RU2647963C2 - Composite material on base of titanium alloy and procedure for its manufacture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to composition and method of manufacturing a composite material with predetermined properties, for example high-class armor protection elements, cutting elements, machine components. Composite material based on a titanium alloy consists of a base metal of a titanium alloy and a modified surface layer. Modified surface layer consists of a face layer with a ceramic structure, layer with a cermet structure and a layer with a transition structure from the cermet layer to the base metal of the titanium alloy and contains a saturated solid solution of nitrogen in titanium with TiN_x ceramic particles embedded in it, and/or TiC_x, and/or Ti_xN_yC_z. Face layer has a thickness of 0.08 mm to 0.5 mm and a hardness of at least 62 HRC. Layer with a cermet structure has a thickness of 0.5 to 24 mm and a hardness of 50 HRC to 74 HRC. Layer with a transition structure has a thickness of 5 to 10 % of thickness of cermet layer and a hardness of 60 to 30 HRC, reducing during the transition from the layer with the cermet structure to the base metal of the titanium alloy. Method of manufacturing a composite material includes heating surface of a titanium alloy with a highly concentrated moving source of thermal energy in a gas atmosphere, containing modifying components. Heating and remelting of the surface of the titanium alloy is carried out by a plasma submerged arc of direct action with a specific heat flux at the center of the spot from 10⁴ to 10⁵ W/cm², current strength of 50–450 A, arc voltage from 20 to 40 V, and a travel speed of a thermal energy source relative to the surface of the titanium alloy from 0.003 to 0.01 m/s, and the gas atmosphere contains a mixture of argon with the addition of modifying nitrogen and/or carbon components in the form of a carbon-containing gas.

EFFECT: material is characterized by high strength, hardness, thermal and corrosion resistance and wear resistance.

8 cl, 3 dwg, 1 tbl

Description

The invention relates to the field of metallurgy and mechanical engineering, and in particular to the composition and method of production of composite material with predetermined properties, which allows producing structures that can be used for the manufacture of structural elements for various purposes, for example, high-class armor protection elements, cutting elements for various purposes, machine tool elements structures combining high hardness at the level of instrumental cermet alloys with strength Tew at the level of carbon low- and medium alloy steels, and high surface thermal resistance.

The use of materials with desired properties in the modern industry is dictated by the need to improve the operational characteristics of products and equipment through the use of new structural materials that combine high hardness, wear resistance and temperature resistance while maintaining satisfactory ductility, as well as having a low specific weight (aviation industry, defense equipment and personal protective equipment, power engineering, oil and gas, engineering, manufacturing of the tool for various purposes, including cutting, medical, consumer, and others.). Currently, for such purposes, various types of composite materials, both multilayer and dispersion hardened, are widely used. The use of modified metal alloys as elements of armor protection, cutting tools, as well as elements of machine tools is advisable from the point of view of ensuring the conformity of products manufactured with their use to the requirements typically presented for such products.

Titanium and its alloys have high specific strength, corrosion resistance, ductility. Technological processes for the production of various products from titanium alloys are well developed. The main obstacle to using them for the production of a number of products in the above technical fields is the low surface hardness of titanium alloys (practically no more than 43 HRC), while a possible increase in hardness due to volumetric heat treatment reduces ductility, impact strength, fracture toughness, which leads to cracking and further destruction of the material.

Limit the use of titanium alloys and their relatively low resistance to surface oxidation when exposed to temperatures above 600 ° C in air. Under these conditions, alloys are oxidized to form titanium oxides (TiO ₂ and Ti ₂ O ₃ ) and subsurface layers with a high oxygen content on the surface, in which solid solutions of α-stabilizers are replaced by solid oxygen solutions.

For the purpose of imparting hardness to the surface layer of a metal, it is known to use a thin protective coating of titanium nitride, carbide or carbonitride obtained by gas-plasma spraying on the surface of a finished part. The specified material does not allow to fully use the advantages of refractory titanium compounds due to the small thickness of the sprayed layer.

More promising from the point of view of improving the technological properties of the material is dispersed hardening of a titanium alloy with refractory compounds of nitrogen and / or carbon with titanium.

Known nanostructured composite material based on pure titanium according to the patent of the Russian Federation for invention No. 2492256 (applicant Panin S.V., IPC C22C 1/05, C22C 14/00, B22F 3/14, B82Y 30/00, application No. 20112120251 of 16.05 .2012). The material proposed in this patent relates mainly to the field of medicine and is a composite material containing a matrix of pure titanium, with a grain size of ≤250 nm, dispersively hardened by nanosized particles of carbide, boride or nitride, thermally stable and chemically resistant to titanium titanium, with a particle size of 2-10 nm, while the reinforcing particles are evenly distributed in the volume of the material, and their total share in the volume of the material is 0.05-0.50 vol.%.

According to the description of the said patent, the material is obtained by forming a mechanical mixture of pure titanium with inclusions of nitride and carbonitride microparticles, followed by the formation of the material by isostatic thermal pressing, so the resulting powder composite is a solid wear-resistant components in a titanium binder. The resulting material with the content of hardening components up to 0.5 vol.% Cannot provide high performance properties under shock loads with high and ultrahigh kinetic energy under high long-term static and dynamic loads under all types of loading (compression, tension, bending, torsion and etc.). Therefore, the range of tasks for which composite material is used is limited exclusively to use in medicine.

A known method of obtaining wear-resistant and having high fatigue strength surface layers on parts made of titanium alloys and a part made by this method according to the patent of the Russian Federation for invention No. 2407822 (applicant Siemens AG, IPC C23C 14/28, C23C 8/06, application No. 2007104837 from 07/08/2005). According to the description and claims to the said patent, a titanium alloy part with a wear-resistant surface layer obtained by laser alloying from the gas phase. The wear-resistant surface layer has a thickness tR ranging from 0.1 to 3.5 mm and consists of a mixture of the finest grains of α- and β-titanium with the elements of the reaction gas present in the titanium alloy as a solid solution without the formation of nitride, carbide, oxide or boride phases, has a surface hardness HS, measured on a polished surface, in the range from 360 to 500 HV 0.5 or microhardness HR, measured on a polished transverse section at a depth of 0.1 mm from its surface, in the range from 360 to 560 HV 0 ,one.

The method eliminates the formation of nitride phases due to the control of the partial pressure of the reaction gas, and provides only for the formation of a solution of introduction. Thus, hardening is limited both in depth (at the level of hundreds of micrometers) and in mechanical properties.

As the closest analogue selected technical solution disclosed in the patent for invention No. 2407822. The claimed technical solution allows to overcome these disadvantages.

The problem to which the proposed technical solution is directed is to increase the hardness of a heterogeneous monolithic composite material while maintaining ductility, while maintaining the physical characteristics of the material under conditions of multiple shock loads with high kinetic energy, and during surface machining. The result of this combination of properties will be an increase in the wear resistance of the material, an improvement in a number of operational characteristics, such as hardness, strength, increased thermal and corrosion resistance, as well as an increase in the hardness and strength of the products to the required depth, ensuring the necessary performance of the structures.

The claimed technical result is achieved in that the composite material based on a titanium alloy with a modified region consisting of a front layer having a ceramic structure of a layer with a cermet structure and a layer with a transition structure from a layer with a cermet structure to a titanium alloy of the base metal contains nitrogen in the form of a saturated solid interstitial solution and ceramic particles TiN _x and / or TiC _x and / or Ti _x N _y C _z , the front layer with a ceramic structure having a thickness of from 0.08 mm to 0.5 mm, solid not less than 62 HRC with a mass fraction of ceramic particles of more than 15%, a value of not more than 1.0 μm, located in a titanium matrix with a grain size of not more than 240 μm, a layer with a cermet structure has a thickness of 0.5 to 24 mm, hardness from 50 HRC to 74 HRC with a ceramic particle size of less than 1.0 μm and a mass fraction of 2 to 14% located in a titanium matrix with a grain size of not more than 500 μm, a layer with a transition structure has a thickness of 5 to 10% of the thickness of the cermet layer , hardness from 60 to 30 HRC, decreasing upon transition from the layer with metallocer matic structure to the titanium alloy of the base metal.

The similarity of the proposed technical solution with the selected closest analogue lies in the fact that it is made of a titanium alloy with a modified region.

In the general case, the distinguishing features of the proposed technical solution are that the modified region consists of a front layer with a ceramic structure, a layer with a cermet structure and a layer with a transition structure from a layer with a cermet structure to a titanium alloy of the base metal, contains nitrogen in the form of a saturated interstitial solid solution and ceramic particles TiN _x, and / or TiC _x, and / or Ti _x N _y C _z, wherein the facing layer with the ceramic structure has a thickness of from 0.08 mm to 0.5 mm, a hardness of at least 62 HRC with mass with a fraction of ceramic particles of more than 15%, a value of not more than 1.0 μm, located in a titanium matrix with a grain size of not more than 240 μm, a layer with a cermet structure has a thickness of 0.5 to 24 mm, hardness of 50 HRC to 74 HRC with ceramic particles of less than 1.0 μm and mass fractions of 2 to 14% located in a titanium matrix with a grain size of not more than 500 μm, the layer with the transition structure has a thickness of 5 to 10% of the thickness of the cermet layer, hardness of 60 to 30 HRC, decreasing during the transition from a layer with a cermet structure to t an ethanol alloy of the base metal.

In the particular case of performing a composite material based on a titanium alloy with a modified region, the modified region further comprises TiB _x , Ti _y B _x .

In the development of this particular case, a composite material based on a titanium alloy with a modified region is further characterized in that the mass fraction of TiB _x , Ti _y B _x in the front layer with a ceramic structure is more than 10%, in the layer with a cermet structure from 2 to 10%.

The inventive material is a heterogeneous monolithic structure consisting of four layers: a high-strength solid wear-resistant and heat-resistant layer with a ceramic structure, a relatively solid and heat-resistant cermet layer, a thermal influence layer formed during the chemical-thermal processing of the material and a plastic back layer containing, in mainly titanium, despite the fact that all layers are firmly connected to each other by a metal bond. The combination of dispersively hardened metal layers and a multilayer structure in one composite material allows one to obtain a material that combines the positive aspects of two types. The nature of the properties of the finished material is also determined by the dispersion and size of the phases of incorporation into the alloy matrix. Upon receipt of the material, the size and volume of the dispersed phase can be set artificially. High dispersion of strong refractory inclusions allows to obtain high strength of the material, without leading to excessive brittleness. The size of the introduction phase is due to the peculiarity of the process of introduction of substances from the gas phase.

The manifested reactivity of titanium with nitrogen, carbon, and boron is based on the fact that titanium is the strongest carbide former (Sarrak V.I. Fragile Fracture of Materials. UFN, vol. LXVII, issue 2, February 1959, pp. 338-361), it can make up a very solid biphasic TiC eutectic like iron carbide Fe ₃ C (cementite), only the matrix will be not iron, but titanium. Titanium nitride and titanium carbonitride are formed according to the same scheme and have similar properties. The strength of ceramics and the metal matrix are based on different physical phenomena. The strength of ceramics is determined by the energy of free surface formation (Griffith theory), a metal matrix, the presence of a dislocation, but both mechanisms are related to the grain size, the smaller it is, the stronger the material (Cutting tools equipped with superhard and ceramic materials. V.P. Zhed et al. . Reference. M., Engineering, 1987).

Ceramic inclusions in the modified layer consist of TiN _x and / or TiC _x and / or Ti _x N _y C _z . In the particular case, ceramic inclusions can be formed by combining titanium with boron (TiB _x , Ti _y B _x ). Nitrogen- and / or carbon-containing and / or boron-containing compounds, when implanted into the titanium matrix during crystallization, form highly dispersed refractory compounds with titanium. During mechanical action on a material containing stable compounds of titanium with nitrogen and / or carbon, the plastic deformation resistance occurs due to the braking of dislocations on obstacles in the form of nanosized particles. The formation of these compounds occurs through their separation from the supersaturated solid solution formed during the remelting process.

The outer layer with a ceramic structure with a thickness of 0.08 mm to 0.5 mm protects titanium alloy products from oxidation at temperatures up to 900 ° C. The layer thickness is selected empirically and is provided by the process technology.

The cermet layer contains ceramic particles TiN _x and / or TiC _x and / or Ti _x N _y C _{z with a} size of less than 1.0 μm, which are located in a titanium matrix with a grain size of not more than 500 μm. An increase in the size of ceramic particles and grain sizes of titanium alloys of more than these sizes causes a violation of the stability of the mechanical properties of the modified layer. When the content of ceramic particles is less than 2%, a minimum hardness of 50 HRC is not ensured. The content of ceramic particles of more than 15% leads to an undesirable decrease in the ductility and fracture toughness of the material.

During the interaction of ionized nitrogen with titanium, titanium nitride (TiN) is formed, characterized by high refractoriness, T _pl. = 2930 ° C, refractoriness and chemical resistance at elevated temperatures, hardness. The finely divided titanium nitride compounds are composed of individual dendrites, mainly cubic. The crystal lattice, in comparison with the state of massive bodies, is characterized by a reduced interatomic distance and static nonequilibrium, which determines the main features of the technological properties of nitride, in particular high hardness.

In the titanium-carbon system, there is one carbide phase TiC with a wide homogeneity region (37-50% atomic carbon). Carbide crystallizes in cubic syngony, the period of the crystal lattice depends on the carbon content and varies in the range of 0.4299-0.4329 nm. The compound has a high refractoriness T _pl. = 3420 K and microhardness, which are necessary parameters to achieve the claimed technical result.

In the Ti - B system, the most common compound is TiB ₂ (titanium diboride). Boron atoms, in this case, form layers alternating with layers of titanium atoms, thus forming graphite-like flat networks. The compound of titanium with boron has a high refractoriness T _pl. = 3230 ° C and microhardness. The indicated properties of titanium boride allow in the particular case to solve the problem. The content of titanium compounds with boron in the ceramic layer should be at least 10% to give the modified material sufficient surface strength.

Hardening of the face layer is also achieved by modifying with nitrogen to obtain high-strength structural components of the alloy of the α and α + β type and by incorporating the finely dispersed compounds described above into the titanium matrix. The result is achieved by implementing solid-solution and dispersion hardening mechanisms. Two-phase titanium alloys with nanocrystalline and submicrocrystalline structures have increased characteristics of hardness, strength, fatigue resistance, wear resistance.

The thickness of the cermet layer can be performed, depending on the need (operational requirements for the product), in the range from 0.5 mm to 25.0 mm In this case, the scatter of hardness values over the layer thickness should not exceed more than 30%. When this value is exceeded, the stability of the properties of the layer in terms of hardness is violated, the layer ceases to work as a whole. The protective properties of the modified layer are sharply reduced, especially under pulsed concentrated and distributed loads of high intensity.

The intermediate layer with a thickness of at least 5% of the thickness of the cermet layer has a smooth gradient of the change in the elastic properties from the less elastic cermet layer to the elastic properties corresponding to the properties of the main volume of the titanium alloy. This avoids peak stresses at the boundary of the layers leading to the formation of cracks.

A titanium alloy of a base metal with a hardness of up to 40 HRC consists of an unmodified titanium alloy. Titanium alloys with the indicated hardness parameter have a relatively high ductility and are well subjected to heat treatment. It is undesirable to exceed the indicated value in hardness, since in this case there is a decrease in the ductility of the main metal alloy, contributing to the formation of cracks during repeated exposure to shock loads on the material.

The most suitable alloys, from the point of view of the effectiveness of exposure to them by heat treatment and implantation of refractory highly dispersed compounds, may be alloys assigned to the martensitic class, according to the classification, i.e. to alloys with a β-phase content in equilibrium from 5 to 25%. In the annealed state, they usually have good ductility. When they are quenched from the β-region, martensitic β-α'- or β-αʺ-transformations occur. The most widely used are currently industrial alloys of this class VT6, VT14, VTZ-1, VT23, VT16. Of the alloys produced abroad, this class includes the following: Ti-3Al-2,5V; Ti-6AI-4V; Ti-6Al-6V-2Sn and Ti-Al-2Sn-4Zn-4Mo.

The modified region formed by chemical thermal treatment possesses stable microhardness parameters for a thickness of up to 5 mm, at least. Microhardness data were obtained experimentally by the Vickers method in accordance with GOST 2999-75 and are shown in FIG. one.

Hardening of titanium-based alloys can be carried out by spraying a thin layer on the surface of the alloy. This method cannot provide a significant improvement in performance due to the small thickness of the sprayed layer. The scope of materials obtained in this way is limited to cutting tools and decorative coatings.

Methods are also used that allow surface hardening of materials based on alloys, including titanium, by saturation of the surface layer with nitrogen.

In particular, there is a known method for surface nitriding of steel products in a glow discharge, according to the patent of the Russian Federation No. 2276201 (applicant GOU VPO "UGATU", IPC C23C 8/36, application No. 2004132581 dated 11/11/2004), which is carried out by vacuum heating of the products in plasma nitrogen of increased density formed between the part and the screen due to the hollow cathode effect. The nitriding process is carried out at a temperature of 700-750 ° C. After nitriding, surface quenching is carried out by cooling in an argon stream at a rate exceeding the critical rate of steel quenching. Among the disadvantages of this method, it is possible to distinguish: the impossibility of nitriding titanium alloys in high-density plasma, since the use of steel screens can lead to atomized iron particles getting on the treated surface and blocking the diffusion of nitrogen inside the treated surface, reducing the efficiency of nitrogen diffusion deep into the processed products, since nitriding occurs in a nitrogen environment, which leads to the formation of a continuous nitride film on the surface.

There is also known a method of hardening titanium alloys in a gaseous medium according to the patent of the Russian Federation No. 2365671 (applicant GOU VPO "VSTU", IPC C23C 8/80, application No. 2007145303 from 06.12.2007). According to the claims, for surface hardening, high-temperature nitriding is carried out at temperatures of 700-750 ° C for 10-30 minutes. The disadvantage of this method is also the small thickness of the processed layer, since hardening occurs due to the diffusion of nitrogen into the surface layer.

The thermal effect on the material remains much lower than its melting temperature, the crystal structure of the material does not undergo significant changes, therefore, the penetration depth of nitrogen is insignificant, moreover, a nitride film is formed on the surface of the material, which prevents further diffusion.

Closest to the proposed technical solution is a method of surface hardening of titanium alloys based on the use of arc and plasma heat sources according to RF patent No. 2427666 (applicant GOU VPO SibGAU, IPC C22F 1/18, C23C 8/36, application No. 2009147581 dated 27.08. 2011). According to the claims, the method includes heating the surface of the product in a nitrogen environment, the heating is carried out by a concentrated heat source with a power density of 103-104 W / cm ² , a current of 80-150 A and a source moving speed relative to the product of 0.005-0.01 m / from.

As a disadvantage of this method, one can single out the fact that hardening occurs due to local heating of the upper titanium layer by a concentrated high-temperature source of thermal energy in a nitrogen atmosphere, and as a result, diffuse saturation of the surface layer of the product. In this case, the heating temperature of the treated surface does not exceed the liquidus temperature. Thus, there is thermal diffusion saturation of the surface layer with nitrogen in the form of an interstitial solution, with the possible formation of a small amount of titanium nitrides. The depth of the nitrided layer according to the patent can reach 1.5 mm, and there may be a large gradient of physical properties along the processing depth, hardening to a greater depth with this method is not possible. There is also a limitation on the hardness of the obtained layer, which is associated with a low nitrogen concentration in the interstitial solution and a low content of nitride component. The disadvantage of this method is the small thickness (0.5 mm) of the solid layer with a material hardness of up to 10,000 MPa HV, titanium nitride. Small thicknesses of solid surface layers limit the performance of titanium alloy products with a high level of mechanical impact of the external environment.

These disadvantages are eliminated by the application of the proposed method. The problem to which the claimed method is directed is to increase the nitrogen content in the processed volume of the material along with a significant increase in the depth of the processed layer, which will lead to an increase in the hardness of the modified area and, as a result, to increased wear resistance, reduction, brittleness and plasticity of the composition as a whole .

The claimed technical result is achieved by applying a method that sequentially includes heating the surface of a titanium alloy with a highly concentrated moving source of thermal energy in a gas atmosphere containing modifying components, the heating being carried out by a plasma submerged direct-acting arc with a specific heat flux in the center of the spot of heating by a compressed arc from 10 ⁴ to 10 ⁵ W / cm ² , current 50-450 A, arc voltage from 20 to 45 V and the speed of movement of the heat source relative to the surface titanium alloy from 0.003 to 0.01 m / s. The gas atmosphere is formed by a mixture of argon with the addition of nitrogen and / or gas containing carbon.

The similarity of the proposed method for manufacturing a composite material based on a titanium alloy with a modified region with the closest analogue lies in the fact that the proposed method involves heating the surface of a titanium alloy with a highly concentrated moving source of thermal energy in a gas atmosphere.

In general, the proposed method for manufacturing a composite material based on a titanium alloy with a modified region differs from the closest analogue in that the heating is performed by a direct-acting plasma submerged arc with a specific heat flux in the center of the spot of heating by a compressed arc from 10 ⁴ to 10 ⁵ W / cm ² , current strength of 50-450 A, arc voltage from 20 to 45 V and the velocity of the heat source relative to the surface of the titanium alloy from 0.003 to 0.01 m / s, and the gas atmosphere is formed by a mixture of argon with the addition of azo a and / or carbon-containing gas.

In the particular case, this problem is additionally solved by the fact that the formation of the modified region is performed with overlapping passages by 45-60% of their width.

In the particular case, this problem is additionally solved by the fact that after completion of the remelting process, heat treatment is carried out.

In the development of this particular case, this problem is additionally solved by the fact that the heat treatment is carried out by annealing at a temperature of 800-850 ° C.

In the development of this particular case, this problem is additionally solved by the fact that the heat treatment is carried out by tempering at a temperature of 600-650 ° C.

The hardening process is as follows. A plasma arc burning in a mixture of gases containing nitrogen, argon and carbon dioxide moves along the treated surface at a speed V in the range from 0.003 to 0.01 m / s and performs local heating and melting of the product surface. When the metal is heated and melted, the liquid bath is saturated with ionized nitrogen and carbon dioxide, which dissociates into CO and O ₂ , titanium is oxidized, and then reduced to form carbide. Nitrogen dissolves in the titanium matrix to form titanium sub-nitride and mononitride, part of the nitrogen remains in the matrix as a saturated interstitial solution as a result of the high cooling rate.

As a result of crystallization of a liquid metal bath, a composite is formed consisting of three zones: a surface layer saturated with ceramic particles in the form of compounds TiN _x and / or TiC _x and / or Ti _x N _y C _z , a zone representing a ceramic-metal structure with uniformly distributed finely dispersed nitride, carbide and carbonitride inclusions and a heat-affected zone, which is a transition zone in which the structure and properties change from cermet to the initial alloy.

The process parameters provide a specific heat flux in the center of the spot of heating by a compressed arc at the level of 10 ⁴ -10 ⁵ W / cm ² depending on the mode. In order to obtain a layer of a given depth during remelting, the welding current varies in the range from 50 to 350 A, with an arc voltage of 20 to 45 V. The speed of movement of the heat source in the remelting direction varies in the range from 0.003 to 0.01 m / s.

The method of obtaining the inventive composite material is based on short-term intense heating of the surface of the starting material to the state of destruction of the crystal lattice of the alloy, i.e. remelting occurs when the surface is locally heated to a significant excess of the liquidus temperature. The use of modifying gas (gas mixture) in conjunction with the melting of the material layer allows deep alloying and material modification, which distinguishes it from diffuse saturation methods in which the penetration depth of alloying elements is significantly limited by the dense atomic structure of the alloy. Local remelting with subsequent crystallization leads to the formation of highly dispersed nitride, carbide or carbonitride structures (depending on the composition of the modifying gas or gas mixture). Upon recrystallization, a multiphase structure is formed with an interstitial solution and highly dispersed inclusions of titanium compounds with nitrogen and / or carbon in the α and α + β matrix of the titanium alloy.

The depth of the remelted material is controlled by a change in the specific heat flux in the center of the spot of heating by a compressed arc through a direct change in the strength of the welding current and the voltage and velocity of the heat source.

Since remelting is carried out during local heating of a surface portion of a titanium alloy, for remelting the entire surface, it is necessary to carry out the movement of a highly concentrated source of thermal energy relative to the surface. The scanning method of movement allows remelting the entire surface by sequential passage along the tracks on the surface of the material, both with mutual overlapping of the remelted sections, and without it. In the particular case, the mutual overlap of the remelted sections (passages) is from 45 to 60% of their width. The specified parameter allows you to get a modified area of approximately the same depth of the entire processed material. Obviously, in the case of overlapping passages of less than 45%, due to the geometric shape of the liquid bath during the melt of the material, it will not be possible to achieve an even horizontal layer boundary. Exceeding the overlap parameter of 60% means re-remelting the main volume of the already modified region, which is impractical.

Subsequent annealing at a temperature of 800-850 ° C allows you to normalize the structure of the obtained material, partially reducing thermal stresses. A temperature below 800 ° C does not allow a significant improvement in the properties of the material, and a temperature above 850 ° C leads to a decrease in the ductility of the back layer.

Annealing with further cooling with a furnace is used to reduce residual thermal stresses at temperatures of 600-650 ° C, which minimize phase and structural transformations in α, α + β alloys.

The speed of movement of the energy source relative to the surface of the material in the range of 0.003-0.01 m / s allows sequential remelting of the entire surface of the titanium alloy.

The current strength and voltage of the heat energy source is set depending on the specified depth of the processed layer.

The presence of a protective gas during the remelting process ensures that there is no contact of the protected object, in this case, the titanium alloy to be hardened, with air, preventing the formation of oxides. In this case, argon is the preferred shielding gas to achieve the technical result, however, the method involves the use of a mixture of shielding gases.

The advisability of using a plasma torch as a source of thermal energy is due to its structural properties, allowing both melting and modification of the titanium alloy being processed. In addition, the plasma torches have wide possibilities for heating the plasma in the temperature range up to (1-20) ⋅10 ³ K, which allows locally heating the processed alloy to temperatures exceeding the melting temperature.

The preference for using a plasma torch for welding metals is due to a number of design features of devices of this type: a gas that performs the function of forming a plasma arc determines the region of local remelting, and the relatively low plasma velocity in the nozzle of the plasma torch avoids blowing metal out of the remelting region (liquid bath).

The technology for producing a high-strength, hard cermet layer is a remelting of the initial titanium alloy on a typical plasma torch for welding metals with a tungsten electrode containing inlets for mixing and supplying modifying (N ₂ ), protective and plasma-forming gases (Ar) into the melt zone. The remelting is carried out in the selected modes depending on the required geometry of the composite material, the programmed properties of the remelted cermet and varies: remelting speed V _sv in the range from 10 to 30 m / h, at the welding current I _sv depending on the thickness of the remelted layer in the range from 50 to 300 A, at a voltage U _dv range from 20 to 40 V. In particular, the gas flow rate for nitride modification is: the flow rate of argon used as a plasma-forming gas, Q _Ar up to 9 l / min of nitrogen used as of modifying gas, Q _N up to 40 l / min, flow rate of argon used as a protective gas, Q _Ar up to 15 l / min.

The claimed technical solution allows to obtain a composite material with the following characteristics: Rockwell hardness 60-74 HRC, strength at least 1350 MPa, high heat resistance, allowing the material to work for a long time at a temperature of 800-900 ° C, high corrosion resistance.

The results and characteristics of the material are confirmed by a set of studies based on methods of electron microscopy, X-ray diffraction analysis, microhardness and surface hardness measurements, tensile tests, as well as ballistic tests of samples of armored elements created from developed alloys.

The invention is illustrated by the following drawings.

FIG. 1. The distribution of microhardness in the hardened layer of a composite material based on the VST 2 alloy (microhardness is given in units of Rockwell hardness HRC).

FIG. 2. The structure of the composite material based on titanium alloy:

1 - layer with a ceramic structure;

2 - layer with cermet structure;

3 - layer with a transition structure;

4 - base metal.

FIG. 3. The structure of the cermet layer of the molten metal (increase 450 times).

The invention can be illustrated by the following examples.

A product with a modified area based on a titanium alloy was tested as part of a multilayer armored barrier (armored barrier).

A sheet blank of pseudo-β-titanium alloy VST 2, with a density of 4.5 g / cm ³ and a thickness of 6.7 mm, is subjected to surface treatment on a plasma installation with the following technological conditions: remelting current was 180 A, at a voltage of 25 V, remelting speed 0.004 m / s, in a mixture of a plasma-forming gas containing 50% nitrogen, the rest is argon Ar, and a mixture of a protective gas containing 65% nitrogen, the rest is argon Ar. The composition of the modified alloy is given in table. one

The armored barrier also included a substrate made of aluminum alloy AMG-6, 4 mm thick and a package of ballistic fabric Texar TT, consisting of 14 layers, the thickness of the package was 6 mm. The thickness of this multilayer barrier is within 18 mm, the surface density is 44 kg / m ² .

The multi-layer armored obstacle was tested with two shots from a 7.62 mm Dragunov sniper rifle (SVD, GRAU 6V1), B-32 bullet type, first bullet approach speed - 776 m / s, second - 803 m / s, distance 10 m, normal, nutation 0, room temperature. Shots were fired at a distance of 50 mm from each other.

When examining a multilayer armored obstacle, it was found that the armored obstacle is not pierced through. Noses of the cores were destroyed.

The specified multilayer armored barrier based on products with a modified surface to protect against environmental influences provides:

- protection against several B-32 bullets of a caliber of 7.62 mm SVD, with a distance between hits of 50 mm or less in an object;

- the surface density of the multilayer armored barrier is not more than 44 kg / m ² , this criterion is at the level of the best world samples made on the basis of ceramics, in particular, based on silicon carbide;

- the use of a heterogeneous plate based on a titanium alloy in a multilayer armored barrier instead of ceramic gives a significant reduction in price, for example, the relative cost of structures of elements from titanium will be more than two times lower compared to structures of a similar purpose using silicon carbide.

Using the proposed method, a product with a modified area based on a titanium alloy was obtained and used for the manufacture of a metal-cutting tool - a through turning tool.

An α-titanium alloy sheet stock with a density of 4.5 g / cm ³ and a thickness of 9 mm was subjected to surface treatment to a depth of 4.5 mm in a plasma installation with the following technological conditions: remelting current was 200 A, at a voltage of 26 V, remelting speed 0.003 m / s in a mixture of a plasma-forming gas containing 50% nitrogen, the rest is argon Ar, and a mixture of a protective gas containing 65% nitrogen, the rest is argon Ar. The blank for the cutter was obtained using the installation of water-jet cutting of metal.

In the study of the obtained material, it was found that the microhardness of the material over the cross section of the workpiece in the equivalent of the HRC scale was 54-67 units. The tensile strength of the alloy during the tensile test was 1450 MPa. The resulting structure is an α-titanium alloy matrix with uniformly distributed fine particles of titanium nitride.

Testing of tool life was carried out during turning of a bar of steel 30, with a cutting depth of 0.5 and 1 mm, a feed speed of 0.4 and 0.2 mm / rev, the spindle speed was 400 min ^-1 . Evaluation of resistance showed that, a tool based on a composite has resistance at the level of high-speed steel P6M5.

A composite material with a modified region based on a titanium alloy was used to make the lining of the drilling rod of the rig.

An α-titanium alloy sheet blank with a density of 4.5 g / cm ³ and a thickness of 8 mm was subjected to surface treatment to a depth of 4.05 mm in a plasma installation with the following technological conditions: remelting current was 180 A, at a voltage of 25 V, remelting speed 0.0035 m / s in a mixture of plasma-forming gas containing 45% nitrogen, the rest is argon Ar, and a mixture of protective gas containing 65% nitrogen, the rest is argon Ar. A blank for the lining was obtained using a water-jet cutting machine for metal and equipment for the abrasive processing of materials.

In the study of the obtained material, it was found that the microhardness of the material over the cross section of the workpiece in the equivalent of the HRC scale was 58-65 units. The tensile strength of the alloy during the tensile test was 1350 MPa. The resulting structure is an α-titanium alloy matrix with uniformly distributed fine particles of titanium nitride.

The tests of the prototype showed high strength and resistance to abrasion, exceeding the resistance of standard grippers manufactured by the industry.

The proposed invention can be implemented using well-known tools and materials, can find, as follows from the above examples of implementation, widespread use in industry.

Claims (8)

1. A composite material based on a titanium alloy, consisting of a base metal of a titanium alloy and a modified surface layer, characterized in that the modified surface layer consists of a front layer with a ceramic structure, a layer with a cermet structure and a layer with a transition structure from a layer with a cermet structure base metal comprises a titanium alloy and a saturated solid solution of nitrogen in titanium from TiN _x ceramic particles embedded therein, and / or TiC _x, and / or Ti _x N _y C _z, wherein the front layer with a ceramic structure and a mass fraction of ceramic particles of more than 15% with a size of not more than 1.0 μm, located in a titanium matrix with a grain size of not more than 240 μm, has a thickness of 0.08 mm to 0.5 mm and a hardness of at least 62 HRC, a layer with a cermet structure and a mass fraction of 2 to 14% with a size of less than 1.0 μm, located in a titanium matrix with a grain size of not more than 500 μm, has a thickness of 0.5 to 24 mm and a hardness of 50 HRC to 74 HRC , and a layer with a transition structure from a layer with a cermet structure to the base metal of titanium alloy has a thickness of from 5 to 10% of the thickness of the cermet layer and a hardness of 60 to 30 HRC, declining at the transition from the structure of the sintered layer to the base metal of the titanium alloy. 2. The composite material according to claim 1, characterized in that the modified surface layer further comprises TiB _x , Ti _y B _x . 3. The composite material according to claim 2, characterized in that the mass fraction of TiB _x , Ti _y B _x in the front layer with a ceramic structure is more than 10%, and in the layer with a cermet structure from 2 to 10%. 4. A method of manufacturing a composite material based on a titanium alloy, comprising heating the surface of the titanium alloy with a highly concentrated moving source of thermal energy in a gas atmosphere containing modifying components, characterized in that the heating and remelting of the surface of the titanium alloy is carried out by a direct immersed plasma arc with a specific heat flux in the center of the spot is from 10 ⁴ to 10 ⁵ W / cm ² , current strength is 50-450 A, arc voltage is from 20 to 40 V and the speed of movement of the source of thermal energy and relative to the surface of the titanium alloy from 0.003 to 0.01 m / s, and the gas atmosphere contains a mixture of argon with the addition of nitrogen and / or carbon modifying components in the form of a carbon-containing gas. 5. The method according to p. 4, characterized in that the source of thermal energy is moved relative to the surface, ensuring that the remelted sections overlap by 45-60% of their width. 6. The method according to p. 4, characterized in that after remelting the surface of the titanium alloy, heat treatment is carried out. 7. The method according to p. 6, characterized in that the heat treatment is carried out by annealing at a temperature of 800-850 ° C. 8. The method according to p. 6, characterized in that the heat treatment is carried out by tempering at a temperature of 600-650 ° C.

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