High-hardness corrosion-resistant laser cladding coating on surface of titanium-zirconium alloy and preparation method of high-hardness corrosion-resistant laser cladding coating

Abstract

The invention belongs to the technical field of laser cladding, and particularly relates to a titanium-zirconium alloy surface high-hardness corrosion-resistant laser cladding coating and a preparation method thereof.The preparation method comprises the steps that firstly, cladding materials are mixed; ti powder, Zr powder, Nb powder, Mo powder and elementary substance powder are put into a planetary ball mill according to the equal molar ratio, then the ball mill is started for powder mixing, and after powder mixing is finished, the powder is taken out and put into a vacuum drying box for vacuum drying storage; before cladding, the surface of a workpiece is pretreated according to the sequence of rough grinding, cleaning, flushing and scrubbing. According to the high-hardness corrosion-resistant laser cladding coating on the titanium-zirconium alloy surface and the preparation method, in the treatment process of a cladding material and a workpiece, the cladding material is subjected to ball-milling mixing treatment, so that elemental metal powder is mixed more uniformly, and the obtained laser cladding coating is more uniform in component, and the corrosion resistance of the coating is improved; and the prepared coating is subjected to heat treatment, so that the purpose of reducing cracks in the cladding layer is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of laser cladding, and in particular to a high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy and a preparation method thereof. Background Art

[0002] Titanium-zirconium alloy, as a metal material with low density, high specific strength and high heat resistance, has been widely used in aerospace, biomedicine, weapons and equipment and other fields. However, as a key component of equipment, titanium-zirconium alloy has problems such as easy surface scratches, easy corrosion in humid climates, poor hardness, and easy wear and failure under long-term service conditions, which greatly limits its service life in key components. Although commonly used surface modification technologies such as heat treatment, ion implantation, and thermal spraying can improve the surface properties of titanium-zirconium alloy to a certain extent, their performance is still unsatisfactory for aircraft that need to face complex service conditions.

[0003] As an advanced remanufacturing technology with low energy consumption, short process, high flexibility, and integrated forming and organizational performance control, laser cladding technology solves many problems that cannot be processed or are difficult to process with conventional methods, greatly improves production efficiency and processing quality, and provides an advanced and effective technical means for surface strengthening. It has been well applied in many fields such as aerospace, military and national defense. Although laser cladding technology can prepare coatings with good performance, due to the different melting points of coating powders, the fast cooling speed of laser cladding, and the difference in thermal expansion coefficients, cracks are easily generated in the cladding layer. At the same time, due to the high processing temperature, part of the metal vaporizes or the protective gas is drawn into the molten pool and has no time to escape, forming pores or holes in the cladding layer, which deteriorates the performance of the coating. Therefore, the preparation of high-performance titanium alloy coatings on the surface of titanium-zirconium alloy substrates is still a technical problem that needs to be solved urgently in this field. Summary of the invention

[0004] Based on the existing technical problems, the present invention proposes a high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy and a preparation method thereof.

[0005] The invention provides a high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy, which comprises single-substance powders of Ti powder, Zr powder, Nb powder and Mo powder.

[0006] Preferably, the Ti powder, Zr powder, Nb powder and Mo powder are in an equimolar ratio.

[0007] A method for preparing a high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy comprises the following steps: first, mixing cladding materials; putting Ti powder, Zr powder, Nb powder and Mo powder into a planetary ball mill in an equimolar ratio, then starting the ball mill to mix the powders, and after mixing the powders, taking them out and putting them into a vacuum drying oven for vacuum drying and storage.

[0008] Step 2. Workpiece pretreatment; before cladding, the workpiece surface is pretreated in the order of rough grinding, cleaning, rinsing, and scrubbing.

[0009] Step 3. Laser cladding; place the workpiece in a protective container, open the top opening of the container, place a titanium-zirconium alloy substrate at the bottom of the container, then introduce argon into the container to remove the air inside, and then put the titanium alloy powder into the powder bucket of the laser cladding machine and start the workbench of the laser cladding machine.

[0010] Step 4. Coating heat treatment; put the prepared coating into a vacuum tube furnace, evacuate the furnace to a vacuum state, start the tube furnace, keep it warm, cool it in the furnace, and take out the specimen.

[0011] Preferably, the ball milling speed of the planetary ball mill is between 180 r / min and 220 r / min, the ball-to-material ratio is any one of 3:1 or 4:1, and the ball milling time is between 1.5 h and 3 h.

[0012] Preferably, the temperature of the vacuum drying oven is 80 °C.

[0013] Preferably, in Step 2, the rough grinding is carried out with silicon carbide sandpaper, then the cleaning is carried out with an alcohol solution, then rinsed with deionized water, and finally the surface of the workpiece is scrubbed with an acetone solution.

[0014] Preferably, in Step 3, before starting the laser cladding machine, the laser cladding power, scanning speed, and overlapping rate parameters are preset in advance, start the laser cladding device, and carry out the laser cladding experiment;

[0015] During the cladding process, argon needs to be continuously introduced for protection to obtain a cladding coating.

[0016] Preferably, in Step 3, the laser cladding power of the laser cladding machine is set between 1000 W and 1600 W, the scanning speed is 10 mm / s, the overlapping rate is 50%, the spot diameter is 2 mm, and the powder feeding rate is 0.3 r / / min. After setting, start the laser cladding device and carry out the laser cladding experiment.

[0017] Preferably, in Step 4, when starting the vacuum tube furnace, vacuum treatment is required, argon is introduced, and the heating-up time, holding temperature, and holding time parameters are set.

[0018] Preferably, in Step 4, the heating-up time is between 110 min and 136 min, the holding temperature is between 655 °C and 700 °C, and the holding time is between 2 h and 3 h.

[0019] The beneficial effects of the present invention are:

[0020] 1. During the processing of the cladding material and the workpiece in the present invention, the cladding material is subjected to ball milling and mixing treatment, making the elemental metal powders more evenly mixed. As a result, the composition of the laser cladding coating obtained is also more uniform. Moreover, the prepared coating is heat-treated to reduce the cracks in the cladding layer. In addition, the surface of the workpiece is polished with sandpaper of a coarse mesh number to increase the surface roughness of the cladding, which can increase the absorption rate of the laser and improve the uniformity and quality of the cladding layer.

[0021] 2. The titanium alloy powder used in the present invention has a relatively wide particle size range, and there is no need for processes such as sieving powder, effectively reducing the production cost of the coating. The process is simple, energy-saving and environmentally friendly. The present invention has overcome the problems of cracking and poor performance in preparing titanium alloy coatings on the surface of titanium-zirconium alloys by laser cladding, providing new ideas and theoretical basis for metal protection and having good application prospects.

[0022] 3. The laser cladding coating provided by the present invention includes a high-performance titanium alloy coating formed by powder metallurgy bonding of a titanium-zirconium alloy substrate and titanium alloy powder. The overall structure of the laser cladding coating is dense, without defects such as cracks and pores. The titanium-zirconium alloy substrate has not deformed, and the interfacial bonding strength is high. The laser cladding coating has high hardness and corrosion resistance, and can effectively resist the attack of chloride ions in the atmosphere, ocean and other environments on the titanium-zirconium alloy substrate, thereby effectively improving the service life of titanium-zirconium alloy parts.

[0023] 4. Due to the differences in thermophysical properties between the cladding material and the substrate, as well as the rapid solidification and cooling process of the molten pool, complex thermal stresses and phase transformation stresses will be generated in the cladding layer and its surrounding areas. Through heat treatment, the release and redistribution of residual stresses inside the coating can be promoted, and at the same time, the microstructure and mechanical properties of the coating can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a preparation method of a high-hardness and corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy proposed by the present invention;

[0025] Figure 2 It is an XRD pattern of a titanium-zirconium alloy substrate and a titanium alloy coating of a preparation method of a high-hardness and corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy proposed by the present invention;

[0026] Figure 3 It is a scanning electron microscope image of a titanium-zirconium alloy substrate and a titanium alloy coating of a preparation method of a high-hardness and corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy proposed by the present invention;

[0027] Figure 4 It is a hardness distribution diagram of a titanium-zirconium alloy substrate and a titanium alloy coating of a preparation method of a high-hardness and corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy proposed by the present invention;

[0028] Figure 5 The potentiodynamic polarization curve diagram of the titanium-zirconium alloy substrate and the titanium alloy coating for a method of preparing a high-hardness and corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy proposed by the present invention. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0030] Embodiment 1

[0031] Referring to Figure 3 As shown, a high-hardness and corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy, wherein the elemental powders of Ti powder, Zr powder, Nb powder, and Mo powder are in an equimolar ratio. By using a relatively wide particle size range of titanium alloy powder, there is no need for processes such as sieving powder, effectively reducing the production cost of the coating. The process is simple, energy-saving, and environmentally friendly.

[0032] The laser cladding coating provided by the present invention includes a high-performance titanium alloy coating formed by powder metallurgy bonding of a titanium-zirconium alloy substrate and titanium alloy powder. The overall structure of the laser cladding coating is dense, without defects such as cracks and pores. The titanium-zirconium alloy substrate does not deform, and the interfacial bonding strength is high. The laser cladding coating has high hardness and corrosion resistance, and can effectively resist the attack of chloride ions in environments such as the atmosphere and the ocean on the titanium-zirconium alloy substrate, thereby effectively improving the service life of titanium-zirconium alloy parts.

[0033] Embodiment 2

[0034] Referring to Figure 1 , Figure 2 , Figure 4 and Figure 5 As shown, a method for preparing a high-hardness and corrosion-resistant coating on the surface of a titanium-zirconium alloy includes the following steps:

[0035] In order to avoid problems such as cracking and poor performance of the titanium alloy coating prepared by laser cladding on the surface of the titanium-zirconium alloy, set S1: Put the elemental powders of Ti powder, Zr powder, Nb powder, and Mo powder into a planetary ball mill according to an equimolar ratio, set the ball milling parameters of rotation speed 180 r / min, ball-to-material ratio 4:1, and ball milling time 3 h, and then start the ball mill for powder mixing. After the powder mixing is completed, take it out and put it into a vacuum drying oven, and adjust the temperature to 80 °C for vacuum drying and storage.

[0036] S2: First, cut the titanium-zirconium alloy substrate into 50×15×5 mm with a wire cutting machine, and polish it with 150-mesh silicon carbide sandpaper to remove the surface oxide and make the surface of the titanium-zirconium alloy substrate rough.

[0037] S3. Clean the surface of the roughened titanium-zirconium alloy substrate in step S1 with acetone to remove oil stains.

[0038] S4. Set the laser cladding parameters: power 1200 W, scanning speed 10 mm / s, overlapping rate 50%, spot diameter 2 mm, powder feeding rate 0.3 r / min. Start the laser cladding device to conduct the laser cladding experiment, thus providing new ideas and theoretical basis for metal protection and having good application prospects. Among them, set the parameters of the vacuum tube furnace: heating-up time 120 min, holding temperature 680 °C, holding time 2.5 h.

[0039] As Figure 4 shown, the hardness of the laser cladding layer is 1.28 times that of the substrate, and the corrosion resistance is improved by one order of magnitude compared with the substrate. Due to the differences in thermophysical properties between the cladding material and the substrate, as well as the rapid solidification and cooling process of the molten pool, complex thermal stress and phase transformation stress will be generated in the cladding layer and its surrounding areas. Through heat treatment, the release and redistribution of residual stress inside the coating can be promoted, and at the same time, the microstructure and mechanical properties of the coating can be improved.

[0040] In the process of treating the cladding material and the workpiece in the present invention, the cladding material is subjected to ball milling and mixing treatment, so that the elemental metal powders are mixed more uniformly, and thus the composition of the obtained laser cladding coating is also more uniform, achieving the purpose of reducing cracks in the cladding layer. In addition, the surface of the workpiece is polished with sandpaper of a coarse mesh number to increase the surface roughness of the cladding, which can increase the absorption rate of the laser and improve the uniformity and quality of the cladding layer.

[0041] Example 3

[0042] Referring to Figure 1 , Figure 2 , Figure 4 and Figure 5 shown, a preparation method for preparing a high-hardness and corrosion-resistant coating on the surface of a titanium-zirconium alloy includes the following steps:

[0043] To avoid the problems of cracking and poor performance of the titanium alloy coating prepared by laser cladding on the surface of the titanium-zirconium alloy, set S1. Put the elemental powders of Ti powder, Zr powder, Nb powder, and Mo powder into a planetary ball mill according to an equimolar ratio, set the ball milling parameters: rotation speed 220 r / min, ball-to-powder ratio 3:1, ball milling time 1.5 h, then start the ball mill for powder mixing. After the powder mixing is completed, take it out and put it into a vacuum drying oven, and adjust the temperature to 80 °C for vacuum drying and storage.

[0044] S2. First, cut the titanium-zirconium alloy substrate into 50×15×5 mm with a wire cutting machine, and polish it with 200-mesh silicon carbide sandpaper to remove the surface oxide and make the surface of the titanium-zirconium alloy substrate rough.

[0045] S3. Clean the surface of the roughened titanium-zirconium alloy substrate in step S1 with acetone to remove oil stains.

[0046] S4. Set the laser cladding parameters: power 1400 W, scanning speed 10 mm / s, overlapping rate 50%, spot diameter 2 mm, powder feeding rate 0.3 r / min. Start the laser cladding device to conduct the laser cladding experiment. Set the parameters of the vacuum tube furnace: heating-up time 115 min, holding temperature 660 °C, holding time 2.2 h.

[0047] As Figure 4 shown, the hardness of the laser cladding layer is 1.17 times that of the substrate, and the corrosion resistance is improved by 30% compared with the substrate. Due to the differences in thermophysical properties between the cladding material and the substrate, as well as the rapid solidification and cooling process of the molten pool, complex thermal stresses and phase transformation stresses will be generated in the cladding layer and its surrounding areas. Heat treatment can promote the release and redistribution of residual stresses inside the coating, and at the same time improve the microstructure and mechanical properties of the coating.

[0048] In the process of treating the cladding material and the workpiece in the present invention, the cladding material is subjected to ball milling and mixing treatment to make the elemental metal powders more uniformly mixed, so that the composition of the obtained laser cladding coating is also more uniform, achieving the purpose of reducing cracks in the cladding layer. In addition, the surface of the workpiece is polished with sandpaper of a coarse mesh number to increase the surface roughness of the cladding, which can increase the absorption rate of the laser and improve the uniformity and quality of the cladding layer.

[0049] Comparative Example 1

[0050] Refer to Figure 1 , Figure 2 and Figure 4 shown. The laser cladding power is set to 1000 W, and other process parameters are the same as those in Example 2. Specifically, it is a preparation method for preparing a high-hardness and corrosion-resistant coating on the surface of a titanium-zirconium alloy, including the following steps:

[0051] S1. Put the elemental powders of Ti powder, Zr powder, Nb powder, and Mo powder into a planetary ball mill according to an equimolar ratio. Set the ball milling parameters: rotation speed 180 r / min, ball-to-material ratio 4:1, ball milling time 3 h. Then start the ball mill for powder mixing. After the powder mixing is completed, take it out and put it into a vacuum drying oven, and adjust the temperature to 80 °C for vacuum drying and storage.

[0052] S2. First, cut the titanium-zirconium alloy substrate into 50×15×5 mm with a wire cutting machine, and polish it with 150-mesh silicon carbide sandpaper to remove the surface oxide and make the surface of the titanium-zirconium alloy substrate rough.

[0053] S3. Clean the surface of the roughened titanium-zirconium alloy substrate in step S1 with acetone to remove oil stains.

[0054] S4. Set the laser cladding parameters, with a power of 1000 W, a scanning speed of 10 mm / s, an overlapping rate of 50%, a spot diameter of 2 mm, and a powder feeding rate of 0.3 r / / min. Start the laser cladding device to conduct the laser cladding experiment. Set the parameters of the vacuum tube furnace, with a heating-up time of 110 min, a holding temperature of 655 °C, and a holding time of 2 h.

[0055] Comparative Example 2

[0056] Refer to Figure 1 、 Figure 2 and Figure 4 As shown, the laser cladding power is set to 1600 W, and other process parameters are the same as those in Example 2. Specifically, a preparation method for preparing a high-hardness and corrosion-resistant coating on the surface of a titanium-zirconium alloy includes the following steps:

[0057] S1. Put the elemental powders of Ti powder, Zr powder, Nb powder, and Mo powder into a planetary ball mill according to an equimolar ratio. Set the ball milling parameters: a rotation speed of 180 r / min, a ball-to-powder ratio of 4:1, and a ball milling time of 3 h. Then start the ball mill for powder mixing. After the powder mixing is completed, take it out and put it into a vacuum drying oven, and adjust the temperature to 80 °C for vacuum drying and preservation.

[0058] S2. First, use a wire cutting machine to cut the titanium-zirconium alloy substrate into 50×15×5 mm, and polish it with 150-mesh silicon carbide sandpaper to remove the surface oxide and make the surface of the titanium-zirconium alloy substrate rough.

[0059] S3. Clean the surface of the roughened titanium-zirconium alloy substrate in step S1 with acetone to remove oil stains.

[0060] S4. Set the laser cladding parameters, with a power of 1600 W, a scanning speed of 10 mm / s, an overlapping rate of 50%, a spot diameter of 2 mm, and a powder feeding rate of 0.3 r / / min. Start the laser cladding device to conduct the laser cladding experiment. Set the parameters of the vacuum tube furnace, with a heating-up time of 100 min, a holding temperature of 650 °C, and a holding time of 2 h.

[0061] As mentioned above, the above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy, characterized in that: Including Ti powder, Zr powder, Nb powder and Mo powder.

2. The high-hardness, corrosion-resistant laser cladding coating on the surface of titanium-zirconium alloy according to claim 1 is characterized in that: The Ti powder, Zr powder, Nb powder and Mo powder are single substance powders in an equal molar ratio.

3. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on a titanium-zirconium alloy surface according to claim 1, characterized in that: The method comprises the steps of: mixing cladding materials; putting Ti powder, Zr powder, Nb powder and Mo powder into a planetary ball mill in an equal molar ratio, and then starting the ball mill to mix the powders; after the mixing is completed, taking out the powders and putting them into a vacuum drying oven for vacuum drying and storage; Step 2: Pretreatment of workpiece: Before cladding, the workpiece surface is pretreated in the order of rough grinding, cleaning, rinsing and scrubbing; Step 3: Laser cladding: Place the workpiece in a protective container, open the top of the container, place a titanium-zirconium alloy substrate at the bottom of the container, then introduce argon gas into the container to remove the air in the container, then place the titanium alloy powder into the powder barrel of the laser cladding machine, and turn on the workbench of the laser cladding machine; Step 4: Heat treatment of the coating: Place the prepared coating in a vacuum tube furnace, evacuate the furnace, start the tube furnace, heat-insulate, cool with the furnace, and take out the sample.

4. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy according to claim 3, characterized in that: The ball milling speed of the planetary ball mill is between 180 r / min and 220 r / min, the ball-to-material ratio is any one of 3:1 and 4:1, and the ball milling time is between 1.5 h and 3 h.

5. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on a titanium-zirconium alloy surface according to claim 3, characterized in that: The temperature of the vacuum drying oven is 80°C.

6. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on a titanium-zirconium alloy surface according to claim 3, characterized in that: In the step 2, silicon carbide sandpaper is used for rough grinding, followed by cleaning using an alcohol solution, followed by rinsing with deionized water, and finally scrubbing the workpiece surface with an acetone solution.

7. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on a titanium-zirconium alloy surface according to claim 3, characterized in that: In the step 3, the laser cladding power, scanning speed, and overlap rate parameters are pre-set before starting the laser cladding machine, and the laser cladding device is started to perform a laser cladding experiment; During the cladding process, argon gas needs to be continuously introduced for protection to obtain the cladding coating.

8. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy according to claim 7, characterized in that: In the step three, the laser cladding power of the laser cladding machine is set between 1000W and 1600W, the scanning speed is 10mm / s, the overlap rate is 50%, the spot diameter is 2mm, and the powder feeding rate is 0.3r / / min. After the settings are completed, the laser cladding machine is started to carry out the laser cladding experiment.

9. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on a titanium-zirconium alloy surface according to claim 3, characterized in that: In the step 4, the vacuum tube furnace is started, a vacuum treatment is required, argon gas is introduced, and the parameters of heating time, insulation temperature and insulation time are set.

10. The method for preparing a high-hardness, corrosion-resistant laser cladding coating on the surface of a titanium-zirconium alloy according to claim 9, characterized in that: In the step 4, the heating time is between 100 min and 136 min, the insulation temperature is between 650° C. and 700° C., and the insulation time is between 2 h and 3 h.

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