Ti2Hot isostatic pressing process of AlNb alloy powder
阅读说明：本技术 一种Ti2AlNb合金粉末的热等静压工艺 (Ti2Hot isostatic pressing process of AlNb alloy powder ) 是由 吴杰 徐磊 郭瑞鹏 杨锐 于 2019-08-21 设计创作，主要内容包括：本发明公开了一种Ti_2AlNb合金粉末的热等静压工艺,属于粉末冶金钛合金领域。该工艺首先将装有Ti_2AlNb粉末的包套放入热等静压设备中进行第一阶段的低温保压处理,以使材料致密化；然后继续加热,使包套随炉升温至热等静压温度T2并保温一段时间,以使材料组织均匀；停止加热,随炉冷却至室温,获得Ti_2AlNb合金构件。本发明可以提高粉末Ti_2AlNb合金复杂构件各部位的致密度,从而提高粉末Ti_2AlNb合金的持久寿命。(The invention discloses a Ti 2 A hot isostatic pressing process of AlNb alloy powder belongs to the field of powder metallurgy titanium alloy. The process first will be loaded with Ti 2 Placing the AlNb powder sheath into a hot isostatic pressing device to perform low-temperature pressure maintaining treatment in the first stage so as to densify the material; then heating is continued, so that the capsule is heated to the hot isostatic pressing temperature T2 along with the furnace and is kept for a period of time, and the material structure is uniform; stopping heating, and cooling to room temperature along with the furnace to obtain Ti 2 An AlNb alloy member. The invention can improve the powder Ti 2 The compactness of each part of the AlNb alloy complex component is improved, thereby improving the powder Ti 2 Endurance life of the AlNb alloy.)
1.Ti2The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: the process comprises the following steps:
(1) preparation of Ti2The method comprises the following steps of (1) pre-alloying AlNb powder, screening the powder to obtain powder with the size less than or equal to 250 micrometers, filling the screened powder into a carbon steel or stainless steel sheath, degassing at high temperature and sealing and welding;
(2) and (3) low-temperature pressure maintaining treatment: putting the sheath filled with the powder obtained in the step (1) into hot isostatic pressing equipment, and performing low-temperature pressure maintaining treatment after the temperature and the pressure reach a preset temperature T1 and a preset pressure F1 in a mode of simultaneously raising the temperature and the pressure or raising the temperature and then raising the pressure so as to ensure the tissue densification of the material;
(3) hot isostatic pressing treatment: after the low-temperature pressure maintaining treatment in the step (2), continuing heating, heating the sheath to the hot isostatic pressing temperature T2 along with the furnace, and keeping the temperature for a period of time to ensure that the material tissue is uniform;
(4) stopping heating, and cooling to room temperature along with the furnace to obtain Ti2An AlNb alloy member.
2. The Ti of claim 12The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: in the step (1), the Ti2The AlNb prealloying powder is prepared by a crucible-free induction melting ultrasonic gas atomization method or a plasma rotating electrode atomization method.
3. The Ti of claim 12The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: in the step (2), the value range of the preset temperature T1 is Wherein:is Ti2O + B2+ alpha of AlNb alloy2→B2+α2At the point of phase transition,the pressure F1 is more than or equal to 100 MPa.
4. The Ti of claim 1 or 32The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: in the step (2), the time of the low-temperature pressure maintaining treatment is 30 min-2 h.
5. The Ti of claim 12The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: in the step (3), the value range of the hot isostatic pressing temperature T2 is (T)B2-25℃)～(TB2-5 ℃), wherein: t isB2Is Ti2Alpha of AlNb alloy2+ B2 → B2 phase transition point, TB2＝1055℃。
6. The Ti of claim 1 or 52The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: in the step (3), the heat preservation time is 2-5 h.
7. The Ti of claim 1 or 52The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: in the step (3), the pressure in the heat preservation process is more than or equal to 100 MPa.
8. The Ti of claim 12The hot isostatic pressing process of the AlNb alloy powder is characterized by comprising the following steps: the process is suitable for Ti2The hot isostatic pressing consolidation forming and the uniform densification of the AlNb alloy powder are realized, and the process improves Ti2The compactness of each part of the AlNb alloy component is improved, thereby improving the Ti2Endurance life of the AlNb alloy.
Technical Field
The invention relates to the technical field of powder metallurgy titanium alloy, in particular to Ti2And (3) hot isostatic pressing process of AlNb alloy powder.
Background
Ti2The AlNb alloy is a Ti-Al series intermetallic compound alloy which takes an O phase with an orthogonal structure as a main component phase, has excellent strength, fracture toughness and creep resistance at 650-750 ℃, and has lower density and good oxidation resistance, so that Ti is2The AlNb alloy has strong application potential in hot end components of aircraft engines. Ti2At present, the AlNb alloy complex component mainly adopts a forming process of precision casting or split forging and welding, and the precision casting has casting defects of shrinkage cavity, looseness, component segregation and the like which are difficult to thoroughly solve, so that the rejection rate is high, and the out-of-tolerance use is common; the forging and welding combined method has the disadvantages of low material utilization rate and cracking risk of a welding joint, and is difficult to meet the requirements of high reliability and weight reduction of modern aeroengines.
In recent years, with the development of powder process technology and powder near-net-shape technology, the hot isostatic pressing near-net-shape technology can solve the problems of casting and deforming Ti2The problems of macrosegregation, nonuniform microstructure and the like of the AlNb alloy break through the limitation of ingot size and thermal deformation equipment to the deformed Ti2Due to the limitation of the shape and the size of the AlNb alloy, large-size complex components can be formed, and the components and the microstructure of the components are uniform and the performance consistency is good. Ti was found by Micro-CT analysis2Alloy elements such as Al and Nb are easy to segregate along the forging streamline direction during AlNb forging, and the powder metallurgy alloy has no obvious component segregation.
But powder Ti produced by powder metallurgy process2The AlNb alloy also has the defects of the AlNb alloy, such as the phenomenon of nonuniform density when a large-size complex component is prepared, the service life of the powder alloy is shorter than that of a forged alloy, and the bulk performance and the test bar performance of the large-size complex component are poor. To powder Ti2The high-temperature endurance life of the AlNb alloy, and domestic and foreign researchers develop a series of methods, which mainly comprise the following steps: after powder hot isostatic pressing consolidation, the powder blank is subjected to deformation with large deformation amount by adopting the processes of extrusion, isothermal forging, annular rolling and the like so as to improve the phase distribution and uniformity of the powder alloy; these methods have no doubt limited the field of application of the material.
Disclosure of Invention
The object of the present invention is to provide a Ti2The hot isostatic pressing process of AlNb alloy powder can directly obtain powder Ti with excellent durability through hot isostatic pressing forming2AlNb alloy billets.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
ti2The hot isostatic pressing process of the AlNb alloy powder comprises the following steps:
(1) preparation of Ti2The method comprises the following steps of (1) cleaning AlNb prealloying powder, screening the powder to obtain powder with the size less than or equal to 250 micrometers, filling the screened powder into a carbon steel or stainless steel sheath, degassing at high temperature and sealing and welding;
(2) and (3) low-temperature pressure maintaining treatment: putting the sheath filled with the powder obtained in the step (1) into hot isostatic pressing equipment, and performing low-temperature pressure maintaining treatment after the temperature and the pressure reach a preset temperature T1 and a preset pressure F1 in a mode of simultaneously raising the temperature and the pressure or raising the temperature and then raising the pressure so as to ensure the tissue densification of the material;
(3) hot isostatic pressing treatment: after the low-temperature pressure maintaining treatment in the step (2), continuing heating, heating the sheath to the hot isostatic pressing temperature T2 along with the furnace, and keeping the temperature for a period of time to ensure that the material tissue is uniform;
(4) stopping heating, and cooling to room temperature along with the furnace to obtain the Ti-Al alloy component.
In the above step (1), the Ti is2The AlNb clean prealloyed powder is prepared by crucible-free induction melting ultrasonic gas atomization (EIGA) or plasma rotating electrode atomization (PREP).
In the step (2), the predetermined temperature T1 has a value range of To (c) to (d); wherein:is Ti2O + B2+ alpha of AlNb alloy2→B2+α2At the point of phase transition,the pressure F1 is more than or equal to 100 MPa.
In the step (2), the time of the low-temperature pressure maintaining treatment is 30 min-2 h.
In the step (3), the value range of the hot isostatic pressing temperature T2 is (T)B2-25℃)～(TB2-5 ℃), wherein: t isB2Is Ti2Alpha of AlNb alloy2+ B2 → B2 phase transition point, TB2＝1055℃。
In the step (3), the heat preservation time is 2-5 h.
In the step (3), the pressure in the heat preservation process is more than or equal to 100 MPa.
The process of the invention is applicable to Ti2The hot isostatic pressing consolidation forming and the uniform densification of the AlNb alloy powder are realized, and the process improves Ti2The compactness of each part of the AlNb alloy component is improved, thereby improving the Ti2Endurance life of the AlNb alloy.
The invention has the advantages and beneficial effects that:
1. the process of the invention comprises two steps, wherein the temperature T1 range of the first step of low-temperature pressure maintaining is as follows: meanwhile, the gas pressure F1 should be more than or equal to 100MPa, and the heat preservation time is 30 min-2 h. After the first step of low-temperature pressure maintaining is finished, the material is continuously heated to the temperature T2 of hot isostatic pressing along with the furnace and is kept warm, and the temperature T2 is in the range of (T2)B2-25℃)～(TB2At the temperature of minus 5 ℃, the gas pressure is more than or equal to 100MPa during the heat preservation, the heat preservation time is 2h to 5h, the material is continuously densified, and the uniform tissue of the material is ensured, and the process is the second step. And maintaining the pressure of the alloy along with the furnace and cooling to room temperature after the heat preservation process is finished. The invention is used for hot isostatic pressing consolidation forming of rapidly solidified Ti-Al series alloy powder, eliminates the defect of macro pores, and improves the density of each part of a complex component, thereby improving the comprehensive mechanical property of the alloy, particularly prolonging the service life.
2. The process can be realized on a traditional hot isostatic pressing machine, and the process has the application range of Ti-Al series alloy (Ti)2AlNb、Ti3Al and TiAl) powder.
3. The invention is simple and practical, and can improve the overall metallurgical quality of the powder alloy and prolong the service life of the powder alloy, thereby reducing the manufacturing cost of the powder alloy.
4. The process is suitable for preparing the powder metallurgy titanium alloy component formed by direct hot isostatic pressing.
Drawings
FIG. 1 is a graph of a hot isostatic pressing process; wherein: (a) the process system B and the process system B are the process system C.
Detailed Description
The invention relates to Ti capable of improving the overall metallurgical quality of powder alloy and prolonging the service life of the powder alloy2The AlNb alloy powder hot isostatic pressing process specifically comprises the following steps:
1. preparing Ti by crucible-free induction melting ultrasonic gas atomization (EIGA) or plasma rotating electrode atomization (PREP)2The AlNb clean prealloying powder is sieved to obtain powder with the size less than or equal to 250 micrometers, the powder is filled into a low-carbon steel or stainless steel sheath, and sealing welding is carried out after high-temperature degassing. The use of powders having a size of 250 microns or less is intended to reduce the amount of hollow powders; the carbon steel or stainless steel sheath is used because the sheath material is completely solid and has certain strength in the temperature range used by the invention; the high-temperature degassing is used for removing gas adsorbed on the surface of the powder to the maximum extent, the temperature range of the high-temperature degassing is 150-350 ℃, and the degassing time is 8-16 hours.
2. And (3) putting the powder sheath prepared in the first step into hot isostatic pressing equipment, achieving the process conditions of the first stage in a mode of raising temperature and raising pressure along with a furnace or raising temperature and raising pressure first and then starting low-temperature pressure-maintaining treatment. The low-temperature pressure maintaining temperature of the first step is selectedThe gas pressure should be greater than or equal to 100MPa for a period of time greater than or equal to 30 minutes and less than or equal to 2 hours. The temperature of the low-temperature pressure maintaining treatment of the first stage process is selectedFirst, conventional powder titanium alloys (e.g., Ti-6Al-4V alloy and Ti-5Al-2.5Sn alloy) have a hot isostatic pressing temperature of 920 ℃ to 960 ℃ and Ti2Compared with the traditional titanium alloy, the AlNb intermetallic compound has high strength and large heat deformation resistance, so the hot isostatic pressing temperature is higher; second, Ti2The chemical activity of the AlNb intermetallic compound is stronger than that of the traditional titanium alloy, the AlNb intermetallic compound reacts with almost all ceramic crucible and nozzle materials, and is easily contaminated by impurities such as oxygen, and the specific surface area is increased after the AlNb intermetallic compound is prepared into powder, so that the AlNb intermetallic compound is more easily contaminated, and therefore, the hot isostatic pressing temperature is higher than that of the traditional titanium alloy, so that the original particle boundary of the powder is crushed, and the defect of macroscopic pores is. The incubation time of the first step is greater than or equal to 30 minutes and less than or equal to 2 hours for the following reasons: first, complete compaction of the powder compact takes at least 30 minutes within the temperature range of the first step of the selection of the present invention; secondly, the alloy is subjected to phase change after the heat preservation time is too long, and the mechanical property is influenced.
3. After the first step is finished, continuing heating, and heating the powder sheath to (T) along with the furnaceB2-25℃)～(TB2The temperature is kept between minus 5 ℃ and a period of time, and the process is a hot isostatic pressing treatment stage of the second step; the holding time of the second step is more than or equal to 2 hours and less than or equal to 5 hours to ensure that the material structure is uniform, the pressure is more than or equal to 100MPa, and the heating and furnace cooling are stopped to room temperature after the second step is completed. The second process step is designed for the following reasons: firstly, the uniformity and the consistency of the density of each part of the powder alloy complex component are improved by controlling slow densification through a creep diffusion mechanism, so that the consistency and the stability of the mechanical property of each part of the complex component are ensured; second, raising the hot isostatic pressing temperature is equivalent to performing a high temperature solution heat treatment, which can promote α2The phase of the alloy is completely converted from the O phase to the B2 phase, the alloy microstructure is stabilized, and the comprehensive mechanical property of the material is further improved.
The present invention will be described in further detail below with reference to the drawings, comparative examples and examples.
The compositions of the following comparative and example alloys are shown in table 1:
TABLE 1.Ti2AlNb alloy composition (wt.%)
Powder Ti2AlNb alloy main transformation point:
α2+ B2 → B2, alloy phase transition point TB2＝1055℃；
O+B2+α2→B2+α2Alloy phase transition point
Comparative example 1
Comparative example 1 powders of the alloy were prepared by argon atomization, powders below 250 microns in size were loaded into a carbon steel capsule, vacuum degassed and hot isostatically pressed. The following process system (A) is selected for the alloy:
raising the temperature and the pressure along with the furnace to reach the hot isostatic pressing condition: 1030 ℃ and 100MPa/3 hours, and cooling along with the furnace after completion.
Comparative example 2
The difference from comparative example 1 is that the hot isostatic pressing pressure was 140 MPa.
Comparative example 2 powders of the alloy were prepared by argon atomization, powders below 250 microns in size were loaded into a carbon steel capsule, vacuum degassed and hot isostatically pressed. The following process system (B) is selected for the alloy, the curve of the process system (B) is shown in figure 1(a), and the specific conditions are as follows:
raising the temperature and the pressure along with the furnace to reach the hot isostatic pressing condition: 1030 ℃/140MPa/3 hours, and cooling along with the furnace after completion;
table 2 shows the powder Ti prepared by the process system (A) and the process system (B)2The comprehensive mechanical properties of the AlNb alloy show that the powder Ti prepared by the process system (A) and the process system (B)2The tensile properties and the durability of the AlNb alloy are not different, because the temperature influence is most obvious in the hot isostatic pressing parameters (time, temperature and pressure)The pressure effect is small.
TABLE 2 powder metallurgy Ti prepared by Process A and Process B2Mechanical properties of AlNb alloy