃ , where d _{1 is the} distance between the surface of the part and the grounded electrode.

The exact number of emission slots, their width is determined depending on the required heterogeneity of the ion current density distribution over the azimuth of the cylindrical part, its diameter, and the graphical analytical method shown in FIG. 3-7. To obtain the necessary uniformity in the distribution of the ion current density, one can use elementary ribbon beams with divergence angles θ _⊥ = 4–20 ^q . Such divergence angles are obtained by rounding the edges of the emission slits in the emission electrode. For this, tubes of plastic molybdenum-vanadium alloy grade 4604 with a diameter of 3-4 mm and a wall thickness of 0.3-0.5 mm can be used.

 The value of the accelerating voltage supplied to the ion source from the power source 15 is selected from the optimal process conditions: ion surface cleaning from contamination, stimulation of the application of protective coatings by ion bombardment, ion implantation, with the formation of nitrides, carbides, borides, oxides, ion lithography; the necessary performance of these processes; as well as the necessary energy efficiency of the installation of ion-beam processing of machine parts, tools, endoprostheses, seeds of grain and vegetable crops.

For example, the speed of ionic surface cleaning is determined by the formula:
v _p = 10 ^-5 j ₊ S _pl M _m / ρ _pl , (8)
where U _{p is} the distribution rate, cm / s, J _{+ is} the current density of the bombarding ions, A / cm ² , S _{pl is} the sputtering coefficient of the contaminating film, M _{m is the} molecular weight of the film material, ρ _pl is the film density, g / cm ³ . The sputtering coefficient of most materials with argon ions increases rapidly with increasing ion energy and reaches 2–3 at / ion at an energy of 10–20 keV. Therefore, for the process of ionic cleaning of surfaces from contamination, the aforementioned ion energy range is optimal from the point of view of the necessary spraying rate. Keep in mind that at angles of incidence of ions on the surface of 50 85 ^{o the} value of the sputtering coefficient increases by 2 -4 times, and for light ions up to 10 times.

The implantation of nitrogen ions in various structural and instrumental metal materials on experimental industrial implants is carried out at maximum ion currents in the beam of 20-30 mA, current density of 5 10 μA / cm ² at an ion energy of 40 100 keV, sometimes 2 3 MeV, but at currents ions of the order of 1 mA. In experiments with mixed beams of carbon and hydrogen ions with an energy of 200 300 keV at an ion current density of 100 200 A / cm ² and a pulse duration of 50 100 ns, the optimal energy density in one pulse of 3 J / cm ^{2 was established} .

In our experiments using beams of nitrogen ions, mixed beams of ions of nitrogen and hydrogen, nitrogen and helium with an ion current of 5 7 A, with an ion current density of 1 80 mA / cm ² , an ion energy of 15 25 keV, a pulse duration of 1 20 ms and a density energy in one pulse 3 1200 J / cm ^{2 the} optimal dose of ion processing energy is found to be equal to 300 400 J / cm ² . The possibility of increasing 2 3 times the wear resistance of a number of structural and tool steels is shown: 3, 65G, SHH15, 40X, HRG, high-speed steels R6M5, P18, hard alloys T15K6, T5K10, as well as corrosion resistance 3 6 times stainless steel X18H10T and titanium alloy VT1 in solutions of sulfuric acid, and aluminum alloy D16 3 times standard test solution.

Processing Art. 3 by nitrogen ions with a dose of 1 • 10 ¹⁷ cm ^-2 led to a decrease in the friction coefficient by 19%, an increase in microhardness by 20% and an increase in wear resistance by a factor of 2.5. Elements of the working bodies of 65G steel tillage tools implanted with nitrogen ions during abrasion tests at a speed of 2 m / s on a loosening length of 96 km of soil consisting of sand (67%) and clay (33%) showed a decrease in linear wear of the blade 1.9 times compared with unimplanted samples. The floating nylon cutting knives of the Eva and Eva-R hosiery machines made of 65G steel, treated with nitrogen ions, worked for 10 weeks under the production conditions of the hosiery factory, while non-irradiated ones were replaced after 2 weeks of operation.

The productivity of the processes of ion processing of the surface layers of all kinds of materials is determined by the values of current and current density of ions on the part, as well as the mode of operation of the ion source. In the prototype, the current of nitrogen ions reached 3 mA, and the current density of 0.091 mA / cm ² . In the proposed method and device, the ion current to the part (the rod of the suspension strut of a passenger car with a diameter of 24 mm, a total length of 388 mm, a length of a hardened section of 258 mm) at optimal ion energies of 15 20 keV in continuous operation is 95 126 mA, and the current density nitrogen ions 0.49 0.69 mA / cm ² . The performance of ion processing will increase 16 22 times.

If you use for implantation of nitrogen ions with a dose of 2 • 10 ¹⁷ cm ^-2 Z 100 implant with a source of Freeman ions with one tape beam of nitrogen ions with a cross section of 2 x 20 cm ² with a current of 7 mA and an energy of 100 keV, at an ion current density of 0.175 mA / cm ² , then to uniformly irradiate the working surface of the part, it will be necessary to irradiate it in at least 8 positions at 45 ^o around the circumference, in each of which it is necessary to move the part to the full length of the hardened area. The implantation performance of the proposed ion source in comparison with the source of Freeman is 29 41 times higher.

 The ion sputtering coefficient of argon ions is 2 3 times greater than that of nitrogen ions; therefore, the rate of ion cleaning from contamination by argon ions will be 2 3 times higher than nitrogen ions.

When using beams of nitrogen ions having a current density of 1 mA / cm ² and above, the depth of the hardened layer is several microns, approximately 300 times greater than the range of nitrogen ions with an energy of 15 20 keV. When using pulsed beams of nitrogen ions with a current density of more than 10 mA / cm ^{2 the} thickness of the layer of steel ШХ15 with a microhardness of 900 kgf / mm ² reaches 50 μm and at a depth of 125 μm decreases to 700 kgf / mm ^{2 of} hardened steel. If you use a beam consisting of nitrogen ions and hydrogen ions, then the microhardness of the surface layer decreases slightly (to 860 kgf / mm ² ), while the thickness of the hardened layer increases to 80 μm and decreases to the microhardness of hardened steel at a depth of 150 μm. Similar results are obtained by implanting a mixed beam of nitrogen ions with helium ions in tool steel X12M. Subsequent thermal annealing increases the depth of the hardened layer of this steel to 200,250 microns, which is ten thousand times the ion range.

The heterogeneity of the distribution of ion current density on the surface of the workpiece in the mentioned industrial and other implants is 50-60% of the average value. In the proposed variants of ion sources with elementary tape bundles converging to the axis, this heterogeneity can be equal to 1.2 7.5%
The pressure of the working gas and polluting gases in the prototype is 1 • 10 ^-1 Pa, and in the proposed source they can be 6.1 • 10 ^-3 Pa.

 The adhesion of the protective coating to the surface of the workpiece increases by 2 3 times due to the cleaning of the surface from contamination, the formation of condensation centers and the energy activation of condensation processes and the formation of chemical compounds.

 Lowering the accelerating voltage from 100 300 to 15 20 keV reduces the wavelength of X-ray radiation by 5 20 times, which is created by ions and secondary electrons of the beam. X-ray radiation becomes "soft" and is almost completely absorbed by the walls of the vacuum chamber.

 A decrease in the accelerating voltage by a factor of 5–20 increases approximately the same amount of energy by the energy efficiency of the implant.

Claims (9)

1. The method of ionic processing of machine parts and tools, including ionic cleaning of the surface from contaminants, applying a protective layer to the work surface and implantation of nitrogen ions to form metal nitride on the surface of the part, characterized in that the surface is cleaned by an intense beam of argon ions obtained from plasma a gas discharge with a high concentration of ions (10 ¹⁰ 10 ¹³ cm ^-3 ) in a gas discharge chamber with an argon pressure of 0.7 4.7 Pa, and on the surface of the workpiece a working gas pressure P _rg and partial yes the _{occurrence of} surface polluting gases P _{zg is} supported from the conditions P _rg 10 ^-2 10 ^-3 Pa, P _zg << (2.2 • 10 ^-2 • j ₊ • S _pl • M _zg ^{1 / 2} / f), where j ₊ current density of argon ions, A / cm ² , S _{PL the} coefficient of dispersion of the polluting film, at / ion, M _{sg the} molecular weight of the polluting gas, T the temperature of this gas, K, f the coefficient of adhesion of molecules or atoms of polluting gas to the surface of the part. 2. The method according to claim 1, characterized in that as the metal nitride on the surface form Cr ₂ N or Fe ₄ N.  3. The method according to p. 1, characterized in that the implantation is carried out by bundles of nitrogen ions, additionally containing hydrogen ions, or helium, or copper.  4. The method according to claim 1, characterized in that the plasma is exposed to a magnetic field of acute-angled geometry with a strength of 500 to 2000 E.  5. The method according to p. 1, characterized in that the ion processing is carried out in a pulsed or pulse-frequency regime of the electrical power of the ion source.  6. A device for ion processing of machine parts and tools, containing an evaporator, a part, direct heating cathodes, an anode, an electrical power system and a vacuum pumping system, characterized in that it is equipped with a cylindrical gas discharge chamber and an ion-optical system made in the form of three coaxial located electrodes with slots for focusing and acceleration in radial planes directed to the device axis of argon or nitrogen ion beams or mixed ion beams, the external of which is emission the morning wall of the gas discharge chamber, and the subsequent electrodes are accelerating and grounded, the anode and the evaporator are installed in the gas discharge chamber, and the direct glow cathodes are located in the gas discharge chamber uniformly around the circumference and height of the outer wall, while the anode is made in the form of two rings.  7. The device according to claim 6, characterized in that it is equipped with permanent magnets located on the outer surface of the gas discharge chamber. 8. The device according to claim 6, characterized in that the area of the emission of electrons from the surface of the cathodes is 4.0 to 6.5% of the area of the inner walls of the gas discharge chamber, the distance between the grounded and accelerating electrodes is 0.3 0.8 the distance d ₃ between accelerating and emission electrodes, which is selected from the condition of electric strength U = 80 d $\genfrac{}{}{0ex}{}{\text{0.8}}{\text{3}}$ , the length of the radiation gap is 1.1 1.2 the length of the treated part area, the number of slots is determined from the ratio N _u = πD / b _pd , and b _pd = Δ _u + 2d ₁ tgθ where N _u number of slots, b _p. the width _d of the radiation beam on the workpiece, D the diameter of items, Δ _u - slit width, θ beam divergence angle perpendicular to the slit, d ₁ - the distance between the workpiece surface and a grounded electrode, U accelerating potential difference equal to 10 to 40 kV for optimum implantation conditions.  9. The device according to claim 6, characterized in that the electric power system is made in the form of cathode electric power sources, an accelerating electrode, an arc discharge and a high-voltage electric power source of an ion source connected by a positive terminal to the gas discharge chamber body, and a negative one with an accelerating electrode, which is connected to the negative terminal of the accelerating electrode electric power source, the direct cathodes are made of tungsten or its alloys or lanthanum hexaboride in ide straight wires or bifilar winding.

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