Preparation method of wear-resistant and corrosion-resistant metal ceramic coating on surface of titanium alloy

Abstract

The invention relates to a preparation method of a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface, which comprises the following steps of: designing spherical WC-CoCr metal ceramic powder components, sieving the spherical WC-CoCr metal ceramic powder, and drying in a drying oven; the TA15 titanium alloy disc is polished through water-soluble abrasive paper to form a base material, and then after the surface of the base material is subjected to impurity removal, the base material is taken out and placed in a drying oven to be dried; and finally, the dried spherical WC-CoCr metal ceramic powder is deposited on a base material through a laser melting deposition technology under the protection of protective gas, and the WC-CoCr metal ceramic coating is generated through single-layer snakelike reciprocating type printing. According to the method, the WC-CoCr powder is deposited on the TA15 base material through laser melting deposition, so that the WC-CoCr metal ceramic coating which is free of defects such as pores and the like, is well combined with the TA15 base material and has good wear resistance and corrosion resistance is obtained, and the wear resistance and corrosion resistance of the coating are effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser additive manufacturing, and in particular to a method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on the surface of a titanium alloy. Background Art

[0002] TA15 (Ti-6.5Al-2Zr-1Mo-1V) is a titanium alloy with low density, good corrosion resistance and excellent high-temperature mechanical properties. Therefore, it is often used as load-bearing parts in the aerospace field, such as aircraft landing gear. The landing gear has been subjected to high-speed wear caused by strong impact forces for a long time, and in coastal areas, it also faces atmospheric corrosion due to high humidity and high salt content. For a long time, aviation parts such as landing gear often use hard chrome plating as a protective coating to improve their wear and corrosion resistance. However, the plating solution used in hard chrome electroplating technology contains hexavalent chromium, which causes serious environmental problems. At the same time, the hard chrome plating is not completely dense, and the improvement of alloy performance is limited. WC-CoCr metal ceramic coating has been widely reported as a "clean coating" to replace hard chrome plating due to its high hardness and excellent wear and corrosion resistance.

[0003] At present, WC-CoCr metal ceramic coatings are often prepared using thermal spraying processes, such as plasma spraying or supersonic flame spraying, but the metal ceramic layers prepared by thermal spraying still have the following problems: 1. Micropores and microcracks are common in the coating; 2. The coating and the substrate cannot be metallurgically bonded; 3. The coating structure cannot be designed. Studies have shown that the shedding of carbide particles is a wear mechanism that exists in various WC-CoCr coating wear systems, and the WC particles near the primary pores are more likely to fall off during the wear process. At the same time, the low bonding strength between the coating and the substrate also makes the coating's wear resistance poor; in addition, the pores, oxide inclusions and non-uniform carbide dissolution in the coating will affect the corrosion behavior of the coating. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on the surface of a titanium alloy, so as to solve the problems in the above-mentioned background technology.

[0005] The technical problem solved by the present invention is achieved by adopting the following technical solutions: A method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface, the specific steps are as follows: Step 1) using agglomeration sintering technology to prepare spherical WC-CoCr metal ceramic powder, selecting spherical WC-CoCr metal ceramic powder with a particle size in the range of 15-53 μm as a deposition raw material, and then placing the deposition raw material in a 120° C. oven to dry for 4 hours; Step 2) polishing the TA15 titanium alloy disc with water-soluble sandpaper to form a substrate, and then removing impurities from the surface of the substrate. After the substrate is removed from the substrate, it is taken out and placed in an oven at 120° C. for drying; Step 3) A three-way coaxial powder feeder is used to deposit the dried deposition material in step 1) onto the substrate formed in step 2) by laser melting deposition technology under the protection of protective gas, and a single-layer serpentine reciprocating printing is performed to generate a WC-CoCr metal ceramic coating with a size of 15 mm × 15 mm, which is naturally cooled to room temperature after printing.

[0006] In the present invention, in step 1), the composition of the spherical WC-CoCr metal ceramic powder is designed to be: WC: 86 mass%, Co: 10 mass%, Cr: 4 mass%, and the total percentage is 100 mass%.

[0007] In the present invention, in step 1), spherical WC-CoCr metal ceramic powder with a particle size in the range of 15 to 53 μm is selected and sieved using a 325-mesh screen.

[0008] In the present invention, in step 2), a TA15 titanium alloy disc with a thickness of 20 mm and a diameter of 30 mm is polished in sequence using 320 mesh, 600 mesh, and 1200 mesh water-soluble sandpaper to form a substrate, and then the substrate is ultrasonically cleaned in a mixed solution of acetone and anhydrous ethanol for 20 minutes to remove impurities from the surface of the substrate.

[0009] In the present invention, in step 3), the rate at which the three-way coaxial powder feeder conveys the deposition raw material is 3.5 g / min.

[0010] In the present invention, in step 3), protective argon gas is selected to transport the deposition raw material, and the argon flow rate is 5~15L / min; the process parameters of laser melting deposition metal ceramic layer are: the powder output is 3-6g / min, the laser spot diameter is 1~3mm, the laser power is designed to be 600~1500W according to the laser energy density, the scanning speed is 600~2000 mm / min, and the overlap rate is 25~60%; the preferred laser melting deposition parameters are: the powder output is 3.5g / min; the preferred laser melting deposition parameters are: the laser spot diameter is 2mm, the laser power is 1200W, the scanning speed is 800mm / min, the overlap is 0.9mm, and the argon flow rate is 10L / min.

[0011] A wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface, wherein the metal ceramic coating is composed of a metal phase W and a ceramic phase TiC, TiWC 2 The metal ceramic coating forms a TiO 2 dense passivation film.

[0012] Beneficial effects: The present invention designs the composition of the spherical WC-CoCr metal ceramic powder, and then uses laser melting deposition to deposit the spherical WC-CoCr metal ceramic powder on a TA15 substrate to obtain a WC-CoCr metal ceramic coating that is free of defects such as pores and cracks, is well bonded to the TA15 substrate, and has good wear resistance and corrosion resistance, thereby effectively improving the wear resistance and corrosion resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The XRD patterns of WC-CoCr metal ceramic coatings prepared under different laser powers in a preferred embodiment of the present invention.

[0014] Figure 2 This is a cross-sectional morphology of a WC-CoCr metal ceramic coating prepared by a laser with a power of 800 W in a preferred embodiment of the present invention.

[0015] Figure 3 This is a cross-sectional morphology of a WC-CoCr metal ceramic coating prepared by a laser with a power of 1000W in a preferred embodiment of the present invention.

[0016] Figure 4 This is a cross-sectional morphology of a WC-CoCr metal ceramic coating prepared by a laser with a power of 1200W in a preferred embodiment of the present invention.

[0017] Figure 5 This is a comparison chart of the microhardness of the WC-CoCr metal ceramic coating and the hard chrome coating prepared at different laser powers in a preferred embodiment of the present invention.

[0018] Figure 6 The wear scar cross-sectional profile diagram of the WC-CoCr metal ceramic coating and the hard chrome plating prepared at different laser powers in the preferred embodiment of the present invention.

[0019] Figure 7 This is a comparison chart of the specific wear rates of the WC-CoCr metal ceramic coating and the hard chrome coating prepared at different laser powers in a preferred embodiment of the present invention.

[0020] Figure 8 The potentiodynamic polarization curves of the WC-CoCr metal ceramic coating and the hard chromium coating prepared at different laser powers in the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0022] In the following embodiments, the coating hardness test is carried out under the following conditions: at room temperature (25°C), the surface hardness of the metal ceramic coating on the TA15 disc sample is measured using a micro Vickers hardness tester (HVD-10AP), a load of 9.8N is applied during the measurement, and the holding time is 15 seconds; the obtained values ​​are obtained after more than 10 measurements are performed in randomly selected areas.

[0023] In the following examples, a wear test was performed on a disc sample with a metal ceramic coating using an HT-1000 ball-on-disc wear tester at room temperature and the specific wear rate was used to characterize the wear resistance of the coating: a Si with a diameter of 4 mm was selected. 3 N 4 The ceramic ball was used as a friction pair. A force of 10N was applied to the friction pair and the ball was rotated at a speed of 300r / min on a track with a radius of 5mm for 40 minutes. The wear scar was scanned using a JB-5C profilometer to obtain a cross-sectional view of the wear scar. After 10 measurements, the specific wear rate of the coating was calculated.

[0024] In the following examples, the electrochemical corrosion resistance of the WC-CoCr coating was tested using a REF3000-32117 electrochemical workstation: the test was carried out at room temperature in a 3.5wt% NaCl solution environment, the sample size was 5mm×5mm×3mm, and a classic three-electrode cell (a platinum electrode was the auxiliary electrode, a saturated calomel electrode was the reference electrode, and the sample was the working electrode) was used to test the Nyquist curve and the potentiodynamic polarization curve of the coating.

[0025] A method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface, the specific steps are as follows: Step 1) Use agglomeration sintering technology to prepare spherical WC-CoCr metal ceramic powder, select spherical WC-CoCr metal ceramic powder with a particle size in the range of 15~53μm as a deposition raw material, and then place the deposition raw material in a 120℃ oven for 4h; and the spherical WC-CoCr metal ceramic powder has full particles, high sphericity, and low oxygen content. The composition of the spherical WC-CoCr metal ceramic powder is designed to be: WC: 86mass%, Co: 10mass%, Cr: 4mass%, and the total percentage is 100mass%; Step 2) using 320 mesh, 600 mesh, and 1200 mesh water-soluble sandpaper to polish a TA15 titanium alloy disc with a thickness of 20 mm and a diameter of 30 mm in sequence to form a substrate, and then ultrasonically cleaning the substrate in a mixed solution of acetone and anhydrous ethanol for 20 minutes, taking it out and drying it in an oven at 120° C.; Step 3) using a three-way coaxial powder feeder under argon protection, the deposition raw material dried in step 1) is deposited on the substrate formed in step 2) by laser melting deposition technology, the delivery rate of the deposition raw material is 3.5 g / min, and a single-layer serpentine reciprocating printing is performed to generate a WC-CoCr metal ceramic coating with a size of 15 mm×15 mm. The laser melting deposition is printed out of the box at room temperature and naturally cooled to room temperature after the printing is completed; the laser melting deposition parameters are as follows: the laser spot diameter is 2 mm, the laser power is 1200 W, the scanning speed is 800 mm / min, the overlap is 0.9 mm, and the argon flow rate is 10 L / min; Step 4) Use a CNC machine tool to cut the generated WC-CoCr metal ceramic coating into small samples of 5 mm × 5 mm along the direction perpendicular to the scanning direction, use a Bruker D8ADVANCE X-ray diffractometer to characterize the phase composition of the coating, use a field emission scanning electron microscope to observe the cross-sectional micromorphology of the coating, and use an X-ray energy spectrum to analyze the phase composition of the coating. The WC-CoCr metal ceramic coating has a uniform microstructure distribution, no defects such as holes and cracks, and has a good metallurgical bond with the substrate.

[0026] In this embodiment, the XRD results of the WC-CoCr metal ceramic coating are as follows: Figure 1 As shown in Figure 2, the main components of the WC-CoCr metal ceramic coating are W, TiC and TiWC. 2 , due to the decarburization of WC at high temperature, TiC and TiWC are precipitated 2 , and with the increase of laser power, the relative content of metal phase W is less, and the relative content of ceramic phase increases.

[0027] In this embodiment, the cross-sectional morphology of the WC-CoCr metal ceramic layer is as follows: Figure 2 , 3 , 4, where Figure 2 a. Figure 3 a and Figure 4 a is the cross-sectional morphology of the WC-CoCr metal ceramic layer at low magnification, the coating is dense and well bonded to the substrate; Figure 2 b. Figure 3 b and Figure 4 b is the cross-sectional morphology of the WC-CoCr metal ceramic layer at high magnification. It is clearly observed that there are three phases with different contrasts inside the WC-CoCr metal ceramic layer. The white phase is W, the granular black phase is TiC, and the light white matrix phase is TiWC. 2 ,With the increase of laser power, the W phase decreases, which is consistent with the XRD results.

[0028] In this embodiment, the microhardness test results of the WC-CoCr metal ceramic layer are as follows: Figure 5As shown in the figure, the microhardness of the WC-CoCr metal ceramic layer is significantly higher than that of the hard chrome layer. The WC-CoCr metal ceramic layer prepared at 1200W power has a hardness of 1197.9±97.4HV 1 .

[0029] In this embodiment, Figure 6 The cross-sectional profile of the wear scar directly reflects the wear resistance of the WC-CoCr metal ceramic layer. Figure 7 is the specific wear rate of the WC-CoCr metal ceramic layer and the hard chrome coating under different laser powers. The wear resistance of the WC-CoCr metal ceramic layer is still higher than that of the hard chrome coating. Among them, the specific wear rate of the WC-CoCr metal ceramic layer prepared with a power of 1200W is 2.4×10 -5 mm 3 / N·m, because it has the highest hardness and contains more ceramic phase, it has the best wear resistance.

[0030] In this embodiment, the electrochemical corrosion performance test results of the WC-CoCr metal ceramic layer are as follows: Figure 8 As shown in the figure, the corrosion resistance of the WC-CoCr metal ceramic layer is significantly higher than that of the hard chrome coating. The polarization curve shows that with the increase of laser power, the corrosion current density of the WC-CoCr metal ceramic layer decreases, and the corrosion resistance of the WC-CoCr metal ceramic layer increases. In addition, the 1000W and 1200W curves have obvious passivation intervals, indicating that the WC-CoCr metal ceramic layer is spontaneously passivated under the corrosion potential. It is only because the Ti element in the substrate diffuses into the WC-CoCr metal ceramic layer during the laser melting deposition process. During the corrosion period, the surface of the WC-CoCr metal ceramic layer forms a TiO 2 dense passivation film.

[0031] In this embodiment, a wear-resistant and corrosion-resistant metal ceramic coating is provided on the surface of a titanium alloy. The metal ceramic coating has a surface containing TiO 2 The dense passivation film includes W, TiC, TiWC 2 , Co, Cr.

[0032] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface, characterized in that: The specific steps are as follows: Step 1) Spherical WC-CoCr metal ceramic powder is prepared by agglomeration sintering technology, and spherical WC-CoCr metal ceramic powder with a particle size in the range of 15~53μm is selected as a deposition raw material, and then the deposition raw material is placed in a 120℃ oven for 4h; and the composition of the spherical WC-CoCr metal ceramic powder is designed to be: WC: 86mass%, Co: 10mass%, Cr: 4mass%, and the total percentage is 100mass%; Step 2) polishing the TA15 titanium alloy disc with water-soluble sandpaper to form a substrate, and then removing impurities from the surface of the substrate. After the substrate is removed from the substrate, it is taken out and placed in an oven at 120° C. for drying; Step 3) A three-way coaxial powder feeder is used to deposit the dried deposition material in step 1) onto the substrate formed in step 2) by laser melting deposition technology under the protection of protective gas, and a single-layer serpentine reciprocating printing is performed to generate a WC-CoCr metal ceramic coating, which is naturally cooled to room temperature after printing.

2. The method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface according to claim 1, characterized in that: In step 1), spherical WC-CoCr metal ceramic powder with a particle size ranging from 15 to 53 μm is sieved using a 325-mesh screen.

3. The method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface according to claim 1, characterized in that: In step 2), a TA15 titanium alloy disc with a thickness of 20 mm and a diameter of 30 mm is polished in sequence using 320-mesh, 600-mesh, and 1200-mesh water-soluble sandpaper to form a substrate.

4. The method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface according to claim 3, characterized in that: The substrate was ultrasonically cleaned in a mixed solution of acetone and anhydrous ethanol for 20 min to remove impurities from the substrate surface.

5. The method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface according to claim 1, characterized in that: In step 3), the rate of conveying the deposition raw material by the three-way coaxial powder feeder is 3.5 g / min.

6. The method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface according to claim 1, characterized in that: In step 3), protective argon gas is used to transport the deposition raw materials, and the argon flow rate is 5~15L / min; the process parameters of laser melting deposition metal ceramic layer are: powder output is 3-6g / min, laser spot diameter is 1~3mm, laser power is designed to be 600~1500W according to laser energy density, scanning speed is 600~2000 mm / min, and overlap rate is 25~60%.

7. The method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface according to claim 6, characterized in that: Laser melting deposition parameters: powder output is 3.5 g / min; laser melting deposition parameters are: laser spot diameter is 2 mm, laser power is 1200 W, scanning speed is 800 mm / min, overlap is 0.9 mm, and argon flow rate is 10 L / min.

8. The method for preparing a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface according to any one of claims 1 to 7 is used to prepare a wear-resistant and corrosion-resistant metal ceramic coating on a titanium alloy surface, characterized in that: The metal ceramic coating is composed of metal phase W and ceramic phase TiC, TiWC2, and during the electrochemical corrosion process, the surface of the metal ceramic coating forms a layer containing TiO2 dense passivation film.

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