Method for improving tissue structure and bonding strength of blue laser remelting plasma spraying coating

Abstract

The invention provides a blue laser remelting plasma spraying coating structure and bonding strength improving method which comprises the steps that S1, a base body with a spraying state coating is placed on the surface of a remelting table, and the focal point of a blue laser beam is adjusted to be located on the surface of the spraying state coating; and S2, carrying out blue laser remelting under the protection of local inert gas, and finally improving the organization structure and the bonding strength of the spraying state coating. According to the method, the tissue structure and the bonding strength of the plasma spraying coating are improved by adopting a blue laser remelting method, and the tissue structure and the bonding strength of the coating are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of composite protective coating, and particularly relates to a method for improving the microstructure and bonding strength of a blue laser remelted plasma sprayed coating. BACKGROUND

[0002] As the most commonly used thermal protection coating preparation technology, the technical principle of plasma spraying technology is to use a plasma torch as a heat source to heat and accelerate powder into a semi-molten state of high-speed flying particles, and then the particles impact the substrate to form a coating. The quality regulation of the coating interface and the interior has always been a key problem faced by plasma sprayed coatings.

[0003] On the one hand, due to the influence of particle flight speed, the coating / substrate interface often shows a poor mechanical bonding mode; on the other hand, due to the restriction of the melting degree of the powder, the internal structure of the plasma sprayed coating is often porous, especially for high-melting-point ablation protective coatings.

[0004] Under thermal shock environment, the mismatch of the thermal expansion coefficient between the coating and the substrate easily leads to premature failure of the coating interior and interface. The method of preparing a transition layer can alleviate the mismatch of the thermal expansion coefficient between the coating and the substrate to a certain extent, which is the most commonly used method.

[0005] Zhang et al. showed that the introduction of a SiC / HfC composite transition layer between the SiC substrate and the HfC coating not only reduced the defects within the HfC coating but also improved the coating bond strength from 6.5 N to 20 N <Lu W, Qiang-gang F, Feng-ling Z. A novel gradient SiC-ZrB2-MoSi2 coating for SiC coated C / C composites by supersonic plasma spraying. Surf Coatings Technol 2017;313:63-72.>. Wang et al. prepared a SiC-ZrB2-MoSi2 gradient coating on the surface of C / C, compared with the single MoSi2 coating, the gradient coating has lower internal stress and longer thermal shock life in thermal shock environment <Zhang J, Zhang Y, Fu Y, Li T, Meng J. Effect of HfC-SiC transition layer on the ablation resistance of SiC / HfC-SiC / HfC multi-layer coating for C / C composites. Vacuum 2019;169:108886>. In addition, there are also studies that improve the internal and interface state of plasma sprayed coating by laser remelting method.

[0006] However, the test results show that the laser remelting technology is more to melt the surface of the coating and then modify the densification, and the modification of the internal interface of the coating is not obvious. SUMMARY

[0007] The purpose of the present application is to solve the problem of high porosity and poor interface bonding of the commonly used metal material surface plasma sprayed coating, and to provide an improvement method for the microstructure and bonding strength of blue light laser remelted plasma sprayed coating.

[0008] The present application provides an improvement method for the microstructure and bonding strength of blue light laser remelted plasma sprayed coating, comprising: S1, placing the substrate with the sprayed coating on the surface of the remelting table, adjusting the focus of the blue light laser beam on the surface of the sprayed coating; S2, blue light laser remelting under the protection of local inert gas, finally improving the microstructure and bonding strength of the sprayed coating.

[0009] Optionally, the laser power of blue light laser remelting is 300-500 W, the remelting speed is 8-12 mm / s, and the lap rate is 40-60%.

[0010] Optionally, before S1, the method further comprises: S01, polishing the surface in a sprayed state using #400~#800 sandpaper, and then soaking the polished substrate with a sprayed coating in anhydrous ethanol for ultrasonic cleaning, to obtain a cleaned substrate with a sprayed coating.

[0011] Optionally, after S01, the method further comprises: S02, placing the cleaned substrate with a sprayed coating into a drying box for drying treatment at a temperature of 60-100℃, to obtain a substrate with a sprayed coating for blue laser remelting.

[0012] Optionally, the melting point of the substrate material is greatly different from that of the coating material.

[0013] Optionally, the coating is a ceramic thermal protection material.

[0014] Optionally, the ceramic thermal protection material is YSZ, ZrB2 or SiO2.

[0015] Optionally, the substrate material is iron-based alloy, nickel-based alloy, aluminum alloy or copper alloy.

[0016] The present application provides a method for improving the microstructure and bonding strength of plasma sprayed coating after blue laser remelting, which improves the microstructure and bonding strength of plasma sprayed coating and improves the microstructure and bonding strength of the coating. After blue laser remelting, the internal pores of the coating are repaired and the bonding state at the interface is changed to interlocking characteristics. The bonding strength of the plasma sprayed coating after blue laser remelting is tested by tensile test. The bonding strength of the coating after blue laser remelting is improved from 17.9MPa to 35.7MPa. The method in this study is simple, easy to implement and significantly improves the microstructure and bonding strength of the plasma sprayed coating. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0018] Figure 1 The original morphology of the plasma sprayed coating on the surface of 6061 aluminum alloy in Example 1 (a) and the coating morphology after blue laser remelting (b); Figure 2The results of the coating adhesion strength test of the plasma sprayed coating on the surface of the 6061 aluminum alloy in Example 1 and the coating after laser remelting by blue light; Figure 3 The coating morphology after the coating adhesion strength test of the plasma sprayed coating on the surface of the 6061 aluminum alloy in Example 1 and the coating after laser remelting by blue light.

[0019] Figure 4 The coating morphology of the plasma sprayed coating on the surface of the 6061 aluminum alloy in Example 2 after laser remelting by blue light.

[0020] Figure 5 The coating morphology of the plasma sprayed coating on the surface of the 6061 aluminum alloy in Example 3 after laser remelting by blue light. DETAILED DESCRIPTION

[0021] The method for improving the microstructure and adhesion strength of a plasma sprayed coating remelted by blue light laser will be described in further detail below with reference to the accompanying drawings.

[0022] The present application takes into account the characteristics of the red laser used for laser remelting, which has a low energy density and poor penetration. Blue light is a light source with a wavelength of 450 nm. In the field of material processing, compared with the most commonly used red light laser, it has a higher absorption rate and faster heating efficiency. By remelting the surface of the plasma sprayed coating with a blue light high-energy laser beam, it is expected to improve the microstructure and adhesion strength of the sprayed coating by virtue of its high laser absorption rate and heating rate.

[0023] As shown in Figures 1-5 , the present application provides a method for improving the microstructure and adhesion strength of a plasma sprayed coating remelted by blue light laser.

[0024] The method for improving the microstructure and adhesion strength of a plasma sprayed coating according to the present application is to improve the microstructure and adhesion strength of the plasma sprayed coating by blue light laser remelting. Under the irradiation of the blue light laser beam, the sprayed coating remains in its original state, while the substrate surface layer is melted. The loose and porous structure inside the sprayed coating provides diffusion channels for the melted substrate, which improves the microstructure inside the coating and at the interface under the guidance of capillary effect, and finally improves the adhesion strength of the coating.

[0025] In the present application, the sprayed coating that has not been remelted by blue light laser has a high porosity inside and a mechanical bonding state at the interface, which is improved during the blue light laser remelting process. The melted substrate fills and repairs under the guidance of capillary effect, and the interface changes from a mechanical bonding state to a more reliable interlocking structure.

[0026] The method for improving the microstructure and bonding strength of a plasma sprayed coating by blue laser remelting is implemented according to the following steps: I. The surface of the as-sprayed coating is polished using sandpaper with a grit size of #400 to #800, and then the polished substrate with the as-sprayed coating is immersed in anhydrous ethanol for ultrasonic cleaning, thereby obtaining a cleaned substrate with the as-sprayed coating; II. The cleaned substrate with the as-sprayed coating is placed in a drying box and dried at a temperature of 60-100 DEG C, thereby obtaining a substrate with the as-sprayed coating for blue laser remelting; III. The substrate with the as-sprayed coating is placed on the surface of a remelting platform, the focal point of a blue laser beam is adjusted to be located on the surface of the as-sprayed coating, the laser power is controlled to be 300-500 W, the remelting speed is controlled to be 8-12 mm / s, the overlap rate is controlled to be 40-60 %, and the blue laser remelting is performed under the protection of a local inert gas, thereby finally improving the microstructure and bonding strength of the as-sprayed coating; wherein the substrate material is a commonly used iron-based alloy (Q195, Q235, Q215, etc.), a nickel-based alloy (Inconel600, Inconel625, etc.), an aluminum alloy (5052, 6061, 7075, etc.), or a copper alloy (H90, H65, QAl5, etc.); and the coating is a commonly used ceramic thermal protection material such as YSZ, ZrB2, SiO2, etc.

[0027] The application provides a method for improving the microstructure and bonding strength of a plasma sprayed coating, which improves the internal microstructure and bonding strength of the plasma sprayed coating by a blue laser remelting technology.

[0028] Specific embodiment I: The method for improving the microstructure and bonding strength of a plasma sprayed coating by blue laser remelting is implemented according to the following steps: I. The surface of the as-sprayed coating is polished using sandpaper with a grit size of #400 to #800, and then the polished substrate with the as-sprayed coating is immersed in anhydrous ethanol for ultrasonic cleaning, thereby obtaining a cleaned substrate with the as-sprayed coating; II. The cleaned substrate with the as-sprayed coating is placed in a drying box and dried at a temperature of 60-100 DEG C, thereby obtaining a cleaned substrate with the as-sprayed coating for blue laser remelting; Three, the substrate with the as-sprayed coating is placed on the surface of the remelting table, the focal point of the blue laser beam is adjusted to be located on the surface of the as-sprayed coating, the laser power is controlled to be 300 W, the remelting speed is 8 mm / s, the overlap rate is 50%, and the blue laser remelting is performed under the protection of the local inert gas, so that the microstructure and the bonding strength of the as-sprayed coating are finally improved; As Figure 1 shown in FIG. 2 are cross-sectional morphologies of the plasma as-sprayed coating (a) and the coating after blue laser remelting (b) in Example 1. It can be seen from Figure 1 (a) that the as-sprayed coating has a high porosity inside and shows a clear mechanical bonding state at the interface. It can be seen from Figure 1 (b) that the coating after blue laser remelting has the internal porosity repaired and filled and shows a clear interlocking feature at the interface. Tensile tests are performed on the two coatings to test the bonding strength of the coatings. As Figure 2 shown in the test results, the bonding strength of the coating after blue laser remelting is increased from 17.9 MPa to 35.7 MPa. It can be seen from Figure 3 that the as-sprayed coating has a large area of coating falling off after the tensile test, which indicates that the loose and porous morphology of the coating leads to a low interlayer bonding force of the coating, and the coating after blue laser remelting only has an unobvious falling off at the edge part after the test.

[0029] Specific implementation method two: the method for improving the microstructure and the bonding strength of the plasma as-sprayed coating by blue laser remelting is implemented according to the following steps: One, the surface of the as-sprayed coating is polished by using #400-#800 sandpaper, and then the substrate with the as-sprayed coating after polishing is soaked in anhydrous ethanol for 100 W ultrasonic cleaning for 3 min to obtain the substrate with the as-sprayed coating after cleaning; Two, the substrate with the as-sprayed coating after cleaning is placed in a drying box and dried at a temperature of 80°C for 15 min to obtain the substrate with the as-sprayed coating for blue laser remelting; Three, the substrate with the as-sprayed coating is placed on the surface of the remelting table, the focal point of the blue laser beam is adjusted to be located on the surface of the as-sprayed coating, the laser power is controlled to be 200 W, the remelting speed is 8 mm / s, the overlap rate is 50%, and the blue laser remelting is performed under the protection of the local inert gas, so that the microstructure and the bonding strength of the as-sprayed coating are finally improved; As Figure 4 shown in FIG. 3 is the cross-sectional morphology of the coating after blue laser remelting in Example 2. There are still a large number of pores in the coating after blue laser remelting, which indicates that when the blue laser power of the blue laser remelting deviates from the set range, the improvement effect of the coating is not obvious.

[0030] Specific embodiment three: the method for improving the microstructure and bonding strength of plasma sprayed coating by blue laser remelting is implemented according to the following steps: I. The surface of the as-sprayed coating is polished using sandpaper with grit #400~#800, and then the polished substrate with the as-sprayed coating is immersed in anhydrous ethanol for ultrasonic cleaning at 100W for 3min to obtain a cleaned substrate with the as-sprayed coating; II. The cleaned substrate with the as-sprayed coating is placed in a drying box and dried at a temperature of 80℃ for 15min to obtain a substrate with the as-sprayed coating for blue laser remelting; III. The substrate with the as-sprayed coating is placed on the remelting table, the focal point of the blue laser beam is adjusted to be on the surface of the as-sprayed coating, the laser power is controlled to be 300W, the remelting speed is controlled to be 15mm / s, the overlap rate is controlled to be 50%, and the blue laser remelting is performed under the protection of local inert gas to finally improve the microstructure and bonding strength of the as-sprayed coating; As shown in FIG. 6, the coating cross-sectional morphology after blue laser remelting in Example 3 is shown. Figure 5 As shown in FIG. 6, the coating cross-sectional morphology after blue laser remelting in Example 3 is shown.

[0031] In summary, the method for improving the microstructure and bonding strength of plasma sprayed coating by blue laser remelting is provided. The blue laser remelting within the process parameter range defined in the present application can significantly improve the microstructure and bonding strength of the coating. However, when the blue power and remelting speed exceed the limited range of the present application, the laser heat input will be too high or too low, which will result in that the microstructure and bonding strength of the coating cannot be improved. These obvious defects are great hidden dangers in the service process of the coating, which reduces the safety of the coating protection. Within the process range defined in the present application, the microstructure and bonding strength of the plasma sprayed coating can be greatly improved by the method of blue laser remelting.

[0032] The method for improving the microstructure and bonding strength of plasma sprayed coating by blue laser remelting provided in the present application is mainly aimed at the problem that the internal porosity morphology and interface mechanical bonding characteristics of the current plasma sprayed coating result in insufficient coating bonding force. Limited by the current limited modification means, the present application proposes a method of blue laser remelting. The differential melting of the coating and the substrate in the blue laser remelting process will automatically improve the microstructure of the coating and the interface under the driving of the capillary effect, and significantly improve the coating bonding strength. The method of the present application can well solve the problems of internal organizational defects and low bonding strength of the plasma sprayed coating.

Claims

1. A method for improving the microstructure and bond strength of a laser remelted plasma sprayed coating of blue light, characterized in that, The method comprises the following steps: S1, placing the substrate with a sprayed coating on the surface of a remelting table, and adjusting the focal point of a blue laser beam to be located on the surface of the sprayed coating; S2, performing blue laser remelting under the protection of a local inert gas, and finally improving the microstructure and bonding strength of the sprayed coating.

2. The method for improving microstructure and bond strength of laser remelted plasma sprayed coating of blue laser according to claim 1, wherein, The laser power of the blue laser remelting is 300-500 W, the remelting speed is 8-12 mm / s, and the overlap rate is 40-60%.

3. The method for improving microstructure and bond strength of laser remelted plasma sprayed coating of blue laser according to claim 1, wherein, Before S1, the method further comprises: S01, polishing the surface of the sprayed coating by using #400-#800 sandpaper, then immersing the polished substrate with the sprayed coating in anhydrous ethanol for ultrasonic cleaning, and obtaining the cleaned substrate with the sprayed coating.

4. The method for improving microstructure and bond strength of laser remelted plasma sprayed coating of blue laser according to claim 1, wherein, After S01, the method further comprises: S02, placing the cleaned substrate with the sprayed coating into a drying box, and performing drying treatment at a temperature of 60-100 DEG C, to obtain the substrate with the sprayed coating for blue laser remelting.

5. The method of improving microstructure and bond strength of laser remelted plasma sprayed coating of blue laser according to claim 1, wherein, The melting point of the substrate material is greatly different from the melting point of the coating material.

6. The method for improving microstructure and bond strength of laser remelted plasma sprayed coating of blue light according to claim 5, wherein, The coating is a ceramic thermal protection material.

7. The method of improving microstructure and bond strength of laser remelted plasma sprayed coating of blue light according to claim 6, wherein, The ceramic thermal protection material is YSZ, ZrB2 or SiO2.

8. The method for improving microstructure and bond strength of laser remelted plasma sprayed coating of blue light according to claim 5, wherein, The substrate material is an iron-based alloy, a nickel-based alloy, an aluminum alloy or a copper alloy.

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