TZM alloy for large-size isothermal forging die, manufacturing process therefor and use thereof

Abstract

The present invention relates to the technical field of alloy manufacture, and specifically provides a TZM alloy for a large-size isothermal forging die, a manufacturing process therefor and the use thereof. The present invention uses a powder metallurgy + hot isostatic pressing + forging process to manufacture TZM alloy, provides complete process parameters and processing solutions, and can manufacture TZM alloy for large-size isothermal forging dies. Using the process can manufacture high-density, high-hardness and high-strength TZM alloy blanks.

Description

TZM alloy for large-size isothermal forging dies, its preparation process and application Technical Field

[0001] The present invention relates to the technical field of alloy preparation, and specifically provides a TZM alloy for a large-size isothermal forging die, a preparation process thereof, and an application thereof. Background Art

[0002] With the rapid development of my country's aerospace technology, aircraft engines, as the core of aviation weaponry, need to achieve higher thrust-to-weight ratios to carry greater loads. Hot-end components, such as combustion chambers, turbine disks, and blades, must withstand higher temperature loads, requiring high-performance high-temperature structural materials. Because high-temperature alloys have a narrow forging temperature range and high deformation resistance, they must undergo plastic deformation within a specific forging temperature range. Currently, key aircraft engine components, such as turbine disks, are mostly forged using isothermal forging. With the continuous upgrading of aircraft engines, higher thrust-to-weight ratios are a major development goal, requiring materials for hot-end components to exhibit enhanced thermal fatigue resistance. For example, TiAl intermetallic compounds, a promising lightweight structural material, require isothermal forging temperatures above 1100°C. This development of hot-end component materials places higher demands on isothermal forging die materials. To develop isothermal forging die materials that can operate at higher temperatures, researchers are focusing on high-melting-point refractory metals. Metallic molybdenum is one of the refractory metals with a melting point of up to 2620°C, ranking sixth among natural elements. It has good room temperature processing performance, so it is considered to use molybdenum and its alloys in the preparation of large-size isothermal forging dies.

[0003] TZM alloys have a high melting point (2617°C), excellent high-temperature strength, high stiffness, low thermal expansion coefficient, high thermal conductivity, and good creep resistance, making them suitable for the development of large-scale vacuum isothermal forging die materials. Currently, Western countries, led by the United States, all use TZM alloys for vacuum isothermal forging dies above 1000°C. To keep pace with international advances and enhance my country's independent research and production capabilities, rapid research on TZM alloys for isothermal forging dies is necessary, as well as exploring the evolution of microstructure and properties during hot working of TZM alloys.

[0004] Hot isostatic pressing can repair defects in powder-sintered TZM alloys, increase the density of powder-sintered TZM alloys, and improve the processing properties of TZM alloys, but its effect on regulating the microstructure of TZM alloys is limited. Hot deformation can further reduce the void defects in the billet, refine the grains, introduce high-density substructure strengthening, and improve material properties. Currently, domestic research on hot deformation of TZM alloys mainly focuses on rolling, and TZM alloys are mostly in the form of plates. However, plates limit the size of alloy products. There are few reports on hot deformation research of TZM alloys for large-scale isothermal forging dies, and there are also few reports on the evolution of microstructure and properties of TZM alloys during forging.

[0005] In view of this, the present invention is proposed.

[0006] Summary of the Invention

[0007] The first object of the present invention is to provide a preparation process of TZM alloy for large-size isothermal forging dies.

[0008] The second object of the present invention is to provide a TZM alloy prepared by the above preparation process.

[0009] A third object of the present invention is to provide uses of the TZM alloy.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A preparation process of a TZM alloy for a large-size isothermal forging die comprises the following steps:

[0012] S1: TZM alloy powder is subjected to ball milling, cold isostatic pressing and sintering in sequence to obtain PM state TZM alloy billet;

[0013] The pressure of cold isostatic pressing is 140-160 MPa, and the sintering condition is 2000-2100℃ for 2.5-3.5h;

[0014] S2: Hot isostatic pressing is performed on the PM state TZM alloy billet in S1 to obtain PM+HIP state TZM alloy billet;

[0015] The conditions for hot isostatic pressing are 1200-1400°C and 120-140 MPa for 2-3 hours;

[0016] S3: Forging the PM+HIP TZM alloy billet in S2 to obtain a large-size isothermal forging die TZM alloy;

[0017] The forging conditions are as follows: the starting forging temperature is set at 1300-1500°C, the final forging temperature is set at 1100-1200°C, the deformation during the forging process is controlled to be ≥40%, and then the TZM alloy ingot is returned to the high-temperature furnace to continue heating to the forging temperature. After forging is completed, it is cooled to room temperature with the furnace.

[0018] Furthermore, the TZM alloy powder in S1 includes: TiH2 powder 0.45% to 0.65%, with a particle size of 2 to 5 μm; ZrH2 powder 0.10% to 0.15%, with a particle size of 2 to 5 μm; C powder 0.04% to 0.08%, with a particle size of 1 to 2 μm; and the rest is molybdenum powder with a particle size of 2 to 5 μm.

[0019] Furthermore, the ball milling conditions in S1 include: a ball milling speed of 240-260 r / min, a ball-to-material ratio of 2:1, and a ball milling time of 2 h.

[0020] Furthermore, hydrogen is used as the protective gas during sintering in S1.

[0021] Furthermore, the hot isostatic pressing conditions in S2 are as follows: stainless steel is used as the sheath material, placed in a degassing furnace for evacuation and welding of the sheath, then placed in a hot isostatic press, inert gas is used as the pressure gas, the heating temperature is 1200-1400°C, the pressure is 120-140 MPa, and after hot isostatic pressing, it is cooled to room temperature with the furnace.

[0022] Furthermore, the inert gas is argon.

[0023] Furthermore, the heating temperature is 1300° C. and the pressure is 130 MPa.

[0024] Furthermore, the starting temperature of forging in S3 is set to 1400°C, and the final forging temperature is set to 1150°C.

[0025] The TZM alloy prepared by the above preparation process.

[0026] The use of the above-mentioned TZM alloy in the preparation of large-size isothermal forging dies.

[0027] Compared with the prior art, the technical effects of the present invention are:

[0028] (1) The present invention uses a powder metallurgy + hot isostatic pressing + forging process to prepare a TZM alloy, providing complete process parameters and processing solutions. This allows the preparation of a TZM alloy for large-scale isothermal forging dies. The alloy achieves a density of 98.5%, an average grain size of 51 μm, a hardness of 259 HV, and a tensile strength of 672 MPa at 600°C. The tensile strength at 1200°C is 398 MPa. This process can produce a TZM alloy billet with high density, high hardness, and high strength.

[0029] (2) The present invention uses HIP to repair and eliminate PM state void defects, improve alloy density, and combine with forging technology to improve the overall performance of the alloy;

[0030] (3) The present invention adopts forging as a thermal deformation method to effectively improve the density and high-temperature strength of the TZM alloy. After forging, a large number of substructures are formed inside the grains, which plays a deformation strengthening role.

[0031] (4) The present invention adopts powder metallurgy + hot isostatic pressing + forging process. Compared with the conventional rolling method, the TZM alloy billet obtained by this process is more suitable as a large-size isothermal forging die material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The various technical features of the present invention and the relationships between them are further explained below with reference to the accompanying drawings. The accompanying drawings are exemplary, and some technical features are not shown in actual proportion. In addition, some drawings may omit technical features that are commonly used in the technical field to which the present invention belongs and are not essential for understanding and implementing the present invention, or additional technical features that are not essential for understanding and implementing the present invention may be shown. In other words, the combination of the various technical features shown in the accompanying drawings is not intended to limit the present invention. In addition, throughout the present invention, the same figure numbers refer to the same content. The specific description of the drawings is as follows:

[0033] FIG1 is a photograph of the microstructure and grain size of a PM-state TZM alloy billet in Example 1 of the present invention;

[0034] FIG2 is a photograph of the microstructure and grain size of the PM+HIP TZM alloy billet in Example 1 of the present invention;

[0035] FIG3 shows the microstructure and grain size of the PM+HIP+F state TZM alloy billet in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] Hereinafter, specific embodiments of the present invention will be described in detail.

[0037] Titanium-zirconium-molybdenum alloy (TZM alloy) is an alloy composed of molybdenum metal as a matrix, doped with a certain amount of Ti (titanium) and Zr (zirconium). The alloy content is generally less than 1%. TZM alloy has excellent high-temperature performance, is not prone to recrystallization, and has relatively good workability at room temperature. TZM alloy also has good weldability and is currently the most widely used molybdenum-based alloy.

[0038] Powder metallurgy (PM), consisting of powder preparation, ball milling, compacting, and sintering, is currently the predominant method for producing molybdenum-based alloys. Powder metallurgy offers low sintering temperatures and relatively low equipment requirements, as well as high production efficiency, low cost, no component segregation, and the ability to achieve near-net-net shapes. By precisely adjusting the material composition ratios and process parameters using Powder Metallurgy technology, optimal porosity can be achieved. By leveraging the interactions between the various materials, composite materials with diverse properties can be produced.

[0039] Hot isostatic pressing (HIP) typically involves placing a workpiece (billet, casting, etc.) inside a closed container filled with a pressure medium, typically nitrogen or argon. Under the combined effects of high temperature and pressure, the resulting alloy achieves a higher density than pressureless sintering. The heating temperature is typically 0.7 to 0.9 times the melting point.

[0040] Forging (F) is a processing method that applies pressure to a metal billet, utilizing the principle of plastic deformation to impart specific mechanical properties, shape, and dimensions to the billet. Using a suitable forging process can achieve deformation strengthening effects on TZM alloys and help eliminate porosity defects within the alloy ingot.

[0041] Alloys produced by powder metallurgy contain internal defects such as pores, shrinkage cavities, and cracks, which significantly impact material performance and make them unsuitable for high-temperature isothermal forging dies. While large deformations and high deformation rates can partially overcome these issues, the resulting slabs are unsuitable for producing large-scale dies. However, the present invention, based on powder metallurgy-based TZM alloy production, further utilizes hot isostatic pressing and forging to improve the alloy's internal defects such as pores and cracks, increase its density, and enhance its overall performance.

[0042] Specifically, the present invention provides a preparation process of a TZM alloy for a large-size isothermal forging die, characterized in that it comprises the following steps:

[0043] S1: TZM alloy powder is subjected to ball milling, cold isostatic pressing and sintering in sequence to obtain PM state TZM alloy billet;

[0044] The pressure of cold isostatic pressing is 140-160 MPa, and the sintering conditions are sintering at 2000-2100° C. for 2.5-3.5 hours.

[0045] S2: Hot isostatic pressing is performed on the PM state TZM alloy billet in S1 to obtain PM+HIP state TZM alloy billet;

[0046] The conditions for hot isostatic pressing are 1200-1400°C and 120-140 MPa for 2-3 hours.

[0047] S3: Forging the PM+HIP TZM alloy billet in S2 to obtain a large-size isothermal forging die TZM alloy;

[0048] The forging conditions are as follows: the starting forging temperature is set at 1300-1500°C, the final forging temperature is set at 1100-1200°C, the deformation during the forging process is controlled to be ≥40%, and then the TZM alloy ingot is returned to the high-temperature furnace to continue heating to the forging temperature. After forging is completed, it is cooled to room temperature with the furnace.

[0049] In some embodiments, the TZM alloy powder in S1 includes: TiH2 powder 0.45% to 0.65%, with a particle size of 2 to 5 μm; ZrH2 powder 0.10% to 0.15%, with a particle size of 2 to 5 μm; C powder 0.04% to 0.08%, with a particle size of 1 to 2 μm; and the rest is molybdenum powder with a particle size of 2 to 5 μm.

[0050] In some embodiments, the ball milling conditions in S1 include: the ball milling conditions include: ball milling speed of 240-260 r / min, ball-to-material ratio of 2:1, and ball milling time of 2 h.

[0051] In some embodiments, hydrogen is used as a shielding gas during sintering in S1. Hydrogen serves two purposes during powder sintering. First, it isolates the powder from air and prevents oxidation. Molybdenum oxidizes at around 400°C, and the oxidation rate increases significantly above 600°C. Hydrogen protects against the formation of molybdenum trioxide (MoO3), which could volatilize and contaminate the equipment and environment. Second, hydrogen reduces oxidized MoO3 on the surface of the alloy billet to Mo.

[0052] The primary purpose of hot isostatic pressing (HIP) is to further increase the density of PM-phase TZM alloys. In some embodiments, the HIP conditions in S2 are as follows: stainless steel is used as the sheath material, which is then placed in a degassing furnace for degassing and welded. The sheath is then placed in a HIP press using an inert gas as the pressurized gas, heated to a temperature of 1200-1400°C and a pressure of 120-140 MPa. After HIP, the alloy is cooled to room temperature in the furnace. The inert gas is preferably argon, the heating temperature is preferably 1300°C, and the pressure is preferably 130 MPa.

[0053] In some embodiments, forging utilizes a combined controlled deformation process involving both recrystallized and unrecrystallized zones, with a starting temperature of 1400°C and a final forging temperature of 1150°C. The TZM alloy ingot is then returned to the high-temperature furnace and heated to a temperature of 1400-1500°C. The deformation during the entire forging process is controlled to be ≥40%. Deformation in the recrystallized zone refines the alloy grain size, while deformation in the unrecrystallized zone increases substructure density, enhancing the substructure strengthening effect.

[0054] Example 1

[0055] This example uses TZM alloy powder manufactured by Jinduicheng Company as the original alloy powder.

[0056] Preparation of the original alloy powder: Molybdenum oxide powder is mechanically crushed and ball-milled to produce ultrafine molybdenum oxide powder. MoO3 is then reduced with H2 to obtain high-purity molybdenum powder with a particle size of approximately 2-5μm. Appropriate amounts of TiH2, ZrH2, and C powders are added to the mixture according to the following ratio: TiH2 powder 0.52%, particle size 2.0μm; ZrH2 powder 0.12%, particle size 2.2μm; C powder 0.05%, particle size 1.0μm; the remainder is molybdenum powder, particle size 2.5μm). The resulting TZM alloy powder is then mixed.

[0057] Powder Metallurgy (PM) Process: The raw TZM alloy powder is ball-milled and then cold isostatically pressed at 150 MPa. The resulting cold isostatically pressed billet is then sintered at 2050°C for 3 hours to produce a PM-grade TZM alloy billet. Hydrogen is used as both a protective and reducing atmosphere during the sintering process.

[0058] The microstructure and grain size of the PM TZM alloy billet are shown in Figure 1, where (a) is a picture of the PM TZM alloy billet before corrosion. The density of the PM TZM alloy is 94.2%. (b) is an OM photo of the powder metallurgy billet after corrosion. It can be seen that the grain boundaries are obvious and the grains remain equiaxed. The average grain size calculated by the intercept method is 48μm.

[0059] Hot isostatic pressing (HIP) process: The PM state TZM alloy billet is further hot isostatic pressed, the billet is covered with stainless steel material, placed in a degassing furnace for degassing, and the cover is welded. Then it is placed in a hot isostatic press, the heating temperature is set to 1300℃, the pressure is set to 130MPa, the hot isostatic pressing time is 2.5h, and argon is used as the pressure gas in the sintering process. After sintering, it is cooled to room temperature with the furnace to obtain a PM+HIP state TZM alloy billet.

[0060] The microstructure and grain size of the PM+HIP TZM alloy billet are shown in Figure 2, where (a) is a picture of the PM+HIP TZM alloy billet before corrosion. The density of the PM+HIP state is 95.6%, which is slightly improved compared with before HIP. (b) is a metallographic photograph after corrosion. The grains still remain equiaxed. The average grain size of the PM+HIP TZM alloy is 50μm, which is very close to that of the PM state.

[0061] Forging (F) process: The starting forging temperature is set at 1400°C, the final forging temperature is set at 1150°C, and the deformation during the forging process is about 40%. The TZM alloy ingot is then returned to the high-temperature furnace and continued to be heated to the forging temperature. After sintering, it is cooled to room temperature in the furnace to obtain a PM+HIP+F state TZM alloy billet.

[0062] The microstructure and grain size of the resulting PM+HIP+F-treated TZM alloy are shown in Figure 3, where (a) shows the microstructure before corrosion and (b) shows the metallographic photograph after corrosion. The PM+HIP+F-treated TZM alloy achieved a density of 98.5%, an average grain size of 51 μm, and a hardness of 259 HV. The tensile strength at 600°C was 672 MPa, and the elongation at break was 10%. The tensile strength at 1200°C was 396 MPa.

[0063] Comparative Example 1PM process

[0064] In this comparative example, TZM alloy powder manufactured by Jinduicheng Company was used as the original alloy powder.

[0065] Preparation of the original alloy powder: Molybdenum oxide powder is mechanically crushed and ball-milled to produce ultrafine molybdenum oxide powder. MoO3 is then reduced with hydrogen to produce high-purity molybdenum powder with a particle size of approximately 2 to 5 μm. Appropriate amounts of TiH2, ZrH2, and C powders are added according to the desired ratio, and the resulting TZM alloy powder is obtained through a powder mixing process.

[0066] Powder Metallurgy (PM) Process: The raw TZM alloy powder is ball-milled and then cold isostatically pressed at 150 MPa. The resulting cold isostatically pressed billet is then sintered at 2050°C for 3 hours to produce a PM-grade TZM alloy billet. Hydrogen is used as both a protective and reducing atmosphere during the sintering process.

[0067] The PM-treated TZM alloy has a density of 94.2%, an average grain size of 48 μm, a hardness of 169 HV, a room temperature tensile strength of 426 MPa, and an elongation of 3.5%. At 600°C, the tensile strength is 398 MPa, and the elongation is 19%.

[0068] Comparative Example 2PM+HIP process

[0069] In this comparative example, TZM alloy powder manufactured by Jinduicheng Company was used as the original alloy powder.

[0070] Preparation of the original alloy powder: Molybdenum oxide powder is mechanically crushed and ball-milled to produce ultrafine molybdenum oxide powder. MoO3 is then reduced with hydrogen to produce high-purity molybdenum powder with a particle size of approximately 2 to 5 μm. Appropriate amounts of TiH2, ZrH2, and C powders are added according to the desired ratio, and the resulting TZM alloy powder is obtained through a powder mixing process.

[0071] Powder Metallurgy (PM) Process: The raw TZM alloy powder is ball-milled and then cold isostatically pressed at 150 MPa. The resulting cold isostatically pressed billet is then sintered at 2050°C for 3 hours to produce a PM-grade TZM alloy billet. Hydrogen is used as both a protective and reducing atmosphere during the sintering process.

[0072] Hot isostatic pressing (HIP) process: The PM state TZM alloy billet is further hot isostatic pressed, the billet is covered with stainless steel material, placed in a degassing furnace for degassing, and the cover is welded. Then it is placed in a hot isostatic press, the heating temperature is set to 1300℃, the pressure is set to 130MPa, the hot isostatic pressing time is 2.5h, and argon is used as the pressure gas in the sintering process. After sintering, it is cooled to room temperature with the furnace to obtain a PM+HIP state TZM alloy billet.

[0073] The PM+HIP TZM alloy achieves a density of 95.6%, an average grain size of 50 μm, and a hardness of 172 HV. The room-temperature tensile strength of the PM+HIP TZM alloy is 448 MPa, approximately 22 MPa higher than that of the PM-treated TZM alloy. The average room-temperature elongation of the PM+HIP TZM alloy is 4.0%. At 600°C, the tensile strength is 400 MPa, and the elongation is 19%, significantly lower than that of the PM+HIP+F alloy.

[0074] Comparative Example 3PM+F process

[0075] In this comparative example, TZM alloy powder manufactured by Jinduicheng Company was used as the original alloy powder.

[0076] Preparation of the original alloy powder: Molybdenum oxide powder is mechanically crushed and ball-milled to produce ultrafine molybdenum oxide powder. MoO3 is then reduced with hydrogen to produce high-purity molybdenum powder with a particle size of approximately 2 to 5 μm. Appropriate amounts of TiH2, ZrH2, and C powders are added according to the desired ratio, and the resulting TZM alloy powder is obtained through a powder mixing process.

[0077] Powder Metallurgy (PM) Process: The raw TZM alloy powder is ball-milled and then cold isostatically pressed at 150 MPa. The resulting cold isostatically pressed billet is then sintered at 2050°C for 3 hours to produce a PM-grade TZM alloy billet. Hydrogen is used as both a protective and reducing atmosphere during the sintering process.

[0078] Forging (F) process: The starting forging temperature is set at 1400°C, the final forging temperature is set at 1150°C, the deformation during the forging process is about 40%, and then the TZM alloy ingot is returned to the high-temperature furnace and continued to be heated to the forging temperature. After sintering is completed, it is cooled to room temperature in the furnace to obtain a PM+F state TZM alloy billet.

[0079] The tensile strength of PM+F state TZM alloy at 600℃ is 620MPa, and the elongation after fracture is 7%. The strength and plasticity are lower than those of PM+HIP+F state alloy.

[0080] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. In the event of any inconsistency, the meanings described in the present invention or derived from the contents described in the present invention shall prevail. In addition, the terms used in this specification are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0081] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the technical concept of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A preparation process of TZM alloy for large-size isothermal forging dies, characterized in that: The following steps are involved: S1: ball milling, cold isostatic pressing and sintering of TZM alloy powder in sequence to obtain PM state TZM alloy billet; The pressure of cold isostatic pressing is 140-160 MPa, and the sintering condition is 2000-2100℃ for 2.5-3.5h; S2: hot isostatic pressing the PM state TZM alloy billet in S1 to obtain a PM+HIP state TZM alloy billet; The conditions of hot isostatic pressing are 1200-1400°C and 120-140 MPa for 2-3 hours; S3: Forging the PM+HIP TZM alloy billet in S2 to obtain a large-size isothermal forging die TZM alloy; The forging conditions are as follows: the starting forging temperature is set at 1300-1500°C, the final forging temperature is set at 1100-1200°C, the deformation amount during the forging process is controlled to be ≥40%, and then the TZM alloy ingot is returned to the high-temperature furnace to continue heating to the forging temperature, and after the forging is completed, it is cooled to room temperature with the furnace.

2. The preparation process according to claim 1, characterized in that: The TZM alloy powder in S1 includes: TiH2 powder 0.45% to 0.65% with a particle size of 2 to 5 μm; ZrH2 powder 0.10% to 0.15% with a particle size of 2 to 5 μm; C powder 0.04% to 0.08% with a particle size of 1 to 2 μm; and the rest is molybdenum powder with a particle size of 2 to 5 μm.

3. The preparation process according to claim 1, characterized in that: The ball milling conditions in S1 include: ball milling speed of 240-260 r / min, ball-to-material ratio of 2:1, and ball milling time of 2 h.

4. The preparation process according to claim 1, characterized in that: In the sintering step S1, hydrogen is used as the protective gas.

5. The preparation process according to claim 1, characterized in that: The hot isostatic pressing conditions in S2 are: using stainless steel as the sheath material, placing it in a degassing furnace for evacuation and welding the sheath, then placing it in a hot isostatic press, using inert gas as the pressure gas, heating temperature of 1200-1400°C, pressure of 120-140MPa, and cooling to room temperature with the furnace after hot isostatic pressing.

6. The preparation process according to claim 5, characterized in that: The inert gas is argon.

7. The preparation process according to claim 5, characterized in that: The heating temperature is 1300° C. and the pressure is 130 MPa.

8. The preparation process according to claim 1, characterized in that: The starting temperature of forging in S3 is set to 1400°C, and the final forging temperature is set to 1150°C.

9. The TZM alloy prepared by the preparation process according to any one of claims 1 to 8.

10. Use of the TZM alloy according to claim 9 in preparing large-size isothermal forging dies.

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