RU1670968C - Method for steel articles treatment - Google Patents

Abstract

The invention relates to metallurgy, in particular to methods for surface hardening of steels. The aim of the invention is to increase the wear resistance of products by increasing the depth of the modified layer, its microhardness and process performance. The method includes hardening of steel products and implantation with beams of positive ions of nitrogen or nitrogen and hydrogen, or nitrogen and gels with an energy of 10-20 keV, fluence 2 "1016- 2-1017 cm 2 at a current density of 500 mA / cm and a pulse duration of the ion current of 1 20 A. Determined from the ratio oot (T-T) rrpck / 4x (iE). where T is permissible; n addend 0 | 1 is the product surface temperature, °C; T is the initial surface temperature of the article, °C; p.ck, respectively, density, specific heat and thermal conductivity of steel; j and E are the current density and ion energy, respectively. With a chain to further increase wear resistance by further increasing the depth of the modified layer, after implantation, tempering is carried out at 520-700 ° C. This allows you to increase the depth of the hardened layer by several orders of magnitude, increase the microhardness by 1.3 - 1.6 times, wear resistance by 1.5 - 2.0 times in comparison with the prototype 1

Description

The invention relates to metallurgy. in particular, surface hardening methods for steels.

The aim of the invention is to increase the wear resistance of products by increasing the depth of the modified layer, its microhardness and process productivity.

The method includes hardening of steel products and implantation with beams of positive ions of nitrogen, or nitrogen and hydrogen, or nitrogen and gel with an energy of 10-20 keV, fluence 2 1016-2 10 at a current density of 1-500 mA / cm and the duration of the ion current pulse 1-20 A, determined from the ratio:

Guy (TDop-T) 2 pc1 / 40E) 2,

where Tdop - permissible temperature on the surface of the part;

T - initial surface temperature

sti, C;

/ e, s, k — density, respectively, specific heat and thermal conductivity of steel;

j and E are the current and ion densities.

In order to further increase the wear resistance by further increasing the thickness of the hardened layer after implantation, tempering is carried out at a temperature of 520-700 ° C. The increase in surface hardness is 130-150% compared with the prototype, and the thickness of the hardened layer increases by 3-25 thousand times.

At ion current densities less than 1 mA / cm, there is no process of a substantial increase in the thickness of the hardened layer compared to the mean free path of ions in steel (Table 1). In addition, with an ion current density of less than 1 mA / cm, the process of ion implantation requires a long time.

It is difficult to obtain ion beams with a current density above 500 mA / cm and a nitrogen ion current of more than 20 A with a current pulse duration of 1-1000 ms due to the limitation of current density by volume charge and electrical devices. The introduction of 10% of H or He ions into a nitrogen ion beam increases the thickness of the hardened layer by 20% (see table).

The proposed method of processing steel products is implemented as follows.

The implantation of intense pulsed beams of nitrogen ions or mixed beams of nitrogen and nitrogen ions or nitrogen and gel ions is carried out using a vacuum clmer with a volume of 1 mg using HOHOEI sources generating ion beams with a current of 10-30 A, an energy of 10-40 keV, and a pulse duration of 1-1000 ms The drawing shows a diagram of an electrophysical installation for implantation.

The drawing shows: an ion source 1, a vacuum chamber 2, an ion beam 3, a movable rotating target 4, article 5, a stationary target 6, probes 7, pipe 8 /

Wilson seal 9, buffer volume 10, gate 11.

In a vacuum chamber using diffusion pumps equipped with traps cooled by liquid nitrogen,

get a vacuum of 5 Pa. An ion accelerating voltage and a voltage are applied to the electrodes of the ion-optical system, which inhibits the electrons produced in the beam plasma. In an ion source at

nitrogen pulse or a mixture of nitrogen and hydrogen or nitrogen or gel is supplied from a mixer cylinder by means of a pulsed leakage with an electromagnetic valve. Tungsten wire cathodes are heated

up to 3150 K to obtain an electron emission current of 30 A / cm. A voltage is applied between the cathodes and the anode and the discharge is ignited. In an ion source without an external magnetic field of the IVM-5 type at optimal

At a discharge current of 1300 A, at a discharge voltage of 50 V, 42 elementary beam bundles with a hydrogen ion current of 35 A are pulled out of 42 emission slots with an area of 67 cm and an accelerating voltage of 25 kV. The initial beam cross section is 8x18 cm2. The beam divergence angle across the emission cracks is 2 °, and along the cracks 0.5 °.

In an ion source with a peripheral constant magnetic field around an IPM-2 gas-discharge plasma with a discharge current in nitrogen of 828 A and an accelerating voltage of 21.2 kV, a beam of nitrogen ions with a current of 9.4 A was obtained with a pulse duration of 20 ms.

A beam of nitrogen ions or a mixed beam of nitrogen and hydrogen ions or nitrogen and gel ions is directed to a stationary target 6, where the current density distribution is measured using probes 7 installed through 20 and 26 mm along the X and Y axes

ions along these directions. Changing the geometry of the emission, accelerating, and grounded electrodes, for example, along a radius of 2 or 3 m, and / or displacing two or four lattices of the accelerating electrode relative to the central lattice of the emission electrode, and also changing the discharge current and the ratio of voltages at the accelerating and intermediate ELRKFLD-CH receive either uniform or

distribution of the ion current density over the surface of a stationary target.

Samples or parts mounted on the upper and lower planes of the movable target 4, along the axis of this target, are introduced from the buffer volume into the vacuum chamber 2. Depending on the required dose of ions, 10-100 pulses of ion current are applied to the movable target with flat parts . Parts of a cylindrical shape, for example, a set of cutting mills made of high-speed steel P9, P18, P6M5. in the amount of 50-100 pcs, are implanted with rotation around the axis by 45-60 ° C depending on their diameter (19-75 mm).

In a number of cases, the mechanically and thermally treated parts should not be heated above 300 ° C during ion implantation using intense and powerful pulsed beams. In accordance with the above formula, when irradiating iron, s / e-7.9 x 10 kg / m3 with 450 J / mg deg to - 59 W / m deg ion beam with an energy of 20 keV and a current density of 20 and 200 mA / cm2, the duration of the pulses leading to a temperature increase of 300 ° C is 900 and 9 ms, respectively. The ion fluence per pulse will be 1.1 1017 and 1.1 1016 cm 2, respectively. However, in the first case, one pulse is possible within 1 s, and in the second case, in principle, 100 times more, but taking into account possible overheating from the sequence pulses and heat sink conditions - approximately 30 pulses.

Example 1. In the described installation, nitrogen ions were implanted in the form of disks with a diameter of 30 mm and a thickness of 2 mm made of low-alloy steel ШХ-15, widely used in ball-bearing industry.

The microhardness in a layer up to 125 microns thick varies from up to an initial value of 700 kg / mm2.

Example 2. Samples of steel SHKh-15 according to example 1 were irradiated with a mixture of N + H ions with an energy of 15 keV with a fluence of 6 1017 cm and pulses of a duration of 20 ms at an ion current density of 100 mA / cm2. The thickness of the hardened layer increased to 150 microns.

Example 3. Conducted ion treatment of alloyed tool steel of the ledeburite class grade X12M (1.6% C, 12% C, 0.2% V. 0.5% Mo). After quenching to HRC 56-57, samples were implanted.

a mixture of nitrogen and hydrogen ions with an energy of 20 keV pulses lasting 7 ms to a fluence of 2 1017 cm. The thickness of the hardened layer with a change in Nuo from 900 to 650 kg / mm2 was 120 μm. Then, the samples were tempered at 450, 500, 600, 700, and 750 ° С, including critical points of phase crystallization and coagulation of perlite and austenite phases for 1.5 h. The thickness of the hardened layer increased to 250 μm, and the microhardness to 1100 kg / mm in the surface layer.

Example 4. Conducted implantation of steel X12M with a mixture of nitrogen ions and gels with an energy of 20 keV to a fluence of 3 101. The thickness of the hardened layer with a microhardness of N 100 700-650 kg / mm2 was 150 μm. Then, the samples were tempered at a temperature of 450, 500, 600, 700, and 750 ° С for 1.5 h. The thickness of the hardened layer with a Newo microhardness of 820–640 kg / mm increased to 275 μm.

The thickness of the hardened layer after implantation of intense pulsed beams of nitrogen ions and mixed beams of nitrogen and hydrogen ions or nitrogen and gel ions amounted to 100-150 μm compared to 0.011-0.34 μm in the prototype. Additional heat treatment increased the thickness of the hardened layer to 225-275 microns. The microhardness of the hardened layer was 900-1100 kg / mm2.

The proposed method of ion implantation by intense pulsed mixed ion beams provides hardening of steels by a thickness of 100-180 microns, which is 2900-25500 times the thickness of the hardened layer of the prototype. The microhardness of the hardened layer is increased by 130-160% compared with the unimplanted deep layer of steel or by 113-125% compared with the prototype. The implantation and ion nitriding of steels was carried out at 100-300 ° C, which is 1.8-5.5 times lower than the temperature of gas nitriding, equal to 550 ° C. Intense pulsed ion beams with a surface density of 2-60 MW / m2 and an energy of 1-1200 kJ / m with a beam cross-sectional area of 10x40 cm2 also provide high-temperature implantation, quenching and melting of the surface layer of steels and refractory metals, including tantalum and tungsten.

(56) U.S. Patent Mg 3900636, cl. C 23 C 17/00, 1975.

Note - hiding length of indenter ligonation

Claims (1)

The claims 1 METHOD FOR PROCESSING STEEL PRODUCTS comprising hardening and ion implantation, characterized in that, in order to increase the wear resistance of products by increasing the depth of the modified layer, its microhardness and productivity of the process, the implantation is carried out by intense pulsed beams of positive ions of nitrogen, or nitrogen and hydrogen, or nitrogen and gels with an energy of 10 - 20 keV, fluence of 2 1016 - 2 10 cm at a current density of 1 - 500 mA / cm and a pulse duration of the ion current of 1 - 20 A, defined by the following relation ty (Tdop - T) 2lrsk / 4G JE) 2 where Tdop - allowable surface temperature of the product, C, T - initial surface temperature products, С, р, с, к - density, respectively specific heat and coefficient thermal conductivity of steel J and E - current density and ion energy 2 The method according to claim 1, characterized in that, in order to further increase the wear resistance by further increasing the depth of the modified layer, after implantation, the wire; at 520 - 700 C at . 9 J-u k j Th 10 eleven | i. N  G-1 fl f-lL L v with Nz g + Ng N2 + He