A thermal spraying pretreatment method for synergistically improving fatigue performance and bonding strength of titanium alloy deposit

Abstract

The application discloses a kind of hot spraying pretreatment methods for synergistically improving the fatigue performance and bonding strength of titanium alloy deposit, and belongs to the field of material surface modification and coating technology.The technical scheme used includes the following steps:1) shot blasting treatment is carried out on the to-be-sprayed area of the substrate;2) one-time sand blasting is performed to maintain the substrate roughness at Ra4-8 μm, and micron-level primary roughness is prepared;3) secondary sand blasting is performed to increase the surface undulation of Ra0.6-1.6 μm on the substrate after one-time sand blasting, and sub-micron-level secondary roughness is prepared;4) residual sand particles on the substrate are removed by cleaning to obtain titanium alloy deposit with improved fatigue performance and bonding strength of the deposit.The application can effectively improve the bonding strength and fatigue performance of the coating, thereby solving the technical problem that the current technology cannot simultaneously consider the fatigue performance of the substrate and the bonding strength of the coating.

Description

Technical Field

[0001] This invention belongs to the field of material surface modification and coating preparation technology, specifically relating to a thermal spraying pretreatment method that synergistically improves the fatigue performance and bonding strength of titanium alloy deposits. Background Technology

[0002] Thermal spraying is a process in which coating materials such as powder or filaments are fed into a heated and accelerated source (plasma arc, combustion flame, high-speed gas) and accelerated to a certain degree, then sprayed onto the substrate surface to form a coating. Surface pretreatment for thermal spraying aims to remove contaminants such as oxide films and oil stains from the substrate surface, and increases the surface undulations to enhance the mechanical bonding points between the sprayed particles and the substrate, thereby improving the adhesion strength of the coating. This is a necessary step before most thermal spraying processes.

[0003] Titanium alloys are commonly used materials in the aerospace field. During sandblasting, polygonal abrasive particles can create sharp notches on the substrate surface. Under the influence of stress concentration and surface hardening, these notches become crack initiation points for fatigue failure, significantly reducing the fatigue strength of the substrate. Some studies have proposed using shot peening instead of sandblasting for pretreatment. Larger particles can create deeper compressive stress zones, while spherical shot peening particles can avoid creating sharp notches on the substrate, thus further improving the fatigue resistance of the substrate. However, shot peening results in a smaller and more uniform surface undulation of the substrate, leading to weaker bonding strength between the coating and the substrate. Consequently, the fatigue performance of the substrate and the bonding strength of the coating cannot be simultaneously improved. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a thermal spraying pretreatment method that synergistically improves the fatigue performance and bonding strength of titanium alloy deposits, so as to solve the technical problem that existing substrate pretreatment methods cannot take into account both the fatigue performance of deposits and the bonding strength of coatings.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a thermal spraying pretreatment method for synergistically improving the fatigue performance and bonding strength of titanium alloy deposits, comprising the following steps:

[0007] 1) Perform shot blasting on the area of ​​the substrate to be coated, with a shot blasting intensity of 0.10-0.2 mmA and a coverage of 100%;

[0008] 2) The substrate treated in step 1) is sandblasted once to maintain the substrate roughness between Ra 4 and 8 μm, thus preparing micron-level main roughness;

[0009] 3) The substrate treated in step 2) is subjected to secondary sandblasting to increase the surface undulation of Ra0.6~1.6μm on the substrate after the first sandblasting, thus preparing submicron level secondary roughness;

[0010] 4) Clean and remove residual sand particles from the matrix to obtain a titanium alloy deposit with improved fatigue performance and bonding strength.

[0011] Preferably, in step 1), the shot peening particles are glass shot or ceramic shot, the shot particle size is 0.2 to 0.7 mm, and the shot peening pressure is 0.3 to 0.6 MPa.

[0012] Preferably, in step 2), a single sandblasting operation is performed using 16-36 mesh alumina sand, with a sand consumption of 0.2-1.0 kg / cm² per unit area. 2 .

[0013] More preferably, the sandblasting angle of a single sandblasting operation is maintained at 75° or higher.

[0014] Preferably, in step 3), 220-320 mesh SiC sand is used for secondary sandblasting, and the sand consumption per unit area is 0.03-0.15 kg / cm². 2 .

[0015] More preferably, the blasting angle of the secondary sandblasting is maintained at 80-90°.

[0016] More preferably, when the sandblasting angle does not meet 80-90°, two mutually perpendicular paths are selected, and the sandblasting angle is maintained at 45-65° for reciprocating sandblasting.

[0017] Preferably, in step 3), a polished test plate is used as a reference test plate, and the reference test plate and the substrate treated in step 2) are subjected to secondary sandblasting together, and the roughness of the reference test plate is used as a reference value for the submicron level roughness of the substrate.

[0018] Preferably, when spraying the pretreated substrate, the product of the cube of the relative humidity and the dwell time in minutes should be less than 15, depending on the relative humidity at the time of construction; otherwise, the substrate should be dried to above 80°C.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention discloses a thermal spraying pretreatment method for synergistically improving the fatigue performance and bonding strength of titanium alloy deposits. On one hand, shot peening is performed before sandblasting to pre-introduce a greater depth of residual compressive stress on the substrate. Using larger-diameter shot increases the depth and magnitude of the residual compressive stress, allowing beneficial residual compressive stress to be better retained in subsequent processing, thereby improving the fatigue resistance of the substrate. Simultaneously, limiting the shot peening pressure prevents over-peening that could cause the substrate's fatigue performance to deviate from its optimal state. Furthermore, the work hardening generated by shot peening prevents the formation of sharp notches and stress concentration caused by sand particles impacting the substrate during subsequent sandblasting. On the other hand, sandblasting is performed in two stages. The first sandblasting aims to increase the surface roughness of the substrate, thereby promoting the bonding between the coating and the substrate. The second sandblasting ensures a more uniform stress distribution at the layer-substrate interface during service, further improving the bonding strength of the coating.

[0021] Furthermore, the use of larger-diameter alumina particles and higher blasting pressure in a single shot blasting process effectively increases the surface roughness of the substrate, thereby promoting the bonding between the coating and the substrate. The impact of the large particles disperses the tensile stress concentration generated during shot blasting, and by limiting the blasting angle of a single shot blasting to greater than 75°, excessive surface deformation of the substrate during shot blasting is avoided, preventing the formation of large-scale tensile stress zones and further optimizing the fatigue performance of the substrate.

[0022] Furthermore, the use of small SiC particles in the secondary sandblasting can generate a more regular submicron-level secondary roughness during the undulations of the primary sandblasting, further increasing the bonding surface area between the coating and the substrate. By controlling the angle of the secondary sandblasting between 80° and 90°, or between 45° and 65° on mutually perpendicular reciprocating paths, the secondary roughness is evenly distributed on both sides of the primary roughness, and the stress distribution at the layer-substrate interface of the deposit is more uniform during service, thereby further improving the bonding strength of the coating. Attached Figure Description

[0023] Figure 1 A schematic diagram illustrating the implementation process and effects of a thermal spraying pretreatment method for synergistically improving the fatigue performance and bonding strength of titanium alloy deposits, provided by this invention.

[0024] Figure 2 A schematic diagram illustrating the effect of conventional sandblasting and thermal spraying pretreatment methods;

[0025] Figure 3 The diagram shows the distribution of combined strength and fatigue limit for each embodiment. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings:

[0029] See Figure 1 To provide a pretreatment method for thermal spraying that synergistically enhances the fatigue performance and bonding strength of titanium alloy deposits according to the present invention, the area to be sprayed is first shot-peened. During this process, the shot peening intensity is selected as 0.10–0.2 mmA, the coverage is 100%, the shot particles are glass or ceramic, the particle size is 0.2–0.7 μm, and the shot peening pressure is 0.3–0.6 MPa. This treatment creates a relatively deep residual compressive stress on the substrate. Subsequently, a secondary sandblasting is performed using 220–320 mesh alumina sand, with a sand consumption of 0.2–1 kg / cm² per unit area. 2 The blasting angle is maintained above 75°. This treatment creates a micron-level roughness of Ra 4–8 μm on the substrate and reduces the tensile stress concentration caused by shot peening. Furthermore, the treated substrate and reference sample are subjected to secondary blasting using 220–320 mesh abrasive, with SiC abrasive used. The abrasive consumption per unit area is 0.03–0.15 kg / cm². 2By maintaining the sandblasting angle between 55° and 65°, the above treatment can create surface undulations of Ra 0.6–1.6 μm on the substrate, further homogenizing the pre-existing stress and subsequent service stress. The two sandblasting processes create a rich variety of surface morphologies and homogenize the stress. Combined with the deep compressive stress pre-set by shot peening, this can synergistically improve the fatigue performance and bonding strength of the titanium alloy deposit.

[0030] See Figure 2 As a conventional sandblasting and thermal spraying pretreatment method, it can be seen that during sandblasting, polygonal sand particles will form sharp notches on the substrate surface. Under the influence of factors such as stress concentration and surface hardening, these notches become crack sources for fatigue failure.

[0031] Example 1

[0032] In this embodiment, the above-described method is used for pre-treatment of TC4 titanium alloy by shot peening. First, 0.7 μm diameter ceramic shot is used for shot peening at a pressure of 0.3 MPa, with a shot peening intensity of 0.1 mmA. Then, 16-mesh corundum abrasive is used for sandblasting at a 90° blasting angle, with a sand consumption of 1.0 kg / cm² per unit area. 2 The surface roughness of the substrate after treatment was Ra 4μm. Subsequently, it was sandblasted using 220-mesh SiC sand at a blasting angle of 60°, with a sand consumption of 0.05 kg / cm² per unit area. 2 The secondary sandblasting was terminated when the roughness of the reference smooth TC4 sample reached Ra 1 μm. A WC coating was prepared on the TC4 substrate using supersonic flame spraying technology. The results showed that the coating adhesion strength was 62 MPa. (1×10⁻⁶ sample) 6 The median fatigue limit for the second cycle is 566 MPa.

[0033] Example 2

[0034] In this embodiment, the above-described method is used for pre-treatment of TC4 titanium alloy by shot peening. First, 0.4 μm diameter ceramic shot is used for shot peening at a pressure of 0.5 MPa, with a shot peening intensity of 0.15 mmA. Then, 24-mesh corundum abrasive is used for sandblasting at a 90° blasting angle, with a sand consumption of 1.5 kg / cm² per unit area. 2 The surface roughness of the substrate after treatment was Ra 6μm. Subsequently, it was sandblasted using 320-mesh SiC sand at a blasting angle of 60°, with a sand consumption of 0.10 kg / cm² per unit area. 2 The secondary sandblasting was terminated when the roughness of the reference smooth TC4 sample reached Ra 0.6 μm. A WC coating was prepared on the TC4 substrate using supersonic flame spraying technology. The results showed that the coating adhesion strength was 65 MPa. (1×10⁻⁶ sample)6 The median fatigue limit for the second cycle is 538 MPa.

[0035] Example 3

[0036] In this embodiment, the above-described method is used for pre-treatment of TC4 titanium alloy by shot peening. First, 0.6 μm diameter ceramic shot is used for shot peening at a pressure of 3 bar, with a shot peening intensity of 0.15 mmA. Then, 36-mesh corundum abrasive is used for sandblasting at a 90° blasting angle, with a sand consumption of 1.5 kg / cm² per unit area. 2 The surface roughness of the substrate after treatment was Ra 4μm. Subsequently, sandblasting was performed using 220-mesh SiC sand at a blasting angle of 60°, with a sand consumption of 0.15 kg / cm² per unit area. 2 The secondary sandblasting was terminated when the roughness of the reference smooth TC4 sample reached Ra 1.2 μm. A WC coating was prepared on the TC4 substrate using supersonic flame spraying technology. The results showed that the coating adhesion strength was 58 MPa. (1×10⁻⁶ sample) 6 The median fatigue limit for the second cycle is 554 MPa.

[0037] Example 4 (Control Example)

[0038] To compare with the three embodiments described above, this embodiment uses the above method to perform conventional spraying pretreatment on TC18 titanium alloy, directly using 24-mesh corundum abrasive at a 90° blasting angle, with a sand consumption of 2.5 kg / cm² per unit area. 2 The surface roughness of the treated substrate was Ra 6.2 μm. A WC coating was prepared on the TC18 substrate using supersonic flame spraying technology. The results showed that the coating adhesion strength was 46 MPa. The number of sprayed samples was 1 × 10⁻⁶. 6 The median fatigue limit for the second cycle is 312 MPa.

[0039] See Figure 3 The data on bonding strength and fatigue limit of the above embodiments and comparative examples show that the thermal spraying pretreatment method proposed in this invention, which synergistically improves the fatigue performance and bonding strength of titanium alloy deposits, can effectively improve the bonding strength and fatigue performance of the coating. Therefore, it can effectively solve the technical problem that current technologies cannot simultaneously address the fatigue performance of the substrate and the bonding strength of the coating.

[0040] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A thermal spraying pretreatment method for synergistically improving the fatigue performance and bonding strength of titanium alloy deposits, characterized in that, Includes the following steps: 1) Perform shot peening on the area of ​​the substrate to be coated. Select a shot peening intensity of 0.10-0.2 mmA and a coverage of 100%. The shot particle size is 0.2-0.7 mm and the shot peening pressure is 0.3-0.6 MPa. 2) The substrate treated in step 1) is subjected to a single sandblasting process to maintain the substrate roughness between Ra 4 and 8 μm, thus preparing a micron-level principal roughness; a single sandblasting is performed using 16-36 mesh alumina sand, with a sand consumption of 0.2-1.0 kg / cm² per unit area. 2 The sandblasting angle for each shot is maintained above 75°. 3) The substrate treated in step 2) is subjected to secondary sandblasting to increase surface undulations of Ra 0.6–1.6 μm on the substrate after the first sandblasting, thus preparing submicron-level secondary roughness; 220–320 mesh SiC sand is used for secondary sandblasting, and the sand consumption per unit area is 0.03–0.15 kg / cm². 2 The blasting angle for the second blasting is maintained at 55° to 65°. 4) Clean and remove residual sand particles from the matrix to obtain a titanium alloy deposit with improved fatigue performance and bonding strength.

2. The thermal spraying pretreatment method for synergistically improving the fatigue performance and bonding strength of titanium alloy deposits according to claim 1, characterized in that, In step 1), the shot peening particles are glass shot peening or ceramic shot peening.

3. The thermal spraying pretreatment method for synergistically improving the fatigue performance and bonding strength of titanium alloy deposits according to claim 1, characterized in that, In step 3), a polished test plate is used as a reference test plate. The reference test plate and the substrate treated in step 2) are subjected to secondary sandblasting together. The roughness of the reference test plate is used as a reference value for the submicron level roughness of the substrate.

4. The thermal spraying pretreatment method for synergistically improving the fatigue performance and bonding strength of titanium alloy deposits according to any one of claims 1 to 3, characterized in that, When spraying the pretreated substrate, spraying should be carried out when the product of the cube of the relative humidity and the dwell time in minutes is less than 15, depending on the relative humidity at the time of construction. Otherwise, the substrate should be dried to above 80°C.

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