CN112453390B

CN112453390B - Sintering auxiliary agent-coated titanium powder and preparation method thereof

Info

Publication number: CN112453390B
Application number: CN202011231098.3A
Authority: CN
Inventors: 杨亚锋; 李少夫; 黄志涛; 吕元之; 崔景毅; 王宇枭
Original assignee: Jinan Xinyi Powder Metallurgy Co ltd; Institute of Process Engineering of CAS; AVIC Beijing Aeronautical Manufacturing Technology Research Institute
Current assignee: Jinan Xinyi Powder Metallurgy Co ltd; Institute of Process Engineering of CAS; AVIC Beijing Aeronautical Manufacturing Technology Research Institute
Priority date: 2020-11-06
Filing date: 2020-11-06
Publication date: 2022-02-25
Anticipated expiration: 2040-11-06
Also published as: CN112453390A

Abstract

The invention belongs to the field of manufacturing of powder metallurgy titanium alloy parts, and mainly relates to titanium powder coated with a sintering aid and a preparation method thereof. The sintering auxiliary agent is nano particles uniformly coated on the surface of titanium/titanium alloy powder, and the sintering densification behavior of the titanium powder is enhanced by forming a low-temperature liquid phase in the sintering process of the titanium powder. The invention is realized by a chemical plating technology, a specific metal salt solution is selected, and the sintering auxiliary agent is uniformly, quantitatively and controllably arranged on the surface of the titanium powder by controlling the chemical plating reaction conditions.

Description

Sintering auxiliary agent-coated titanium powder and preparation method thereof

Technical Field

The invention belongs to the field of manufacturing of powder metallurgy titanium alloy parts, and mainly relates to titanium powder coated with a sintering aid and a preparation method thereof.

Background

Titanium and titanium alloy have many advantages such as specific strength and specific stiffness are high, corrosion resistance is excellent, all are improving one of performance, reducing weight, improving one of the best candidate materials of efficiency in fields such as aerospace, weaponry, automobile industry. However, unlike other conventional materials, the complicated melting process and poor machining performance of titanium alloy lead to very high cost of titanium alloy parts produced by the current casting and forging process, the effective utilization rate of the titanium alloy parts from raw materials to final parts is less than 12%, and the high cost leads to severe limitation on the application and development of titanium alloy in various engineering fields.

The powder metallurgy technology is a green process technology for directly processing powder into product parts, and can effectively solve the problems of high processing cost, long production flow and the like of the titanium alloy, thereby becoming a necessary way for reducing the cost of the titanium alloy. However, the titanium alloy powder metallurgy technology is slow to develop, and the main reason is that the sintering density is low and the industrial application standard is difficult to achieve. In order to solve the problem, research teams at home and abroad develop various sintering aids, wherein the sintering aids comprise simple substance sintering aids such as nickel, iron and the like, but the addition amount of the sintering aids usually needs to be more than 8 wt.% to realize high-densification sintering of the titanium alloy, and the addition of a large amount of the sintering aids causes the stroke of a brittle eutectoid body, so that the strength and the plasticity of the titanium alloy are greatly reduced. In order to reduce the addition amount of sintering aids and obtain a high-densification titanium alloy product, researchers develop binary sintering aids such as Ni-B, Fe-Si and the like, and can realize high-densification sintering of the titanium alloy at a low addition amount.

Although the development of the novel binary sintering aid can reduce the addition amount of the sintering aid to a certain extent and simultaneously strengthen the sintering densification behavior of the titanium powder, the particle size of the externally added sintering aid is generally dozens of micrometers, the strengthening sintering capability is limited, and the industrial application standard of 98% of densification cannot be achieved. In contrast, researchers seek to further improve the enhanced sintering performance of the sintering aid by refining the particle size of the aid, but strong van der waals force exists between ultrafine powders, so that the conventional mechanical mixing method cannot realize uniform introduction of the ultrafine sintering aid, and the problems of poor enhanced sintering effect, low uniformity of sintered structures, serious deformation of sintered products and the like are caused. Therefore, it is highly desirable to develop a superfine binary sintering aid capable of obtaining uniform dispersion and high activity in titanium powder, and to realize high densification and uniform sintering of powder metallurgy titanium alloy under the condition of small amount or trace addition.

Disclosure of Invention

The present invention aims to provide a titanium powder coated with a sintering aid. The invention aims at the problems of insufficient enhanced sintering capacity or poor uniformity of sintered product structure and the like caused by the problems of size limitation or poor dispersion uniformity and the like of the traditional sintering auxiliary agent, the chemical plating technology is adopted to prepare the binary sintering auxiliary agent which is uniformly coated on the surface of titanium powder, and the sintering auxiliary agent has a series of advantages of uniform size, small size, high activity, good dispersion uniformity, low impurity content and the like. The sintering aid can be directly used for producing high-density and complex-shaped powder metallurgy titanium alloy parts, but the application is not limited to the method, and the sintering aid can also be used as a phase reaction strengthening raw material in a titanium-based composite material prepared by powder metallurgy or 3D printing technology.

In order to achieve the purpose, the invention adopts the following specific technical scheme:

the sintering aid is uniformly coated on the surface of the titanium powder, the size of the sintering aid is 20 nm-1 mu m, and the coating amount is 0.05wt.% to 10 wt.%.

Preferably, the coated sintering aid is one or more of a V-B binary compound, a Ni-B binary compound and a Co-B binary compound.

Preferably, the titanium powder comprises one or more of Ti powder, Ti-Al-V powder, Ti-Fe-V powder, Ti-Mo-Sn-Zr powder and Ti-Al-Mo-V powder, and the mass purity is more than or equal to 99%.

A preparation method of the titanium powder coated with the sintering auxiliary agent comprises the following steps:

1) preparing a plating solution by adopting metal salt and a complexing agent, and adding an alkali solution into the plating solution to adjust the pH value of the plating solution;

2) and heating the plating solution, adding the titanium powder into the plating solution, stirring, simultaneously dripping a reducing agent solution, carrying out chemical plating reaction, filtering, cleaning, drying and sieving the coated powder after the reaction is finished, thereby obtaining the titanium powder uniformly coated with the sintering auxiliary agent on the surface.

Specifically, the preparation method of the titanium powder coated with the sintering aid comprises the following steps:

1) preparing chemical plating solution and reducing agent solution:

respectively adding a complexing agent and a metal salt into two beakers, pouring deionized water to dissolve the metal salt and the complexing agent to prepare a metal salt solution and a complexing agent solution, uniformly mixing to obtain a mixed solution, and adjusting the pH value; preparing a reducing agent solution in another beaker;

2) establishing a chemical plating experiment platform and performing a chemical plating experiment:

the experimental platform comprises a chemical plating reactor, a heating device, a stirring device and a temperature measuring device, chemical plating solution is added, the chemical plating solution is heated to a target temperature, titanium powder is added into the chemical plating solution and mechanically stirred, a reducing agent is slowly dripped into the chemical plating solution, the experimental device is closed after reaction time is reached, mixed turbid liquid is filtered, the filtered powder is cleaned by deionized water and then is subjected to vacuum drying, and finally, the treated coated titanium powder is sieved and sealed for storage.

Preferably, the plating solution in the step 1) is mainly one or more of salt solutions such as nickel salt, cobalt salt, vanadium salt and the like, the volume of the solution is 100ml to 2000ml, and the volume of the reducing agent solution is 10ml to 500 ml.

Preferably, the complexing agent in the step 1) is one or a combination of more of sodium citrate, citric acid, potassium sodium tartrate, acetic acid, malic acid, sodium acetate, lactic acid and boric acid, and the concentration of the complexing agent is 0.005 mol/L-0.20 mol/L.

Preferably, the pH value of the plating solution in the step 1) is 5-12, the concentration of the alkaline solution is 1-3 mol/L, and the alkaline solution is one or more of NaOH solution, KOH solution and ammonia water.

Preferably, the reducing agent in the step 1) is one of boron-containing reagents of sodium borohydride or potassium borohydride, the reagent is analytically pure, and the solution concentration is 0.01 mol/L-0.3 mol/L.

Preferably, the volume of the chemical plating reactor in the step 2) is 200ml to 5000ml, the heating device can accommodate the chemical plating reactor, the stirring device is matched with the chemical plating reactor in size, the heating device can realize uniform heating of the plating solution in the reactor, a water bath and oil bath heating device is preferred, and a mechanical stirring device is preferred as the stirring device.

Preferably, the target temperature in the step 2) is 40-95 ℃, and the mechanical stirring speed is 100-1000 r/min.

Preferably, the titanium powder in the step 2) comprises one of Ti, Ti-Al-V, Ti-Fe-V, Ti-Mo-Sn-Zr and Ti-Al-Mo-V prepared by a hydrogenation dehydrogenation method or an atomization method, the purity of the titanium powder is higher than 99%, the particle size distribution of the titanium powder is 5-150 μm, and the adding amount of the titanium powder is 10-500 g.

Preferably, the dropping speed of the reducing agent in the step 2) is 0.01-0.20 ml/s, the reaction time is 5-120 min, the vacuum drying temperature of the powder is 40-80 ℃, and the drying time is higher than 2 h.

Preferably, the coated titanium powder in the step 2) is titanium or titanium alloy powder coated with a sintering aid, and the particle size, distribution uniformity and weight fraction of the coated substance in the powder can be controlled by parameters such as plating solution concentration, powder loading capacity and reaction time.

The sintering auxiliary agent is introduced into the titanium powder in a coating structure, mainly comprises binary compounds such as V-B, Ni-B, Co-B and the like, and has the advantages of small size, high activity, good dispersion uniformity, low impurity content and the like.

Compared with the traditional sintering auxiliary agent introduced into the titanium alloy powder by a mechanical mixing method, the invention has the advantages that:

the coated powder metallurgy titanium alloy sintering auxiliary agent has smaller particle size and higher reaction activity, and can realize high-densification sintering of powder metallurgy titanium alloy powder under lower addition content; meanwhile, the sintering auxiliary agent also has the advantages of good dispersion uniformity, low impurity content and the like, can realize high uniformity of a titanium alloy product sintering structure, is more favorable for sample shrinkage and shape control in the sintering process, and simultaneously avoids performance decline and the like caused by introduction of impurities such as oxygen, carbon and the like. The coating type sintering auxiliary agent is mainly introduced through a chemical plating technology, the technology breaks through the technical bottleneck that the traditional nano sintering auxiliary agent cannot be uniformly introduced into titanium powder, solves the problem that the high-efficiency sintering auxiliary agent and the dispersion uniformity thereof are difficult to coordinate, and has the advantages of simple process, short flow, low cost, easiness in large-scale production and the like.

Drawings

FIG. 1 is an SEM image of V-B coated hydrogenated dehydrogenated Ti-6Al-4V powder in example 1 of the present invention;

FIG. 2 is an SEM image of a V-B coated hydrogenated dehydrogenated Ti-6Al-4V powder sintered structure in example 1 of the present invention;

FIG. 3 is an SEM image of Ni-B coated gas atomized spherical titanium powder in example 2 of the present invention;

FIG. 4 is an SEM image of a sintered structure of the Co-B coated hydrogenated titanium dehydrogenated powder in example 3 of the present invention.

Detailed Description

Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. Unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features. The description is only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.

The invention provides a titanium alloy powder coated with a sintering aid, which is mainly used as a raw material of a high-densification sintering powder of a powder metallurgy titanium alloy, wherein the sintering aid is compounded with the titanium powder in a coating structure, and the type of the sintering aid mainly comprises binary compounds such as V-B, Ni-B, Co-B, so that the titanium alloy powder has the advantages of small size, high activity, good dispersion uniformity, low impurity content and the like. As another aspect of the present invention, a method for preparing a sintering aid-coated titanium alloy powder is provided, which has the advantages of high uniformity of introduction of a sintering aid, high degree of densification of a sintered product, uniform sintered structure, high shape accuracy, and the like, compared to a conventional method for introducing a sintering aid by mechanical mixing, and which has the characteristics of simple process, low cost, and the like.

The invention is explained in more detail below with reference to the figures and the embodiments.

Example 1

1. Preparing V-B coated hydrogenated dehydrogenated Ti-6Al-4V powder, wherein the V-B nano sintering auxiliary agent accounts for 4.0 percent of the total weight of the powder, the content of V is 3.8 percent, and the content of B is 0.2 percent. The powder is prepared by a chemical plating method, and the preparation process of the plating solution is as follows, boric acid and anhydrous vanadium chloride are respectively put into two beakers filled with 400ml of deionized water for dissolving and mixing, the boric acid and the anhydrous vanadium chloride are fully complexed by stirring, and the molar concentrations of the boric acid and the anhydrous vanadium chloride in the plating solution are respectively adjusted to be 0.095mol/L and 0.20 mol/L. Putting an electronic pH meter into a beaker filled with the mixed solution, adding 3mol/L NaOH solution while stirring, adjusting the pH to 9.5, adding deionized water until the volume of the plating solution reaches 950ml, putting sodium borohydride into another beaker, adding deionized water to 50ml, and stirring and dissolving to prepare a reducing agent solution.

2. Putting a four-neck glass flask with the volume of 2L into a water bath heating device, connecting a mechanical stirring device, pouring a plating solution into the four-neck glass flask, heating to 85 ℃, adjusting the stirring speed to 400r/min, and adding 200g of hydrogenated and dehydrogenated Ti-6Al-4V powder with the granularity of-100 meshes. And (3) putting the reducing agent solution into a constant-pressure titration funnel, fixing the constant-pressure titration funnel on a four-neck glass flask, opening the constant-pressure titration funnel, and dripping the sodium borohydride reducing agent solution into the plating solution filled with the titanium powder at the speed of 0.04 ml/s. Controlling the reaction time to be 60min, closing the mechanical stirring and heating device, taking out the four-mouth glass flask, filtering the suspension to obtain powder, pouring deionized water to clean the powder, filtering again, placing the powder in a vacuum drying oven, drying for 24h at 60 ℃, sieving by a standard sieve of-100 meshes to obtain target powder, and sealing and packaging.

3. 3g of hydrogenated and dehydrogenated Ti-6Al-4V powder coated with sintering auxiliary agent is put into the sintering furnace

In the cylindrical cold-pressing die, the powder is pressed and formed by selecting the pressure of 600MPa and the dwell time of 30s, then the pressed green body is put into a vacuum tube furnace, the vacuum degree in the furnace is adjusted to 2.0 multiplied by 10^-3And (4) heating and sintering after Pa, wherein the sintering temperature is 1350 ℃, the heat preservation time is 2 hours, and the sample is taken out after being cooled along with the furnace.

FIG. 1 is an SEM image of V-B coated hydrogenated dehydrogenated Ti-6Al-4V powder in example 1. As can be seen, the sintering aid is uniformly coated on the surface of the titanium powder, and the size of the sintering aid is less than 1 μm.

FIG. 2 shows the structure of a titanium alloy sample obtained by cold press forming and vacuum sintering of V-B coated hydrogenated dehydrogenated Ti-6Al-4V powder in example 1, wherein the titanium alloy has high sintering densification degree and good structure uniformity by uniformly introducing the coated nano sintering aid. The density of the sintered material can reach more than 98 percent, and is obviously improved in the aspect of sintering density compared with the traditional method of adding the sintering auxiliary agent in a mixing way, and the titanium alloy powder coated with the sintering auxiliary agent is fully proved to have higher sintering activity.

Example 2

The present embodiment 2 differs from embodiment 1 in that: the titanium powder matrix in the example 1 is replaced by hydrogenated and dehydrogenated Ti-6Al-4V alloy powder into argon atomized spherical pure titanium powder; the metal salt in the plating solution is replaced by anhydrous nickel chloride from anhydrous vanadium chloride for introducing Ni-B sintering auxiliary agent; in addition, the molar concentration of the anhydrous vanadium chloride is adjusted to 0.10mol/L, which is used for verifying that the size of the coated sintering auxiliary agent can be effectively regulated and controlled by controlling the chemical plating condition;

fig. 3 is an SEM image of the Ni-B coated gas atomized spherical titanium powder in example 2, as shown in the figure, the variation in the morphology and composition of the titanium powder does not seriously affect the introduction uniformity of the coated sintering aid, and the size of the coated sintering aid can be accurately controlled by controlling the plating solution conditions, such as concentration and the like.

By sintering the titanium composite powder coated with the Ni-B sintering aid at 1350 ℃ for 2h under the condition of heat preservation, the sintering density can reach over 96.5 percent, which is obviously superior to the sintering effect of adding the Ni-B sintering aid titanium powder by a mixing method.

Example 3

The present embodiment 3 differs from embodiment 1 in that: the titanium powder substrate in the example 1 is replaced by hydrogenated and dehydrogenated Ti-6Al-4V alloy powder, the metal salt in the plating solution is replaced by anhydrous vanadium chloride to be anhydrous cobalt chloride for introducing a Co-B sintering auxiliary agent, acetic acid is selected as a complexing agent, and the pH value is adjusted to 14 from 9.5. The titanium powder was found to be coated with nanoparticles having an average size of 50nm, which were finer than the V-B particles. The Co-B sintering aid-coated titanium composite powder is sintered at 1350 ℃ for 2 hours under heat preservation, and a graph shown in FIG. 4 is an SEM image of a sintering structure of Co-B coated hydrogenated dehydrogenated titanium powder in example 3 of the invention, and the sintering density of the powder after sintering still reaches more than 96 percent, so that the Co-B sintering aid is proved to have excellent auxiliary sintering characteristics after being coated on the surface of the titanium powder.

Example 4

The present embodiment 4 differs from embodiment 1 in that: the metal salt in the plating solution is replaced by anhydrous cobalt chloride from anhydrous vanadium chloride for introducing a Co-B sintering auxiliary agent, acetic acid is selected as a complexing agent, the stirring speed is increased to 950r/min from 400r/min, and the chemical plating time is increased to 120 min. It is found that the surface of the titanium powder can still be coated with Co-B particles, but the rotation speed and the coating time are increased, so that the uniformity of the coated particles on the surface of the powder is not improved, the size of the particles on the surface of the powder is increased, and a plurality of self-nucleating Co-B particles are found in the plating solution, and the coated particles are knocked off from the surface of the powder by the excessively high rotation speed, or the large-size Co-B particles obtained by long-time coating have too large self weight and inertia and are peeled off from the surface of the powder in the chemical plating process.

The method can be realized by upper and lower limit values and interval values of intervals of process parameters (such as temperature, time and the like), and embodiments are not listed.

Conventional technical knowledge in the art can be used for the details which are not described in the present invention.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A preparation method of titanium powder coated with sintering aid comprises the following steps:

1) preparing a plating solution by adopting metal salt and a complexing agent, and adding an alkali solution into the plating solution to adjust the pH value of the plating solution to 5-12;

2) heating the plating solution, adding the titanium powder into the plating solution, stirring, simultaneously dripping a reducing agent solution, carrying out chemical plating reaction, filtering, cleaning, drying and sieving the coated powder after the reaction is finished, and obtaining the titanium powder with the surface uniformly coated with the sintering auxiliary agent;

uniformly coating a sintering aid on the surface of the titanium powder, wherein the size of the sintering aid is 20 nm-1 mu m, and the coating amount is 0.05wt.% to 10 wt.%;

the sintering auxiliary agent is one or more of a V-B binary compound, a Ni-B binary compound and a Co-B binary compound;

the heating temperature for heating the plating solution in the step 2) is 40^oC~95^oC, stirring at a rotating speed of 100 r/min-1000 r/min, and reacting for 5 min-120 min in chemical plating;

the reducing agent solution is an aqueous solution of sodium borohydride or potassium borohydride, the concentration is 0.01-0.3 mol/L, and the dropping speed of the reducing agent solution is 0.01-0.20 ml/s.

2. The method of preparing a sintering aid-coated titanium powder according to claim 1, wherein the titanium powder comprises one or more of Ti powder, Ti-Al-V powder, Ti-Fe-V powder, Ti-Mo-Sn-Zr powder, and Ti-Al-Mo-V powder, and has a mass purity of 99% or more.

3. The preparation method according to claim 1, wherein the metal salt is one of a nickel salt, a cobalt salt and a vanadium salt, and the complexing agent is one or more of sodium citrate, citric acid, potassium sodium tartrate, acetic acid, malic acid, sodium acetate, lactic acid and boric acid.