Composition and method for removing lubricating coating on surface of titanium alloy component

Abstract

The invention discloses a composition for removing a lubricating coating on the surface of a titanium alloy component and a removing method. The composition comprises a first component and a second component in a molten state, wherein the first component comprises one or more of sodium hydroxide powder solids and potassium hydroxide powder solids; and the second component comprises one or more of sodium nitrate and potassium nitrate powdery solids. When the lubricating coating on the surface of the titanium alloy is removed, the titanium alloy only needs to be soaked in molten liquid for a short time and then subjected to rapid nitric acid brightening treatment, the time of the whole process is controlled to be 15-20 minutes, the method has the advantages of being efficient and rapid in reaction, the raw material concentration does not need to be maintained in an adding mode, and the reaction cost and the treatment process of the process are saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium alloy processing, and particularly relates to a composition and method for removing lubricating coating on the surface of a titanium alloy component. BACKGROUND

[0002] In the aerospace industry, bolt fasteners are the largest batch of parts in modern aerospace and aviation structures. In recent years, the demand for fastener products made of high-strength titanium alloy has also rapidly increased in the aviation industry.

[0003] Titanium alloy is a high-melting-point light metal material, which is a new type of metal material. Compared with other materials, it has very high specific strength and can maintain a high strength level while reducing weight. Therefore, it has been widely used in the field of aviation fasteners, fully utilizing its advantages of high strength, high density and light weight.

[0004] The production of titanium alloy bolts includes hot upsetting, reducing, heat treatment, thread rolling, punching, turning, fine grinding and coating. The titanium alloy wire used for hot upsetting is usually covered with a layer of molybdenum disulfide coating, which makes the base material have excellent lubricating properties, greatly reduces the cracking problem during the hot upsetting process, improves the service life of the die, and increases the consistency and stability of the product size. At the same time, the part will be subjected to high temperature during hot upsetting, and molybdenum disulfide as a coating can reduce local burns and overheating caused by contact heating, so that the hot upsetting process does not affect the mechanical properties of the bolt.

[0005] However, the disadvantage of the molybdenum disulfide coating is that if it is not completely removed during the subsequent solid solution heat treatment, it will cause a contamination layer on the surface of the bolt at high temperature, resulting in local oxidation and corrosion, and significantly reducing the mechanical properties of the bolt.

[0006] Currently, the method for removing the molybdenum disulfide coating generally involves first soaking in an alkaline solution and then using sand blasting to remove the coating. However, this process has many disadvantages: (1) low reliability, the alkaline solution can only loosen the coating, and the sand blasting process has limited ability to remove the coating. After heat treatment, there will still be a 10-20 mu m contamination layer on the surface, affecting the strength and service life of the titanium alloy bolt. (2) The surface roughness after sand blasting is low, which will affect the effect of subsequent coating surface treatment and reduce the adhesion, salt spray performance, etc. of the final titanium aluminum coating. (3) During the sand blasting process, the size of the part will change, affecting the dimensional accuracy of the product. (4) Sand blasting can cause scratches between parts, which may result in scrap. (5) The coating removal time is relatively long, generally more than 1 hour, the processing time is long, and the efficiency is low.

[0007] Therefore, a composition and method for removing lubricating coating on the surface of a titanium alloy component are needed to overcome the above-mentioned defects. SUMMARY

[0008] The present application provides a composition and a method for removing a lubricating coating on a titanium alloy component.

[0009] The technical scheme of the present application is as follows.

[0010] A composition for removing a lubricating coating on a titanium alloy component comprises:

[0011] The first component and the second component are in a molten state.

[0012] The first component comprises one or more of sodium hydroxide and potassium hydroxide in a powder form.

[0013] The second component comprises one or more of sodium nitrate and potassium nitrate in a powder form.

[0014] In one embodiment, the first component is sodium hydroxide, the second component is sodium nitrate, and the weight ratio of the sodium hydroxide to the sodium nitrate is (10-20):(80-90).

[0015] In one embodiment, the first component is potassium hydroxide, the second component is potassium nitrate, and the weight ratio of the potassium hydroxide to the potassium nitrate is (10-20):(80-90).

[0016] In one embodiment, the composition further comprises molten potassium permanganate.

[0017] In one embodiment, the first component is sodium hydroxide, the second component is sodium nitrate, and the weight ratio of the sodium hydroxide, the sodium nitrate, and the potassium permanganate is 10:(85-88):(2-5).

[0018] In one embodiment, the first component is potassium hydroxide, the second component is potassium nitrate, and the weight ratio of the potassium hydroxide, the potassium nitrate, and the potassium permanganate is 10:88:2.

[0019] A method for removing a lubricating coating on a titanium alloy component comprises the following steps:

[0020] The first component and the second component are mixed in a tank and heated to a molten state at a temperature of 380 degrees Celsius.

[0021] The titanium alloy component is immersed in the molten composition for 2 minutes.

[0022] The titanium alloy component is removed and immersed in a 30% nitric acid solution for 5 minutes.

[0023] The titanium alloy component is drained and dried.

[0024] In one embodiment, mixing the first and second components into the tank further comprises:

[0025] Mixing potassium permanganate into the mixture of the first and second components.

[0026] Compared with the prior art, the present application has at least the following advantages:

[0027] The present application has the advantage of rapid processing time. When removing the lubricating coating on the surface of the titanium alloy, only a short time of immersion in the molten liquid is required, followed by rapid nitric acid brightening treatment. The entire process time is controlled within 15-20 minutes, which is highly efficient and rapid in reaction. Moreover, the raw material concentration does not need to be maintained by adding, thereby saving the reaction cost and processing flow of the process. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flow chart of the removal method according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings; however, these embodiments are not the only ones that can be implemented by the present application, and thus should not be construed as the only embodiments. Rather, these embodiments are described herein in order to fully convey the scope of the present application to those skilled in the art, and the example embodiments can be implemented in a variety of forms. Identical components are denoted by identical reference numerals throughout the drawings, and thus repetitive descriptions will be omitted.

[0030] The expressions of position and direction described in the present application are described with reference to the drawings, but can be changed as needed, and the changes are included in the scope of the present application.

[0031] Referring to Figure 1 , the present application provides a composition for removing a lubricating coating on the surface of a titanium alloy member, including: a first component and a second component in a molten state; the first component includes one or more of sodium hydroxide and potassium hydroxide in a powder solid state, and the second component includes one or more of sodium nitrate and potassium nitrate in a powder solid state. The first component can include sodium hydroxide or potassium hydroxide, and the second component can include sodium nitrate and potassium nitrate, wherein the first component and the second component are both liquids in a molten state after being heated at a high temperature. According to experimental tests, the first component includes potassium hydroxide, for example, with a molybdenum disulfide coating on the surface of a titanium alloy member.

[0032] The following reactions will occur when working:

[0033] MoS2+KOH→K2MoO4↓+H2S↑

[0034] The molten potassium hydroxide and the molybdenum disulfide coating react to produce potassium molybdate and hydrogen sulfide gas, the hydrogen sulfide gas is collected and treated through the exhaust tower, the melting point of potassium molybdate is 919 DEG C, which is much higher than the temperature of the molten liquid, meanwhile, the density of potassium molybdate is greater than the density of the molten liquid, after the molybdenum disulfide coating is stripped, the formed potassium molybdate will be precipitated in the form of precipitate to the bottom of the tank, during the whole reaction process, the concentration of the molten liquid will not change, and the nitric acid does not participate in the reaction, only for brightening, the concentration will not change, the whole process can be maintained for long-term stable operation, only needs to be supplemented regularly after the liquid level of the tank liquid is lowered, greatly reduces the labor intensity of workers, and the concentration of the molten solution will not be reduced, and the reaction rate will not have a large linear change. The first component and the second component in the molten state can fully remove the coating and do not damage the quality of the titanium alloy surface.

[0035] Preferably, the first component is sodium hydroxide, the second component is sodium nitrate, and the weight ratio of the sodium hydroxide and the sodium nitrate is (10-20):(80-90). Through experimental tests, the combination of the components of sodium hydroxide and sodium nitrate is good for removing the molybdenum disulfide coating on the surface of the titanium alloy, and the surface of the product after film removal is gray.

[0036] Preferably, the first component is potassium hydroxide, the second component is potassium nitrate, and the weight ratio of the potassium hydroxide and the potassium nitrate is (10-20):(80-90). Through experimental tests, the combination of the components of sodium hydroxide and sodium nitrate is good for removing the molybdenum disulfide coating on the surface of the titanium alloy, and the surface of the product after film removal has a blue-green oxide skin.

[0037] Preferably, the first component is potassium hydroxide, the second component is potassium nitrate, and the weight ratio of the potassium hydroxide and the potassium nitrate is (10-20):(80-90). Through experimental tests, the combination of the components of sodium hydroxide and sodium nitrate is good for removing the molybdenum disulfide coating on the surface of the titanium alloy, and the surface of the product after film removal has a blue-green oxide skin.

[0038] Preferably, the first component is sodium hydroxide, the second component is sodium nitrate, and the weight ratio of the sodium hydroxide, the sodium nitrate and the potassium permanganate is 10:(85-88):(2-5). Through experimental tests, the molten solution in this range can fully remove the molybdenum disulfide coating and the oxide layer on the surface of the titanium alloy component, and the surface of the product has good smoothness.

[0039] Preferably, the first component is potassium hydroxide, the second component is potassium nitrate, and the weight ratio of the potassium hydroxide, the potassium nitrate and the potassium permanganate is 10:88:2. Through experimental tests, the molten solution in this range can fully remove the molybdenum disulfide coating and the oxide layer on the surface of the titanium alloy component, and the surface of the product has good smoothness.

[0040] The second aspect of the present application provides a removal method for removing the lubricating coating on the surface of a titanium alloy component, using the composition described above, comprising the steps of:

[0041] The first and second components are mixed in a tank and heated to a molten state at a temperature of 380 degrees Celsius. The first and second components are mixed and added to the heated tank, and the temperature is raised to 380 degrees Celsius, at which point the metal powder melts into a molten state.

[0042] The titanium alloy component is immersed in the molten composition for 2 minutes. The titanium alloy component is immersed in the molten solution by lifting equipment, and the immersion treatment is 2 minutes.

[0043] The titanium alloy component is removed and placed in a 30% nitric acid solution for 5 minutes. After the reaction, the titanium metal component is removed and then immersed in a 30% nitric acid solution for 5 minutes to remove the surface layer.

[0044] The titanium alloy component is drained and dried.

[0045] In one embodiment, mixing the first and second components in the tank further comprises:

[0046] Potassium permanganate is mixed into the mixture of the first and second components. The potassium permanganate acts as a catalyst, and experiments have shown that the molten solution with the potassium permanganate accelerates the reaction rate of removing the lubricating coating.

[0047] Example 1;

[0048] A Ti6Al4V titanium alloy is selected, model AL331AG-8-10BK4, and is hot upset formed using a titanium alloy wire. The wire and the product surface have a blackish gray greasy molybdenum disulfide lubricating coating. According to the mass fraction of sodium hydroxide and sodium nitrate powder at 10%:90%, the mixture is heated and melted at 380°C in a tank. Then the titanium alloy bolt to be removed is placed in a stainless steel frame, and the frame is immersed in the molten alkali solution using a crane, with an immersion time of 2 minutes. After draining, it is placed in a water tank for rinsing. After rinsing, the titanium alloy bolt is placed in a 30% nitric acid solution for 5 minutes, drained, and placed in a water tank for rinsing and drying.

[0049] Example 2:

[0050] Select a Ti6Al4V titanium alloy, model AL331AG-8-10BK4, using titanium alloy fine wire hot upsetting forming, wire and product surface has a layer of blackish gray greasy molybdenum disulfide lubricating coating, according to the mass fraction of 20%:80% of sodium hydroxide, sodium nitrate powder, use 380℃ heating melting in the tank. Then the titanium alloy bolt to be removed into the stainless steel frame, the crane into the molten alkali solution, soaking time is 2 min, after draining into the water tank. After rinsing the titanium alloy bolt into 30% nitric acid solution for 5 minutes, after draining into the water tank, and drying.

[0051] Example 3:

[0052] Select a Ti6Al4V titanium alloy, model AL331AG-8-10BK4, using titanium alloy fine wire hot upsetting forming, wire and product surface has a layer of blackish gray greasy molybdenum disulfide lubricating coating, according to the mass fraction of 20%:80% of sodium hydroxide, sodium nitrate powder, use 380℃ heating melting in the tank. Then the titanium alloy bolt to be removed into the stainless steel frame, the crane into the molten alkali solution, soaking time is 2 min, after draining into the water tank. After rinsing the titanium alloy bolt into 30% nitric acid solution for 5 minutes, after draining into the water tank, and drying.

[0053] Example 4:

[0054] Select a Ti6Al4V titanium alloy, model AL331AG-8-10BK4, using titanium alloy fine wire hot upsetting forming, wire and product surface has a layer of blackish gray greasy molybdenum disulfide lubricating coating, according to the mass fraction of 20%:80% of sodium hydroxide, sodium nitrate powder, use 380℃ heating melting in the tank. Then the titanium alloy bolt to be removed into the stainless steel frame, the crane into the molten alkali solution, soaking time is 2 min, after draining into the water tank. After rinsing the titanium alloy bolt into 30% nitric acid solution for 5 minutes, after draining into the water tank, and drying.

[0055] Example 5

[0056] A Ti6Al4V titanium alloy was selected, model AL331AG-8-10BK4, hot upsetting forming was used for titanium alloy fine wire, the wire and the product surface had a layer of blackish gray greasy molybdenum disulfide lubricating coating, according to the mass fraction of sodium hydroxide, sodium nitrate, potassium permanganate powder was 10%:88%:2%, heated and melted in the tank at 380°C. Then the titanium alloy bolt to be removed from the membrane was put into a stainless steel material frame, the material frame was immersed into the molten alkali solution by the crane, the soaking time was 2 min, and then it was put into a water tank for rinsing after draining. After rinsing, the titanium alloy bolt was immersed in a 30% nitric acid solution for 5 minutes, then it was put into a water tank for rinsing after draining, and then it was dried.

[0057] Example 6:

[0058] A Ti6Al4V titanium alloy was selected, model AL331AG-8-10BK4, hot upsetting forming was used for titanium alloy fine wire, the wire and the product surface had a layer of blackish gray greasy molybdenum disulfide lubricating coating, according to the mass fraction of sodium hydroxide, sodium nitrate, potassium permanganate powder was 10%:88%:2%, heated and melted in the tank at 380°C. Then the titanium alloy bolt to be removed from the membrane was put into a stainless steel material frame, the material frame was immersed into the molten alkali solution by the crane, the soaking time was 2 min, and then it was put into a water tank for rinsing after draining. After rinsing, the titanium alloy bolt was immersed in a 30% nitric acid solution for 5 minutes, then it was put into a water tank for rinsing after draining, and then it was dried.

[0059] Example 7:

[0060] A Ti6Al4V titanium alloy was selected, model AL331AG-8-10BK4, hot upsetting forming was used for titanium alloy fine wire, the wire and the product surface had a layer of blackish gray greasy molybdenum disulfide lubricating coating, according to the mass fraction of sodium hydroxide, sodium nitrate, potassium permanganate powder was 10%:88%:2%, heated and melted in the tank at 380°C. Then the titanium alloy bolt to be removed from the membrane was put into a stainless steel material frame, the material frame was immersed into the molten alkali solution by the crane, the soaking time was 2 min, and then it was put into a water tank for rinsing after draining. After rinsing, the titanium alloy bolt was immersed in a 30% nitric acid solution for 5 minutes, then it was put into a water tank for rinsing after draining, and then it was dried.

[0061] Appearance observation results:

[0062]

[0063]

[0064] Comparative example:

[0065] Comparative example 1:

[0066] The difference from Example 1 is that the alkali solution soaking time is 5 minutes.

[0067] Comparative Example 2:

[0068] The difference from Example 2 is that the nitric acid soaking time is 10 minutes.

[0069] Comparative Example 3:

[0070] The difference from Example 4 is that the alkali solution soaking time is 5 minutes.

[0071] Comparative Example 4:

[0072] The difference from Example 4 is that the nitric acid soaking time is 10 minutes.

[0073] Comparative Example 5:

[0074] The difference from Example 1 is that the nitric acid concentration is 40%.

[0075] Comparative Example 6:

[0076] The difference from Example 4 is that the molten alkali solution temperature is 400°C.

[0077] Comparative Example 7:

[0078] The difference from Example 4 is that the molten alkali solution temperature is 420°C.

[0079] Comparative Example 8:

[0080] The difference from Example 7 is that the molten alkali solution temperature is 400°C.

[0081] Comparative Example 9:

[0082] The difference from Example 7 is that the nitric acid concentration is 40%.

[0083] Comparative Example 10:

[0084] The traditional sodium hydroxide solution soaking + sand blasting process is used to remove the molybdenum disulfide coating.

[0085] The titanium alloy bolt products after pickling in Examples 1-7 and Comparative Examples 1-10 are tested for pollution layer thickness, double shear test, and adhesion test after coating, and the test standards and test results are shown below:

[0086] 1. Pollution layer test:

[0087] The product is cut in half, inlaid, polished, and etched with a 10% nitric acid, 2% hydrofluoric acid, and 88% water solution for 10-30 seconds, and then the edge of the sample is observed under a light microscope at 200 times. The pure white structure is the pollution layer, and the base material can be seen as grains. The test data are shown in Table 1 below:

[0088] Table 1. Corrosion Contamination Layer Test Results

[0089] Example Thickness (pm) Comparative Example Thickness (pm) Example 1 25 pm Comparative Example 1 23 pm Example 2 38 pm Comparative Example 2 33 pm Example 3 34 pm Comparative Example 3 0 pm Example 4 5 pm Comparative Example 4 6 pm Example 5 10 pm Comparative Example 5 20 pm Example 6 0 pm Comparative Example 6 0 pm Example 7 0 pm Comparative Example 7 0 pm Comparative Example 8 0 pm Comparative Example 9 0 pm Comparative Example 10 18 pm Comparative Example 11 0 pm

[0090] From the test data in Table 2, it can be seen that the products of Example 6, Example 7, Comparative Example 3, Comparative Example 6, Comparative Example 7, Comparative Example 8, Comparative Example 9 after heat treatment have no oxidation layer on the surface, Examples 1, 2, 3, Comparative Example 1, Comparative Example 2, Comparative Example 5 have a relatively thick contamination layer, Examples 4, 5, Comparative Example 6, Comparative Example 10 have no obvious contamination layer visible to the naked eye, but there is a slight contamination layer under a microscope.

[0091] 2. Double shear test (mechanical properties):

[0092] Test method: NASM 1312-13 "Fastener Test Methods - Double Shear", ASTM E4 "Standard Specification for Load Verification of Testing Equipment", using INSTRON 3369 tensile testing machine, serial number Q3836;

[0093] The test method is to place the sample in the test fixture, the shear test is carried out in the rod diameter area of the fastener, the double shear force test load is pressurized at a speed of 100,000 psi per minute (100,000 psi), the lb / min load is maintained at 100,000 psi / min, after the product deforms, the program will automatically stop the load force and stop the test, and the corresponding shear force is calculated, the test results are shown below:

[0094] Table 2. Double shear test results

[0095]

[0096]

[0097] From Table 2 above, it can be seen that the surface contamination layer will cause the shear strength of the product to decrease.

[0098] 3. Adhesion test:

[0099] The final product is coated with an Everlube coating solution, tested according to ASTM D 1654, and tested with tape or equivalent tool. The tape is pressed down onto the bolt shank to ensure continuous contact of the tape with the coating. The bonded bolt is separated using a universal testing machine with self-aligning device. The test uses a loading rate of 20 psi / s until the failure load is determined by separating the head connection.

[0100] Table 3. Coating adhesion

[0101]

[0102] It can be seen from the data in Table 3 that the products of Example 6, Example 7, Comparative Example 3, Comparative Example 6, Comparative Example 7, Comparative Example 8, Comparative Example 9 have relatively large adhesion after coating and relatively thick pollution layer, and the adhesion will decrease after coating. The product of Comparative Example 10 uses traditional film stripping process, and the adhesion is relatively low compared with other examples.

[0103] In summary, the composition of the present application can significantly remove the molybdenum disulfide coating on the surface of titanium alloy, and can greatly ensure the metal strength of the titanium alloy component.

[0104] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application without departing from the principles and purposes of the present application, and all these changes should be within the protection scope of the claims of the present application.

Claims

1. A composition for removing a surface lubricating coating from a titanium alloy component, characterized in that, Comprising: a first component and a second component in a molten state; the first component comprising one or more of sodium hydroxide, potassium hydroxide in a powdered solid form; the second component comprising one or more of sodium nitrate and potassium nitrate in a powdered solid form.

2. The composition of claim 1, wherein, the first component is sodium hydroxide and the second component is sodium nitrate, the weight ratio of sodium hydroxide to sodium nitrate being (10-20):(80-90).

3. The composition of claim 1, wherein, the first component is potassium hydroxide and the second component is potassium nitrate, the weight ratio of potassium hydroxide to potassium nitrate being (10-20):(80-90).

4. The composition of claim 1, wherein, further comprising potassium permanganate in a molten state.

5. The composition of claim 4, wherein, the first component is sodium hydroxide and the second component is sodium nitrate, the weight ratio of sodium hydroxide to sodium nitrate to potassium permanganate being 10:(85-88):(2-5).

6. The composition of claim 4, wherein, the first component is potassium hydroxide and the second component is potassium nitrate, the weight ratio of potassium hydroxide to potassium nitrate to potassium permanganate being 10:88:

2.

7. A removal method for removing a lubricating coating on the surface of a titanium alloy member, characterized by, using the composition of claim 1, comprising the steps of: mixing the configured first component and second component into a vat and heating to a molten state at a temperature of 380 degrees Celsius; immersing a titanium alloy component into the molten composition for 2 minutes; removing the titanium alloy component and placing it into a 30% nitric acid solution for 5 minutes; draining the titanium alloy component and drying.

8. The method of claim 7, wherein, mixing the configured first component and second component into a vat further comprises: mixing potassium permanganate into the mixture of the first component and second component.

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