CN111850456A - Titanium alloy segmented vacuum rapid nitriding method and device - Google Patents

Titanium alloy segmented vacuum rapid nitriding method and device Download PDF

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Publication number
CN111850456A
CN111850456A CN202010726954.6A CN202010726954A CN111850456A CN 111850456 A CN111850456 A CN 111850456A CN 202010726954 A CN202010726954 A CN 202010726954A CN 111850456 A CN111850456 A CN 111850456A
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nitriding
reaction tank
pressure
tank
vacuum
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杨闯
雷伦福
王正芹
高雨琪
吴什二
潘文美
赵应飞
刘选文
张茂
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Guizhou Education University
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02—Pretreatment of the material to be coated

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Abstract

The invention discloses a titanium alloy segmented vacuum rapid nitriding method and device, belonging to a metal heat treatment method and device. The method is that the work piece is put into a reaction tank with air removed for vacuum preheating treatment, the nitriding is carried out according to the mode of pressure alternating circulation after the temperature is raised to the nitriding temperature, and then the vacuum diffusion is carried out for a certain time. The device comprises a heating system, a vacuum system and an air supply system, wherein the heating system consists of a reaction tank (4) fixed in a furnace body (1), an electric heating element (2) positioned between the reaction tank and a hearth, a thermocouple (3) extending into the hearth and a furnace door (9) for sealing a tank opening; the vacuum system is composed of an air pump (12) communicated with the reaction tank (4); the gas supply system is composed of a nitrogen cylinder (11) which is communicated with the reaction tank (4) through a gas inlet pipe (5). The invention can accelerate the nitriding speed, promote the nitrogen to diffuse into the matrix, form a gradient nitriding layer and improve the brittleness of the nitrogen layer. Is a metal surface treatment method and a device.

Description

Titanium alloy segmented vacuum rapid nitriding method and device
Technical Field
The invention relates to a titanium alloy nitriding method, in particular to a titanium alloy segmented vacuum rapid nitriding method; the invention also relates to a heat treatment device for implementing the method. Belongs to metal surface treatment and a device.
Background
The titanium alloy has the advantages of high specific strength, good corrosion resistance, high temperature resistance, good biocompatibility and the like, and is widely applied to the fields of aerospace, ships, machinery, petrochemical engineering, biological engineering and the like. However, the titanium alloy has the disadvantages of low surface hardness, poor wear resistance and fatigue resistance, and the like, so the application range of the titanium alloy is greatly limited. Among all alloy elements, nitrogen is the element which influences the hardness of titanium to the maximum, titanium nitride has the advantages of high hardness, excellent chemical stability, low friction coefficient, excellent biocompatibility, good conductivity and the like, and surface nitriding of titanium alloy is the most effective measure for improving the surface hardness, improving the wear resistance, prolonging the service life and further expanding the use range. At present, ion nitriding, laser gas nitriding and common gas nitriding are mainly adopted for carrying out surface nitriding treatment on titanium alloy.
The ion nitriding can obviously improve the surface hardness and the wear resistance of the titanium alloy, but has the defects of strict process requirements, more complex influence factors, difficult control of a nitriding layer, non-uniform nitriding layer, rough surface after nitriding, great reduction of the fatigue strength and the like. The nitriding layer formed by laser nitriding is tightly combined with a matrix and has high strength, but due to the rapid heating of a high-energy density laser beam and the chilling action of the matrix, the nitriding layer of the cladding layer generates great thermal stress, cracks are easy to form, and the nitriding layer cannot be used in actual production.
Generally, neither ion nitriding nor laser nitriding can treat a workpiece having a complicated shape. As the traditional chemical heat treatment, the gas nitriding is independent of the geometric shape of the part, and has the advantages of simple process, low cost, uniform nitriding and the like, thereby being widely applied. However, since titanium alloy is very easily oxidized, a dense oxide protective film can be formed on the surface even at room temperature, and nitriding is difficult to perform. In addition, titanium has a strong affinity for nitrogen, which is difficult to diffuse inward. Therefore, the existing gas nitriding technology for titanium alloy has the defects of long treatment time, thin carburized layer, large carburized layer brittleness and the like, and cannot meet the requirement of practical use.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a titanium alloy segmented vacuum rapid nitriding method which can adapt to workpieces with various complex shapes, can shorten the nitriding time, increase the thickness and hardness of a carburized layer and reduce the brittleness and the abrasion; another object of the present invention is to provide an apparatus for implementing the above method.
In order to achieve the purpose, the method adopts the following technical scheme: it comprises a pretreatment step and a cyclic nitriding step; the specific method comprises the following steps:
1) putting the workpiece subjected to polishing and cleaning treatment into a reaction tank, and introducing high-purity nitrogen with the purity of more than or equal to 99.99% into the reaction tank until all air in the tank is discharged;
2) the reaction tank is vacuumized to 10-3～10-4Pa, heating the reaction tank to 750-780 ℃ and preserving heat for 0.5-1 h;
3) introducing the high-purity nitrogen until the pressure in the tank reaches 30000-60000 Pa, then heating the reaction tank to 800-900 ℃, and preserving the temperature; pumping out nitrogen until the pressure in the tank is reduced to 5000-15000 Pa, and preserving heat; introducing high-purity nitrogen again until the pressure in the tank reaches 30000-60000 Pa, and preserving the temperature; nitriding is carried out according to a high-pressure-low-pressure-high-pressure alternating circulation mode, and the total time of a circulation nitriding process is 1-8 h; in each circulation, the heat preservation time of high-pressure nitriding and low-pressure nitriding is the same and is 15-30 min;
4) the reaction tank is vacuumized to 10 DEG-3～10-4And Pa, performing vacuum diffusion for 1-5 h, and then cooling to room temperature along with the furnace.
The further technical scheme of the invention is that in the step 3), the high-pressure nitriding pressure is 40000-50000 Pa, the low-pressure nitriding pressure is 10000Pa, the heat preservation time is 20-25 min, and the total time of the cyclic nitriding process is 3-6 h; the vacuum diffusion time in the step 4) is 2-4 h.
The preferable technical scheme of the invention is that in the step 3), the high-pressure nitriding pressure is 45000Pa, the low-pressure nitriding pressure is 10000Pa, the heat preservation time is 22min, and the total time of the cyclic nitriding process is 4.5 h; the vacuum diffusion time in the step 4) is 3 h.
In order to realize the method, the device provided by the invention comprises a heating system, a vacuum system and an air supply system;
the heating system consists of a reaction tank fixed in a hearth of the furnace body, a plurality of electric heating elements which are positioned between the reaction tank and the hearth and are uniformly distributed, a thermocouple fixed on the furnace body and extending into the hearth, a flange fixed at a tank opening of the reaction tank, and a furnace door fixed on the flange and sealing the tank opening; the vacuum system consists of an air extraction opening communicated with the reaction tank and an air extraction pump communicated with the air extraction opening through a pipeline; the gas supply system is composed of a gas inlet pipe which is fixed in the reaction tank and is communicated with the nitrogen cylinder through a gas supply pipe, and the reaction tank is provided with a pressure gauge.
A sealing ring is arranged between the flange plate and the furnace door, and a circulating cooling water pipe is coiled on the surface of the flange plate; an exhaust pipe is fixed in the reaction tank, and a plurality of small holes are distributed on the air inlet pipe and the exhaust pipe; a condenser is connected between the pipeline and the air pump; and a pressure release valve communicated with the inside of the reaction tank is fixed on the reaction tank at a position close to the tank opening.
Compared with the prior art, the method has the following advantages due to the adoption of the technical scheme:
1) different from the traditional alloy steel, the surface of the titanium alloy is easy to passivate to form compact oxides, which hinders the nitriding process of the titanium alloy; how to remove the compact oxidation film on the surface of the titanium alloy before nitriding is a great problem of solving the nitriding of the titanium alloy. The method firstly adopts a vacuum preheating method to absorb and diffuse oxygen and adhesive on the surface of the titanium alloy, and activates the surface of the titanium alloy; therefore, the subsequent nitriding process can be greatly promoted and accelerated.
2) The pressure alternating circulation nitriding process is adopted, when the furnace pressure is at low pressure (air extraction), the atmosphere in the slit and the hole is forcibly exhausted, when the furnace pressure is at high pressure (air inflation), fresh nitrogen is forcibly added, and gas exchange can reach any part communicated with furnace gas; therefore, the difficult problem of uneven seepage of a workpiece with a complex shape, such as a slit, a small hole and a deep hole live and blind hole, can be solved.
3) By adopting the pressure alternating circulation nitriding process, the diffusion of surface nitrogen atoms into the titanium alloy matrix is facilitated, and the continuity of the nitriding process can be ensured because nitrogen with certain pressure is always maintained in the furnace, so that a deeper nitriding layer can be obtained, and the performance of the nitriding layer is improved; the inherent defect that nitrogen is difficult to diffuse inwards due to the extremely stable titanium nitride is thoroughly overcome.
4) By adopting the pressure alternating circulation nitriding process, a thin gas layer remained on the surface of a workpiece can be rapidly damaged, new active atoms can be continuously generated in new atmosphere, and the collision between the active atoms and the surface of the alloy matrix is accelerated, so that the surface activity of the alloy matrix can be improved, and the nitriding speed is accelerated.
5) The nitrided layer formed after the gas nitriding of the titanium alloy generally includes an outermost nitride layer and a subsurface nitrogen diffused layer, and the outermost nitride layer is relatively brittle. The nitrogen atoms can be continuously diffused to the inside by adopting a vacuum diffusion process, and the nitride is partially decomposed; thereby improving the compactness of the structure of the nitriding layer, greatly improving the brittleness of the surface of the titanium alloy and improving the performance of the nitriding layer.
The device of the invention adopts the structure, thus having the following advantages:
1) because the sealed reaction tank is added in the hearth, the air inlet pipe communicated with the nitrogen cylinder and the air extraction opening communicated with the air extraction pump are added in the reaction tank, the circulating operation of air inflation, air extraction and air re-inflation can be alternately realized according to actual needs, and the operations of workpiece vacuum preheating treatment, pressure alternating circulating nitriding treatment, vacuum diffusion treatment and the like can be realized.
2) The circulating cooling water pipe is additionally arranged on the flange, so that the temperature of the furnace door can be reduced, the sealing ring is prevented from being rapidly aged, and the service life is prolonged.
3) Because the air inlet pipe and the air exhaust pipe are provided with the small holes, the gas in each part in the reaction tank can be replaced, the partial flow of the inflation body is promoted, dead corners or blind areas are avoided, and meanwhile, the reaction temperature of each part in the tank can be equalized and the temperature balance is ensured through the gas flow.
4) A pressure release valve is added on the reaction tank, so that the furnace cover can be quickly opened and the workpiece can be taken out.
Drawings
FIG. 1 is a graph of a nitriding process according to the method of the present invention;
FIG. 2 is a cross-section diffusion metallographic structure of a TC4 titanium alloy treated by the method for 6 hours;
FIG. 3 is a cross-section diffusion layer metallographic structure of a TC4 titanium alloy treated by a vacuum direct nitriding method for 6 hours;
FIG. 4 is an XRD (X-ray diffraction) pattern of the surface of a TC4 titanium alloy treated by the method of the invention and the vacuum direct nitriding method for 6 hours respectively;
FIG. 5 is a cross-sectional cladding indentation diagram of a TC4 titanium alloy treated by the method of the invention after 6h of nitriding;
FIG. 6 is a cross-sectional cladding indentation diagram of a TC4 titanium alloy treated by a vacuum direct nitriding method for 6 hours;
FIG. 7 is a cross-sectional microhardness distribution curve diagram of TC4 titanium alloy treated by the method of the invention and the vacuum direct nitriding method for 6 hours respectively;
fig. 8 is a schematic diagram of the structure of the device of the present invention.
In the figure: the device comprises a furnace body 1, an electric heating element 2, a thermocouple 3, a reaction tank 4, an air inlet pipe 5, a pressure gauge 6, a cooling water pipe 7, a flange 8, a furnace door 9, a pressure release valve 10, a nitrogen cylinder 11, an air suction pump 12, a condenser 13, an air suction pipe 14 and a controller 15.
Detailed Description
The method of the present invention is further illustrated by the following examples in conjunction with the accompanying drawings.
Example 1
1) Polishing and cleaning a TC4 titanium alloy sample, then placing the titanium alloy sample into a reaction tank, and introducing high-purity nitrogen with the purity of more than or equal to 99.99% into the reaction tank until all air in the tank is discharged;
2) the reaction tank was evacuated to 10 deg.C according to the process curve shown in FIG. 1-3Pa, then raising the temperature of the reaction tank to 780 ℃, and preserving the temperature for 0.5 h;
3) introducing the high-purity nitrogen into the reaction tank according to a process curve shown in figure 1 until the pressure in the reaction tank reaches 60000Pa, then heating the reaction tank to 800 ℃, and preserving the temperature; pumping out nitrogen until the pressure in the tank is reduced to 5000Pa, and preserving heat; introducing high-purity nitrogen into the reaction tank again until the pressure in the reaction tank reaches 60000Pa, and preserving the temperature; performing 8 times of cyclic nitriding according to a pressure alternating cyclic mode of high pressure-low pressure-high pressure, wherein the total time of the cyclic nitriding process is 8 hours; the high-pressure heat preservation time and the low-pressure heat preservation time of each time of cyclic nitriding are both 30 min.
4) The reaction tank is vacuumized to 10 DEG-3Pa, vacuum diffusion for 5h, and cooling to room temperature along with the furnace.
Example 2
The procedure is as in example 1, wherein:
in step 2), the vacuum degree of the reaction tank is 10-4Pa, 750 ℃ and 1h of heat preservation time;
in the step 3), the high pressure in the tank is 30000Pa, the nitriding temperature is 900 ℃, the low pressure in the tank is 15000Pa, the cyclic nitriding is carried out for 2 times, and the total time of the cyclic nitriding process is 1 h; the high-pressure heat preservation time and the low-pressure heat preservation time of each time of cyclic nitriding are both 15 min.
In the step 4), vacuum diffusion is carried out for 1h, and the vacuum degree is 10-4Pa。
Example 3
The procedure is as in example 1, wherein:
in step 2), the vacuum degree of the reaction tank is 10-4Pa, 765 deg.C, keeping the temperature for 0.7 h;
in the step 3), the high pressure in the tank is 50000Pa, the nitriding temperature is 850 ℃, the low pressure in the tank is 10000Pa, the cyclic nitriding is carried out for 9 times, and the total time of the cyclic nitriding process is 6 hours; the high-pressure heat preservation time and the low-pressure heat preservation time of each time of cyclic nitriding are both 20 min.
In the step 4), vacuum diffusion is carried out for 4 hours, and the vacuum degree is 10-3Pa。
Example 4
The procedure is as in example 1, wherein:
in step 2), the vacuum degree of the reaction tank is 10-4Pa, the temperature is 770 ℃, and the heat preservation time is 0.8 h;
in the step 3), the high pressure in the tank is 40000Pa, the nitriding temperature is 880 ℃, the low pressure in the tank is 10000Pa, the high-pressure heat preservation time and the low-pressure heat preservation time of the first cyclic nitriding are 25min, and the high-pressure heat preservation time and the low-pressure heat preservation time of each cyclic nitriding are 20min later; and 3.5 times of cyclic nitriding, wherein the total time of the cyclic nitriding process is 150 min.
In the step 4), vacuum diffusion is carried out for 2 hours, and the vacuum degree is 10-4Pa。
Example 5
The procedure is as in example 1, wherein:
in step 2), the vacuum degree of the reaction tank is 10-4Pa, 760 ℃ and the heat preservation time of 0.6 h;
in the step 3), the high pressure in the tank is 45000Pa, the nitriding temperature is 850 ℃, the low pressure in the tank is 10000Pa, the cyclic nitriding is carried out for 6 times, and the total time of the cyclic nitriding process is about 4.5 h; the high-pressure heat preservation time and the low-pressure heat preservation time of each time of cyclic nitriding are both 22 min.
In the step 4), vacuum diffusion is carried out for 3 hours, and the vacuum degree is 10-4Pa。
Comparative example
For comparison, TC4 titanium alloy samples of the same composition and dimensions were subjected to direct vacuum nitriding for 6 h. The specific method is to polish and clean the TC4 titanium alloy samplePutting the mixture into a reaction tank, and introducing nitrogen to drive air in the tank; the reaction tank was then evacuated to 10 deg.f-3～10-4And Pa, closing the vacuum system after the furnace temperature rises to 820 ℃, introducing 50000Pa high-purity nitrogen into the tank, keeping the temperature for 6 hours, cooling the tank to room temperature, and taking out the titanium alloy sample for relevant detection. The detection results are shown in fig. 3, 4, 6 and 7.
As can be seen from FIGS. 2 and 3, the TC4 titanium alloy treated by the method of the present invention has a depth of 60-80 μm of nitriding layer; the depth of the penetration layer of the direct vacuum nitriding method is only 30-40 μm. In the same time, the depth of the nitriding layer obtained by adopting the method of the invention is improved by 1 time.
As can be seen from FIG. 4, the diffraction peak of TiN was weak when TC4 titanium alloy was treated by the method of the present invention, indicating decomposition of nitride and diffusion of nitrogen into the matrix.
As can be seen from FIGS. 5 and 6, the TC4 titanium alloy treated by the vacuum direct nitriding method has a lot of cracks near the indentation, while the TC4 titanium alloy treated by the method of the present invention has no cracks; the nitriding layer formed by the method of the invention has obviously improved brittleness and higher bonding strength with the substrate.
As can be seen from FIG. 7, the TC4 titanium alloy treated by the method of the invention can obtain higher surface hardness (more than 1100 HV), and the hardness gradient is more gradual.
The device provided by the invention is further explained by combining the drawings and the specific embodiment.
As shown in fig. 8, it includes a heating system, a vacuum system and a gas supply system. Wherein:
the heating system is composed of a reaction tank 4 fixed in a hearth of a furnace body 1, a plurality of electric heating elements 2 which are positioned between the reaction tank and the hearth and are uniformly distributed, a thermocouple 3 fixed on the furnace body 1 and extending into the hearth, a flange plate 8 fixed at a tank opening of the reaction tank 4, and a furnace door 9 which is fixed on the flange plate through hook-shaped bolts (not shown in the figure) and seals the tank opening; the vacuum system is composed of an extraction opening (not shown in the figure) communicated with the reaction tank 4, and a vacuum pump 12 communicated with the extraction opening through a pipeline (not shown in the figure); the gas supply system is composed of a gas inlet pipe 5 which is fixed in a reaction tank 4 and is communicated with a nitrogen cylinder 11 through a gas supply pipe (not marked in the figure), and a pressure gauge 6 is arranged on the reaction tank 4.
In order to increase the sealing performance, a sealing ring (not shown in the figure) is arranged between the flange 8 and the furnace door 9; in order to prevent the seal ring from being aged by a high temperature for a long time, a circulating cooling water pipe 7 is wound on the surface of the flange 8.
In order to promote the gas in the tank to flow sufficiently and avoid dead corners with blind areas, the reaction tank 4 is internally fixed with an air exhaust pipe 14 which is distributed with a plurality of small holes; similarly, in order to ensure that each part in the tank can uniformly supply air, the air inlet pipe 5 is distributed with a plurality of small holes.
In order to avoid water ingress by the suction pump 12, a condenser 13 is connected between the pipe and the suction pump.
In order to open the furnace door 9, a pressure relief valve 10 communicated with the interior of the reaction tank 4 is fixed on the reaction tank 4 at a position close to the tank opening.
In order to increase the degree of vacuum inside the reaction tank 4, the suction pump 12 is a two-stage pump composed of a rotary vane pump and a molecular pump.
For convenient operation, a controller 15 is arranged on the furnace body 1, and the electric heating element 2, the thermocouple 3 and the pressure gauge 6 are respectively and electrically connected with the controller 15.

Claims (8)

1. A titanium alloy segmented vacuum rapid nitriding method comprises a pretreatment step and a cyclic nitriding step; the method is characterized by comprising the following steps:
1) putting the workpiece subjected to polishing and cleaning treatment into a reaction tank, and introducing high-purity nitrogen with the purity of more than or equal to 99.99% into the reaction tank until all air in the tank is discharged;
2) the reaction tank is vacuumized to 10-3～10-4Pa, heating the reaction tank to 750-780 ℃ and preserving heat for 0.5-1 h;
3) introducing the high-purity nitrogen until the pressure in the tank reaches 30000-60000 Pa, then heating the reaction tank to 800-900 ℃, and preserving the temperature; pumping out nitrogen until the pressure in the tank is reduced to 5000-15000 Pa, and preserving heat; introducing high-purity nitrogen again until the pressure in the tank reaches 30000-60000 Pa, and preserving the temperature; nitriding is carried out according to a high-pressure-low-pressure-high-pressure alternating circulation mode, and the total time of a circulation nitriding process is 1-8 h; in each circulation, the heat preservation time of high-pressure nitriding and low-pressure nitriding is the same and is 15-30 min;
4) the reaction tank is vacuumized to 10 DEG-3～10-4And Pa, performing vacuum diffusion for 1-5 h, and then cooling to room temperature along with the furnace.
2. The method for segmented vacuum rapid nitriding of titanium alloy according to claim 1, characterized in that: in the step 3), the high-pressure nitriding pressure is 40000-50000 Pa, the low-pressure nitriding pressure is 10000Pa, the heat preservation time is 20-25 min, and the total time of the cyclic nitriding process is 3-6 h; the vacuum diffusion time in the step 4) is 2-4 h.
3. The method for segmented vacuum rapid nitriding of titanium alloy according to claim 1, characterized in that: in the step 3), the high-pressure nitriding pressure is 45000Pa, the low-pressure nitriding pressure is 10000Pa, the heat preservation time is 22min, and the total time of the cyclic nitriding process is 4.5 h; the vacuum diffusion time in the step 4) is 3 h.
4. A device for realizing the sectional vacuum rapid nitriding method of the titanium alloy as claimed in any one of claims 1-3 comprises a heating system, a vacuum system and a gas supply system; the method is characterized in that:
the heating system consists of a reaction tank (4) fixed in a hearth of the furnace body (1), a plurality of electric heating elements (2) which are positioned between the reaction tank and the hearth and are uniformly distributed, a thermocouple (3) fixed on the furnace body (1) and extending into the hearth, a flange plate (8) fixed at a tank opening of the reaction tank (4), and a furnace door (9) fixed on the flange plate and sealing the tank opening; the vacuum system consists of an air pumping port communicated with the reaction tank (4) and an air pumping pump (12) communicated with the air pumping port through a pipeline; the gas supply system is composed of a gas inlet pipe (5) which is fixed in the reaction tank (4) and is communicated with the nitrogen cylinder (11) through a gas supply pipe, and a pressure gauge (6) is installed on the reaction tank (4).
5. The apparatus of claim 4, wherein: a sealing ring is arranged between the flange (8) and the furnace door (9), and a circulating cooling water pipe (7) is coiled on the surface of the flange (8).
6. The apparatus of claim 4, wherein: an exhaust pipe (14) is fixed in the reaction tank (4), and a plurality of small holes are distributed on the air inlet pipe (5) and the exhaust pipe (14).
7. The apparatus of claim 6, wherein: a condenser (13) is connected between the pipeline and the air pump (12).
8. The apparatus according to any one of claims 4 to 7, wherein: a pressure release valve (10) communicated with the interior of the reaction tank (4) is fixed on the reaction tank (4) at a position close to the tank opening.
CN202010726954.6A 2020-07-26 2020-07-26 Titanium alloy segmented vacuum rapid nitriding method and device Pending CN111850456A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114182196A (en) * 2021-12-02 2022-03-15 贵州师范大学 Titanium alloy vacuum gas step nitriding method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114182196A (en) * 2021-12-02 2022-03-15 贵州师范大学 Titanium alloy vacuum gas step nitriding method
CN114182196B (en) * 2021-12-02 2024-01-19 贵州师范大学 Titanium alloy vacuum gas step nitriding method

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