Method for preventing molybdenum and molybdenum alloy from being oxidized

Abstract

The invention belongs to the technical field of metal surface treatment, and relates to a method for preventing molybdenum and molybdenum alloy from being oxidized. The invention provides a method for preventing molybdenum and molybdenum alloy from being oxidized, which comprises the following steps of: removing oxides on the surface of the molybdenum or the molybdenum alloy, polishing, coating a solid permeating agent on the surface, and permeating at 1000-1400 DEG C for 4-8 hours; the solid permeating agent is prepared from the following active ingredients in parts by weight: 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. The invention aims to solve the technical problems that MoSi2 is seriously oxidized at 400-600 DEG C, and the oxidation resistance is seriously reduced for a long time at the high temperature of 1200 DEG C or above.

Description

Technical Field

[0001] The present 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 cheaper than tungsten, niobium, and tantalum. Therefore, they are widely used in cutting-edge fields such as electronic devices, heating elements, glass fiber processing, protection tubes for temperature measurement, and aerospace. However, the oxidation resistance of molybdenum is poor, which greatly limits the application of molybdenum in high-temperature fields. Therefore, it is of great significance to study and improve the oxidation resistance of molybdenum and its alloys.

[0003] The research on preventing oxidation of molybdenum and molybdenum alloys mainly focuses on "alloying" and "coating methods". Silicide coatings have high-temperature self-healing ability and can play a good protective role for the substrate, so they have become a research hotspot for high-temperature protective coatings for molybdenum and its alloy matrix materials. Due to the small degree of alloying of molybdenum, the processing performance of molybdenum alloys deteriorates after introducing alloying elements, and the oxide film formed by the oxidation of molybdenum alloys cannot effectively block oxygen at high temperatures. Therefore, the "alloying" method is greatly limited in the field of preventing oxidation of molybdenum and its alloys. Currently, the most widely used method is the antioxidant coating method. The surface antioxidant coatings of molybdenum and its alloys mainly include heat-resistant alloy coatings, aluminide coatings, silicide coatings, oxide coatings, and noble metal coatings. Among them, the research on silicide coatings is the most common. MoSi2 is an important coating for preventing oxidation of molybdenum and molybdenum alloys. However, the "pesting" oxidation of MoSi2 at low temperatures and the serious decline in antioxidant ability at high temperatures above 1200 °C for a long time are all technical problems that need to be solved to improve the high-temperature antioxidant performance of molybdenum and molybdenum alloy coatings. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problems that MoSi2 has serious oxidation between 400 and 600 °C and the antioxidant ability seriously declines at high temperatures above 1200 °C for a long time. In this regard, the present invention provides a method for preventing oxidation of molybdenum and molybdenum alloys to meet this need in the art.

[0005] On the one hand, the present invention relates to a method for preventing oxidation of molybdenum and molybdenum alloys, which includes: after removing oxides and polishing the surface of molybdenum or molybdenum alloy, coating the surface with a solid penetrant, and performing pack cementation at 1000 - 1400 °C for 4 - 8 h; By weight, the active ingredients in the solid penetrant are composed of 15 - 20 parts of MoSi2, 10 - 15 parts of Si, 10 - 25 parts of TiB2, 4 - 8 parts of Cu, and 0.1 - 1 part of YF3.

[0006] Further, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the active ingredient in the solid penetrant is crushed to a particle size of 200 to 400 mesh, and then a penetrant accelerating agent accounting for 1 to 2% of the total mass of the active ingredient is added. After ball milling, an organic binder accounting for 1 to 2% of the total mass of the active ingredient is added, and the mixture is applied to molybdenum or molybdenum alloy. After drying, the pack cementation is carried out.

[0007] Further, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the penetrant accelerating agent is NaF.

[0008] Further, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the organic binder is an aqueous solution of polyvinyl alcohol with a concentration of 0.05 to 0.1 g / mL.

[0009] Further, 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 h to 3 h.

[0010] Further, 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.

[0011] Further, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the pack cementation is carried out under vacuum.

[0012] Further, in the method for preventing oxidation of molybdenum and molybdenum alloys provided by the present invention, the vacuum degree of the vacuum is not higher than 1.0×10 -1 Pa.

[0013] On the other hand, the present invention relates to a molybdenum and molybdenum alloy with an antioxidant coating, which is prepared by using the method for preventing oxidation of molybdenum and molybdenum alloys described above.

[0014] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: 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 penetrant. The core technical principle lies in overcoming the bottleneck problems of low-temperature "pesting" oxidation and long-term high-temperature oxidation failure of traditional MoSi2 coatings through the synergistic action of multiple components and structure regulation. Specifically, MoSi2 in the solid penetrant serves as the basic antioxidant phase, and Si forms 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 temperatures, 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 crack propagation caused by differences in thermal expansion coefficients; YF3 acts as an infiltration promoter, promoting the uniform diffusion and reaction of the penetrant components, and at the same time optimizing the coating microstructure through doping with trace rare earth elements to further avoid the problem of antioxidant capacity failure caused by coating cracking due to insufficient fluidity. Compared with single-element modification or simple multi-element co-permeation in the prior art, this technology realizes the comprehensive inhibition 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 extremely high-temperature environments. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 Mass loss of the substrate with an antioxidant coating at 600°C.

[0017] Figure 2 Mass loss of the substrate with an antioxidant coating at 1200°C.

[0018] Figure 3 Coating interface morphology of No. 2.

[0019] Figure 4 Coating interface morphology of No. 1. Detailed Embodiments

[0020] Next, the technical solutions of the present invention will be described in conjunction with embodiments. However, the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described, unless otherwise specified, can be purchased on the market. The % in the following embodiments is the mass percentage content unless otherwise specified. The ratios in the following embodiments are mass ratios unless otherwise specified.

[0021] Example 1 This example provides a method for preventing pure molybdenum from oxidation.

[0022] Take a pure molybdenum metal plate of 50mm×50mm×3mm, use sandpaper to polish off the oxide layer on the surface, and then in an ultrasonic cleaner, clean it with acetone, ethanol and deionized water for 15 minutes respectively, and clean it repeatedly for 3 times, and then dry it in a vacuum constant temperature drying oven.

[0023] Take the following powders according to the groups shown in Table 1, and the purity of each raw material is not less than 99%.

[0024] Table 1, Composition of active ingredients in each group of solid infiltrants (g) MoSi2 Si TiB2 Cu 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 Take the active ingredients in each group of the above solid infiltrants, mix and crush them to less than 400 mesh, and then mix in 1% of NaF based on the active ingredients. After mixing, put them into a planetary ball mill and ball mill at a rate of 300 r / min for 2 h. The medium for ball milling is anhydrous ethanol. Then add an aqueous solution of polyvinyl alcohol with a concentration of 0.08 g / mL according to 1% of the active ingredients, and modulate it into an infiltrant slurry with a certain viscosity. Apply the infiltrant slurry evenly on the surface of the surface-treated pure molybdenum metal plate, and then dry it in a vacuum constant temperature drying oven at 90 °C. After drying, take it out and place it in a ceramic crucible filled with the infiltrant slurry. In a vacuum furnace, control the vacuum degree not higher than 1.0×10 -1 Pa, and then start the pack cementation treatment. The temperature of the pack cementation treatment is 1100 °C, and the time of the pack cementation treatment is 4 h. After the pack cementation treatment is completed, wait for the substrate to cool to room temperature with the furnace, and remove the unadhered infiltrant slurry on the surface to obtain a substrate with an antioxidant coating.

[0025] Carry out isothermal cyclic oxidation experiments on the obtained substrates with antioxidant coatings in a box furnace under an atmospheric environment at 600 °C and 1200 °C respectively. Periodically take out the samples, and after natural cooling, weigh the mass change of the samples with an electronic analytical balance (accuracy 0.1 mg). The test results are as Figure 1 and Figure 2 shown.

[0026] From Figure 1It can be seen that when the MoSi2 coating shown in #2 was subjected to an oxidation experiment at 600 °C, typical low-temperature "pesting" oxidation occurred, that is, a significant mass loss occurred at 10 - 30 h, reaching up to 6.7 mg / cm 2 . For the test groups containing the TiB2 infiltrant slurry (#4 and #5), the function of inhibiting "pesting" was exhibited. The method for preventing the oxidation of pure molybdenum provided in this application showed a more excellent function of inhibiting "pesting", and the maximum mass loss during the 0 - 100 h cycle was only 2.3 mg / cm 2 .

[0027] It can be seen from Figure 2 that when the MoSi2 coating shown in #2 was subjected to an oxidation experiment at 1200 °C, typical antioxidant failure occurred. This is because as the oxidation time extended, the MoSi2 coating became thinner. Since this coating reacted with oxygen to form porous MoO3, it could not protect the substrate, the oxidation rate of the coating increased, and the coating failed rapidly. For the test group containing both Cu and YF3 (#3), the limitations of the single silicide coating at 1200 °C were avoided, showing high strength and creep resistance, and achieving the antioxidant function better. The method for preventing the oxidation of pure molybdenum provided in this application showed a more excellent high-temperature antioxidant function, and the maximum mass loss during the 0 - 100 h cycle was only -3.8 mg / cm 2 .

[0028] Figure 3 and Figure 4 are the coating interface morphologies of #2 and #1 shown respectively after the oxidation experiment at 1200 °C. It can be seen from Figure 3 that the structure of the MoSi2 coating shown in #2 is loose, the formed antioxidant film is not dense enough, there are particles and pores, and the bonding effect with the substrate is poor. It can be seen from Figure 4 that the coating provided by the present invention has a dense structure, no cracks, no particles and no pores, has a good bonding effect with the substrate, and has an excellent protective effect. The lack of any one of the three components of TiB2, Cu, and YF3 cannot take into account both inhibiting the "pesting" effect and providing long-term high-temperature antioxidant protection above 1200 °C.

[0029] Example 2 This example provides a method for preventing the oxidation of TZC alloy.

[0030] Take a 50 mm × 50 mm × 3 mm TZC alloy metal plate, use sandpaper to polish off the surface oxide layer, then in an ultrasonic cleaner, clean it with acetone, ethanol, and deionized water for 18 min respectively, wash it repeatedly 3 times, and then dry it in a vacuum constant temperature drying oven.

[0031] Take the following powders respectively according to the composition shown in Table 2, and the purity of each raw material is not less than 99%.

[0032] Table 2, Composition of active ingredients in solid penetrant (g) MoSi2 Si TiB2 Cu YF3 #6 15 10 10 4 0.1 Take the active ingredients in the above groups of solid penetrants, mix them and crush them to less than 400 mesh, then mix in 1.5% of NaF based on the active ingredients. After mixing, put them into a planetary ball mill and ball mill at a rate of 100 r / min for 1 h. The medium for ball milling is anhydrous ethanol. Then add an aqueous solution of polyvinyl alcohol with a concentration of 0.05 g / mL at 1.5% of the active ingredients to prepare a penetrant slurry with a certain viscosity. Apply this penetrant slurry evenly on the surface of the pure molybdenum metal plate after surface treatment, and then dry it in a vacuum constant temperature drying oven at 90 °C. After drying, take it out and place it in a ceramic crucible filled with penetrant slurry. In a vacuum furnace, control the vacuum degree not higher than 1.0×10 -1 Pa, and then start the pack cementation treatment. The temperature of the pack cementation treatment is 1000 °C, and the time of the pack cementation treatment is 8 h. After the pack cementation treatment is completed, wait for the substrate to cool to room temperature with the furnace, and remove the unadhered penetrant slurry on the surface to obtain a substrate with an antioxidant coating.

[0033] Carry out isothermal cyclic oxidation experiments on the obtained substrates with antioxidant coatings in a box furnace under atmospheric environment at 600 °C and 1200 °C respectively. Periodically take out the samples, and after natural cooling, weigh the mass change of the samples with an electronic analytical balance (accuracy 0.1 mg). It is measured that the maximum mass loss is only 3.6 mg / cm during the 0 - 100 h cycle at 600 °C 2 , and the maximum mass loss is only -4.2 mg / cm during the 0 - 100 h cycle at 1200 °C 2 .

[0034] Example 3 This example provides a method for preventing oxidation of TZM alloy Take a TZM alloy metal plate with dimensions of 50 mm × 50 mm × 3 mm, use sandpaper to polish off the surface oxide layer, and then in an ultrasonic cleaner, clean it with acetone, ethanol and deionized water for 20 min respectively, and clean it repeatedly 3 times, and then dry it in a vacuum constant temperature drying oven.

[0035] Take the following powders respectively according to the composition shown in Table 3, and the purity of each raw material is not less than 99%.

[0036] Table 3, Composition of active ingredients in solid penetrant (g) MoSi2 Si TiB2 Cu YF3 #6 20 15 25 8 1 Take the active ingredients in the above groups of solid infiltrants, mix them and crush to below 400 mesh, then mix in 2% of NaF based on the active ingredients. After mixing, put them into a planetary ball mill and ball mill at a rate of 300 r / min for 3 h. The medium for ball milling is absolute ethanol. Then add an aqueous solution of polyvinyl alcohol with a concentration of 0.1 g / mL at 2% of the active ingredients to prepare an infiltrant slurry with a certain viscosity. Apply the infiltrant slurry evenly on the surface of the surface-treated pure molybdenum metal plate, and then dry it in a vacuum constant-temperature drying oven at 90 °C. After drying, take it out and place it in a ceramic crucible filled with the infiltrant slurry, and control the vacuum degree in the vacuum furnace not to be higher than 1.0×10 -1 Pa, then start the pack cementation treatment. The temperature of the pack cementation treatment is 1400 °C, and the time of the pack cementation treatment is 5 h. After the pack cementation treatment is completed, wait for the substrate to cool to room temperature with the furnace, and remove the unadhered infiltrant slurry on the surface to obtain a substrate with an antioxidant coating.

[0037] Carry out isothermal cyclic oxidation experiments on the obtained substrate with an antioxidant coating in a box furnace at 600 °C and 1200 °C in an atmospheric environment. Periodically take out the samples, and after natural cooling, weigh the mass change of the samples with an electronic analytical balance (accuracy 0.1 mg). It is measured that the maximum mass loss during the 0-100 h cycle at 600 °C is only 3.6 mg / cm 2 , and the maximum mass loss during the 0-100 h cycle at 1200 °C is only -2.7 mg / cm 2 .

[0038] As described above, the basic principle, main features and advantages of the present invention are preferably described. The above embodiments and the description are only descriptions of the preferred embodiments of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the present invention.

Claims

1. A method for preventing the oxidation of molybdenum and molybdenum alloys, characterized in that, Including: After removing oxides and polishing the surface of molybdenum or molybdenum alloy, the surface is coated with a solid penetrant and pack carburized at 1000 - 1400 °C for 4 - 8 h; By weight, the active components in the solid penetrant are composed of 15 - 20 parts of MoSi2, 10 - 15 parts of Si, 10 - 25 parts of TiB2, 4 - 8 parts of Cu, and 0.1 - 1 part of YF3.

2. The method for preventing oxidation of molybdenum and molybdenum alloy according to claim 1, wherein, The active components in the solid penetrant are crushed to a particle size of 200 - 400 mesh, then a penetration accelerator accounting for 1 - 2% of the total mass of the active components is added, and after ball milling, an organic binder accounting for 1 - 2% of the total mass of the active components is added, applied to molybdenum or molybdenum alloy, and after drying, the above-mentioned pack carburizing is carried out.

3. The method for preventing oxidation of molybdenum and molybdenum alloy according to claim 2, characterized in that, The penetration accelerator is NaF.

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

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

6. The method for preventing oxidation of molybdenum and molybdenum alloy 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, characterized in that, The pack carburizing is carried out under vacuum.

8. The method for preventing oxidation of molybdenum and molybdenum alloy according to claim 7, characterized in that, The degree of vacuum of the said vacuum is not higher than 1.0×10 -1 Pa.

9. A molybdenum and molybdenum alloy with an antioxidant coating, characterized in that, Obtained by using the method for preventing oxidation of molybdenum and molybdenum alloy according to any one of claims 1 - 6.

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