High-temperature-resistant creep-resistant tungsten alloy and preparation method and application thereof

Abstract

The invention provides a high-temperature-resistant creep-resistant tungsten alloy, and relates to the technical field of powder metallurgy, the tungsten alloy comprises, by mass, 3-8 wt% of Re, 0.2-1 wt% of carbide, 0.1-0.5 wt% of boride, and the balance tungsten and inevitable impurities; the carbide is selected from one or more of TiC, ZrC, TaC and HfC; the boride is selected from one or more of TiB2 (titanium diboride), HfB2 (hafnium diboride) and ZrB2 (zirconium diboride). The high-temperature-resistant creep-resistant tungsten alloy is prepared by adding low-content rhenium, carbide and boride into pure tungsten and adopting a unique preparation method, and the technical defects that an existing tungsten-rhenium alloy is insufficient in strength and creep resistance at the ultrahigh temperature (larger than or equal to 2000 DEG C), and a traditional multi-pass processing technology is complex are overcome.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder metallurgy, and relates to a high-temperature-resistant and creep-resistant tungsten alloy as well as a preparation method and application thereof. BACKGROUND

[0002] Metal tungsten is widely used in aerospace high-temperature components, nuclear reactor structural materials and other fields due to its high melting point, low thermal expansion coefficient and other characteristics. However, the recrystallization temperature of pure tungsten is about 1200-1400 DEG C, and when the temperature exceeds this temperature, the grain boundary sliding and dislocation movement are intensified, which leads to unacceptable plastic deformation of the material under continuous stress, that is, the creep rate is sharply increased, and it is difficult to meet the requirements of long-term stable work at a high temperature of 2000 DEG C or above and under load.

[0003] In the prior art, the high-temperature performance is usually improved by adding rhenium to form a tungsten-rhenium solid solution (tungsten-rhenium alloy): rhenium atoms cause lattice distortion and hinder dislocation movement, which can improve high-temperature strength and reduce the ductile-brittle transition temperature. However, tungsten alloys with high rhenium content (such as W-Re alloy) still face severe challenges: rhenium is an extremely rare and expensive strategic metal, and high rhenium content (> 10wt%) will greatly increase the cost of the material; the solid solubility of rhenium in tungsten is limited (about 26wt%), and when the rhenium content is too high, brittle intermetallic compound phases such as W2Re3 are easily formed, and the existence of these brittle phases will seriously damage the toughness and processing performance of the material. Even if a higher content of rhenium is added, the deformation resistance (anti-creep performance) of such tungsten-rhenium alloy is still insufficient under long-time service conditions at ultra-high temperature (such as close to or above 2000 DEG C), and it is difficult to effectively inhibit the accelerated creep caused by grain boundary sliding and dislocation climbing.

[0004] Therefore, it is urgent to develop a new type of tungsten alloy and a preparation method thereof, which can significantly reduce the amount of expensive rhenium element, and synergistically improve the room temperature and ultra-high temperature strength, toughness, especially the ultra-high temperature (≥2000 DEG C) anti-creep performance of the material through a composite strengthening mechanism, so as to meet the harsh requirements of the next generation of extreme high-temperature equipment (such as space nuclear reactor thermionic converter) on the comprehensive performance of the material. SUMMARY

[0005] In view of the above deficiencies in the prior art, the purpose of the present application is to provide a high-temperature-resistant and creep-resistant tungsten alloy as well as a preparation method and application thereof. The high-temperature-resistant and creep-resistant tungsten alloy is prepared by adding a low content of rhenium and carbide and boride into pure tungsten and adopting a unique preparation method, so as to solve the technical defects of the existing tungsten-rhenium alloy, such as insufficient strength at ultra-high temperature (≥2000 DEG C), insufficient anti-creep performance and complex traditional multi-pass processing process.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a high-temperature-resistant and creep-resistant tungsten alloy, comprising, in percentage by mass: Re 3-8wt%, carbide 0.2-1wt% and boride 0.1-0.5wt%, and the rest being tungsten and inevitable impurities; the carbide is selected from one or more of TiC, ZrC, TaC and HfC; and the boride is selected from one or more of TiB2, HfB2 and ZrB2.

[0008] In the present application, the addition of a low content of rhenium distorts the tungsten lattice, hinders dislocation movement, can improve high-temperature strength and reduce the ductile-brittle transition temperature, can produce solid solution strengthening effect in the tungsten matrix, and after the addition of rhenium, the number of available slip systems is increased, and at the same time, the extra electrons provided by rhenium can locally soften the lattice and improve plasticity. The simultaneous introduction of carbide and boride can provide stable strengthening phases at high temperatures, such as HfC and ZrC, which have high melting points (greater than 3000℃), and the second phase pins dislocations, making it difficult for dislocations to slip, which can effectively hinder dislocation movement and grain boundary migration; at the same time, the borides HfB2 and ZrB2 also have high melting points and excellent high-temperature stability, and form a high-temperature stable strengthening network in cooperation with the carbides; the interface between the carbide and the boride may form a coherent or semi-coherent structure, further inhibiting dislocation climb and grain boundary sliding. The present application uses the combined action of carbide and boride to hinder dislocation slip or climb by dispersing the second phase in the crystal, and uses the second phase of the grain boundary with a special interface structure to hinder grain boundary sliding to maintain a low steady-state creep rate under ultra-high temperature conditions, prolonging the service life of the material.

[0009] Further, the carbide is selected from one or both of ZrC and HfC; and the boride is selected from one or more of HfB2 and ZrB2.

[0010] Further, the carbide is HfC; and the boride is HfB2.

[0011] Further, the tungsten alloy has an average grain size of ≤13.5μm and a density of ≥99.65%; a tensile strength at room temperature of ≥1600MPa and an elongation after fracture of ≥16.0%; a tensile strength at 2000℃ of ≥210MPa, an elongation after fracture at 2000℃ of ≥18.0%; and a steady-state creep rate at 2000℃ and 50MPa of ≤1.2×10 -6 s -1 .

[0012] In a second aspect, the present application provides a preparation method of the high-temperature-resistant and creep-resistant tungsten alloy according to the first aspect, comprising the following steps:

[0013] (1) mixing powders: mixing tungsten powder, rhenium powder, carbide powder and boride powder to obtain a uniformly mixed composite tungsten alloy powder;

[0014] (2) Compacting: the composite tungsten alloy powder is subjected to forming treatment to obtain a formed blank;

[0015] (3) Pre-sintering: the formed blank is subjected to normal pressure pre-sintering in hydrogen at 2000-2200°C to obtain a pre-sintered blank;

[0016] (4) Hot isostatic sintering: the pre-sintered blank is subjected to hot isostatic sintering in an inert atmosphere at 1400-1600°C and a sintering pressure of 120-180 MPa to obtain a sintered blank;

[0017] (5) Extrusion: the sintered blank is subjected to extrusion deformation treatment with an extrusion ratio ≥5 to obtain an extruded blank;

[0018] (6) Heat treatment: the extruded blank is subjected to heat treatment to obtain a high-temperature-resistant and creep-resistant tungsten alloy.

[0019] Further, in the step (1), the purity of the tungsten powder is ≥99.97%, and the average particle size is 0.8-2.0 μm.

[0020] Further, in the step (1), the purity of the rhenium powder is ≥99.97%, and the average particle size is 1.0-2.0 μm.

[0021] Further, in the step (1), the average particle size of the carbide powder is 0.5-1.0 μm.

[0022] Further, in the step (1), the average particle size of the boride powder is 0.5-1.0 μm.

[0023] Further, in the step (1), ball milling is used for mixing, the ball milling is carried out under inert gas protection, the ball milling time is 8-20 h, and the ball milling rotation speed is 300-500 rpm.

[0024] Further, in the step (1), after ball milling, it further includes passing through an 80-120 mesh sieve.

[0025] Further, in the step (2), cold isostatic pressing is used for forming treatment, the pressure is 150-250 MPa, and the pressure holding time is 10-30 min.

[0026] Further, in the step (3), the pre-sintering holding time is 6-12 h, and preferably, the heating rate is ≤70°C / h.

[0027] Further, in the step (4), the hot isostatic sintering holding time is 4-8 h.

[0028] Further, in the step (5), the extrusion ratio is 5-8.

[0029] Further, in the step (5), the extrusion temperature is 1500-1700 DEG C, the extrusion holding time is 1-3h, and the extrusion speed is 100-200mm / s.

[0030] Further, in the step (5), the final forging temperature is ≥1500 DEG C, and a hot extrusion is performed by using an extruder with a nominal pressure ≥2800T.

[0031] Further, in the step (6), the heat treatment is performed in a hydrogen atmosphere, the heat treatment temperature is 900-1000 DEG C, and the holding time is 0.5-1.5h.

[0032] In a third aspect, the application provides a use of the high-temperature-resistant and creep-resistant tungsten alloy as described in the first aspect or prepared by the method as described in the second aspect in a high-temperature-resistant component of aerospace or a structural material of a nuclear reactor.

[0033] Compared with the prior art, the application has at least one of the following beneficial effects:

[0034] 1) In the application, the addition of a small amount of rhenium distorts the tungsten lattice, hinders dislocation movement, increases the number of available slip systems, and locally softens the lattice by providing additional electrons, thereby improving plasticity. The simultaneous introduction of carbides and borides can provide stable strengthening phases at high temperatures, such as HfC and ZrC, which have high melting points (greater than 3000 DEG C). The second phase pins dislocations, making it difficult for dislocations to slip, and effectively hinders dislocation movement and grain boundary migration. Borides such as HfB2 and ZrB2 also have high melting points and excellent high-temperature stability, forming a high-temperature stable strengthening network in cooperation with carbides. Compared with oxides such as HfO2 and ZrO2, which have larger sizes and poor high-temperature stability, carbides and borides have higher melting points and can form coherent or semi-coherent structures at the interface, further inhibiting dislocation climb and grain boundary sliding. The application utilizes the combined action of carbides and borides to hinder dislocation slip or climb by dispersing the second phase in the crystal, and utilizes the second phase at the grain boundary with a special interface structure to hinder grain boundary sliding to maintain a low steady-state creep rate under ultra-high temperature conditions, thereby prolonging the service life of the material.

[0035] 2) Using "high temperature and large deformation extrusion", single pass large deformation (extrusion ratio ≥ 5) breaks the coarse grains, refines the matrix structure, increases the grain boundary area, reduces the impurity segregation brittleness, and introduces a certain dislocation substructure. At high temperatures, these dislocations are pinned by the second phase, forming stable substructures, which improves the high temperature creep resistance of the material; tungsten alloy grains are elongated and broken, and second phase particles are more uniformly dispersed. After extrusion, the steady-state creep rate at 2000°C is significantly reduced; single pass large deformation extrusion replaces multi-pass annealing, the process cycle is shortened by more than 50%, and grain coarsening is avoided.

[0036] 3) The low-rhenium content combined with carbide and boride composite reinforcement is creatively used in the tungsten alloy composition, breaking through the limitations of traditional high-rhenium alloys, achieving low cost and high performance, and at the same time, synergistically controlling the content of each alloying element to prepare a tungsten alloy material resistant to ultra-high temperature and creep. BRIEF DESCRIPTION OF DRAWINGS

[0037] The following briefly describes the content expressed in each drawing in the specification of the present application and the marks in the drawings:

[0038] Figure 1 The metallographic structure photo of the high-temperature and creep-resistant tungsten alloy prepared in Example 1. DETAILED DESCRIPTION

[0039] To make the purpose, technical scheme and advantages of the present application clearer, the following will combine the embodiments of the present application to clearly and completely describe the technical scheme in the embodiments of the present application. Those skilled in the art should understand that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. The process parameters not specified in the following examples are usually according to the conventional conditions.

[0040] The endpoints of the ranges and any values disclosed in the present application are not limited to the precise values stated. The ranges or values should be interpreted as being approximate. For numeric values, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to obtain one or more new numeric ranges, which should be considered as specifically disclosed in the present application.

[0041] In a first aspect, the present application provides a high-temperature and creep-resistant tungsten alloy, which comprises, by mass percentage: Re 3-8wt%, carbide 0.2-1wt% and boride 0.1-0.5wt%, and the balance being tungsten and unavoidable impurities;

[0042] The carbide is selected from one or more of TiC, ZrC, TaC and HfC; the boride is selected from one or more of TiB2, HfB2 and ZrB2.

[0043] In the present application, the addition of a low content of rhenium distorts the tungsten lattice, hinders dislocation movement, can improve high temperature strength and reduce the ductile-brittle transition temperature, can produce solid solution strengthening effect in the tungsten matrix, the addition of rhenium increases the number of available slip systems, and at the same time the extra electrons provided by rhenium can locally soften the lattice and improve plasticity; the simultaneous introduction of carbides and borides can provide stable strengthening phases at high temperatures, such as HfC, ZrC and other carbides with high melting points (more than 3000℃), the second phase pins dislocations, making it difficult for dislocations to slip, which can effectively hinder dislocation movement and grain boundary migration; at the same time, borides such as HfB2 and ZrB2 also have high melting points and excellent high temperature stability, and form a high temperature stable strengthening network in cooperation with carbides, and the interface between carbides and borides may form a coherent or semi-coherent structure, further inhibiting dislocation climb and grain boundary sliding. The present application utilizes the combined action of carbides and borides to hinder dislocation slip or climb by dispersing the second phase in the crystal, and utilizes the grain boundary second phase with a special interface structure to hinder grain boundary sliding to maintain a low steady-state creep rate under ultra-high temperature conditions, thereby prolonging the service life of the material.

[0044] As an optional embodiment, in the high-temperature-resistant and creep-resistant tungsten alloy, the content of Re is 3-8wt%, for example, it can be 3wt%, 4wt%, 5wt%, 6wt%, 7wt% or 8wt%.

[0045] As an optional embodiment, in the high-temperature-resistant and creep-resistant tungsten alloy, the content of carbide is 0.2-1wt%, for example, it can be 0.2wt%, 0.3wt%, 0.5wt%, 0.8wt% or 1wt%.

[0046] As an optional embodiment, in the high-temperature-resistant and creep-resistant tungsten alloy, the content of boride is 0.1-0.5wt%, for example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt% or 0.5wt%.

[0047] As an optional embodiment, the carbide is selected from one or both of ZrC and HfC; the boride is selected from one or more of HfB2 and ZrB2.

[0048] As an optional embodiment, the carbide is HfC; the boride is HfB2.

[0049] As an optional embodiment, the tungsten alloy has an average grain size of ≤13.5 μm, a density of ≥99.65%, a tensile strength at room temperature of ≥1600 MPa, an elongation at break at room temperature of ≥16.0%, a tensile strength at 2000℃ of ≥210 MPa, an elongation at break at 2000℃ of ≥18.0%, a steady creep rate at 2000℃, 50 MPa of ≤1.2×10 -6 s -1 .

[0050] In a second aspect, the present application provides a preparation method of the high-temperature-resistant and creep-resistant tungsten alloy according to the first aspect, which comprises the following steps:

[0051] (1) mixing powders: mixing tungsten powder, rhenium powder, carbide powder and boride powder to obtain a uniformly mixed composite tungsten alloy powder;

[0052] (2) pressing: performing shaping treatment on the composite tungsten alloy powder to obtain a shaped blank;

[0053] (3) pre-sintering: performing normal-pressure pre-sintering on the shaped blank at 2000-2200℃, which can be 2050℃, 2100℃ or 2150℃, in hydrogen to obtain a pre-sintered blank;

[0054] (4) hot isostatic sintering: performing hot isostatic sintering on the pre-sintered blank at 1400-1600℃, which can be 1450℃, 1500℃ or 1550℃, in an inert atmosphere at a sintering pressure of 120-180 MPa, which can be 125 MPa, 140 MPa, 150 MPa, 160 MPa or 170 MPa, to obtain a sintered blank;

[0055] (5) extrusion: performing extrusion deformation treatment on the sintered blank at an extrusion ratio of ≥5, preferably 5-8, which can be 5, 6, 7 or 8, to obtain an extruded blank;

[0056] (6) heat treatment: performing heat treatment on the extruded blank to obtain the high-temperature-resistant and creep-resistant tungsten alloy.

[0057] The extrusion ratio is the ratio of the original cross-sectional area (A0) of the blank to the cross-sectional area (A1) of the product after extrusion.

[0058] The present application realizes the super-high temperature strength and creep resistance of the alloy by the combined action of the powder mixing, profiling, pre-sintering, hot isostatic sintering, extrusion (extrusion ratio >=5) and heat treatment steps, so that the components of the alloy are uniformly mixed, fully densified and the structure is completely refined. By using "high-temperature large deformation extrusion", single pass large deformation (extrusion ratio >=5) breaks the coarse grains, refines the matrix structure, increases the grain boundary area, reduces the impurity segregation brittleness, and introduces a certain dislocation substructure. At high temperature, these dislocations are pinned by the second phase, forming a stable substructure, which improves the high temperature creep resistance of the material; the tungsten alloy grains are elongated and broken, and the second phase particles are more uniformly dispersed. After extrusion processing, the steady-state creep rate at 2000 DEG C is significantly reduced; single pass large deformation extrusion (three-dimensional stress extrusion deformation) replaces multi-pass deformation and repeated heating (such as air hammer forging, rotary forging, etc.), the process cycle is shortened by more than 50%, and grain coarsening is avoided.

[0059] As an optional embodiment, in the step (1), the purity of the tungsten powder is >=99.97%, and the average particle size is 0.8-2.0 μm, for example, it can be 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm or 2.0 μm.

[0060] As an optional embodiment, in the step (1), the purity of the rhenium powder is >=99.97%, and the average particle size is 1.0-2.0 μm, for example, it can be 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm or 2.0 μm.

[0061] As an optional embodiment, in the step (1), the average particle size of the carbide powder is 0.5-1.0 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm.

[0062] As an optional embodiment, in the step (1), the average particle size of the boride powder is 0.5-1.0 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm.

[0063] As an optional embodiment, in the step (1), ball milling is used for mixing, and the ball milling is carried out under inert gas protection, the ball milling time is 8-20 h, which can be 8 h, 10 h, 12 h, 15 h, 18 h or 20 h, and the ball milling speed is 300-500 rpm, which can be 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm.

[0064] As an optional embodiment, in the step (1), after ball milling, it further includes passing through an 80-120 mesh sieve, which can be 90 mesh, 100 mesh, 110 mesh.

[0065] The present application can reduce the influence of impurities and ensure good fine dispersibility of the powder by limiting the parameters of tungsten powder, rhenium powder, carbide powder and boride powder. Ball milling under inert gas protection (8-20h, 300-500rpm) ensures uniform mixing and avoids oxidation, providing high-quality composite powder for subsequent sintering and forming, and ensuring uniform distribution of the strengthening phase. After ball milling, the powder is sieved through an 80-120 mesh sieve to remove large particles, obtaining a uniform tungsten alloy powder.

[0066] As an optional embodiment, in step (2), cold isostatic pressing is used for forming treatment, the pressure is 150-250MPa, which can be 160MPa, 180MPa, 200MPa, 210MPa, 230MPa or 240MPa, and the holding time is 10-30min, which can be 10min, 15min, 20min, 25min or 30min.

[0067] The present application can obtain a shaped blank with uniform density by cold isostatic pressing (150-250MPa, holding for 10-30min), which lays the foundation for densification in the sintering stage, reduces internal porosity of the final material, and thus improves the density and mechanical properties of the final product.

[0068] As an optional embodiment, in step (3), the holding time for pre-sintering is 6-12h, which can be 6h, 8h, 10h or 12h.

[0069] As an optional embodiment, in step (4), the holding time for hot isostatic pressing sintering is 4-8h, which can be 4h, 5h, 6h or 8h.

[0070] As an optional embodiment, the pre-sintering is atmospheric pressure sintering in a hydrogen atmosphere, and the heating rate is ≤70℃ / h, which can be 40℃ / h, 50℃ / h, 60℃ / h or 70℃ / h.

[0071] In the present application, the high sintering temperature used in hydrogen sintering allows the tungsten matrix to be fully densified, while the carbide and boride particles can maintain a very high temperature, and the low heating rate allows the tungsten to be fully reduced at a low temperature, reducing the content of impurity elements. The tungsten alloy subjected to high-temperature hydrogen pre-sintering in step (3) is subjected to hot isostatic pressing sintering in an inert atmosphere in step (4), which closes the residual pores to further improve the density.

[0072] As an optional implementation form, in the step (5), the extrusion temperature is 1500-1700℃, which can be 1550℃, 1600℃ or 1650℃, the extrusion holding time is 1-3h, which can be 1h, 2h or 3h, and the extrusion speed is 100-200mm / s, which can be 120mm / s, 150mm / s, 180mm / s or 190mm / s.

[0073] As an optional implementation form, in the step (5), the final forging temperature is ≥1500℃, and a hot extrusion is implemented by using an extruder with a nominal pressure ≥2800T.

[0074] The present application controls the extrusion temperature, the extrusion holding time, the extrusion speed and the final forging temperature, in the extrusion process, the tungsten alloy grains are elongated and broken, and the dynamic recrystallization can also be avoided, the final forging temperature is controlled to refine the alloy organization, the second phase particles are dispersed more uniformly, and after the extrusion processing, the density of the tungsten alloy is significantly improved. A large-tonnage extruder (≥2800T) is used to ensure a high extrusion ratio (≥5) for one-time forming and improve the creep resistance.

[0075] As an optional implementation form, in the step (6), the heat treatment is performed in the atmosphere of hydrogen, the heat treatment temperature is 900-1000℃, which can be 920℃, 950℃ or 980℃, and the holding time is 0.5-1.5h, which can be 0.5h, 1h or 1.5h.

[0076] If the annealing temperature is too high, the grain growth can be induced, which offsets the extrusion refinement effect. The present application uses low-temperature heat treatment (900-1000℃) to inhibit recrystallization, retain dislocation substructure strengthening, and release processing stress to improve the elongation after fracture.

[0077] In a third aspect, the present application provides a use of the high-temperature-resistant and creep-resistant tungsten alloy according to the first aspect or prepared by the preparation method according to the second aspect in aerospace high-temperature-resistant parts or nuclear reactor structural materials.

[0078] The present application will be further described in detail in combination with specific examples and comparative examples.

[0079] Example 1

[0080] A preparation method of the high-temperature-resistant and creep-resistant tungsten alloy, the method comprising the following steps:

[0081] (1) Mixing: tungsten powder with an average particle size of 1 μm (purity≥99.97%), rhenium powder with a particle size of 1.5 μm (purity≥99.97%), HfC powder with an average particle size of 0.5 μm and HfB2 powder with an average particle size of 0.5 μm are mixed according to the mass percentage (W-3wt%Re-1wt%HfC-0.3wt%HfB2). High-energy ball milling is carried out under argon protection, the rotation speed is 400 rpm, the time is 8 h, and the composite tungsten alloy powder is obtained after being sieved through a 100 mesh sieve.

[0082] (2) Compacting: the composite tungsten alloy powder is loaded into a mold for cold isostatic pressing forming, the pressure is 240 MPa, and the pressure holding time is 30 min, to obtain a formed blank.

[0083] (3) Pre-sintering: the formed blank is loaded into a sintering furnace in a hydrogen atmosphere for normal pressure pre-sintering to obtain a pre-sintered blank, the sintering furnace is heated to 2200°C at a rate of 60°C / h, and the temperature is maintained for 10 h.

[0084] (4) Hot isostatic pressing sintering: the pre-sintered blank is placed in a hot isostatic pressing furnace for sintering to obtain a sintered blank with a diameter of 100 mm, the temperature of the hot isostatic pressing furnace is 1500°C, the sintering pressure is 150 MPa, and the holding time is 4 h.

[0085] (5) Extrusion: the sintered blank is heated at 1650°C for 1 h, and hot extrusion is carried out (nominal pressure 3000T) with an extrusion ratio of 6 and an extrusion speed of 180 mm / s, the final forging temperature is≥1500°C, and an extruded blank with a diameter of 41 mm is obtained.

[0086] (6) Heat treatment: the extruded blank is annealed in a hydrogen atmosphere heating furnace under hydrogen protection, the annealing temperature is 1000°C, the holding time is 1 h, and a high-temperature creep-resistant tungsten alloy is obtained.

[0087] Figure 1 The microstructure of the high-temperature creep-resistant tungsten alloy prepared in Example 1 is shown in the figure. The average grain size of the tungsten-rhenium alloy is 9.7 μm, and the second phase particles are uniformly dispersed in the tungsten matrix.

[0088] Example 2

[0089] The preparation method of the high-temperature creep-resistant tungsten alloy of Example 2 is basically the same as that of Example 1, except that in step (1), the same tungsten powder, rhenium powder and HfB2 powder as in Example 1, and ZrC powder with an average particle size of 0.5 μm are mixed according to the mass percentage (W-3wt%Re-1wt%ZrC-0.3wt%HfB2).

[0090] Example 3

[0091] The method of preparing the high-temperature resistant and creep resistant tungsten alloy of Example 3 is substantially the same as that of Example 1, except that in step (1), the same tungsten powder and rhenium powder as in Example 1, and TiC powder having an average particle size of 0.5 μm and TiB2 powder having an average particle size of 0.5 μm are mixed in a mass percentage of (W-3wt% Re-1wt% TiC-0.3wt% TiB2).

[0092] Example 4

[0093] The method of preparing the high-temperature resistant and creep resistant tungsten alloy of Example 4 is substantially the same as that of Example 1, except that in step (1), the same tungsten powder and rhenium powder as in Example 1, and ZrC powder having an average particle size of 0.5 μm and ZrB2 powder having an average particle size of 0.5 μm are mixed in a mass percentage of (W-3wt% Re-1wt% ZrC-0.3wt% ZrB2).

[0094] Example 5

[0095] The method of preparing the high-temperature resistant and creep resistant tungsten alloy of Example 5 is substantially the same as that of Example 1, except that in step (1), the same tungsten powder, rhenium powder and HfB2 powder as in Example 1, and TaC powder having an average particle size of 0.5 μm are mixed in a mass percentage of (W-3wt% Re-1wt% TaC-0.3wt% HfB2).

[0096] Example 6

[0097] The method of preparing the high-temperature resistant and creep resistant tungsten alloy of Example 6 is substantially the same as that of Example 1, except that in step (1), the same tungsten powder, rhenium powder, HfC powder and HfB2 powder as in Example 1 are mixed in a mass percentage of (W-3wt% Re-1wt% HfC-0.1wt% HfB2).

[0098] Example 7

[0099] The method of preparing the high-temperature resistant and creep resistant tungsten alloy of Example 7 is substantially the same as that of Example 1, except that in step (1), the same tungsten powder, rhenium powder, HfC powder and HfB2 powder as in Example 1 are mixed in a mass percentage of (W-3wt% Re-0.2wt% HfC-0.3wt% HfB2).

[0100] Example 8

[0101] The method of preparing the high-temperature resistant and creep resistant tungsten alloy of Example 8 is substantially the same as that of Example 1, except that in step (1), the same tungsten powder, rhenium powder, HfC powder and HfB2 powder as in Example 1 are mixed in a mass percentage of (W-3wt% Re-1wt% HfC-0.5wt% HfB2).

[0102] Example 9

[0103] The method for preparing the high-temperature resistant and creep resistant tungsten alloy of Example 9 is basically the same as that of Example 1, except that in step (1), the tungsten powder, the rhenium powder, the HfC powder and the HfB2 powder of the same as Example 1 are mixed in the mass percentage of (W-8wt%Re-1wt%HfC-0.3wt%HfB2).

[0104] Example 10

[0105] The method for preparing the high-temperature resistant and creep resistant tungsten alloy of Example 10 is basically the same as that of Example 1, except that in step (5), hot extrusion is performed with an extrusion ratio of 5 and a speed of 100 mm / s to obtain an extrusion billet with a diameter of 45 mm.

[0106] Comparative Example 1

[0107] The method for preparing the tungsten alloy of Comparative Example 1 is basically the same as that of Example 1, except that no HfB2 powder is added, and in step (1), the tungsten powder, the rhenium powder and the HfC powder of the same as Example 1 are mixed in the mass percentage of (W-3wt%Re-1.3wt%HfC).

[0108] Comparative Example 2

[0109] The method for preparing the tungsten alloy of Comparative Example 2 is basically the same as that of Example 1, except that no HfC powder is added, and in step (1), the tungsten powder, the rhenium powder and the HfB2 powder of the same as Example 1 are mixed in the mass percentage of (W-3wt%Re-1.3wt%HfB2).

[0110] Comparative Example 3

[0111] The method for preparing the tungsten alloy of Comparative Example 3 is basically the same as that of Example 1, except that an oxide is used instead of a boride, and in step (1), the tungsten powder, the rhenium powder and the HfC powder of the same as Example 1, and the HfO2 powder with an average particle size of 0.5 μm are mixed in the mass percentage of (W-3wt%Re-1wt%HfC-0.3wt%HfO2).

[0112] Comparative Example 4

[0113] The method for preparing the tungsten alloy of Comparative Example 4 is basically the same as that of Example 1, except that a larger amount of Re is used, and in step (1), the tungsten powder, the rhenium powder, the HfC powder and the HfB2 powder of the same as Example 1 are mixed in the mass percentage of (W-15wt%Re-1wt%HfC-0.3wt%HfB2).

[0114] Comparative Example 5

[0115] The tungsten alloy of Comparative Example 5 was prepared by the same method as that of Example 1, except that in step (5), the first pass extrusion temperature was 1650℃, the holding time was 1h, and the extrusion ratio was 2, and the second pass extrusion temperature was 1500℃, the holding time was 1h, and the extrusion ratio was 3, to obtain a billet with a diameter of 41mm.

[0116] Comparative Example 6

[0117] The tungsten alloy of Comparative Example 6 was prepared by the same method as that of Example 1, except that only the hydrogen sintering of step (3) of the present application was used without the hot isostatic pressing sintering of step (4).

[0118] Performance test:

[0119] Test method:

[0120] The high temperature tensile test in the examples and comparative examples was performed according to GB / T 4338-2006 "Metallic materials - Tensile testing at elevated temperature".

[0121] The performance test results of the tungsten alloys prepared in Examples 1-10 and Comparative Examples 1-6 are shown in Table 1, and the data in Table 1 are the average values of three samples.

[0122] Table 1

[0123]

[0124]

[0125] Table 1 (continued)

[0126]

[0127]

[0128] From Table 1, it can be seen that:

[0129] (1) In Examples 1-5, different carbides and borides were used to prepare the high temperature resistant and creep resistant tungsten alloy, and the average grain size of the tungsten alloy was ≤12.9μm, the density was ≥99.79%, the tensile strength at room temperature was ≥1640MPa, the elongation after fracture was ≥16.5%, the tensile strength at 2000℃ was ≥232MPa, the elongation after fracture at 2000℃ was ≥21.0%, and the steady creep rate at 2000℃, 50MPa was ≤4.87×10 -7 s -1 Thus, it can be seen that TiC, ZrC, TaC and HfC can be used as carbides, and TiB2, HfB2 and ZrB2 can be used as borides, and the above-mentioned carbides and borides can be randomly combined to prepare a tungsten alloy with high strength and good creep resistance at ultra-high temperature (≥2000℃).

[0130] (2) Examples 6-10 are compared with Example 1 respectively, Example 6 selects the lower limit of the content of boride in the application, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is reduced, the elongation after fracture at room temperature and high temperature is also reduced, and the steady creep rate is increased; Example 7 selects the lower limit of the content of carbide in the application, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is reduced, the elongation after fracture at room temperature and high temperature is reduced, and the steady creep rate is increased obviously; Example 8 selects the upper limit of the content of boride in the application, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is increased, the elongation after fracture at room temperature and high temperature is increased, and the steady creep rate is reduced, and Example 8 is the optimal example; Example 9 selects the upper limit of the content of Re in the application, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is increased, the elongation after fracture at room temperature and high temperature is increased, but the steady creep rate is increased; Example 10 selects the lower limit of the extrusion ratio and the lower limit of the extrusion speed in the application, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is reduced, the elongation after fracture at room temperature and high temperature is reduced, and the steady creep rate is increased.

[0131] (3) Comparative Examples 1-6 are compared with Example 1 respectively, Comparative Example 1 does not add HfB2 powder, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is significantly reduced, the elongation after fracture at high temperature is reduced, and the steady creep rate is increased; Comparative Example 2 does not add HfC powder, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is significantly reduced, the elongation after fracture at high temperature is reduced, and the steady creep rate is increased; Comparative Example 3 uses oxide instead of boride, the average grain size of the tungsten alloy prepared is >15 μm, the tensile strength at room temperature and high temperature is reduced, the elongation after fracture at room temperature and high temperature is reduced, and the steady creep rate is significantly increased; Comparative Example 4 uses more amount of Re >8 wt%, the tensile strength at room temperature and high temperature of the tungsten alloy prepared is increased, the elongation after fracture at room temperature and high temperature is increased, but the steady creep rate is significantly increased; Comparative Example 5 uses multi-pass extrusion, the average grain size of the tungsten alloy prepared is >15 μm, the tensile strength at room temperature and high temperature is significantly reduced, the elongation after fracture at room temperature and high temperature is significantly reduced, and the steady creep rate is significantly increased; Comparative Example 6 only uses hydrogen sintering of step (3) in the application without hot isostatic pressing sintering of step (4), the density of the tungsten alloy prepared is <99.50%, the tensile strength at room temperature and high temperature is reduced, the elongation after fracture at room temperature and high temperature is reduced, and the steady creep rate is increased.

[0132] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-temperature resistant and creep-resistant tungsten alloy, characterized in that, The tungsten alloy comprises, by weight percentage: 3-8 wt% Re, 0.2-1 wt% carbides and 0.1-0.5 wt% borides, with the remainder being tungsten and unavoidable impurities; The carbide is selected from one or more of TiC, ZrC, TaC, and HfC; the boride is selected from one or more of TiB2, HfB2, and ZrB2.

2. The tungsten alloy according to claim 1, characterized in that, The carbide is selected from one or both of ZrC and HfC; the boride is selected from one or more of HfB2 and ZrB2; preferably, the carbide is HfC; and the boride is HfB2.

3. The tungsten alloy according to claim 1 or 2, characterized in that, The tungsten alloy has an average grain size ≤13.5μm and a density ≥99.65%; a room temperature tensile strength ≥1600MPa and an elongation after fracture ≥16.0%; a 2000℃ tensile strength ≥210MPa and an elongation after fracture ≥18.0%; and a steady-state creep rate ≤1.2×10⁻⁶ at 2000℃ and 50MPa. -6 s -1 .

4. A method for preparing a high-temperature resistant and creep-resistant tungsten alloy as described in any one of claims 1-3, characterized in that, The method includes the following steps: (1) Powder mixing: Tungsten powder, rhenium powder, carbide powder and boride powder are mixed to obtain a uniformly mixed composite tungsten alloy powder; (2) Molding: The composite tungsten alloy powder is subjected to molding treatment to obtain a molded blank; (3) Pre-sintering: The formed blank is pre-sintered in hydrogen at 2000-2200℃ under normal pressure to obtain a pre-sintered blank; (4) Hot isostatic pressing sintering: The pre-sintered blank is hot isostatically pressed in an inert atmosphere at 1400-1600℃ and sintering pressure of 120-180MPa to obtain a sintered blank; (5) Extrusion: The sintered billet is subjected to extrusion deformation treatment with an extrusion ratio ≥5, preferably 5-8, to obtain an extruded billet; (6) Heat treatment: The extruded billet is heat treated to obtain a high-temperature resistant and creep-resistant tungsten alloy.

5. The preparation method according to claim 4, characterized in that, In step (1), the tungsten powder has a purity ≥99.97% and an average particle size of 0.8-2.0 μm; and / or, The rhenium powder has a purity ≥99.97% and an average particle size of 1.0-2.0 μm; and / or, The average particle size of the carbide powder is 0.5-1.0 μm; and / or, The average particle size of the boride powder is 0.5-1.0 μm; and / or, The mixture is mixed by ball milling under inert gas protection for 8-20 hours at a speed of 300-500 rpm. Preferably, the material is further passed through an 80-120 mesh sieve after ball milling.

6. The preparation method according to claim 4, characterized in that, In step (2), cold isostatic pressing is used for forming, with a pressure of 150-250 MPa and a holding time of 10-30 min.

7. The preparation method according to claim 4, characterized in that, In step (3), the pre-sintering holding time is 6-12 hours, preferably with a heating rate ≤70℃ / h; and / or, In step (4), the hot isostatic pressing sintering holding time is 4-8 hours.

8. The preparation method according to claim 4, characterized in that, In step (5), the extrusion temperature is 1500-1700℃, the extrusion holding time is 1-3h, and the extrusion speed is 100-200mm / s; Preferably, the final forging temperature is ≥1500℃, and hot extrusion is carried out using an extrusion press with a nominal pressure ≥2800T.

9. The preparation method according to claim 4, characterized in that, In step (6), heat treatment is carried out in a hydrogen atmosphere at a temperature of 900-1000℃ and a holding time of 0.5-1.5h.

10. The use of a high-temperature resistant and creep-resistant tungsten alloy as described in any one of claims 1-3 or a high-temperature resistant and creep-resistant tungsten alloy prepared by the preparation method described in any one of claims 4-9 in high-temperature components for aerospace or structural materials for nuclear reactors.

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