A method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys

Abstract

The present invention belongs to the field of metal surface treatment technology and relates to a method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys. The present invention provides a method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys, comprising: ball-milling Al2O3 powder, Y2O3 powder, TiC powder, CeO2 powder, and Si powder, followed by drying to obtain a penetrant; polishing a substrate to remove a surface oxide layer, followed by heat preservation treatment to obtain a stabilized coating; the active ingredients in the penetrant are, by mass percentage, 10-30% Al2O3 powder, 1-3% Y2O3 powder, 4-8% TiC powder, 0.8-2% CeO2 powder, and the remainder Si powder; the substrate is pure molybdenum or a molybdenum alloy. The present invention is intended to address the technical problem that anti-oxidation coatings on molybdenum and molybdenum alloys are prone to cracking and falling off under thermal shock.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment and relates to a method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys. Background Art

[0002] Refractory metals are characterized by high melting points, good processability, and excellent corrosion resistance and mechanical properties. Molybdenum, among others, exhibits excellent thermal conductivity, low thermal deformation, and good mechanical properties even at 1500°C, making it considered one of the most promising structural materials. However, molybdenum readily forms volatile MoO₃ at around 600°C. As the temperature rises, the volatilization rate of MoO₃ increases, causing a decrease in mechanical properties at high temperatures, which limits the use of molybdenum and its alloys at these temperatures. Currently, there are two main methods for improving the oxidation resistance of molybdenum and its alloys: alloying and anti-oxidation coatings. Alloying with antioxidant elements can enhance the mechanical properties of the material. At high temperatures, an oxide film forms on the surface of the molybdenum alloy, which inhibits oxygen from entering the substrate and thus improves oxidation resistance. However, high alloying element content can reduce the material's processability. Coating the alloy surface is a highly effective method that can significantly improve the alloy's oxidation resistance without altering its mechanical properties. However, the coating design must carefully consider the adhesion between the coating and the substrate to ensure that the coating does not peel or crack at high temperatures.

[0003] Mo-Si binary alloy can generate SiO2 at high temperature, and the higher the Si content, the lower the oxidation rate of the alloy. Low content of Al and Si affects the oxidation resistance of Mo alloy at high temperature. It was found that after adding Al element, a thinner oxide layer of Al2O3 appeared on the surface of the alloy. The addition of Si element is conducive to the increase of the thickness of the oxide film, but it still cannot change the phenomenon of weight loss. The cost of aluminide coating is low and the process is relatively simple. Aluminide coating has little degradation of the mechanical properties of the substrate and good oxidation resistance, but when subjected to thermal shock, the coating is easy to fall off and crack from the substrate, thus affecting the use of the alloy. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problem that the anti-oxidation coating on the surface of molybdenum and molybdenum alloys is prone to cracking and falling off under thermal shock, resulting in coating failure.

[0005] To this end, the present invention provides a method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys to address this need in the art.

[0006] In one aspect, the present invention relates to a method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys, comprising: ball-milling Al2O3 powder, Y2O3 powder, TiC powder, CeO2 powder and Si powder and then drying them to obtain a penetrant;

[0007] The substrate is polished to remove the surface oxide layer and then subjected to heat preservation treatment to obtain a stabilized coating;

[0008] In terms of mass percentage, the effective ingredients in the penetrant are composed of 10-30% Al2O3 powder, 1-3% Y2O3 powder, 4-8% TiC powder, 0.8-2% CeO2 powder and the balance Si powder;

[0009] The substrate is pure molybdenum or a molybdenum alloy.

[0010] Furthermore, in the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention, the heat preservation treatment is to keep the temperature at 1100-1300° C. for 20-25 hours in an inert gas atmosphere.

[0011] Furthermore, in the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention, the inert gas is nitrogen or argon.

[0012] Furthermore, in the preparation method of the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention, the heat preservation treatment is to first keep the temperature at 1150~1250℃ for 10~15h in a nitrogen atmosphere, then keep the temperature at 1550~1650℃ for 2~5h, and finally keep the temperature at 600~800℃ for 20~30h.

[0013] Furthermore, in the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention, the penetrant further comprises a penetration enhancer;

[0014] In terms of mass percentage, the effective ingredients in the penetrant are composed of 10-30% Al2O3 powder, 1-3% Y2O3 powder, 4-8% TiC powder, 0.8-2% CeO2 powder, 1-5% of the penetration enhancer and the balance Si powder.

[0015] Furthermore, in the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention, the penetration enhancer is NaF.

[0016] Furthermore, in the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention, the ball milling rate is 100 to 300 r / min, and the ball milling time is 1 hour to 3 hours.

[0017] Furthermore, in the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention, the ball-to-material ratio of the ball milling is 5~10:1.

[0018] On the other hand, the present invention relates to molybdenum and molybdenum alloys with an anti-oxidation coating, which are prepared by the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloys.

[0019] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0020] The present invention provides a method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys, which forms a dense anti-oxidation coating by chemically reacting a specific ratio of penetrant with a molybdenum or molybdenum alloy substrate in an inert gas atmosphere. At the same time, combined with the use of substrate pretreatment and a penetration promoter, the bonding force between the coating and the substrate is enhanced, and the formation speed and uniformity of the coating are improved. First, it significantly improves the anti-oxidation performance of molybdenum and molybdenum alloys at high temperatures, extending the service life of the material; secondly, through a specific penetrant formula and heat preservation treatment conditions, a good bonding force is formed between the coating and the substrate, and it is not easy to crack and fall off even under thermal shock, solving the problem that traditional anti-oxidation coatings are easy to crack and fall off; in addition, the method significantly improves its anti-oxidation performance without changing the mechanical properties of the molybdenum and molybdenum alloy substrates. The method has a wide range of applications and is not only applicable to pure molybdenum substrates, but also to a variety of molybdenum alloy substrates. Special processes such as segmented heat preservation treatment help to form a more stable and uniform coating structure, improving the stability of the material at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is the surface morphology of the coating of the sample provided in Example 1 after the oxidation resistance test under thermal shock is completed.

[0023] Figure 2 The surface morphology of the coating of the sample provided in Comparative Example 1 after the oxidation resistance test under thermal shock is completed.

[0024] Figure 3 The surface morphology of the coating of the sample provided in Comparative Example 2 after the oxidation resistance test under thermal shock is completed.

[0025] Figure 4 The surface morphology of the coating of the sample provided in Comparative Example 3 after the oxidation resistance test under thermal shock is completed. DETAILED DESCRIPTION

[0026] The technical solutions of the present invention are described below with reference to the following examples. However, the present invention is not limited to the following examples. The experimental methods and detection methods described in each example are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified. The percentages in the following examples are percentages by mass unless otherwise specified. The ratios in the following examples are ratios by mass unless otherwise specified.

[0027] In the following examples, the purity of each powder raw material used was not less than 99.8%.

[0028] Example 1

[0029] This embodiment provides a process for preparing an anti-oxidation coating on a pure molybdenum surface by embedding infiltration.

[0030] A pure molybdenum substrate was wire-cut on a metallographic grinding and polishing machine into a 50 mm × 50 mm × 3 mm metal plate. The surface oxide layer was then removed by polishing with 240-, 400-, 600-, 1000-, and 2000-mesh silicon carbide sandpaper. The sample was then cleaned in an ultrasonic cleaner using acetone, ethanol, and deionized water for 15 minutes each, three times. Finally, the sample was dried in a vacuum oven to obtain the sample.

[0031] The mixture, calculated by mass percentage, consisted of 10% Al2O3 powder, 1% Y2O3 powder, 4% TiC powder, 0.8% CeO2 powder, 1% NaF, and the remainder Si powder. The mixture was wet-milled in a planetary ball mill using anhydrous ethanol at a ball-to-material ratio of 8:1, a rotation speed of 150 r / min, and a milling time of 2 hours. Finally, the mixture was dried in a vacuum drying oven at 80°C for 8 hours to obtain the infiltrated material.

[0032] The sample was buried in the infiltration material and kept at 1200°C for 24 hours in nitrogen to obtain molybdenum with an oxidation-resistant coating.

[0033] Example 2

[0034] This embodiment provides a process for preparing an anti-oxidation coating on a pure molybdenum surface by embedding infiltration.

[0035] A pure molybdenum substrate was wire-cut on a metallographic grinding and polishing machine into a 50 mm × 50 mm × 3 mm metal plate. The surface oxide layer was then removed by polishing with 240-, 400-, 600-, 1000-, and 2000-mesh silicon carbide sandpaper. The sample was then cleaned in an ultrasonic cleaner using acetone, ethanol, and deionized water for 15 minutes each, three times. Finally, the sample was dried in a vacuum oven to obtain the sample.

[0036] The mixture, calculated by mass percentage, consisted of 20% Al2O3 powder, 2% Y2O3 powder, 6% TiC powder, 1.5% CeO2 powder, 3% NaF, and the balance Si powder. The mixture was wet-milled in a planetary ball mill using anhydrous ethanol at a ball-to-material ratio of 8:1, a rotation speed of 150 r / min, and a milling time of 2 hours. Finally, the mixture was dried in a vacuum drying oven at 80°C for 8 hours to obtain the infiltrated material.

[0037] The sample was buried in the infiltration material and kept at 1200°C for 24 hours in nitrogen to obtain molybdenum with an oxidation-resistant coating.

[0038] Example 3

[0039] This embodiment provides a process for preparing an anti-oxidation coating on a pure molybdenum surface by embedding infiltration.

[0040] A pure molybdenum substrate was wire-cut on a metallographic grinding and polishing machine into a 50 mm × 50 mm × 3 mm metal plate. The surface oxide layer was then removed by polishing with 240-, 400-, 600-, 1000-, and 2000-mesh silicon carbide sandpaper. The sample was then cleaned in an ultrasonic cleaner using acetone, ethanol, and deionized water for 15 minutes each, three times. Finally, the sample was dried in a vacuum oven to obtain the sample.

[0041] The mixture, calculated by mass percentage, consisted of 30% Al2O3 powder, 3% Y2O3 powder, 8% TiC powder, 2% CeO2 powder, 3% NaF, and the balance Si powder. The mixture was wet-milled in a planetary ball mill using anhydrous ethanol at a ball-to-material ratio of 8:1, a rotation speed of 150 r / min, and a milling time of 2 hours. Finally, the mixture was dried in a vacuum drying oven at 80°C for 8 hours to obtain the infiltrated material.

[0042] The sample was buried in the infiltration material and kept at 1200°C for 24 hours in nitrogen to obtain molybdenum with an oxidation-resistant coating.

[0043] Example 4

[0044] This embodiment provides a process for preparing an anti-oxidation coating on a pure molybdenum surface by embedding infiltration.

[0045] A pure molybdenum substrate was wire-cut on a metallographic grinding and polishing machine into a 50 mm × 50 mm × 3 mm metal plate. The surface oxide layer was then removed by polishing with 240-, 400-, 600-, 1000-, and 2000-mesh silicon carbide sandpaper. The sample was then cleaned in an ultrasonic cleaner using acetone, ethanol, and deionized water for 15 minutes each, three times. Finally, the sample was dried in a vacuum oven to obtain the sample.

[0046] The mixture, calculated by mass percentage, consisted of 20% Al2O3 powder, 2% Y2O3 powder, 6% TiC powder, 1.5% CeO2 powder, 3% NaF, and the balance Si powder. The mixture was wet-milled in a planetary ball mill using anhydrous ethanol at a ball-to-material ratio of 8:1, a rotation speed of 150 r / min, and a milling time of 2 hours. Finally, the mixture was dried in a vacuum drying oven at 80°C for 8 hours to obtain the infiltrated material.

[0047] The sample was buried in the infiltration material and kept at 1200°C for 12 hours, then at 1600°C for 4 hours, and finally at 700°C for 24 hours in nitrogen to obtain molybdenum with an oxidation-resistant coating.

[0048] Example 5

[0049] This embodiment provides a process for preparing an anti-oxidation coating on a molybdenum alloy surface by embedding infiltration.

[0050] The TZC alloy was wire-cut on a metallographic grinding and polishing machine into a 50 mm × 50 mm × 3 mm metal plate. The plate was then polished using 240-, 400-, 600-, 1000-, and 2000-mesh silicon carbide sandpaper to remove the surface oxide layer. The plate was then cleaned in an ultrasonic cleaner using acetone, ethanol, and deionized water for 15 minutes each, three times. Finally, the plate was dried in a vacuum oven to obtain the sample.

[0051] The mixture, calculated by mass percentage, consisted of 20% Al2O3 powder, 2% Y2O3 powder, 6% TiC powder, 1.5% CeO2 powder, 3% NaF, and the balance Si powder. The mixture was wet-milled in a planetary ball mill using anhydrous ethanol at a ball-to-material ratio of 5:1, a rotation speed of 100 r / min, and a milling time of 1 hour. Finally, the mixture was dried in a vacuum drying oven at 80°C for 8 hours to obtain the infiltrated material.

[0052] The sample was buried in the infiltration material and kept at 1200℃ in nitrogen for 24h to obtain a TZC alloy with an oxidation-resistant coating.

[0053] Example 6

[0054] This embodiment provides a process for preparing an anti-oxidation coating on a molybdenum alloy surface by embedding infiltration.

[0055] The TZM alloy was wire-cut on a metallographic grinding and polishing machine into a 50 mm × 50 mm × 3 mm metal plate. The plate was then polished using 240-, 400-, 600-, 1000-, and 2000-grit silicon carbide sandpaper to remove the surface oxide layer. The plate was then cleaned in an ultrasonic cleaner using acetone, ethanol, and deionized water for 15 minutes each, three times. The sample was then dried in a vacuum oven to obtain the final product.

[0056] The mixture, calculated by mass percentage, consisted of 20% Al2O3 powder, 2% Y2O3 powder, 6% TiC powder, 1.5% CeO2 powder, 3% NaF, and the balance Si powder. The mixture was wet-milled in a planetary ball mill using anhydrous ethanol at a ball-to-material ratio of 10:1, a rotation speed of 300 rpm, and a milling time of 3 hours. Finally, the mixture was dried in a vacuum drying oven at 80°C for 8 hours to obtain the infiltrated material.

[0057] The sample was buried in the infiltration material and kept at 1200℃ in argon for 24h to obtain a TZM alloy with an oxidation-resistant coating.

[0058] Comparative Example 1

[0059] This comparative example is intended to illustrate the effects of the various components in the infiltration material.

[0060] This comparative example is the same as Example 2, except that, when preparing the infiltration material, 20% Al2O3 powder, 2% Y2O3 powder, 6% TiC powder, 3% NaF and the balance Si powder are used for the mixing, calculated by mass percentage.

[0061] Comparative Example 2

[0062] This comparative example is intended to illustrate the effects of the various components in the infiltration material.

[0063] This comparative example is the same as Example 2, except that, when preparing the infiltration material, 20% Al2O3 powder, 2% Y2O3 powder, 6% Ti powder, 1.5% CeO2 powder, 3% NaF and the balance Si powder are used for the mixing, calculated by mass percentage.

[0064] Comparative Example 3

[0065] This comparative example is intended to illustrate the effect of the distribution ratio of each component in the infiltration material.

[0066] This comparative example is the same as Example 2, except that, when preparing the infiltration material, 20% Al2O3 powder, 2% Y2O3 powder, 6% TiC powder, 10% CeO2 powder, 3% NaF and the balance Si powder are used for the mixing, calculated by mass percentage.

[0067] The products prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to a coating adhesion test and an oxidation resistance test under thermal shock.

[0068] Coating adhesion test:

[0069] The coating-substrate bond strength was measured using acoustic emission technology on an automated coating adhesion tester (Lanzhou Zhongke Kaihua WS-2005). Acoustic emission testing is one of the primary detection methods used in automated coating adhesion testers. When the stylus scratches or peels off the coating, it emits a weak acoustic signal. The instrument captures this signal and monitors the bond strength between the coating and the substrate in real time. Acoustic emission testing technology has high sensitivity and can accurately determine the pressure at which the coating will peel or crack. The experiment was conducted in dynamic loading mode, with a loading rate of 30 N / min, a test load of 30 N, and a scratch length of 3 mm.

[0070] Antioxidant performance test under thermal shock:

[0071] Oxidation resistance under thermal shock was tested in a box furnace at 1200°C in air. After heating the box furnace to 1200°C, room temperature specimens were placed in the furnace. The specimens were exposed for 1, 2, 3, 4, 5, and 6 hours, respectively. The specimens were removed and naturally cooled to room temperature before being weighed. After 6 hours, the specimens, which had naturally cooled to room temperature, were placed back in the furnace. The mass change was measured every 2 hours. After oxidizing at 1200°C for 100 hours (the duration of the furnace oxidation), the coating adhesion was measured again.

[0072] The test results are shown in Table 1, where the antioxidant failure time is when the mass loss exceeds 5 mg / cm 2 The maximum mass loss is the mass loss measured when the antioxidant fails or the maximum mass loss during the oxidation process from 0 to 100 h.

[0073] Table 1 Test results

[0074]

[0075] As shown in Table 1, the bonding strength of the samples of Examples 1 to 6 before oxidation all showed relatively high values, ranging from 10.1N to 14.1N, respectively. Although the bonding strength decreased after oxidation, it still remained in the range of 8.4N to 13.4N, indicating a strong bonding strength between the coating and the substrate. In terms of oxidation resistance, the samples of all examples showed no oxidation resistance failure after a 100-hour thermal shock test at 1200°C, and the maximum mass loss was controlled at -3.5mg / cm 2 to -2.2 mg / cm 2The results show that these samples have excellent antioxidant properties. In contrast, the samples of Comparative Examples 1 to 3 show poor results in terms of coating adhesion and antioxidant properties. The sample of Comparative Example 1 has a bonding strength of 7.9N before oxidation, and the coating cracks after oxidation. The antioxidant failure time is only 44 hours, and the maximum mass loss reaches -8.7mg / cm 2 The sample of comparative example 2 has a bonding strength of 8.9N before oxidation. Although the bonding strength decreases slightly after oxidation, no clear indication of cracking is given. However, its antioxidant failure time is extended to 86 hours, and the maximum mass loss is -5.2mg / cm 2 , but still inferior to the performance of the embodiment. The bonding strength of the sample of comparative example 3 before oxidation was 8.6N, and the coating also cracked after oxidation. The anti-oxidation failure time was 94 hours, and the maximum mass loss was -6.9mg / cm 2 , although slightly better than Comparative Examples 1 and 2, it is still not comparable to the embodiment.

[0076] Figure 1 This is the surface morphology of the coating of the sample provided in Example 1 after the oxidation resistance test under thermal shock is completed. Figure 2 The surface morphology of the coating of the sample provided in Comparative Example 1 after the oxidation resistance test under thermal shock is completed. Figure 3 The surface morphology of the coating of the sample provided in Comparative Example 2 after the oxidation resistance test under thermal shock is completed. Figure 4 The surface morphology of the coating of the sample provided in Comparative Example 3 after the oxidation resistance test under thermal shock is completed. Figure 1 It can be seen that the coating provided by the present invention is still dense after the oxidation resistance test under thermal shock, with very few irregular pores and almost no microcracks. Figures 2 to 4 It can be seen that the lack of any component or improper ratio will result in the formation of narrow and long pores in the coating after the anti-oxidation performance test under thermal shock due to the inability to withstand the release of thermal stress. As can be seen from the above figure, the preparation method of the anti-oxidation coating on the surface of molybdenum and molybdenum alloys provided by the present invention has a good solution to the technical problem that the anti-oxidation coating on the surface of molybdenum and molybdenum alloys is prone to cracking and falling off under thermal shock ( Figure 1 ), and the lack of any component or improper proportion will cause cracking problems ( Figure 2 、 Figure 3 and Figure 4 In summary, Examples 1 to 6 successfully prepared molybdenum and molybdenum alloy samples with excellent oxidation resistance and coating adhesion through specific penetrant components, while Comparative Examples 1 to 3 exhibited significant degradation in coating performance and cracking under thermal shock due to improper penetrant components or ratios.

[0077] As described above, the basic principles, main features and advantages of the present invention are well described. The above embodiments and descriptions are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the scope of protection determined by the present invention.

Claims

1. A method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys, characterized in that: include: Al2O3 powder, Y2O3 powder, TiC powder, CeO2 powder and Si powder are ball-milled and then dried to obtain a penetrant; The substrate is polished to remove the surface oxide layer, and then buried in the penetrant and subjected to heat preservation treatment to obtain a stabilized coating; In terms of mass percentage, the effective ingredients in the penetrant are composed of 10-30% Al2O3 powder, 1-3% Y2O3 powder, 4-8% TiC powder, 0.8-2% CeO2 powder and the balance Si powder; The substrate is pure molybdenum or a molybdenum alloy; The heat preservation treatment is carried out in a nitrogen atmosphere, first at 1150-1250° C. for 10-15 hours, then at 1550-1650° C. for 2-5 hours, and finally at 600-800° C. for 20-30 hours.

2. The method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys according to claim 1, wherein: The penetrant further comprises a penetration enhancer; In terms of mass percentage, the effective ingredients in the penetrant are composed of 10-30% Al2O3 powder, 1-3% Y2O3 powder, 4-8% TiC powder, 0.8-2% CeO2 powder, 1-5% of the penetration enhancer and the balance Si powder.

3. The method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys according to claim 2, wherein: The penetration enhancer is NaF.

4. The method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys according to claim 1, wherein: The ball milling speed is 100-300 r / min, and the ball milling time is 1 h-3 h.

5. The method for preparing an anti-oxidation coating on the surface of molybdenum and molybdenum alloys according to claim 4, wherein: The ball-to-material ratio of the ball mill is 5-10:

1.

6. Molybdenum and molybdenum alloys with an oxidation-resistant coating, characterized in that: The anti-oxidation coating on the surface of molybdenum and molybdenum alloy is prepared by the method for preparing the anti-oxidation coating on the surface of molybdenum and molybdenum alloy according to any one of claims 1 to 5.

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