CN120861818A - Vacuum environment treatment method for powder hot isostatic pressing titanium alloy - Google Patents
Vacuum environment treatment method for powder hot isostatic pressing titanium alloyInfo
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Abstract
The invention relates to the technical field of powder metallurgy, and particularly provides a vacuum environment treatment method for powder hot isostatic pressing of titanium alloy. The treatment method comprises the steps of S100, mixing titanium or titanium alloy matrix powder with hydrogenated powder under the protection of inert atmosphere to obtain mixed powder, filling the mixed powder into a container, carrying out controllable dehydrogenation treatment on the container, S200, placing the container treated by S100 into a hot isostatic pressing furnace under the condition of no air exposure to carry out hot isostatic pressing treatment to obtain a crude part, and S300, carrying out vacuum dehydrogenation annealing treatment on the crude part to obtain the powder hot isostatic pressing titanium alloy. According to the invention, titanium hydride is introduced into the powder as an endogenous hydrogen source, and sectional controllable dehydrogenation, stage pressurizing hot isostatic pressing and subsequent vacuum dehydrogenation annealing treatment are combined, so that the alloy density and microstructure uniformity can be effectively improved, and internal pores and inclusions are reduced, thereby improving the ductility and fatigue performance of the material.
Description
Technical Field
The invention relates to the technical field of powder metallurgy, in particular to a vacuum environment treatment method for powder hot isostatic pressing titanium alloy.
Background
Powder metallurgy and Hot Isostatic Pressing (HIP) technologies have become key processes for preparing high-performance titanium and titanium alloy components, and are widely applied to the fields of aerospace, medical implants and high-end manufacturing. HIP can obtain a material structure close to a compact body and excellent mechanical properties through the synchronous action of powder densification and high temperature and high pressure, but has higher requirements on powder pretreatment, furnace atmosphere control and residual impurity content. The chemical purity and microstructure of the material directly determine the fatigue life, ductility and service reliability of the final component, so that gas behavior and removal strategies of the powder during heating and densification must be strictly designed and controlled.
In order to increase the densification efficiency of powder or improve the interfacial bonding force between powder particles, the prior art often adopts the process of adding hydrogenated powder or placing hydrogen as an activation and reduction means. The nascent hydrogen atoms released by the titanium hydride during the thermal decomposition have strong reducibility, and can theoretically reduce oxides on the surface of the powder and clean the surface, thereby improving the sintering activity. However, the method has great challenges in practical industrial application, namely the decomposition kinetics of the hydride are severe, and a large amount of hydrogen is intensively released in the heating process. If the hydrogen release rate is far from the exhaust capacity of the ultra-vacuum system or is not matched with the pressurizing and densification time, closed pores are easily formed in the powder. The hydrogen trapped in the dense metal under high pressure may form a brittle phase of hydride during subsequent cooling, or generate extremely high internal pressure, which initiates hydrogen induced cracking, resulting in increased internal defects and significantly reduced mechanical properties of the product.
Therefore, there is a need for a vacuum environment treatment method for powder hot isostatic pressing of titanium alloys to meet the industrial requirements of high performance titanium alloy parts.
Disclosure of Invention
The invention provides a vacuum environment treatment method for powder hot isostatic pressing titanium alloy, which is characterized in that titanium hydride is introduced into powder as an endogenous hydrogen source, and sectional controllable dehydrogenation, stage pressurizing hot isostatic pressing and subsequent vacuum dehydrogenation annealing treatment are combined, so that the alloy density and microstructure uniformity can be effectively improved, internal pores and inclusions are reduced, and the ductility and fatigue performance of the material are improved.
The invention provides a vacuum environment treatment method of a powder hot isostatic pressing titanium alloy, which comprises the following steps of S100, mixing titanium or titanium alloy matrix powder with hydrogenated powder under the protection of inert atmosphere to obtain mixed powder, filling the mixed powder into a container, and carrying out controllable dehydrogenation treatment on the container, S200, placing the container treated by S100 into a hot isostatic pressing furnace under the condition of no air exposure to carry out hot isostatic pressing treatment to obtain a coarse part, and S300, carrying out vacuum dehydrogenation annealing treatment on the coarse part to obtain the powder hot isostatic pressing titanium alloy.
In any of the above technical solutions, in step S100, the addition amount of the hydrogenated powder is 0.5-10wt% of the total mass of the mixed powder, and the hydrogenated powder includes TiH 2 or a controllable hydrogen alloy powder.
In any of the above technical solutions, in step S100, the controllable dehydrogenation process is performed under a vacuum environment, where the controllable dehydrogenation process includes a preheating section, an initial dehydrogenation section, and a low-speed exhaust section, where the preheating section includes heating the vessel to 200-300 ℃ at a rate of 5-20 ℃ per minute and maintaining the temperature for 30-60min, the initial dehydrogenation section includes heating to 450-650 ℃ at a rate of 5-20 ℃ per minute and maintaining the temperature for 30-180min, and the low-speed exhaust section includes vacuumizing to maintain the pressure at 0.1-1Pa during the initial dehydrogenation section and the subsequent cooling process.
In any of the above embodiments, in the low-speed exhaust section, the partial pressures of H 2 and H 2 O are monitored using a residual gas analyzer, and when the partial pressure of H 2 falls below a predetermined threshold, it is determined that the controllable dehydrogenation process is completed, and the process proceeds to step S200.
In any of the above technical solutions, in step S100, an isolation layer is disposed between the mixed powder and the inner wall of the container, where the isolation layer includes nickel foil or graphite sheet.
In any of the above embodiments, in step S200, the hot isostatic pressing treatment employs a staged pressurization strategy, in which an initial pressure is applied during a temperature-increasing stage, and after the temperature rises to a dehydrogenation plateau and a decrease in the release rate of H 2 is monitored, the pressure is increased to a target final pressure.
In any of the above technical solutions, the initial pressure is 20-50MPa, and the target final pressure is 100-200MPa.
In any of the above technical solutions, in step S200, the temperature of the hot isostatic pressing treatment is 850-950 ℃ and the holding time is 1-4h.
In any of the above technical schemes, in step S300, the vacuum degree of the vacuum dehydrogenation annealing treatment is not higher than 0.1Pa, the temperature is 500-750 ℃, and the heat preservation time is 1-4h.
In any of the above embodiments, after the treatment in step S300, the powder HIP'd titanium alloy has a residual hydrogen content of not more than 10ppm.
After the technical scheme of the invention is adopted, the following technical effects can be achieved:
(1) By introducing the synergistic effect of an endogenous hydrogen source and sectional controllable dehydrogenation, the efficient in-situ reduction and activation of the oxide on the surface of the powder are realized, and the densification efficiency and density of the subsequent hot isostatic pressing are remarkably improved;
(2) The problem of high residual hydrogen content is effectively solved through a combined process of staged pressurizing HIP and final vacuum dehydrogenation annealing, the hydrogen content is stably controlled below 10ppm, hydrogen induced defects are avoided, and the ductility and fatigue performance of the material are obviously improved;
(3) The isolating layer is arranged between the container and the powder to physically isolate the metal of the container from the powder to be in direct contact, so that the diffusion and chemical pollution of the container material are reduced, the interface inclusion and adhesion are reduced, the demolding is convenient, and the reusability and the production stability of the container are improved;
(4) The invention successfully integrates the pretreatment, activation, degassing, densification and final heat treatment of the powder, the whole process is completed under the protection of vacuum or inert atmosphere, and the finally prepared titanium alloy component has ultrahigh density, ultralow impurity content and excellent comprehensive mechanical property, and is greatly improved compared with the traditional process.
Detailed Description
In order that the above-recited objects, features and advantages of the invention will be more clearly understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof. It should be noted that, without conflict, the embodiments of the present invention and features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those described herein, and therefore the scope of the present invention is not limited to the specific embodiments disclosed below.
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanied with present invention are described in detail below.
When the existing powder hot isostatic pressing technology is used for preparing the titanium alloy, the problems of internal air holes, hydrogen embrittlement and performance reduction caused by uncontrollable hydrogen release and asynchronous exhaust-densification of a hydrogen placing process are generally faced, the residual hydrogen content is difficult to stably reduce to ppm level, and the consistency and the production efficiency of high-performance titanium alloy components are seriously restricted. Therefore, there is a need to develop a closed loop process that enables controlled hydrogen release, efficient hydrogen removal and simultaneous densification.
In view of this, this embodiment provides a vacuum environment treatment method for powder hot isostatic pressing of titanium alloy, the treatment method comprising the steps of:
s100, mixing titanium or titanium alloy matrix powder with hydrogenated powder under the protection of inert atmosphere to obtain mixed powder, filling the mixed powder into a container, and performing controllable dehydrogenation treatment on the container;
S200, under the condition of no air exposure, placing the container treated by the S100 into a hot isostatic pressing furnace for hot isostatic pressing treatment to obtain a crude part;
And S300, carrying out vacuum dehydrogenation annealing treatment on the crude part to obtain the powder hot isostatic pressing titanium alloy.
Preferably, in step S100, hydrogen is decomposed when the hydrogenated powder is heated, taking TiH 2 as an example:
TiH2→Ti+H2↑。
In the controllable dehydrogenation process, active hydrogen released by the decomposition of titanium hydride is distributed among the powder in a gas phase form, can react with adsorbed water, hydroxyl and organic pollutants on the surface of titanium powder to desorb the adsorbed water, hydroxyl and organic pollutants, and simultaneously reduces the thin-layer titanium oxide and the suboxide on the surface to generate volatile water vapor. This process effectively cleans the powder surface, exposing fresh, highly reactive metal interfaces. The clean and hydrogen activated surface significantly promotes metal bonding, atomic interdiffusion and sintering neck growth among powder particles, and provides key interface conditions for subsequent densification. Meanwhile, the hydrogen release generates instantaneous gas phase driving force in a pore network, and can effectively take away adsorptive gas and generated volatile matters by matching with vacuum or inert gas replacement pulse. In general, the step can remarkably improve the surface cleanliness and activity of the powder, promote densification and reduce non-closed pores and interfacial inclusions, thereby realizing higher density and more uniform structure under the same or milder temperature and pressure conditions, and further improving the ductility, fatigue life and reliability of the material. Compared with a method of directly introducing a large amount of external reducing gas, the process adopting the internal hydrogen generation source has more process flexibility and industrialization friendliness, is convenient for realizing continuous operation in a closed container, and avoids holes or hydrogen related defects caused by quick hydrogen release by controlling the sectional hydrogen release and the hydrogen release.
Further, in step S100, the addition amount of the hydrogenated powder is 0.5 to 10wt% based on the total mass of the mixed powder, and the hydrogenated powder includes TiH 2 or a controllable hydrogen compound powder. The addition amount of the hydrogenated powder is less than 0.5wt percent, the generated reducing atmosphere is insufficient to effectively clean all powder surfaces, the effect is not obvious, and when the addition amount of the hydrogenated powder is more than 10wt percent, excessive hydrogen is released, the risk of closed pore formation is difficult to completely avoid even if the sectional dehydrogenation is adopted, and the difficulty of process control and the burden of dehydrogenation annealing are increased. TiH 2 is the most common and economical source of hydrogen. The controllable hydrogenated alloy powder refers to hydrogenated powder of other titanium alloys, and the hydrogenated alloy powder can avoid introducing additional kinds of metal elements, and is particularly suitable for occasions with extremely high requirements on component control.
Further, in step S100, the controllable dehydrogenation treatment is performed under a vacuum environment, the controllable dehydrogenation treatment comprises a preheating section, an initial dehydrogenation section and a low-speed exhaust section, the preheating section comprises heating a container to 200-300 ℃ at a speed of 5-20 ℃ per minute and preserving heat for 30-60min, firstly removing adsorbed moisture on the surface, organic volatile and weakly combined adsorbed gas, reducing the initial volatile load of the system, the initial dehydrogenation section comprises heating to 450-650 ℃ at a speed of 5-20 ℃ per minute and preserving heat for 30-180min, covering a hydride decomposition temperature zone, realizing staged decomposition of hydrogenated powder and releasing H 2 at a controlled speed, enabling released hydrogen to be effectively replaced or extracted under lower temperature pressure, and simultaneously partially reducing surface oxides, the low-speed exhaust section comprises maintaining the pressure at 0.1-1Pa in the initial dehydrogenation section and the subsequent cooling process, and avoiding instantaneous air pressure rising and gas sealing by maintaining low-speed air extraction, thereby preventing closed pore formation or hydrogen densification defects in the subsequent pressurizing densification stage. The time and the rate of hydrogen release and hydrogen discharge are matched through sectional controllable dehydrogenation treatment, the surface of the powder is cleaned and activated, the oxygen content of an interface is reduced, gas sealing during high-pressure densification is avoided, the subsequent hot isostatic pressing densification efficiency and density are remarkably improved, the microstructure uniformity is improved, and the reduction of residual hydrogen to ppm level is facilitated, so that the ductility, fatigue performance and reliability of the material are improved.
Furthermore, in the low-speed exhaust stage, the residual gas analyzer is adopted to monitor the partial pressures of H 2 and H 2 O in the cavity on line in real time, so that a definite quantitative endpoint criterion can be provided for the controllable dehydrogenation treatment. Preferably, when the H 2 partial pressure is monitored to drop and stabilize to a predetermined threshold and the H 2/H2 O ratio reaches or exceeds the desired range, it is determined that the dehydrogenation displacement process has been substantially completed, thereby safely entering a subsequent staged supercharging or vacuum annealing step. When the partial pressure of H 2 in the chamber falls to this level, indicating that the free hydrogen released by decomposition of the hydrogenated powder has been effectively displaced, extracted or chemically trapped, the residual content of defectable hydrogen in the chamber atmosphere is extremely low and the risk of continuing densification at high pressure is significantly reduced. Preferably, the partial pressure of H 2 is less than or equal to 0.01Pa, and is used as a quantitative end point of controllable dehydrogenation, and residual gas analysis and time stability criteria are used as trigger conditions, so that the occurrence probability of closed pores and hydrogen induced defects in the high-pressure densification process can be remarkably reduced, higher relative density, more uniform microstructure and better fatigue and extensibility are facilitated to be obtained, and meanwhile, the decision logic is convenient for realizing automatic control and data recording, and a quantifiable control point and acceptance criterion are provided for process amplification and quality assurance.
Preferably, in step S100, an isolation layer is disposed between the mixed powder and the inner wall of the container, where the isolation layer includes nickel foil or graphite flake, and the isolation layer physically cuts off direct contact between the powder and the metal of the container, so as to significantly reduce the risk of diffusion of the container material into the powder or chemical reaction with the powder, thereby preventing the powder from being contaminated by the inner wall and reducing interfacial inclusions, and the isolation layer can also serve as a mechanical and thermal stress buffer layer, reducing adhesion and cold adhesion during hot isostatic pressing and heating-cooling processes, and facilitating demolding and repeated use of the container. In addition, the vessel is typically made of steel, and at high Wen Xiatie elements diffuse into the titanium powder, forming brittle fe—ti intermetallic compounds, which act as sources of fatigue cracks, while the barrier layer acts as a diffusion barrier. The nickel foil is suitable for use as metal isolating layer, and has high temperature strength and high air tightness, no violent reaction with Ti, high heat conducting channel and high heat shock buffering performance, and is favorable to the gas exchange and the replacement inside the pores and reduced local stress concentration. In general, the barrier layer reduces container-powder chemical contamination and interdiffusion, improves cleanliness of the powder surface and densification process, reduces adhesion and disassembly difficulties, improves heat conduction and venting conditions, and thus facilitates higher density, fewer inclusions/defects, and more uniform microstructure and mechanical properties.
Preferably, in step S200, the container after the treatment of S100 is directly placed in a hot isostatic pressing furnace and subjected to hot isostatic pressing treatment under the condition of no air exposure, the surface activation and low oxygen/low adsorption gas state of the powder obtained in the controllable dehydrogenation stage are maintained, and plastic flow, neck growth and diffusion bonding of the powder particles are driven by isothermal high pressure in a closed and controlled temperature-pressure field, so that the pore closure and the connected pore network disappear. Particularly, the staged pressurization can match the hydrogen release time with the pressurization time, so that closed pores or hydrogen induced defects caused by closing the gas which is not exhausted under high pressure are prevented, and meanwhile, the high pressure promotes the dissolution and diffusion of residual gas in pores to be exhausted. The method can maintain the surface cleanliness and low oxygen-containing state of the powder to facilitate interface welding, remarkably improve densification efficiency and relative density, reduce residual pores and inclusions, improve microstructure uniformity and mechanical property, reduce the burden of subsequent processing and vacuum annealing, improve the consistency and yield of products, reduce the oxidation, combustion or pollution risk of the powder in the transferring process, and facilitate the controllability and safety of industrial production. In addition, the powder in the powder container processed by the S100 is in an activated state with clean surface, low oxygen content and less adsorbed gas, and is directly sent into the HIP furnace under the condition of no air exposure, so that the powder is prevented from being secondarily oxidized when being contacted with air in the transferring process.
Further, the hot isostatic pressing treatment adopts a staged pressurizing strategy, namely, initial pressure is applied in a heating stage, and after the temperature rises to a dehydrogenation stage and the reduction of the release rate of H 2 is monitored, the pressure is raised to a target final pressure. In particular, a lower initial pressure, preferably 20-50MPa, is applied during the temperature-increasing phase, the purpose of which is not to achieve densification immediately, but rather to apply a moderate pre-tension. The pre-load is sufficient to cause preliminary plastic deformation and rearrangement of the loose powder particles, creating a mechanical skeleton and a network of interconnected pores in contact with each other, but insufficient to prematurely collapse and close the microscopic channels between the particles. At this lower initial pressure, the hydrogen gas released by the decomposition of the hydrogenated powder in the powder body, as well as other volatile gases desorbed from the powder surface, can efficiently escape the powder along these communicating channels with lower resistance by virtue of its own partial pressure and the pumping action of the system vacuum, and be continuously expelled by the vacuum system of the furnace body. This effectively avoids the risk of high pressure trapping inside the powder at the early stage of densification due to gas exhaustion. When the furnace temperature rises to a temperature at the later stage of the main decomposition plateau of the hydride or higher and the release rate of H 2 is significantly reduced and tends to stabilize as monitored by the integrated residual gas analyzer, it indicates that the main gas release process inside the powder is substantially completed and the powder surface is fully activated and cleaned by the reduction of active hydrogen. At this time, the pressure is again smoothly raised to the target final pressure under program control, preferably 100-200MPa. At this stage, the powder particles are already in a high temperature state, the plasticity is increased sharply, and the surface is clean and activated, and has excellent diffusion and bonding conditions. The application of ultra-high hydrostatic pressure will efficiently drive the powder particles to undergo significant plastic flow, accelerate grain boundary diffusion and bulk diffusion processes, rapidly form firm sintering necks at inter-particle contact points established in the early stage, and eventually cause the remaining isolated pores to be rapidly crushed, contracted and eliminated, thereby achieving complete densification of the material.
Furthermore, the temperature of the hot isostatic pressing treatment is 850-950 ℃ and the heat preservation time is 1-4h, the high temperature provides enough atomic diffusion energy and neck length growth driving force among powder particles, so that diffusion bonding and plastic flow can be quickly generated after the surface activation of the powder particles, the proper heat preservation time ensures the interface to be fully welded and the homogenization of components and temperature fields, and meanwhile, the defect of compactness caused by excessively short heat preservation or the excessive grain growth caused by excessively long heat preservation is avoided. When the method is matched with a sectional hydrogen release and stage pressurization strategy, the temperature and pressure time course can not only steadily raise the final pressure to finish densification after the hydrogen release rate is reduced, but also furthest reduce closed pores and retain the surface state of low oxygen content and low residual hydrogen, thereby obviously improving the relative density, uniform microstructure, the ductility and fatigue performance of the material and simultaneously reducing the burden of the subsequent vacuum dehydrogenation annealing.
Preferably, in step S300, the vacuum degree of the vacuum dehydrogenation annealing treatment is not higher than 0.1Pa, the temperature is 500-750 ℃ and the heat preservation time is 1-4 hours, the vacuum provides strong air pressure gradient and non-oxidizing environment, hydrogen in powder is promoted to escape and be pumped away in a gas phase form, the proper temperature can obviously improve the diffusion rate of hydrogen in alpha/beta titanium phases and crystal boundaries, accelerate the decomposition of metal hydride and be lower than the limit temperature which can cause serious grain growth, so that tissue refinement is maintained while efficient dehydrogenation is realized, and the proper heat preservation time ensures that the gradient of hydrogen concentration in the body is flattened and fully diffused out, reduces residual hydrogen to ppm level and promotes the recovery of lattice stress and the recovery of substructure. In general, residual hydrogen and hydrides can be effectively dissolved and removed, hydrogen embrittlement risk is reduced, internal stress is eliminated, and microstructure is homogenized, so that ductility, fatigue performance and service reliability of the material are remarkably improved, and performance degradation caused by excessive annealing is avoided.
Furthermore, the residual hydrogen content of the powder hot isostatic pressing titanium alloy is not higher than 10ppm, so that the risks of hydride precipitation and hydrogen brittleness can be obviously reduced, microcracks or delayed fracture caused by local hydrogen enrichment are avoided, the ductility, fracture toughness and fatigue life of the material are obviously improved, meanwhile, the consistency and repeatability of mechanical properties are improved, the performance fluctuation among batches is reduced, the problem of crack sensitivity and dimensional stability is avoided during subsequent processing due to low residual hydrogen, the service reliability and applicability of a component are improved, and the long-term service standard of high-requirement applications such as aerospace is met.
Further, even though a very small amount of hydrogen may remain in the material through the steps S100 and S200, the step S300 is a safety and optimization step, and annealing is performed under high vacuum and at a proper temperature, so as to provide a final diffusion escape condition for the residual hydrogen, and ensure that the residual hydrogen content of the final product is stably lower than the severe standard of 10 ppm. Meanwhile, the annealing process is also beneficial to eliminating the internal stress generated in the HIP process, homogenizing the microstructure, and further stabilizing and optimizing the comprehensive mechanical properties of the material.
In general, the embodiment successfully solves a plurality of key problems of densification, impurity removal, tissue homogenization and the like in the powder metallurgy titanium alloy through the synergistic effect of the step S100, the step S200 and the step S300, and finally the prepared titanium alloy component has high compactness, low impurity content and excellent mechanical properties.
Example 1
The embodiment provides a vacuum environment treatment method for powder hot isostatic pressing of titanium alloy, which comprises the following steps:
S100, mixing titanium alloy matrix powder with 5wt% of TiH 2 under the protection of argon atmosphere to obtain mixed powder, filling the mixed powder into a container with a nickel foil isolation layer, carrying out controllable dehydrogenation treatment on the container under a vacuum environment, wherein a preheating section comprises heating the container to 250 ℃ at the speed of 10 ℃ per minute and preserving heat for 45min, an initial dehydrogenation section comprises heating the container to 500 ℃ at the speed of 10 ℃ per minute and preserving heat for 90min, a low-speed exhaust section comprises vacuumizing to maintain the pressure at 0.5Pa in the initial dehydrogenation section and the subsequent cooling process, monitoring the partial pressure of H 2 and H 2 O by using a residual gas analyzer, judging that the controllable dehydrogenation treatment is finished when the partial pressure of H 2 is less than or equal to 0.01Pa, and entering step S200;
S200, under the condition of no air exposure, placing the container treated by the method S100 into a hot isostatic pressing furnace for hot isostatic pressing treatment, wherein the hot isostatic pressing treatment adopts a staged pressurizing strategy, namely 35MPa is applied in a heating stage, after the temperature rises to 900 ℃ and the release rate of H 2 is monitored to be reduced, the pressure is raised to 150MPa, and the temperature is kept for 2 hours, so that a crude part is obtained;
S300, transferring the crude part from the container under the condition of no air exposure, placing the crude part in a vacuum annealing furnace, and carrying out vacuum dehydrogenation annealing treatment under the conditions that the vacuum degree is not higher than 0.1Pa, the temperature is 600 ℃ and the heat preservation time is 2 hours to obtain the powder hot isostatic pressing titanium alloy.
Example 2
The embodiment provides a vacuum environment treatment method for powder hot isostatic pressing of titanium alloy, which comprises the following steps:
S100, under the protection of argon atmosphere, mixing pure titanium powder and 0.5wt% of controllable hydrogenated alloy powder to obtain mixed powder, filling the mixed powder into a container with a graphite sheet isolating layer, performing controllable dehydrogenation treatment on the container in a vacuum environment, wherein a preheating section comprises heating the container to 200 ℃ at a rate of 5 ℃ per minute and preserving heat for 60min, an initial dehydrogenation section comprises heating the container to 450 ℃ at a rate of 5 ℃ per minute and preserving heat for 180min, a low-speed exhaust section comprises vacuumizing to maintain the pressure at 0.1Pa in the initial dehydrogenation section and the subsequent cooling process, monitoring the partial pressure of H 2 and H 2 O by using a residual gas analyzer, and judging that the controllable dehydrogenation treatment is finished when the partial pressure of H 2 is less than or equal to 0.01Pa, and entering step S200;
S200, under the condition of no air exposure, placing the container treated by the method S100 into a hot isostatic pressing furnace for hot isostatic pressing treatment, wherein a staged pressurizing strategy is adopted in the hot isostatic pressing treatment, namely 20MPa is applied in a heating stage, after the temperature rises to 850 ℃ and the release rate of H 2 is monitored to be reduced, the pressure is raised to 100MPa, and the temperature is kept for 4 hours, so that a crude part is obtained;
s300, transferring the crude part from the container under the condition of no air exposure, placing the crude part in a vacuum annealing furnace, and carrying out vacuum dehydrogenation annealing treatment under the conditions that the vacuum degree is not higher than 0.1Pa, the temperature is 500 ℃ and the heat preservation time is 4 hours to obtain the powder hot isostatic pressing titanium alloy.
Example 3
The embodiment provides a vacuum environment treatment method for powder hot isostatic pressing of titanium alloy, which comprises the following steps:
S100, mixing titanium alloy matrix powder with 10wt% of TiH 2 under the protection of argon atmosphere to obtain mixed powder, filling the mixed powder into a container with a nickel foil isolation layer, carrying out controllable dehydrogenation treatment on the container under a vacuum environment, wherein a preheating section comprises heating the container to 300 ℃ at a rate of 20 ℃ per minute and preserving heat for 30min, an initial dehydrogenation section comprises heating the container to 650 ℃ at a rate of 20 ℃ per minute and preserving heat for 30min, a low-speed exhaust section comprises vacuumizing to maintain the pressure at 1Pa in the initial dehydrogenation section and the subsequent cooling process, monitoring the partial pressure of H 2 and H 2 O by using a residual gas analyzer, judging that the controllable dehydrogenation treatment is completed when the partial pressure of H 2 is less than or equal to 0.01Pa, and entering step S200;
S200, under the condition of no air exposure, placing the container treated by the method S100 into a hot isostatic pressing furnace for hot isostatic pressing treatment, wherein a staged pressurizing strategy is adopted in the hot isostatic pressing treatment, namely 50MPa is applied in a heating stage, after the temperature rises to 950 ℃ and the release rate of H 2 is monitored to be reduced, the pressure is raised to 200MPa and the temperature is kept for 1H, so that a crude part is obtained;
S300, transferring the crude part from the container under the condition of no air exposure, placing the crude part in a vacuum annealing furnace, and carrying out vacuum dehydrogenation annealing treatment under the vacuum degree of not higher than 0.1Pa and the temperature of 750 ℃ and the heat preservation time of 1h to obtain the powder hot isostatic pressing titanium alloy.
Example 4
The embodiment provides a vacuum environment treatment method for powder hot isostatic pressing of titanium alloy, which comprises the following steps:
S100, mixing titanium alloy matrix powder with 8wt% of TiH 2 under the protection of argon atmosphere to obtain mixed powder, filling the mixed powder into a container with a nickel foil isolation layer, carrying out controllable dehydrogenation treatment on the container under a vacuum environment, wherein a preheating section comprises heating the container to 280 ℃ at the speed of 18 ℃ per minute and preserving heat for 40min, an initial dehydrogenation section comprises heating to 630 ℃ at the speed of 18 ℃ per min and preserving heat for 40min, a low-speed exhaust section comprises vacuumizing and maintaining the pressure at 1Pa in the initial dehydrogenation section and the subsequent cooling process, monitoring the partial pressure of H 2 and H 2 O by using a residual gas analyzer, judging that the controllable dehydrogenation treatment is finished when the partial pressure of H 2 is less than or equal to 0.01Pa, and entering into step S200;
S200, under the condition of no air exposure, placing the container treated by the method S100 into a hot isostatic pressing furnace for hot isostatic pressing treatment, wherein a staged pressurizing strategy is adopted in the hot isostatic pressing treatment, namely 40MPa is applied in a heating stage, after the temperature rises to 950 ℃ and the release rate of H 2 is monitored to be reduced, the pressure is raised to 180MPa and the temperature is kept for 2 hours, so that a crude part is obtained;
S300, transferring the crude part from the container under the condition of no air exposure, placing the crude part in a vacuum annealing furnace, and carrying out vacuum dehydrogenation annealing treatment under the vacuum degree of not higher than 0.1Pa and the temperature of 700 ℃ and the heat preservation time of 1h to obtain the powder hot isostatic pressing titanium alloy.
Example 5
The embodiment provides a vacuum environment treatment method for powder hot isostatic pressing of titanium alloy, which comprises the following steps:
S100, under the protection of argon atmosphere, mixing pure titanium powder and 2.5wt% of controllable hydrogenated alloy powder to obtain mixed powder, filling the mixed powder into a container with a graphite sheet isolating layer, performing controllable dehydrogenation treatment on the container in a vacuum environment, wherein a preheating section comprises heating the container to 220 ℃ at a rate of 8 ℃ per minute and preserving heat for 50min, an initial dehydrogenation section comprises heating the container to 480 ℃ at a rate of 8 ℃ per minute and preserving heat for 100min, a low-speed exhaust section comprises vacuumizing and maintaining the pressure at 0.1Pa in the initial dehydrogenation section and the subsequent cooling process, monitoring the partial pressure of H 2 and H 2 O by using a residual gas analyzer, and judging that the controllable dehydrogenation treatment is finished when the partial pressure of H 2 is less than or equal to 0.01Pa, and entering step S200;
S200, under the condition of no air exposure, placing the container treated by the method S100 into a hot isostatic pressing furnace for hot isostatic pressing treatment, wherein a staged pressurizing strategy is adopted in the hot isostatic pressing treatment, namely 30MPa is applied in a heating stage, after the temperature rises to 850 ℃ and the release rate of H 2 is monitored to be reduced, the pressure is raised to 120MPa, and the temperature is kept for 3 hours, so that a crude part is obtained;
S300, transferring the crude part from the container under the condition of no air exposure, placing the crude part in a vacuum annealing furnace, and carrying out vacuum dehydrogenation annealing treatment under the conditions that the vacuum degree is not higher than 0.1Pa, the temperature is 520 ℃ and the heat preservation time is 3 hours to obtain the powder hot isostatic pressing titanium alloy.
Comparative example 1
The present example provides a powder HIP titanium alloy that uses conventional HIP processes, i.e., without endogenous hydrogen source addition and staged dehydrogenation control.
Test data
The following performance tests were performed on the powder HIP titanium alloy samples obtained in examples 1 to 5 and comparative example 1;
(1) Density testing, namely measuring by adopting an Archimedes drainage method according to GB/T3850-2015 'density measuring method for compact sintered Metal Material and hard alloy', wherein the results are shown in Table 1;
(2) Determination of residual hydrogen content by inert gas melting-thermal conductivity method according to GB/T4698.15-2011 "determination of hydrogen content by chemical analysis method of titanium and titanium alloy", the results are shown in Table 1;
(3) Room temperature tensile property test a standard tensile specimen was processed and tested according to GB/T228.1-2021 section 1 Metal Material tensile test: room temperature test method, the results are shown in Table 1;
(4) Microhardness test is carried out according to GB/T4340.1-2009 "Vickers hardness test of Metal Material part 1: test method", and the results are shown in Table 1;
TABLE 1
From the test data in Table 1, it is clear that all of examples 1-5 of the present invention achieved excellent overall performance under the synergistic process of controlled hydride addition, staged controlled dehydrogenation and staged pressurization.
The density of all the examples of the invention is higher than 99.5%, which is significantly higher than 98.5% of comparative example 1, demonstrating the excellent effect of the process of the invention in eliminating voids.
Residual hydrogen content all examples of the invention have a hydrogen content well below the aviation standard of 10ppm, whereas comparative example 1 is as high as 45ppm, with a serious risk of hydrogen embrittlement.
The strength, hardness and elongation after breaking of the inventive examples are all better than comparative example 1. The elongation after breaking is greatly improved, and the advantages of the invention in the aspects of reducing defects and purifying interfaces are fully proved.
In summary, through a set of systematic vacuum environment treatment method and process parameter control, the relative density of the invention is improved, residual hydrogen is reduced, and the tensile strength and the elongation after fracture are both improved, so that the process can effectively reduce the defects related to internal pores and hydrogen, improve the uniformity of microstructure and obviously improve the ductility and strength of the material. The comprehensive test result supports the technical feasibility and superiority of the invention in preparing the high-density and high-reliability powder hot isostatic pressing titanium alloy component.
In the description of the present specification, the terms "one embodiment," "some embodiments," "particular embodiments," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.
Claims (10)
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