Strengthening-coating integrated surface life prolonging method for Ti2AlNb alloy

Abstract

The invention belongs to the technical field of metal surface modification, and particularly relates to a strengthening-coating integrated surface life prolonging method for Ti2AlNb alloy. The method comprises the following steps: firstly, carrying out impact treatment on a Ti2AlNb alloy matrix by adopting pulse laser, inducing the surface of the matrix to generate phase change from an alpha2 phase to a B2 phase and an O phase, and meanwhile, generating pressure stress on the surface of the matrix; then pressure stress machining is adopted, the surface of the base body subjected to impact treatment is subjected to certain machining, the roughness meets the coating manufacturing requirement, and meanwhile a pressure stress layer generated by impact cannot be damaged; and finally, coating on the surface in a pressure stress state to manufacture the wear-resistant coating by utilizing metallurgical bonding between a phase generated by phase change and a coating. Large residual compressive stress is generated on the surface of the Ti2AlNb alloy through laser shock, the surface hardness and fatigue performance of the pipe bending die steel are improved, meanwhile, the bonding strength of a base body and a coating is improved by means of dislocation, twin crystals and other substructures formed by surface laser shock of the pipe bending die steel and phase change caused by dislocation, twin crystals and other substructures, and the service life of the pipe bending die steel is prolonged. And therefore, the service life of the Ti2AlNb alloy is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface modification, and specifically relates to a Ti2AlNb alloy strengthening-coating integrated surface life extension method, that is, a Ti2AlNb alloy strengthening-coating integrated manufacturing surface life extension method. Background Art

[0002] Ti-Al alloys have the advantages of high specific strength, good oxidation resistance, high temperature creep resistance, etc. and are widely used in the aerospace field. After adding a certain amount of Nb element, the α2-Ti3Al phase gradually transforms into an ordered orthorhombic structure Ti2AlNb, which has better plasticity, ductility, fracture toughness and other characteristics. However, it is still prone to component segregation, microstructure inhomogeneity, and poor wear resistance during the smelting process. Therefore, it is necessary to adopt certain surface modification methods to improve this problem.

[0003] Although hard wear-resistant coatings can improve the wear resistance of the substrate to a certain extent, the coating often causes poor bonding between the coating and the substrate and stress concentration during the coating process. In order to reduce this phenomenon, the substrate can be pre-treated before the coating is deposited. Common pre-treatment processes include sandblasting and shot peening. Although these pre-treatment processes can introduce residual compressive stress on the substrate surface, enhance the bonding between the coating and the substrate to a certain extent and reduce stress concentration, they may also cause surface defects such as particle embedding and dents.

[0004] Therefore, how to provide a surface life extension method for Ti2AlNb alloy strengthening-coating integrated manufacturing with a simple method, easy operation and good stability is a technical problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0005] In view of this, the present invention discloses a Ti2AlNb alloy strengthening-coating integrated surface life extension method.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A surface life extension method for Ti2AlNb alloy strengthening-coating integrated manufacturing, comprising the following steps:

[0008] Step 1: Clean the surface of the Ti2AlNb alloy component to ensure that there is no dirt on the surface;

[0009] Step 2: Using pulsed laser to impact the substrate, inducing phase change on the substrate surface and generating compressive stress;

[0010] Step 3: After laser shock treatment, the substrate surface is subjected to compressive stress machining, while ensuring that the surface roughness of the component substrate meets the requirements;

[0011] Step 4: After the roughness meets the requirements, the wear-resistant coating is manufactured in situ on the substrate surface by utilizing the metallurgical bonding between the physical phase produced by the surface compressive stress and phase change and the coating.

[0012] It should be noted that laser shock is a non-contact surface modification method that induces plastic deformation of materials through high-power density, short-pulse lasers, resulting in residual compressive stress fields and gradient structures on the surface of materials. It has good reliability and can improve the surface hardness, wear resistance and fatigue performance of the substrate. At the same time, laser shock can produce substructures such as dislocations and twins, and can significantly reduce the grain size of Ti2AlNb alloy near the surface, causing phase transformation from α2 to B2 and O phases, and improving the bonding strength between the substrate and the coating. Compressive stress machining methods such as roller polishing can reduce the surface roughness of the substrate while ensuring the presence of residual compressive stress on the substrate surface, thereby greatly improving the wear resistance of the substrate surface.

[0013] Furthermore, the surface cleaning process described in step 1 includes surface grinding, polishing and ultrasonic cleaning, and the surface roughness of the component after surface pretreatment should be less than 0.8 μm.

[0014] Furthermore, in the laser shock process described in step 2, a 1 mm thick deionized water layer is used as a constraining layer, a 100 μm thick aluminum foil is pasted on the surface of the Ti2AlNb alloy substrate as an absorption layer, the laser energy is 6-10 J, the number of shocks is 1-3 times, and the overlap rate is 50%.

[0015] It should be noted that the laser shock described in step 2 can induce plastic deformation on the substrate surface, thereby causing microstructural changes, thereby inducing a phase transition from α2 phase to B2 phase and O phase, and can significantly reduce the grain size near the surface of the Ti2AlNb alloy. The physical phase produced by this phase transition can be metallurgically bonded with the coating, which is beneficial to improve the bonding strength between the substrate and the specific coating.

[0016] Moreover, the residual compressive stress introduced on the substrate surface by the laser shock in step 2 has the same stress state as that of the coating, which is beneficial to reducing the stress concentration phenomenon at the interface and improving the crack resistance of the coating under vertical load.

[0017] Furthermore, the compressive stress machining described in step 3 includes roller polishing, ultrafine grinding, grinding and other processing methods, which reduce the roughness while ensuring that the residual compressive stress on the substrate surface still exists. The surface roughness after machining should reach 0.8-1.6μm.

[0018] It should be noted that compressive stress machining requires ensuring that the surface roughness meets the requirements (0.8-1.6 μm) while not destroying the gradient residual compressive stress field after laser shock.

[0019] Furthermore, the coating process described in step 4 should be performed in-situ on the substrate surface after the machining process is completed.

[0020] Furthermore, the coating technology described in step 4 may be multi-arc ion plating, plasma spraying and the like.

[0021] Furthermore, the wear-resistant coating described in step 4 includes a Ni-based alloy coating, a Ti-based alloy coating, and the like.

[0022] It should be noted that coating improves the wear resistance of parts, and laser impact and compressive stress machining are both for enhancing the bonding strength between coating and substrate and reducing stress concentration.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing proposed in the present invention has the characteristics of simple method, easy operation and good stability.

[0025] (2) The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing proposed in the present invention can not only improve the surface hardness, wear resistance and fatigue performance of the components, but also enhance the bonding strength between the substrate and the wear-resistant coating, thereby solving the problem of insufficient life of Ti2AlNb alloy due to poor wear resistance and poor coating bonding. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 This is the microstructure diagram of the Ti2AlNb alloy component obtained in Example 1 of the present invention before surface treatment.

[0028] Figure 2 This is a microstructure diagram of the Ti2AlNb alloy component obtained in Example 1 of the present invention after laser impact and compressive stress machining.

[0029] Figure 3The microhardness data of the Ti2AlNb alloy parts obtained in Examples 1 and 2 of the present invention and the comparative example before and after the surface treatment by the strengthening-coating integrated manufacturing.

[0030] Figure 4 The residual stress data of the Ti2AlNb alloy parts obtained in Examples 1 and 2 of the present invention and the comparative example before and after the surface treatment by the strengthening-coating integrated manufacturing. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0033] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0034] The present invention should not be construed as being limited to the fact that any device or component must have a specific orientation, be constructed and operate in a specific orientation.

[0035] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0036] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present application.

[0037] The invention discloses a Ti2AlNb alloy strengthening-coating integrated surface life extension method.

[0038] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0039] Embodiment 1:

[0040] This embodiment uses the strengthening-coating integrated manufacturing method provided by the present invention to perform surface life extension treatment on Ti2AlNb alloy, and the specific operations are as follows:

[0041] Step 1: Clean the surface of the Ti2AlNb alloy component to ensure that there is no dirt on the surface;

[0042] Step 2: using a pulsed laser to impact treat the Ti2AlNb alloy substrate cleaned in step 1, so as to induce a phase change on the substrate surface and generate residual compressive stress;

[0043] Step 3: After the laser shock treatment in step 2, the surface of the substrate is subjected to compressive stress machining, while ensuring that the surface roughness of the component substrate meets the requirements;

[0044] Step 4: After the roughness meets the requirements, the wear-resistant coating is manufactured in situ on the substrate surface by utilizing the metallurgical bonding between the physical phase produced by the surface compressive stress and phase change and the coating.

[0045] Specifically, the surface cleaning treatment includes ultrasonic cleaning, grinding and polishing processes to make the surface roughness of the substrate reach 0.2μm. During the laser impact process, a deionized water layer with a thickness of 1mm is used as a constraint layer, a 100μm thick aluminum foil is used as an absorption layer, the laser energy is 8J, the number of impacts is 3 times, and the overlap rate is 50%; the mechanical processing method after laser impact is roller polishing to make the surface roughness of the substrate reach 0.8μm; in the process of coating to manufacture wear-resistant coatings, the selected coating method is plasma spraying, and the wear-resistant coating is a Ti-based alloy coating.

[0046] Figure 1 , 2 The microstructures of Ti2AlNb alloy parts before surface treatment and after laser shock and compressive stress machining are shown in the figure. From the figure, we can observe the three-phase structure of α2 phase of equiaxed HCP crystal type, B2 phase of matrix BCC crystal type and O phase of lath-shaped orthorhombic crystal type. It can be clearly found that after laser shock and compressive stress machining, the grains are significantly refined, the diameter of α2 phase grains is reduced, and the transformation from α2 phase to B2 phase and O phase occurs. The phase produced by this phase change can be metallurgically bonded with the coating, which is beneficial to improve the bonding strength between the substrate and the specific coating.

[0047] The Vickers hardness tester was used to test the surface hardness of Ti2AlNb alloy before and after the surface treatment of the strengthening-coating integrated manufacturing. The surface hardness of the components after the surface treatment increased from 355.4HV to 470.9HV, an increase of 32.5% (such as Figure 3 ); The residual stress on the surface of Ti2AlNb alloy parts was tested by X-ray residual stress tester. After surface treatment, the maximum residual compressive stress of the parts increased from -13.4MPa to -504.3MPa (such as Figure 4 ).

[0048] Embodiment 2:

[0049] This embodiment uses the strengthening-coating integrated manufacturing method provided by the present invention to perform surface life extension treatment on Ti2AlNb alloy, and the specific operations are as follows:

[0050] Step 1: Clean the surface of the Ti2AlNb alloy component to ensure that there is no dirt on the surface;

[0051] Step 2: using a pulsed laser to impact treat the Ti2AlNb alloy substrate cleaned in step 1, so as to induce a phase change on the substrate surface and generate residual compressive stress;

[0052] Step 3: After the laser shock treatment in step 2, the surface of the substrate is subjected to compressive stress machining, while ensuring that the surface roughness of the component substrate meets the requirements;

[0053] Step 4: After the roughness meets the requirements, the wear-resistant coating is manufactured in situ on the substrate surface by utilizing the metallurgical bonding between the physical phase produced by the surface compressive stress and phase change and the coating.

[0054] Specifically, the surface cleaning treatment includes ultrasonic cleaning, grinding and polishing processes to make the surface roughness of the substrate reach 0.2μm. During the laser impact process, a deionized water layer with a thickness of 1mm is used as a constraint layer, and a 100μm thick aluminum foil is used as an absorption layer. The laser energy is 6J, the number of impacts is 2 times, and the overlap rate is 50%; the mechanical processing method after laser impact is roller polishing to make the surface roughness of the substrate reach 0.8μm; in the process of coating to manufacture wear-resistant coatings, the selected coating method is plasma spraying, and the wear-resistant coating is a Ni-based alloy coating.

[0055] The Vickers hardness tester was used to test the surface hardness of Ti2AlNb alloy before and after the surface treatment of strengthening-coating integrated manufacturing. The surface hardness of the surface treated parts increased from 350.3HV to 395.6HV, an increase of 12.9% (such as Figure 3); The residual stress on the surface of Ti2AlNb alloy parts was tested by X-ray residual stress tester. After surface treatment, the maximum residual compressive stress of the parts increased from -12.6MPa to -379.6MPa (such as Figure 4 ).

[0056] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are used to further illustrate the technical features disclosed in the present invention, but they should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above invention content without inventive work are also considered to fall within the scope of protection of the present invention.

[0057] Comparative Example 1

[0058] The comparative example eliminates step 2 and step 3, and the remaining specific operation steps are the same as those in Example 1.

[0059] Step 1: Clean the surface of the Ti2AlNb alloy component to ensure that there is no dirt on the surface;

[0060] Step 2: After the roughness meets the requirements, the wear-resistant coating is manufactured in situ on the substrate surface by utilizing the metallurgical bonding between the physical phase produced by the surface compressive stress and phase change and the coating.

[0061] Specifically, the surface cleaning treatment includes ultrasonic cleaning, grinding and polishing processes to make the surface roughness of the substrate reach 0.2μm. In the process of coating to manufacture the wear-resistant coating, the selected coating method is plasma spraying, and the wear-resistant coating is a Ti-based alloy coating.

[0062] Vickers hardness tester was used to test the surface hardness of Ti2AlNb alloy after coating. The surface hardness of the component after coating reached 443.1MPa (such as Figure 3 ); The residual stress on the surface of Ti2AlNb alloy parts was tested by X-ray residual stress tester. The average residual compressive stress on the surface of the parts after coating was -104.2MPa (such as Figure 4 ). This comparative example omits the laser shock treatment and surface compressive stress machining steps before coating. Although the hardness is improved to a certain extent compared with the components before treatment, the introduction of residual compressive stress is significantly different from the strengthening-coating integrated surface life extension method provided by the present invention.

[0063] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A surface life extension method for Ti2AlNb alloy strengthening-coating integrated manufacturing, characterized in that: The following steps are involved: Step 1: Clean the surface of the Ti2AlNb alloy component to ensure that there is no dirt on the surface; Step 2: using a pulsed laser to impact treat the Ti2AlNb alloy substrate cleaned in step 1, so as to induce a phase change on the substrate surface and generate residual compressive stress; Step 3: After the laser shock treatment in step 2, the surface of the substrate is subjected to compressive stress machining, while ensuring that the surface roughness of the component substrate meets the requirements; Step 4: After the roughness meets the requirements, the wear-resistant coating is manufactured in situ on the substrate surface by utilizing the metallurgical bonding between the physical phase produced by the surface compressive stress and phase change and the coating.

2. The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing according to claim 1 is characterized in that: The surface cleaning process described in step 1 includes surface grinding, polishing and ultrasonic cleaning, and the surface roughness of the component after surface pretreatment should be less than 0.8 μm.

3. The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing according to claim 1 is characterized in that: In the laser shock process described in step 2, a 1 mm thick deionized water layer is used as a constraining layer, a 100 μm thick aluminum foil is pasted on the surface of the Ti2AlNb alloy substrate as an absorption layer, the laser energy is 6-10 J, the number of shocks is 1-3 times, and the overlap rate is 50%.

4. The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing according to claim 1 is characterized in that: The compressive stress machining described in step 3 includes roller polishing, superfine grinding and grinding, which reduces the roughness while ensuring that the residual compressive stress on the substrate surface still exists. The surface roughness after machining should reach 0.8-1.6μm.

5. The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing according to claim 1 is characterized in that: The coating process described in step 4 should be performed in situ on the substrate surface at the end of the machining process.

6. The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing according to claim 5 is characterized in that: The coating technology described in step 4 includes multi-arc ion plating and plasma spraying.

7. The surface life extension method of Ti2AlNb alloy strengthening-coating integrated manufacturing according to claim 1 is characterized in that: The wear-resistant coating includes a Ni-based alloy coating and a Ti-based alloy coating.

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