A method for preventing oxidation of molybdenum and molybdenum alloys

Abstract

The present invention belongs to the field of metal surface treatment technology and relates to a method for preventing the oxidation of molybdenum and molybdenum alloys. The present invention provides a method for preventing the oxidation of molybdenum and molybdenum alloys, comprising: removing oxides from the surface of the molybdenum or molybdenum alloy and polishing it, then coating the surface with a solid infiltrant and infiltrating it at 1000-1400°C for 4-8 hours; the active ingredients in the solid infiltrant are, by weight, 15-20 parts MoSi2, 10-15 parts Si, 10-25 parts TiB2, 4-8 parts Cu, and 0.1-1 part YF3. The present invention aims to address the technical problems of MoSi2's severe oxidation between 400-600°C and its severe decline in antioxidant capacity over long periods of time at high temperatures above 1200°C.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment and relates to a method for preventing oxidation of molybdenum and molybdenum alloys. Background Art

[0002] Molybdenum and its alloys have excellent high-temperature mechanical properties and corrosion resistance, and are more affordable than tungsten, niobium, and tantalum. Consequently, they are widely used in cutting-edge fields such as electronics, heating elements, fiberglass processing, temperature measurement protection tubes, and aerospace. However, molybdenum's poor oxidation resistance significantly limits its application in high-temperature applications. Therefore, research and improvement of the oxidation resistance of molybdenum and its alloys are of great significance.

[0003] Research on the oxidation protection of molybdenum and its alloys primarily focuses on alloying and coating methods. Silicide coatings, with their high-temperature self-healing ability and excellent substrate protection, have become a hot topic in the field of high-temperature protective coatings for molybdenum and its alloys. However, due to the low alloyability of molybdenum, the processing properties of molybdenum alloys deteriorate after the introduction of alloying elements. Furthermore, the oxide film formed by oxidation of molybdenum alloys cannot effectively block oxygen at high temperatures. Therefore, the application of alloying methods in the oxidation protection of molybdenum and its alloys is significantly limited. Currently, the most widely used method is oxidation-resistant coatings. Surface oxidation-resistant coatings for molybdenum and its alloys primarily include heat-resistant alloy coatings, aluminide coatings, silicide coatings, oxide coatings, and precious metal coatings, with silicide coatings being the most widely studied. MoSi2 is an important coating for the oxidation protection of molybdenum and its alloys. However, MoSi2 undergoes "pesting" oxidation at low temperatures, and its oxidation resistance decreases significantly over time at temperatures above 1200°C. These are technical challenges that need to be addressed to improve the high-temperature oxidation resistance of molybdenum and its alloy coatings. Summary of the Invention

[0004] The present invention aims to address the technical problems of MoSi2 being severely oxidized between 400°C and 600°C, and its oxidation resistance being severely reduced over long periods of time at high temperatures above 1200°C. To this end, the present invention provides a method for preventing oxidation of molybdenum and molybdenum alloys to address this need in the art.

[0005] In one aspect, the present invention relates to a method for preventing oxidation of molybdenum and molybdenum alloys, comprising: removing oxides from the surface of molybdenum or molybdenum alloys and polishing the surface, coating the surface with a solid infiltrant, and infiltrating at 1000-1400° C. for 4-8 hours;

[0006] In parts by weight, the effective ingredients in the solid penetrant are composed of 15 to 20 parts of MoSi2, 10 to 15 parts of Si, 10 to 25 parts of TiB2, 4 to 8 parts of Cu, and 0.1 to 1 part of YF3.

[0007] Furthermore, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the active ingredients in the solid penetrant are crushed to a particle size of 200 to 400 mesh, and then a penetration enhancer of 1 to 2% of the total mass of the active ingredients is added. After ball milling, an organic binder of 1 to 2% of the total mass of the active ingredients is added, and the mixture is applied to molybdenum or molybdenum alloy, and then dried for the encapsulation.

[0008] Furthermore, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the penetration enhancer is NaF.

[0009] Furthermore, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the organic binder is a 0.05-0.1 g / mL aqueous solution of polyvinyl alcohol.

[0010] Furthermore, in the method for preventing oxidation 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.

[0011] Furthermore, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the molybdenum or molybdenum alloy is pure molybdenum, TZC alloy or TZM alloy.

[0012] Furthermore, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the infiltration is carried out under vacuum.

[0013] Furthermore, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the vacuum degree is not higher than 1.0×10 -1 Pa.

[0014] 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 preventing oxidation of molybdenum and molybdenum alloys.

[0015] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0016] The method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention significantly improves the oxidation resistance of molybdenum and molybdenum alloys in a wide temperature range through the design of a composite solid infiltrant. The core technical principle is to overcome the bottleneck problem of traditional MoSi2 coating in low-temperature "pesting" oxidation and high-temperature long-term antioxidant failure through the synergistic effect of multiple components and structural regulation. Specifically, MoSi2 in the solid infiltrant serves as the basic antioxidant phase, and Si generates a dense SiO2 layer through oxidation to achieve self-healing protection; TiB2 forms a high-melting-point Ti-Si-O composite glass layer at high temperature, inhibiting oxygen diffusion and enhancing the thermal stability of the coating; the introduction of B and Cu synergistically improves the ductility of the coating and alleviates the crack propagation caused by the difference in thermal expansion coefficient; YF3 acts as a penetration promoter, promoting the uniform diffusion and reaction of the infiltrant components, and at the same time optimizing the coating microstructure by doping with trace rare earth elements, further avoiding the problem of oxidation resistance failure caused by cracking of the coating due to insufficient fluidity. Compared with the single element modification or simple multi-element co-penetration in existing technologies, this technology achieves comprehensive suppression of "pesting" oxidation, element diffusion and thermal stress failure through multi-phase synergy and process matching, providing reliable protection for the application of molybdenum-based materials in extreme high temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] Figure 1 is the mass loss of the substrate with the anti-oxidation coating at 600°C.

[0019] Figure 2 is the mass loss of the substrate with the anti-oxidation coating at 1200°C.

[0020] Figure 3 This is the interface morphology of coating 2#.

[0021] Figure 4 This is the interface morphology of coating 1#. DETAILED DESCRIPTION

[0022] 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.

[0023] Example 1

[0024] This embodiment provides a method for preventing pure molybdenum from oxidation.

[0025] A 50 mm × 50 mm × 3 mm pure molybdenum metal plate was taken and polished with sandpaper to remove the surface oxide layer. Then, it was cleaned in an ultrasonic cleaner with acetone, ethanol, and deionized water for 15 minutes each, repeated three times, and then dried in a vacuum constant temperature drying oven.

[0026] The following powders were obtained according to the groups shown in Table 1. The purity of each raw material was not less than 99%.

[0027] Table 1. Composition of active ingredients in each group of solid permeation preparations (g)

[0028] <![CDATA[MoSi2]]> Si <![CDATA[TiB2]]> Cu <![CDATA[YF3]]> #1 18 12 14 6 0.5 #2 18 12 0 0 0 #3 18 12 0 6 0.5 #4 18 12 14 0 0.5 #5 18 12 14 6 0

[0029] The active ingredients from each group of solid penetrants were mixed and crushed to a size of less than 400 mesh. Then, 1% NaF was added to the mixture. After mixing, the mixture was placed in a planetary ball mill and ball-milled at 300 r / min for 2 hours. The milling medium was anhydrous ethanol. Then, a 0.08 g / mL aqueous solution of polyvinyl alcohol was added at 1% of the active ingredient to prepare a penetrant slurry with a certain viscosity. The penetrant slurry was evenly applied to the surface of the surface-treated pure molybdenum metal plate and then dried in a vacuum constant temperature drying oven at 90°C. After drying, the mixture was taken out and placed in a ceramic crucible filled with the penetrant slurry. The vacuum degree in the vacuum furnace was controlled to be no higher than 1.0×10 -1 After Pa, the coating treatment was started at a temperature of 1100°C for 4 hours. After the coating treatment was completed, the substrate was cooled to room temperature in the furnace and the unattached penetrant slurry was removed to obtain a substrate with an antioxidant coating.

[0030] The samples were subjected to isothermal cyclic oxidation experiments in an atmospheric environment in a box furnace at 600°C and 1200°C to obtain substrates with antioxidant coatings. The samples were taken out periodically and weighed with an electronic analytical balance (accuracy 0.1 mg) after natural cooling. The test results are shown in the figure. Figure 1 and Figure 2 shown.

[0031] Depend on Figure 1It can be seen that when the MoSi2 coating shown in #2 was subjected to the oxidation resistance test at 600℃, typical low-temperature "pesting" oxidation occurred, that is, a significant mass loss occurred from 10 to 30 hours, reaching as high as 6.7 mg / cm 2 The test groups (#4 and #5) containing TiB2 infiltrant slurry showed the function of suppressing the "pesting" inhibition effect. The method for preventing pure molybdenum oxidation provided by this application showed an even better function of suppressing the "pesting" inhibition effect, with the maximum mass loss in the 0-100h cycle being only 2.3mg / cm 2 .

[0032] Depend on Figure 2 It can be seen that when the MoSi2 coating shown in #2 was subjected to an anti-oxidation test at 1200°C, typical anti-oxidation failure occurred. This is because the MoSi2 coating becomes thinner as the oxidation time increases. Since the coating reacts with oxygen to form porous MoO3, it cannot protect the substrate, the oxidation rate of the coating is accelerated, and the coating quickly fails. The test group (#3) containing both Cu and YF3 avoids the limitations of a single silicide coating at 1200°C, exhibits higher strength and creep resistance, and better realizes the anti-oxidation function. The method for preventing pure molybdenum oxidation provided in this application exhibits even more excellent high-temperature resistance and anti-oxidation function, with the maximum mass loss in the 0~100h cycle being only -3.8mg / cm 2 .

[0033] Figure 3 and Figure 4 The interface morphologies of coatings #2 and #1 are after the anti-oxidation test at 1200℃. Figure 3 It can be seen that the structure of the MoSi2 coating shown in #2 is loose, the anti-oxidation film formed is not dense enough, there are particles and holes, and the bonding effect with the substrate is poor. Figure 4 As can be seen, the coating provided by the present invention has a dense structure, is free of cracks, particles, and holes, and has a good bond with the substrate, providing excellent protection. However, the absence of any of the three components—TiB2, Cu, and YF3—cannot simultaneously suppress the "pesting" effect and provide long-term high-temperature antioxidant protection above 1200°C.

[0034] Example 2

[0035] This embodiment provides a method for preventing TZC alloy from oxidation.

[0036] A 50 mm × 50 mm × 3 mm TZC alloy metal plate was taken and sanded to remove the surface oxide layer. Then, it was cleaned in an ultrasonic cleaner with acetone, ethanol, and deionized water for 18 min each, repeated three times, and then dried in a vacuum constant temperature drying oven.

[0037] According to the composition shown in Table 2, the following powders are taken respectively, and the purity of each raw material is not less than 99%.

[0038] Table 2. Composition of active ingredients in solid permeation preparations (g)

[0039] <![CDATA[MoSi2]]> Si <![CDATA[TiB2]]> Cu <![CDATA[YF3]]> #6 15 10 10 4 0.1

[0040] The active ingredients from each group of solid penetrants were mixed and crushed to a size of less than 400 mesh. Then, 1.5% NaF was added to the mixture. After mixing, the mixture was placed in a planetary ball mill and ball-milled at a rate of 100 r / min for 1 hour. The milling medium was anhydrous ethanol. Then, a 0.05 g / mL aqueous solution of polyvinyl alcohol was added at 1.5% of the active ingredient to prepare a penetrant slurry with a certain viscosity. The penetrant slurry was evenly applied to the surface of the surface-treated pure molybdenum metal plate and then dried in a vacuum constant temperature drying oven at 90°C. After drying, the mixture was taken out and placed in a ceramic crucible filled with the penetrant slurry. The vacuum degree in the vacuum furnace was controlled to be no higher than 1.0×10 -1 After Pa, the coating treatment was started at a temperature of 1000°C for 8 hours. After the coating treatment was completed, the substrate was cooled to room temperature in the furnace and the unattached penetrant slurry was removed to obtain a substrate with an antioxidant coating.

[0041] The samples were subjected to isothermal cyclic oxidation experiments in an atmospheric environment in a box furnace at 600°C and 1200°C, respectively. The samples were taken out periodically and weighed with an electronic analytical balance (accuracy 0.1 mg) after natural cooling. The maximum mass loss at 600°C during the 0-100h cycle was only 3.6 mg / cm 2 The maximum mass loss in the 0~100h cycle at 1200℃ is only -4.2mg / cm 2 .

[0042] Example 3

[0043] This embodiment provides a method for preventing TZM alloy from oxidation

[0044] A 50 mm × 50 mm × 3 mm TZM alloy metal plate was taken and polished with sandpaper to remove the surface oxide layer. Then, it was cleaned in an ultrasonic cleaner with acetone, ethanol, and deionized water for 20 min each, and the cleaning was repeated three times. Finally, the plate was dried in a vacuum constant temperature drying oven.

[0045] According to the composition shown in Table 3, the following powders are taken respectively, and the purity of each raw material is not less than 99%.

[0046] Table 3. Composition of active ingredients in solid permeation preparations (g)

[0047] <![CDATA[MoSi2]]> Si <![CDATA[TiB2]]> Cu <![CDATA[YF3]]> #6 20 15 25 8 1

[0048] The active ingredients from each group of solid penetrants were mixed and crushed to a size of less than 400 mesh. Then, 2% NaF was added to the mixture. After mixing, the mixture was placed in a planetary ball mill and ball-milled at 300 r / min for 3 hours. The milling medium was anhydrous ethanol. Then, a 0.1 g / mL aqueous solution of polyvinyl alcohol was added at 2% of the active ingredient to prepare a penetrant slurry with a certain viscosity. The penetrant slurry was evenly applied to the surface of the surface-treated pure molybdenum metal plate and then dried in a vacuum constant temperature drying oven at 90°C. After drying, the slurry was removed and placed in a ceramic crucible filled with the penetrant slurry. The vacuum degree in the vacuum furnace was controlled to be no higher than 1.0×10 -1 After Pa, the coating treatment was started at a temperature of 1400°C for 5 hours. After the coating treatment was completed, the substrate was cooled to room temperature in the furnace and the unattached penetrant slurry was removed to obtain a substrate with an antioxidant coating.

[0049] The samples were subjected to isothermal cyclic oxidation experiments in an atmospheric environment in a box furnace at 600°C and 1200°C, respectively. The samples were taken out periodically and weighed with an electronic analytical balance (accuracy 0.1 mg) after natural cooling. The maximum mass loss at 600°C during the 0-100h cycle was only 3.6 mg / cm 2 The maximum mass loss in the 0~100h cycle at 1200℃ is only -2.7mg / cm 2 .

[0050] 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 preventing oxidation of molybdenum and molybdenum alloys, characterized in that: include: After the surface of molybdenum or molybdenum alloy is subjected to surface oxide removal and polishing treatment, the surface is coated with a solid infiltrant and infiltrated at 1000-1400°C for 4-8 hours; In parts by weight, the effective ingredients in the solid penetrant are composed of 15 to 20 parts of MoSi2, 10 to 15 parts of Si, 10 to 25 parts of TiB2, 4 to 8 parts of Cu, and 0.1 to 1 part of YF3.

2. The method for preventing oxidation of molybdenum and molybdenum alloys according to claim 1, wherein: The active ingredients in the solid permeate are crushed to a particle size of 200-400 mesh, and then a permeation enhancer of 1-2% of the total mass of the active ingredients is added. After ball milling, an organic binder of 1-2% of the total mass of the active ingredients is added, and the mixture is applied to molybdenum or molybdenum alloy, and then dried for the encapsulation.

3. The method for preventing oxidation of molybdenum and molybdenum alloys according to claim 2, wherein: The penetration enhancer is NaF.

4. The method for preventing oxidation of molybdenum and molybdenum alloys according to claim 2, wherein: The organic binder is a 0.05-0.1 g / mL polyvinyl alcohol aqueous solution.

5. The method for preventing oxidation of molybdenum and molybdenum alloys according to claim 2, wherein: The ball milling speed is 100-300 r / min, and the ball milling time is 1 h-3 h.

6. The method for preventing oxidation of molybdenum and molybdenum alloys according to claim 1, wherein: The molybdenum or molybdenum alloy is pure molybdenum, TZC alloy or TZM alloy.

7. The method for preventing oxidation of molybdenum and molybdenum alloys according to claim 1, wherein: The infiltration is carried out under vacuum.

8. The method for preventing oxidation of molybdenum and molybdenum alloys according to claim 7, wherein: The vacuum degree is not higher than 1.0×10 -1 Pa.

9. Molybdenum and molybdenum alloys with an oxidation-resistant coating, characterized in that: The invention is prepared by the method for preventing oxidation of molybdenum and molybdenum alloys according to any one of claims 1 to 6.

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