Preparation method of high-adhesiveness speckle suitable for fuel gas impact environment at temperature of 2700 DEG C or above

Abstract

The invention relates to the technical field of speckle preparation, in particular to a preparation method of a high-adhesiveness speckle suitable for a fuel gas impact environment at the temperature of 2700 DEG C or above. According to the invention, black and white high-temperature-resistant particles are adopted, a layer of compact white ground color and randomly distributed black particle spots are formed on the surface of a substrate through a plasma spraying technology, a standard speckle feature is formed, and the particles stably exist in a gas impact state for a long time by virtue of high adhesiveness and high temperature resistance of the particles. The speckle manufactured by the method can resist high temperature of 2700 DEG C, can stably exist in a fuel gas high-speed impact environment for a long time, and well meets the requirement of a DIC technology for stably capturing the characteristics of a sample strain field for a long time in a simulated aero-engine environment. In addition, black speckles are formed after the white bottom layer is formed, and obvious contrast with a substrate can be formed.

Description

Technical Field

[0001] This invention relates to the field of speckle preparation technology, and in particular to a method for preparing highly adhesive speckles suitable for gas impact environments above 2700°C. Background Technology

[0002] With the rapid development of science and technology and the continuous expansion of national defense, the country is paying increasing attention to the development of aerospace technology. To improve the performance of gas turbine engines, it is necessary to start by increasing the thrust-to-weight ratio and fuel thermal efficiency of aero engines, which leads to a further increase in the operating temperature of hot-end components of the turbine engine. Analyzing the damage mechanism of hot-end components under extreme environments mainly involves two methods: one is contact testing, which mainly involves pre-embedding strain gauges on rotor blades to analyze the strain and stress changes of the blades. However, this contact testing usually only targets a few points and can damage the surface of the engine body, and is prone to detachment at high speeds; the other is non-contact testing, which mainly uses digital image correlation (DIC) technology. DIC mainly calculates mechanical data such as strain by measuring the displacement of marked points (speckle patterns). This method has advantages that other experimental solid mechanics testing methods do not possess, such as: 1. Non-destructive testing, without direct damage to the tested material; 2. Non-contact testing, reducing experimental errors caused by contact and significantly improving the accuracy of the test results.

[0003] The selection and preparation process of speckle patterns are crucial and essential steps affecting the accuracy of digital image correlation (DIC) testing. DIC primarily calculates displacement and strain by measuring the displacement of a point before and after deformation. Since there are generally no natural reference points on the surface of the measured component, a speckle layer needs to be prepared on the surface to serve as a carrier for surface deformation.

[0004] Conventional preparation methods include laser speckle and artificial speckle. Laser speckle, due to the damage to the substrate surface caused by laser etching, is susceptible to detachment along defects during high-speed combustion gas impact. Traditional artificial speckle, relying on matte paint or suspension spraying and printing, suffers from weak adhesion between printed and sprayed speckles and the substrate, and cannot withstand prolonged high temperatures. Therefore, it oxidizes and detaches under high-temperature, high-speed combustion gas impact.

[0005] In summary, existing speckle patterns suitable for DIC technology generally suffer from problems such as difficulty in long-term preservation, easy detachment, and inability to use DIC technology for long-term strain monitoring of samples under simulated aero-engine test environments. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for preparing highly adhesive speckle patterns suitable for combustion gas impact environments above 2700°C. The speckle patterns prepared by this invention are not easily detached and can be retained for a long time under extreme conditions simulating aircraft engine testing.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing highly adhesive speckle patterns suitable for combustion gas impact environments above 2700℃, comprising the following steps:

[0009] White high-temperature resistant particles are sprayed onto the substrate surface using a first plasma spraying method to form a white underlayer; the melting point of the white high-temperature resistant particles is above 2700℃.

[0010] Black high-temperature resistant particles are plasma-sprayed onto the surface of the white base layer to form black speckles; the melting point of the black high-temperature resistant particles is above 2800℃.

[0011] Preferably, the white high-temperature resistant particles comprise boron nitride and / or zirconium oxide.

[0012] Preferably, the black high-temperature resistant particles include one or more of titanium carbide, tantalum carbide, tungsten carbide, and zirconium carbide.

[0013] Preferably, the black high-temperature resistant particles have a particle size of 50-100 μm.

[0014] Preferably, the white high-temperature resistant particles have a particle size of 50-100 μm.

[0015] Preferably, the conditions for the first plasma spraying include: a powder feeding rate of 2-10 g / min, an ionization current of 300-380 A, and nitrogen as the ionization gas, with a nitrogen flow rate of 60-100 SLM.

[0016] Preferably, the conditions for the second plasma spraying include: a powder feeding rate of 1-3 g / min, an ionization current of 300-380 A, and nitrogen as the ionization gas, with a flow rate of 60-100 SLM.

[0017] Preferably, the thickness of the white substrate is 10-20 μm.

[0018] Preferably, the distance of the first plasma spraying is 15-25cm.

[0019] Preferably, the distance for the second plasma spraying is 15-25cm.

[0020] This invention provides a method for preparing highly adhesive speckle patterns suitable for gas impact environments above 2700℃, comprising the following steps: spraying white high-temperature resistant particles onto the surface of a substrate using a first plasma spraying method to form a white underlayer; the melting point of the white high-temperature resistant particles is above 2700℃; and spraying black high-temperature resistant particles onto the surface of the white underlayer using a second plasma spraying method to form black speckle patterns; the melting point of the black high-temperature resistant particles is above 2800℃.

[0021] This invention employs black and white dual-color high-temperature resistant particles—forming a dense white base layer and randomly distributed black particle spots on the substrate surface using plasma spraying technology—to create a standard speckle pattern. Relying on the high adhesion and high-temperature resistance of the particles, it achieves long-term stability under combustion gas impact conditions. The speckle pattern produced by this invention can withstand temperatures up to 2700℃ and remain stable in a high-speed combustion gas impact environment for extended periods, perfectly meeting the requirements of DIC technology for long-term stable capture of the strain field of samples in simulated aero-engine environments. Furthermore, the method of forming a white base layer followed by black speckles creates a clear contrast with the substrate. Attached Figure Description

[0022] Figure 1 A schematic diagram illustrating the principle of speckle pattern fabrication;

[0023] Figure 2 A schematic diagram of the equipment used for speckle pattern fabrication in operation.

[0024] Figure 3 This is a photograph of the speckle pattern from Example 1;

[0025] Figure 4 This is a confidence cloud map of the speckle pattern in Example 1. Detailed Implementation

[0026] This invention provides a method for preparing highly adhesive speckle patterns suitable for combustion gas impact environments above 2700℃, comprising the following steps:

[0027] White high-temperature resistant particles are sprayed onto the substrate surface using a first plasma spraying method to form a white underlayer; the melting point of the white high-temperature resistant particles is above 2700℃.

[0028] Black high-temperature resistant particles are plasma-sprayed onto the surface of the white base layer to form black speckles; the melting point of the black high-temperature resistant particles is above 2800℃.

[0029] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available products well known in the art.

[0030] The present invention employs a first plasma spraying method to spray white high-temperature resistant particles onto the substrate surface to form a white underlayer.

[0031] In this invention, the white high-temperature resistant particles have a melting point above 2700℃; the white high-temperature resistant particles preferably include boron nitride (melting point 3000℃) and / or zirconium oxide (melting point 2715℃); the particle size of the white high-temperature resistant particles is preferably 50-100μm, and in specific embodiments it can be 50μm, 60μm, 70μm, 80μm, 90μm or 100μm.

[0032] In this invention, the conditions for the first plasma spraying include: a powder feed rate preferably of 2-10 g / min, which in specific embodiments can be 2 g / min, 4 g / min, 6 g / min, 8 g / min, or 10 g / min; an ionization current preferably of 300-380 A, which in specific embodiments can be 300 A, 320 A, 340 A, 360 A, or 380 A; and an ionization gas preferably nitrogen, with a flow rate preferably of 60-100 SLM, which in specific embodiments can be 60 SLM, 70 SLM, 80 SLM, 90 SLM, or 100 SLM. In this invention, a white underlayer is first sprayed onto the substrate surface to form a white underlayer, firstly to cover the original metallic luster and prevent surface reflection under stroboscopic effects; and secondly to create a clear contrast with the black particles. In this invention, the thickness of the white underlayer is preferably 10-20 μm.

[0033] In this invention, the distance of the first plasma spraying (i.e., the distance between the spray gun nozzle and the substrate, which is vertical spraying in this invention) is preferably 15-25cm, and in specific embodiments it can be 15cm, 18cm, 20cm or 25cm.

[0034] After forming a white base layer, the present invention applies a second plasma spray coating of black high-temperature resistant particles onto the surface of the white base layer to form black speckles.

[0035] In this invention, the black high-temperature resistant particles have a melting point above 2800℃; the black high-temperature resistant particles preferably include one or more of titanium carbide (melting point 3160℃), tantalum carbide (melting point 3880℃), tungsten carbide (melting point 2870℃), and zirconium carbide (melting point 3540℃); the particle size of the black high-temperature resistant particles is preferably 50-100μm, and in specific embodiments it can be 50μm, 60μm, 70μm, 80μm, 90μm, or 100μm.

[0036] In this invention, the conditions for the second plasma spraying include: a powder feed rate preferably of 1-3 g / min, which in specific embodiments can be 1 g / min, 2 g / min, or 3 g / min; an ionization current preferably of 300-380 A, which in specific embodiments can be 300 A, 320 A, 340 A, 360 A, or 380 A; and an ionization gas of nitrogen, wherein the nitrogen flow rate is preferably 60-100 SLM, which in specific embodiments can be 60 SLM, 70 SLM, 80 SLM, 90 SLM, or 100 SLM.

[0037] In this invention, the distance of the second plasma spraying (i.e., the distance between the spray gun nozzle and the substrate, which is vertical spraying in this invention) is preferably 15-25cm, and in specific embodiments it can be 15cm, 18cm, 20cm or 25cm.

[0038] This invention uses high-melting-point white and black high-temperature resistant particles, which can not only remain stable at 2700℃ for a long time, but also form a good degree of confidence with the substrate surface.

[0039] Furthermore, this invention employs plasma spraying technology, which creates a surface that can effectively resist the impact of combustion gases.

[0040] Figure 1 This is a schematic diagram illustrating the principle of speckle pattern fabrication. Taking tungsten carbide particles as an example, such as... Figure 1 As shown, in this invention, tungsten carbide particles are fed into the powder feeding port of a plasma spray gun through a powder feeder, and then enter the flame area. The tungsten carbide particles are fully mixed and melted with the plasma heat source, and then sprayed out at supersonic speed. They splash onto the surface of the workpiece substrate and cool and bond rapidly, so that the tungsten carbide particles are tightly bonded to the workpiece substrate and form stable black characteristic spots.

[0041] This invention controls the powder feeding rate within the aforementioned range to prevent excessive mixing and sintering of tungsten carbide particles falling on the workpiece due to an excessively high powder feeding rate, thus hindering the formation of speckle patterns with high confidence suitable for DIC (Discrete Injection) technology. When spraying a white base coat, an insufficient powder feeding rate results in an uneven and thin white undercoat on the sample surface, causing reflections during stroboscopic effects. Conversely, when spraying black particles, an insufficient powder feeding rate leads to an overly sparse distribution of black speckle patterns on the surface, preventing the formation of good confidence levels. Confidence level is the evaluation criterion for the DIC algorithm in assessing the quality of speckle distribution on the captured image surface.

[0042] Secondly, the current and working gas content of the plasma equipment will affect the heat source temperature and speed of the plasma spray gun. When the heat source temperature of the spray gun is too high and the particle speed is too slow, the molten tungsten carbide liquid will accumulate, causing large tungsten carbide particles to be sprayed out, affecting the quality of speckle production. After repeated optimization, the ionization current and nitrogen content of the ion spraying equipment were determined to be 300-380A and 60-100SLM, respectively.

[0043] The following detailed description, in conjunction with embodiments, illustrates the preparation method of the highly adhesive speckle material suitable for gas impact environments above 2700°C, provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] use Figure 2 The device shown is used to prepare speckle patterns. The specific steps are as follows:

[0046] Weigh 200g of zirconium oxide particles with a particle size of 50-100μm and place them in the powder feeder of the plasma spraying equipment;

[0047] Turn on the power of the plasma equipment and adjust the position of the robotic arm so that the nozzle of the spray gun is 20cm (vertical distance) away from the sample to be produced with speckle patterns.

[0048] Turn on the nitrogen generator and let it run stably for half an hour to produce nitrogen.

[0049] Turn on the air compressor to remove the heat generated during the preparation process in a timely manner to prevent local overheating of the equipment;

[0050] Turn on the run button on the plasma spray gun control cabinet to raise it to run mode with default parameters;

[0051] After the spray gun flame stabilizes, adjust the ionization current and nitrogen content of the plasma spraying equipment to 360A and 70SLM, respectively.

[0052] After the plasma spray gun stabilizes under the above parameters, turn on the powder feeder to allow the zirconia particles to enter through the powder feed port in the spray gun. When the powder feed rate stabilizes at 8 g / min, spray the sample surface to create a white base layer. Stop spraying after 2-3 minutes. After the sample cools down, observe the surface spraying effect. If the surface is relatively smooth and the thickness is 10-20 μm, the process is complete.

[0053] Weigh 100g of tungsten carbide particles with a diameter of 50-100μm and place them in the powder feeder of the plasma spraying equipment;

[0054] Turn on the power of the plasma equipment and adjust the position of the robotic arm so that the nozzle of the spray gun is 20cm (vertical distance) away from the sample to be produced with speckle patterns.

[0055] Turn on the nitrogen generator and let it run stably for half an hour to produce nitrogen.

[0056] Turn on the air compressor to remove the heat generated during the preparation process in a timely manner to prevent local overheating of the equipment;

[0057] Turn on the run button on the plasma spray gun control cabinet to raise it to run mode with default parameters;

[0058] After the spray gun flame stabilizes, adjust the ionization current and nitrogen content of the plasma spraying equipment to 350A and 80SLM, respectively.

[0059] After the plasma spray gun stabilizes under the above parameters, turn on the powder feeder to allow tungsten carbide particles to enter through the powder feed port in the spray gun. When the powder feed rate stabilizes at 3 g / min, spray the sample surface to create speckle patterns. A photograph of the speckle pattern is shown below. Figure 3 As shown.

[0060] The prepared speckled sample was tested to check if its speckle pattern met the standard. The testing method was as follows: the spray gun was turned on and run. After it stabilized, WC (tungsten carbide) powder was fed into the spray gun. The temperature of the tungsten carbide particles when they were ejected was measured using a particle velocimeter. This temperature can be approximated as the actual temperature of the flame. The parameters of the gas simulation tester were adjusted so that the particle temperature measured by the particle velocimeter reached 2700℃. The parameters were then fixed and the spray gun was turned off. The sample with speckled coating was then placed in front of the spray gun of the gas simulation tester and fixed. The spray gun was run and flames were emitted using the above parameters. At this time, no tungsten carbide powder was fed into the spray gun. If the sample could withstand impact in this environment for 1 hour and the speckle pattern on the sample surface did not fall off, and the DIC confidence cloud map was good, then the prepared speckled sample was qualified. The test results are as follows: Figure 4 As shown. The more purple the confidence contour, the better the speckle imaging, size, and distribution. Figure 4 It can be seen that the speckle pattern prepared by the present invention has high quality and can withstand 2700℃.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing highly adhesive speckle patterns suitable for combustion gas impact environments above 2700℃, characterized in that, Includes the following steps: White high-temperature resistant particles are sprayed onto the substrate surface using a first plasma spraying method to form a white underlayer; the melting point of the white high-temperature resistant particles is above 2700℃. Black high-temperature resistant particles are plasma-sprayed onto the surface of the white base layer to form black speckles; the melting point of the black high-temperature resistant particles is above 2800℃.

2. The preparation method according to claim 1, characterized in that, The white, high-temperature resistant particles include boron nitride and / or zirconium oxide.

3. The preparation method according to claim 1, characterized in that, The black high-temperature resistant particles include one or more of titanium carbide, tantalum carbide, tungsten carbide, and zirconium carbide.

4. The preparation method according to claim 1 or 3, characterized in that, The black high-temperature resistant particles have a particle size of 50-100μm.

5. The preparation method according to claim 1 or 2, characterized in that, The white high-temperature resistant particles have a particle size of 50-100 μm.

6. The preparation method according to claim 1, characterized in that, The conditions for the first plasma spraying include: a powder feeding rate of 2-10 g / min, an ionization current of 300-380 A, and nitrogen as the ionization gas, with a nitrogen flow rate of 60-100 SLM.

7. The preparation method according to claim 1, characterized in that, The conditions for the second plasma spraying include: a powder feed rate of 1-3 g / min, an ionization current of 300-380 A, and nitrogen as the ionization gas, with a flow rate of 60-100 SLM.

8. The preparation method according to claim 1 or 6, characterized in that, The thickness of the white base layer is 10-20 μm.

9. The preparation method according to claim 1 or 6, characterized in that, The distance for the first plasma spraying is 15-25cm.

10. The preparation method according to claim 1 or 7, characterized in that, The distance for the second plasma spraying is 15-25cm.

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