Method of surface modification of titanium alloys

 

(57) Abstract:

Method of surface modification of titanium alloys involves removal by electrochemical etching of the surface layer to a depth of structural irregularities formed during mechanical preparation, removal by diffusion vacuum annealing dissolved in the surface layer of the alloy strip with thickness, the greater the estimated depth of penetration under the action of high-power pulsed beam, and the irradiation surface of powerful ion beam of nanosecond duration. The surface layer is removed by a thickness of 4-7 μm, annealing is carried out in the period of 2-2 .5 hours at a temperature of 550-600°C and a pressure of 510-4- 110-5mm RT. Art., irradiation of the prepared surface shall exercise a powerful ion beam composition: 30%+and 70% of N+with the energy of 200-400 Kev, a current density of 50 to 150 A/cm2, 1-3 pulses 30-50 NS. 3 C.p. f-crystals.

The invention relates to radiation-beam technologies modification of materials and can be used to obtain structural materials with unique properties for use in engine-building, aviation and chemical industries.

The known method obrany beam of nanosecond duration, characterized in that with a view to enhancing the operational stability of the tool, the irradiation is performed with the energy flow 1-3 j/cm2, dose 2,51013-1014cm-2in the impulse.

The disadvantage of this method is the formation of microcraters on the exposed surface (see Solow C. A., Remnev, E., Nocona N. A. and other Phenomenon createrootpane in the interaction of powerful ion beams with the surface of metals and alloys: influence of preliminary preparation of the surface// the Surface. Physics, chemistry, mechanics.- 1995. N 11. C. 24-35). Formed on the surfaces of metals and alloys craters can lead to a reduced level of performance properties of products, primarily to the decrease in fatigue strength and corrosion resistance (see Solow C. A., Remnev, E., Nocona N. A. and other Phenomenon createrootpane in the interaction of powerful ion beams with the surface of metals and alloys //Surface. Physics, chemistry, mechanics. -1994. N. 7. S. 117-128).

There is a method of ion-beam processing tool (Patent RF N 2111264, IPC 6 C 21 D 1/09, BI N 14, 1998), which includes a processing tool of a powerful ion beam of nanosecond duration, characterized in that the tool is irradiated by the beam from the medium to the e of 0.1 to 3.0 j/cm2.

The disadvantage of this method is the formation of microcraters on the surface of the tool during irradiation, which may lead to lower levels of operational properties processed by this method products (for example, you can initiate the destruction of craters).

There is a method of restoring the operational properties of parts made of heat-resistant alloys (RF Patent N 2094521, IPC 6 C 22 F 3/00, B N 30, 1997), including the removal of damaged during the operation of coating and cleaning of the surface by treatment with a concentrated flow of energy (in the range of 0.1 to 30 j/cm2charged particles nanosecond duration with subsequent finishing heat treatment at the temperature of use of the product.

The disadvantage of this method is the formation at these energy densities of microcraters on the surface of heat-resistant alloys during irradiation, which may lead to lower levels of operational properties (especially under cyclic loads) restored by this method products (see Solow C. A., Remnev, E., Nocona N. A. and other Physico-chemical processes occurring in the surface layers of titanium alloys by ion-tx2">

Closest to the claimed is a method of improving the corrosion resistance of metals and alloys (A. C. USSR N 1486538, IPC 4 C 22 F 3/00, BI N 22, 1989), which consists in irradiation with accelerated ions of the working surface pulsed beam of nanosecond duration. In this method, the sample is placed in a special box accelerator with technical vacuum of 10-4mm RT. Art. , is irradiated with high-power pulsed beam of carbon, hydrogen or nitrogen with an energy of 200 to 500 Kev, a current density of 120 to 200 A/cm2not less than 5 pulses of 50-100 NS. The disadvantage of this method, as in the previous cases, is the formation of microcraters on the surface of the exposure that can lead to the reduction of fatigue strength and stress corrosion cracking in the area of microcraters. Because the weakest area of microcrater is its bottom, it is most likely start corrosion cracking it from the bottom.

The present invention is to provide a method of modification of titanium alloys for reducing the size and density of craters on the irradiated surface and leads consequently to improve the efficiency of modification of titanium alloys.

Sudeshna beam of nanosecond duration, before irradiation by electrochemical etching to remove the surface layer to a depth of structural irregularities formed during mechanical preparation, and then by diffusion vacuum annealing removes dissolved in the surface layer of the alloy gas with the thickness, the greater the estimated depth of penetration under the action of high-power pulsed beam.

In particular, if you remove the surface layer of a thickness of 4-7 μm, diffusion vacuum annealing is carried out in for 2-2 .5 hours at a temperature of 550 - 600oC and a pressure of 510-4- 110-5mm RT.art., irradiation of the prepared surface shall exercise a powerful ion beam composition 30%oC+and 70% H+with the energy of 200-400 Kev, a current density of 50 to 150 A/cm2, 1-3 pulses 30-50 NS.

In the preliminary preparation of metals and alloys, including electrochemical removal of the layer of titanium alloy with a thickness of 4-7 microns, is the removal of the work-hardened layer formed by mechanical processing of the material, as well as foreign surface inclusions. Subsequent vacuum annealing of titanium alloys at temperatures -550 - 600oC and a pressure of 510-4- 110-5mm RT. senior removes dissolved in igodit to significant (up to 50-fold decrease in density is formed on the exposed surface craters that provides improved operational properties of titanium alloys (fatigue strength, corrosion resistance and so on).

This technical result is achieved due to complex modifications, including preliminary electrochemical etching, diffusion vacuum annealing and subsequent processing of powerful ion beam. Using a preliminary electrochemical etching is the removal of the layer of material with increased defections, and vacuum annealing at a temperature of 550 - 600oC and a pressure of 510-4- 110-5mm RT. Art. for 2-2,5 hours provides the removal of the surface layer dissolved gases. These local concentrations of dissolved titanium gases, primarily hydrogen, because of its high mobility lead when it comes out on the free molten powerful pulsed beam surface to the formation of craters.

The decrease of the density of craters is achieved by reducing the concentration of gases found in the surface layers of irradiated metals and alloys, as well as removal of the damaged layer, which occurs during mechanical preparation of materials.

To implement the claimed ability, the structural irregularities of the surface layers during mechanical preparation of materials;

the temperature and time of vacuum diffusion annealing, since the removal of dissolved gases must be ensured at depths greater than the depth of penetration of the material under the action of powerful ion beam specified current density and duration. The most effective was the removal of the layer thickness of 4-7 microns and a vacuum annealing at a temperature of 550-600oC for 2-2,5 hours.

Modification of metals and alloys was carried out as follows.

Example 1. Samples of titanium alloy VT-6 (or W-8) was subjected to electrochemical etching for removal of the work-hardened layer thickness of 4-7 microns. Then they were placed in a vacuum furnace for carrying out thermal annealing at a temperature of 600oC for 2 hours under a pressure of 510-4- 110-5mm RT.article After annealing, the samples were mounted in a fixture located in a vacuum chamber technology accelerator "Temp", and was irradiated with high-power pulsed ion beam consisting of 30% H+and 70% C+, with an energy of 300 Kev, a current density of 50 to 150 A/cm2duration 50 NS. Samples of modified titanium alloys was investigated using optical and electron microscopy to determine the density and up to 50 times compared with irradiation without prior surface preparation.

1. Method of surface modification of titanium alloys, including the irradiation of the surface of powerful ion beam of nanosecond duration, characterized in that before the irradiation by electrochemical etching to remove the surface layer to a depth of structural irregularities formed during mechanical preparation, and then by diffusion vacuum annealing removes dissolved in the surface layer of the alloy gas with the thickness, the greater the estimated depth of penetration, under the action of high-power pulsed beam.

2. Method of surface modification on p. 1, wherein removing the surface layer of a thickness of 4-7 microns.

3. Method of surface modification on p. 1, characterized in that a diffusion vacuum annealing is carried out in the period of 2-2 .5 hours at a temperature of 550-600oC and a pressure of 510-4-110-5mm RT.article.

4. Method of surface modification on p. 1, characterized in that the irradiation of the prepared surface shall exercise a powerful ion beam composition 30%C+and 70%H+with the energy of 200-400 Kev, a current density of 50 to 150 A/cm2, 1-3 pulses 30-50 NS.

 

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