CN113953516A

CN113953516A - Powder filling sintering repair method for surface defects of titanium or titanium alloy parts

Info

Publication number: CN113953516A
Application number: CN202111082720.3A
Authority: CN
Inventors: 路新; 张策; 张帅华; 刘鑫
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2022-01-21
Anticipated expiration: 2041-09-15
Also published as: CN113953516B

Abstract

The invention provides a powder filling sintering repair method for surface defects of titanium or titanium alloy workpieces, which comprises the following steps: before repairing, surface cleaning is carried out on the surface defects of the workpiece and the areas near the defects; selecting raw material powder, and uniformly mixing the raw material powder according to a certain proportion to prepare repair powder; coating the repair powder to fill the defect and compacting the repair powder to obtain a filled workpiece; and (4) carrying out vacuum sintering on the filled workpiece to obtain the repaired workpiece. The powder filling sintering repair method realizes the repair of the surface defects of the titanium or the titanium alloy, ensures the repair quality of the surface defects of the titanium or the titanium alloy product, can avoid the defects of a heat affected zone, deformation and the like generated by the traditional fusion welding repair, also solves the problems of low strength, overlarge difference with matrix components and the like of the traditional brazing repair, and has the advantages of simple and easy operation, high repair efficiency and excellent performance after repair.

Description

Powder filling sintering repair method for surface defects of titanium or titanium alloy parts

Technical Field

The invention relates to the technical field of powder metallurgy, in particular to a powder filling sintering repair method for surface defects of titanium or titanium alloy workpieces.

Background

Titanium and titanium alloy have the excellent characteristics of light weight, high strength, good corrosion resistance and the like, and are widely applied to the fields of aerospace, biomedical treatment and energy. But the sensitivity to gaps, scratches and the like is high, and defects such as embrittlement, cracking, holes and the like are easily generated, and the defects can reduce the service life of equipment and even directly cause product rejection. In such cases, manufacturers often resort to continued use or replacement of parts, resulting in extended production cycles and increased costs; if the prototype machine is adopted, the number of replaceable parts is very small, the prototype machine can only be directly used, and the risk is improved. Therefore, the defective index is often reduced by a repairing method, and the production cost is reduced.

The prior art for repairing the surface defects of titanium alloy workpieces comprises fusion welding and brazing repair. Fusion welding is further classified into argon arc welding repair, laser and electron beam welding repair, etc. according to different heat sources. Due to the rapid heating and cooling processes, the problems of large thermal stress of a repair area, easy cracking and deformation of a product and the like are caused. Laser and electron beam welding repair is limited by equipment, and often cannot reach repair welding positions such as the inner part of a workpiece. The multi-element alloy brazing filler metal is adopted for brazing and repairing, and the problems that the strength of a repaired part is low, the deviation between the brazing filler metal and a matrix component is large and the like exist often.

Therefore, a new technology for repairing titanium alloy is sought, and the technology has practical engineering value for titanium alloy application.

Disclosure of Invention

In view of the above disadvantages, the main object of the present invention is to provide a powder filling sintering repair method for surface defects of titanium or titanium alloy parts, which fills the defects with repair powder, compacts the repair powder and then performs vacuum sintering, thereby realizing repair of the surface defects of titanium or titanium alloy parts, ensuring the repair quality of the surface defects of titanium or titanium alloy parts, avoiding the defects of heat affected zone, deformation and the like caused by the conventional fusion welding repair, and also improving the problems of low strength, excessive difference from the base component and the like of the conventional brazing repair, and the repair method has the advantages of simple and easy operation, high repair efficiency and excellent performance after repair.

In order to achieve the purpose, the invention provides a powder filling sintering repair method for surface defects of titanium or titanium alloy parts.

The powder filling sintering repair method for the surface defects of the titanium or titanium alloy parts comprises the following steps:

defect cleaning: before repairing, surface cleaning is carried out on the surface defects of the workpiece and the areas near the defects;

preparation of repair powder: selecting raw material powder, and uniformly mixing according to a certain proportion to prepare the repair powder; wherein the raw material powder comprises titanium and/or titanium alloy powder and a sintering aid;

powder filling and compacting: coating the repair powder to fill the defect and compacting the repair powder to obtain a filled workpiece;

and (3) sintering: and carrying out vacuum sintering on the filled workpiece to obtain a repaired workpiece.

Further, the sintering aid is at least one of copper powder and tin powder.

Further, the mass percent of the titanium or titanium alloy powder is 75-90 wt.%; the mass percent of the copper powder is preferably 0-5 wt.%, and the mass percent of the tin powder is preferably 0-15 wt.%.

Further, the raw material powder further comprises at least one of nickel powder and zirconium powder; the mass percent of the nickel powder and the mass percent of the zirconium powder are both preferably 0-5 wt.%.

Furthermore, the particle sizes of all component powders in the raw material powder are 5-50 μm.

Further, compacting the repair powder by using a cold isostatic pressing process; the pressing pressure of the cold isostatic pressing process is preferably 100-250 MPa, and the pressure maintaining time is preferably 10-30 s.

Further, the vacuum sintering adopts a segmented sintering process, which specifically comprises the following steps:

sintering at the first stage, heating to 250-350 ℃, and keeping the temperature for 0.5-1 h;

the second stage of sintering, heating to 600-750 ℃, and keeping the temperature for 0.5-1 h;

and (3) sintering in the third stage, heating to 1150-1300 ℃, wherein the sintering time is 2-4 h.

Further, the heating rate of the first-stage sintering and the second-stage sintering is 2-4 ℃/min, and the heating rate of the third-stage sintering is 5 ℃/min.

Further, surface cleaning is carried out on the surface defects of the workpiece and the areas near the defects by adopting a mechanical or manual polishing mode; and then sequentially carrying out acid washing and water washing on the cleaned surface.

Further, the method also comprises the following steps of carrying out post-treatment on the repaired workpiece: and polishing the repaired part of the repaired workpiece.

The traditional brazing method uses a low-melting-point brazing filler metal as a repairing material, the brazing filler metal mainly made of titanium or titanium alloy is generally Ti-Cu-Ni, Ti-Zr-Cu-Ni and the like, the content of titanium is generally less than 60%, and other alloy elements are generally higher than 20%, so that the difference between a repairing material and a base material is too large, and various performances such as the strength, the corrosion resistance and the like of the repairing material are influenced, and therefore the technology has a large defect.

The invention takes titanium or titanium alloy powder as a main body, adds a proper amount of liquid phase sintering auxiliary agent to form repair powder, and then sinters and repairs the repair powder at the defect of a titanium or titanium alloy part. Generally, in order to ensure sufficient strength and toughness of the repaired part, the mass fraction of the titanium element is generally greater than or equal to 80%, and the contents of tin and copper are strictly controlled within 15% and 5%, so that the repaired part material is still considered as the component proportion of common titanium or titanium alloy. Compared with the traditional fusion welding repair method, the powder filling sintering repair method does not generate internal stress in the repair process, and does not generate cracks and deformation after repair; the repaired part is well combined with the matrix, no obvious transition area exists, the filling powder is close to the matrix component, homogeneous repair can be realized, and the mechanical property of the repaired area can reach 70-90% of that of the matrix.

In addition, on the basis of adding the liquid-phase sintering aid, a proper amount of nickel powder and zirconium powder can be added, and the nickel powder, the zirconium powder and the titanium or titanium alloy powder form eutectic phases in the sintering process, so that the strength and the toughness of the repaired part can be further improved.

The invention has the beneficial effects that:

1. the powder filling sintering in the invention can realize the simultaneous repair of a plurality of workpieces and a plurality of defective parts, thereby greatly improving the repair efficiency.

2. Compared with the traditional melting welding repair method, the powder filling sintering in the invention can not generate a heat affected zone, has no influence on surrounding tissues, can not generate internal stress in the repair process, and can not generate cracks and deformation after repair.

3. The repaired part is well combined with the matrix, no obvious transition area exists, the filling powder is close to the matrix component, homogeneous repair can be realized, and the mechanical property of the repaired area can reach 70-90% of that of the matrix.

4. Compared with the melting welding cost, the invention obviously reduces the alloy brazing filler metal used in the brazing repair.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is a flow chart of a powder-filled sintering repair method for surface defects of titanium or titanium alloy articles according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a defect in an embodiment of the present invention before repair of a titanium or titanium alloy article;

FIG. 3 is a macroscopic topography of an interface of a repaired titanium or titanium alloy article according to an embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

According to the specific embodiment of the invention, the powder filling sintering repair method for the surface defects of the titanium or titanium alloy part is provided.

Referring to fig. 1, the powder filling sintering repair method includes the following steps:

defect cleaning: and before repairing, surface cleaning is carried out on the surface defects of the workpiece and the areas near the defects.

In the step, surface cleaning is carried out on the surface defects of the workpiece and the areas near the defects by adopting a mechanical or manual polishing mode; and then sequentially carrying out acid washing and water washing on the cleaned surface to remove an oxidation film and oil stains.

Preparation of repair powder: selecting raw material powder, and uniformly mixing the raw material powder according to a certain proportion to prepare repair powder; wherein the content of the first and second substances,

the raw material powder comprises titanium and/or titanium alloy powder and a sintering aid; the sintering aid can be at least one of copper powder and tin powder, and is selected according to the repair requirement.

In an embodiment of the present invention, the mass percentage of the titanium or titanium alloy powder is 75 to 90 wt.%.

In the embodiment of the invention, the mass percent of the copper powder is 0-5 wt.%.

In the embodiment of the invention, the mass percent of the tin powder is 0-15 wt.%.

In another embodiment of the present invention, the raw material powder further includes at least one of nickel powder and zirconium powder, which is selected according to the repair requirement.

In a specific embodiment, the nickel powder is 0-5 wt.%.

The mass percent of the zirconium powder is 0-5 wt.%.

In the embodiment of the invention, the particle sizes of all the component powders in the raw material powder are 5-50 μm, that is, the particle sizes of the titanium and/or titanium alloy powder, the copper powder, the tin powder, the nickel powder and the zirconium powder are all within the range of 5-50 μm.

Powder filling and compacting: coating the repair powder to fill the defects, then firmly wrapping the repaired part and the workpiece by using wrapping pieces such as plastic cloth and the like, and then compacting the repair powder by using a cold isostatic pressing process to obtain the filled workpiece.

In the step, the pressing pressure of the cold isostatic pressing process is 100-250 MPa, and the pressure maintaining time is 10-30 s.

And (3) sintering: and (4) carrying out vacuum sintering on the filled workpiece to obtain the repaired workpiece.

The vacuum sintering adopts a segmented sintering process, which specifically comprises the following steps:

the first stage of sintering, heating to 250-350 ℃, heating up at a rate of 2-4 ℃/min, and keeping the temperature for 0.5-1 h;

the second stage of sintering, heating to 600-750 ℃, heating up at a rate of 2-4 ℃/min, and keeping the temperature for 0.5-1 h;

and (3) third-stage sintering, heating to 1150-1300 ℃, wherein the heating rate is 5 ℃/min, and the sintering time is 2-4 h.

And (3) post-treatment: and polishing the repaired part of the repaired workpiece until the size of the repaired part is consistent with that of the original product.

The post-treatment step further includes performing nondestructive testing on the repaired part, and after the repaired part is completely repaired, polishing and surface cleaning are performed on the repaired part of the repaired workpiece.

The powder filling sintering repair method of the present invention will be described in detail below by way of specific examples.

Example 1:

the method shown in figure 1 is adopted to repair the surface defects of the pure titanium casting

S1: cleaning the surface before repairing, and removing impurities, oil stains and oxidation films from the defects of shrinkage cavities, air holes and the like on the surface of the casting by adopting polishing, pickling and washing modes.

S2: preparing filling raw materials, weighing 90 wt.% of titanium powder, 5 wt.% of copper powder and 5 wt.% of tin powder according to the alloy component ratio, and mechanically stirring and uniformly mixing.

S3: and (5) filling and compacting, namely coating and filling the powder prepared in the step S2 to the defect position, firmly wrapping the filled part and the workpiece by using a preservative film, compacting the powder by cold isostatic pressing, wherein the pressing pressure is 180MPa, and the pressure maintaining time is 30S.

S4: and (4) sintering and repairing, namely performing vacuum sintering on the workpiece with the filled defects obtained in the step S3, and performing vacuum sintering densification on the workpiece with the filled defects by adopting a segmented sintering process, wherein the segmented sintering process specifically comprises the following steps:

the first stage is heated to 300 ℃, the heating rate is 4 ℃/min, and the temperature is kept for 1 h;

heating to 1100 deg.C in the second stage at a heating rate of 5 deg.C/min, and maintaining for 1 h;

the third section is heated to 1200 ℃, the heating rate is 5 ℃/min, and the temperature is kept for 1 h.

S5: and (4) post-treatment, namely polishing the repaired part of the titanium alloy workpiece to the product size.

Example 2:

repairing surface defects of Ti-6.5Al-1Mo-1V-1.5Zr (TA15) stent by using method shown in figure 1

S1: and (3) cleaning the surface before repairing, completely removing the defects by adopting a mechanical or manual polishing mode, and cleaning the surfaces of the defects and nearby areas to completely remove oil stains and oxidation films.

S2: preparing filling raw materials, weighing 80 wt.% of TA15 powder, 2 wt.% of copper, 12 wt.% of tin, 3 wt.% of zirconium and 3 wt.% of nickel powder according to the alloy component ratio, and mechanically stirring and uniformly mixing.

S3: and (5) filling and compacting, namely coating and filling the powder prepared in the step S2 to the defect position, firmly wrapping the filled part and the workpiece by using a preservative film, compacting the powder by cold isostatic pressing, wherein the pressing pressure is 200MPa, and the pressure maintaining time is 30S.

the third section is heated to 1300 ℃, the heating rate is 5 ℃/min, and the sintering time is 2 h.

Example 3:

the method shown in figure 1 is adopted to repair the surface defects of the Ti-6Al-4V (TC4) blade

S2: preparing filling raw materials, weighing 87 wt.% of Ti-6Al-4V powder, 3 wt.% of copper powder and 10 wt.% of tin powder according to the alloy component ratio, and mechanically stirring and uniformly mixing.

the third section is heated to 1250 ℃, the heating rate is 5 ℃/min, and the sintering time is 2 h.

In the invention, the performance of the titanium alloy part repaired by the repairing method in the embodiments 1 to 3 is tested by adopting a conventional testing method in the prior art, and the test results are summarized as shown in table 1.

TABLE 1 Properties of parts obtained after repair in examples 1 to 3

As can be seen from Table 1, the strength of the pure titanium matrix obtained by repairing in example 1 is within the range of 400-500 MPa, and basically reaches or even exceeds the strength of the pure titanium matrix; the strength of the TA15 titanium alloy obtained by repairing in the embodiment 2 is in a range of 721-812 MPa, and reaches about 70-80% of the strength of a matrix; the strength of the TC4 titanium alloy obtained by repairing in the embodiment 3 is within 650-740 MPa, and reaches about 72-82% of the strength of the matrix.

Therefore, the repair method disclosed by the invention adopts simpler element powder, realizes the repair of the specific titanium alloy defects through powder pressing and sintering, and the repair mechanical property meets the use requirement. Meanwhile, the repair area keeps the alloy composition with titanium as the main component (> 80%), and the corrosion resistance of the repair area cannot be seriously deteriorated.

The mechanical properties of the repaired part obtained by the repairing method in the embodiment of the invention will be described in detail through comparative tests.

Comparative example 1:

and (3) performing argon arc welding repair on the surface of the TC4 blade, wherein the repair material is a TC wire. And carrying out annealing treatment after repairing.

Comparative example 2:

the TC4 blade was braze repaired with a braze of Ti-Zr-Cu-Ni, where Zr was 13 wt.%, Cu was 10 wt.%, and Ni was 15 wt.%. The brazing temperature is 950 ℃, and the temperature is kept for 30 min.

TABLE 2 comparison of the properties of the parts obtained in example 3 after repair with those of comparative examples 1-2

As can be seen from Table 2, the tensile strength of the product after argon arc welding repair is high, but the deformation of the thin-wall product is caused by local excessive thermal stress, which seriously affects the use of the product; and the local strength after brazing repair is too low, and the difference between the alloy composition in the repair area and the matrix is too large. Compared with common high-energy beam fusion welding repair and brazing repair, the powder coating sintering repair technology has moderate strength after repair, can meet the use requirement, has the advantages of low stress and small deformation in brazing repair, keeps the titanium element as the main component in the repair area, and ensures the performances of corrosion resistance and the like of the repair area.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A powder filling sintering repair method for surface defects of titanium or titanium alloy workpieces is characterized by comprising the following steps:

2. The powder filling sintering repair method according to claim 1, wherein the sintering aid is at least one of copper powder and tin powder.

3. The powder fill sintering repair method of claim 2, wherein the titanium or titanium alloy powder is 75-90 wt.%; the mass percent of the copper powder is preferably 0-5 wt.%, and the mass percent of the tin powder is preferably 0-15 wt.%.

4. The powder fill sintering repair method of claim 1, wherein the raw material powder further comprises at least one of nickel powder and zirconium powder; the mass percent of the nickel powder and the mass percent of the zirconium powder are both preferably 0-5 wt.%.

5. The powder filling sintering repair method according to claim 1 or 4, wherein the particle sizes of all component powders in the raw material powder are 5 to 50 μm.

6. The powder filling sintering repair method according to claim 1, wherein the repair powder is compacted using a cold isostatic pressing process; the pressing pressure of the cold isostatic pressing process is preferably 100-250 MPa, and the pressure maintaining time is preferably 10-30 s.

7. The powder filling sintering repair method according to claim 1, wherein the vacuum sintering employs a staged sintering process, specifically:

8. The powder filling sintering repair method according to claim 7, wherein the temperature rise rate of the first stage sintering and the second stage sintering are both 2-4 ℃/min, and the temperature rise rate of the third stage sintering is 5 ℃/min.

9. The powder filling sintering repair method according to claim 1, characterized in that the surface of the workpiece and the area near the surface defect are cleaned by mechanical or manual grinding; and then sequentially carrying out acid washing and water washing on the cleaned surface.

10. The powder filled sintered repair method of claim 1, further comprising post-processing the repaired part: and polishing the repaired part of the repaired workpiece.