Method for modifying surface layer of titanium alloy part

Abstract

FIELD: alloys.SUBSTANCE: invention relates to a method for modifying the surface layer of a part made of a titanium alloy. The surface of the part is activated by magnetic pulse treatment with a pulse energy selected from the range of 3.0 to 5.0 kJ, with a number of pulses from 10 to 50. Then, ion-implantation treatment of the surface of the part is carried out with nitrogen ions at an ion energy of 20 to 40 keV, a radiation dose of 1.2⋅1017 to 1.3⋅1017 cm-2 and the rate of increase in radiation dose from 0.7⋅1015 to 1.2⋅1015 s-1.EFFECT: increased fatigue strength of titanium alloy parts.1 cl, 1 ex

Description

[0001] The invention relates to metallurgy, in particular to methods of chemical-thermal treatment of parts made of titanium and titanium alloys, and can be used in aircraft and power engineering for surface hardening of parts operating under conditions of alternating loads.

[0002] Methods for modifying the surface layer of a component (SU 1441792 A1, RU 2111264 C1) are known. These methods involve irradiating the entire work surface with a high-energy, nanosecond-duration ion beam with a significant pulse dose. This creates a molten layer on the surface of the irradiated component, approximately equal in depth to the ion path length in the metal being processed. Upon cessation of irradiation, thermal conductivity causes the bulk of the material to heat up and the surface to cool. This results in the formation of a glassy layer, followed by a layer with a modified phase composition and a high density of dislocations, loops, and stacking faults, as well as smaller grain sizes and interphase boundaries than the original sample. This modified layer extends to a depth of 80-200 μm.

[0003] A disadvantage of known methods (SU 1441792 A1, RU 2111264 C1) is the formation of microcraters on the irradiated surface. Craters formed on the surface of parts made of metals and alloys can lead to a decrease in the level of operational properties of the products, primarily a decrease in fatigue strength and corrosion resistance (see Shulov V.A., Remnev G.E., Nochovnaya N.A. et al. The phenomenon of crater formation during the interaction of powerful ion beams with the surface of metals and alloys / / Surface. Physics, Chemistry, Mechanics. - 1994. N. 7. pp. 117-128).

[0004] A method is known for modifying the surface layer of a part, which consists in the fact that before applying a multilayer coating, ion implantation with nitrogen ions and post-implantation tempering are carried out, which is combined with the application of the multilayer coating, and the multilayer coating is applied by multiple alternation of layers of titanium and titanium nitrides, and post-implantation tempering and application of the multilayer coating are carried out in one vacuum volume in one technological cycle (RU 2226227 C1).

[0005] However, the known method (RU 2226227 C1) does not ensure an increase in the fatigue strength of the treated parts, since the difference in the properties of the coating and the base material and their abrupt change leads to the emergence of mechanical stress concentrators at their boundary.

[0006] A method for modifying the surface layer of a part is also known, which includes placing the part in the working chamber of the installation, activating the surface of the part before nitriding, feeding a working saturating medium into the chamber, heating the part to nitriding temperatures and holding it at these temperatures until the required thickness of the nitrided layer is formed (SU 1574679 A1).

[0007] The disadvantage of the known method is the low fatigue strength of the part due to the heterogeneity of the diffusion layer and the formation of brittle phases in the diffusion layer, as well as the formation of a nitride network.

[0008] The closest method to the claimed method is for modifying the surface layer of a titanium or titanium alloy part, which involves surface activation and ion implantation treatment of the part's surface with nitrogen ions. Surface activation is performed using ion cleaning at an energy of 8 to 10 keV and a current density of 130 μA / cm 2 up to 160 μA / cm 2for 0.3 to 1.0 h, and ion implantation treatment of the surface of the part is carried out at an energy of 25 to 30 keV (RU 2479667 C2).

[0009] The main disadvantage of this method is the insufficiently high performance characteristics of parts made of titanium and titanium-based alloys due to the significant heterogeneity of the properties of the surface layer.

[0010] The problem that the claimed technical solution is aimed at solving is increasing the durability of a part, for example, gas turbine engine compressor blades made of titanium alloys.

[0011] The objective of the invention is to create a method for surface modification of products made of titanium alloys, ensuring an increase in fatigue strength.

[0012] The technical result of the proposed invention is to increase the fatigue strength of parts made of titanium alloys.

[0013] The technical result is achieved due to the fact that in the method for modifying the surface layer of a part made of titanium or titanium alloy, including the activation of the surface of the part and its ion-implantation treatment with nitrogen ions, unlike the prototype, the activation of the surface of the part is carried out by magnetic-pulse treatment at a pulse energy selected from the range from 3.0 to 5.0 kJ, with a number of pulses from 10 to 50, and then ion-implantation treatment of the surface of the part is carried out with nitrogen ions at an ion energy of 20 to 40 keV, with a irradiation dose of 1.2⋅10 17 cm -2 up to 1.3⋅10 17 cm -2 , the rate of increase in radiation dose from 0.7⋅10 15 With -1 up to 1.2⋅10 15 With -1 .

[0014] The method is carried out as follows. The part is subjected to magnetic pulse treatment. For this, it is placed in an inductor, providing a magnetic field across the entire surface of the part to be treated. Magnetic pulse treatment is then carried out at a pulse energy selected from the range of 3.0 to 5.0 kJ, with a number of pulses from 10 to 50. Under the influence of a pulsed magnetic field, eddy currents are generated in the surface layer of the part, ensuring surface layer treatment. After magnetic pulse treatment, the parts are placed in a vacuum chamber of an ion implantation unit and treated with nitrogen ions at an ion energy of 20 to 40 keV, with a irradiation dose of 1.2⋅10 17 cm -2 up to 1.3⋅10 17 cm -2 , the rate of increase in radiation dose from 0.7⋅10 15 With -1 up to 1.2≥10 15 With -1 .

[0015] Example. To evaluate the performance properties of parts processed using the proposed method, the following tests were conducted. Samples of VT0 titanium and VT6, VT 18-U, and VT9 titanium alloys were processed using both the prototype method (RU 2479667 C2), in accordance with the processing conditions and modes specified therein, and variations of the proposed method. If the evaluated performance properties of the test part processed using the modes of the proposed method did not exceed those of the prototype (RU 2479667 C2), the processing modes were considered unsatisfactory (U.S.). If the characteristics were higher, the modes were marked as satisfactory (U.S.).

[0016] Sample processing modes.

[0017] The difference in the preparation of samples for nitriding using the prototype method (RU 2479667 C2) and the proposed method was the presence of a magnetic pulse treatment stage in the proposed method.

[0018] Ion implantation was performed using the Victoria-2 facility in continuous mode. The titanium alloy components used were gas turbine engine compressor blades. An extended gas plasma generator, capable of operating with nitrogen and with an output aperture of 600 x 100 mm, was used for ion implantation.

[0019] In the magnetic pulse treatment mode (used only for the proposed method), the pulse energies were selected from the range of 3.0 to 5.0 kJ with a number of pulses from 10 to 50 (the MIU-3 unit was used):

[0020] - pulse energy: 2.0 kJ (N.R.); 3.0 kJ (U.R.); 4.0 kJ (U.R.); 5.0 kJ (U.R.); 6.0 kJ (N.R.);

[0021] - for the number of pulses from 10 to 50: 8 (N.R.); 10 (U.R.); 20 (U.R.); 40 (U.R.); 50 (U.R.); 60 (N.R.).

[0022] Endurance and cyclic strength tests were carried out on samples of titanium alloys VT6, VT 18-U and VT9 in air.

[0023] As a result of the experiment, the following was established: the average value of the conditional fatigue limit (σ-1) of samples from the specified alloys in the initial state was from 360 to 370 MPa, for samples hardened using the prototype method - 380-390 MPa, and using the proposed method - 410-420 MPa.

[0024] Thus, the comparative tests conducted have shown that the proposed method of modifying the surface layer of a titanium alloy part allows for the stated technical result to be achieved - an increase in the fatigue strength of titanium alloy parts.

Claims

A method for modifying the surface layer of a titanium alloy part, including activating the surface of the part and subjecting it to ion-implantation treatment with nitrogen ions, characterized in that the surface of the part is activated by magnetic-pulse treatment at a pulse energy selected from the range of 3.0 to 5.0 kJ, and a number of pulses from 10 to 50, and then subjecting the surface of the part to ion-implantation treatment with nitrogen ions at an ion energy of 20 to 40 keV, a radiation dose of 1.2⋅10 17 up to 1.3⋅10 17 cm -2 and the rate of increase in radiation dose from 0.7⋅10 15 up to 1.2⋅10 15 With -1 .