Method for improving corrosion resistance of in-situ nanoparticle reinforced fecrb-based composite to aluminum liquid

Abstract

The application discloses a method for improving the corrosion resistance of nano-particle reinforced FeCrB alloy to molten aluminum; the method is characterized in that: the nano-particle reinforced FeCrB-based composite material is subjected to pre-oxidation treatment, so that a continuous dense multilayer structure oxide film with a certain thickness is formed on the surface of the alloy, the oxide film is composed of a Cr2O3 layer in the inner layer, a B2O3-SiO2 amorphous layer in the intermediate layer and a Cr2O3 layer in the outer layer. The oxide film reduces the wetting of the molten aluminum and the substrate in the initial stage of corrosion, and inhibits the direct contact. Then, the diffusion and reaction of Al atoms to the substrate can be reduced, the reaction of the oxide film with the molten aluminum also delays the corrosion of the molten aluminum to the substrate. The thickness of the formed intermetallic compound layer is reduced. Therefore, the corrosion resistance of the nano-particle reinforced FeCrB-based composite material to the molten aluminum is improved.

Description

Technical Field

[0001] This invention belongs to the field of liquid metal corrosion and wear technology, specifically relating to a method for improving the resistance of in-situ nanoparticle-reinforced FeCrB-based composite materials to aluminum liquid corrosion. Background Technology

[0002] In the aluminum alloy forming process, molten aluminum inevitably comes into contact with components such as punches and barrels in the die-casting machine. Due to the extremely high chemical reactivity of aluminum alloys at high temperatures, and the fact that the components in contact with the molten aluminum are in an alternating temperature and stress field, corrosion and even failure of the components can occur. FeCrB alloys, due to their excellent wear resistance, low price, and simple manufacturing process, have broad application prospects in high-temperature corrosion fields. Furthermore, FeCrB alloys possess continuous network-like borides and exhibit stronger resistance to molten aluminum corrosion than the matrix, inhibiting the diffusion of molten aluminum into the matrix, thus demonstrating good resistance to molten aluminum corrosion. However, FeCrB alloys still suffer from poor mechanical properties, which is a major limiting factor for their large-scale application. Therefore, it is necessary to improve their mechanical properties while maintaining excellent resistance to molten aluminum corrosion, which has significant practical application value.

[0003] Application number CN201911247606.4 discloses a nanoparticle-reinforced FeCrB-based composite material. Adding Ti to the FeCrB alloy allows for the in-situ generation of TiB2 and TiC nanoparticles. These nanoparticles aggregate on the surface of borides, forming a nanoparticle shell that restricts boride growth, thereby refining boride size and improving morphology. Simultaneously, the nanoparticles dispersed in the matrix strengthen the FeCrB alloy. Therefore, the in-situ generated nanoparticles effectively improve the strength and plasticity of the FeCrB-based composite material. Furthermore, the borides and nanoparticles in the nanoparticle-reinforced FeCrB-based composite material effectively inhibit the diffusion of aluminum atoms into the matrix, while the skeletal borides hinder the exfoliation and dissolution of corrosion products, thus significantly improving resistance to molten aluminum corrosion. Compared to traditional mold steels such as H13 and FeCrB alloys, the in-situ nanoparticle-reinforced FeCrB-based composite material exhibits superior mechanical properties and resistance to molten aluminum corrosion. However, even after prolonged exposure to molten aluminum, the matrix still corrodes, resulting in significant losses. Therefore, it is necessary to further improve the resistance of in-situ nanoparticle-reinforced FeCrB-based composites to aluminum melt corrosion.

[0004] Surface treatment is an economical and practical method often used to improve the corrosion resistance of iron-based alloys. Related literature shows that the oxide film obtained through surface treatment can significantly improve the resistance of the iron substrate to aluminum molten corrosion. However, due to its unstable nature and prolonged corrosion time, the oxide film formed on the surface will break down and fail. Application number CN 113174545A discloses an in-situ nanoparticle-reinforced FeCrB alloy with high-temperature oxidation resistance, which forms a continuous and dense oxide film mainly composed of Cr2O3 during high-temperature oxidation. According to related literature, a Cr2O3 protective film also forms on the surface of the FeCrB alloy during oxidation. This Cr2O3 oxide film can improve the substrate's resistance to aluminum molten corrosion, but the improvement in resistance is limited, only reaching 0.425 μm / min, and further improvement is needed. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a method for improving the resistance of in-situ nanoparticle-reinforced FeCrB-based composite materials to aluminum molten corrosion.

[0006] The objective of this invention is achieved through the following techniques:

[0007] This invention relates to a method for improving the corrosion resistance of in-situ nanoparticle-reinforced FeCrB-based composite materials to molten aluminum. The method involves pre-oxidizing the in-situ nanoparticle-reinforced FeCrB-based composite material to generate a multi-layered oxide film. The pre-oxidation temperature is 600–800°C, and the pre-oxidation time is 5–30 hours. The preferred pre-oxidation temperature is 600–700°C.

[0008] Furthermore, the pre-oxidation treatment is carried out at a pre-oxidation temperature of 700°C for 10 hours.

[0009] In one embodiment of the present invention, the oxidizing gas in the pre-oxidation treatment is air, and the heating rate is 5-10°C / min.

[0010] Furthermore, the heating rate is 8°C / min.

[0011] In this invention, after pre-oxidation treatment, a multi-layered oxide film (of a certain thickness) is generated on the alloy surface. The oxide film consists of an inner Cr2O3 layer, a middle B2O3-SiO2 amorphous layer, and an outer Cr2O3 layer. The thickness of the multi-layered oxide film is 0.5 to 2 μm.

[0012] As one embodiment of the present invention, the nanoparticles in the in-situ nanoparticle-reinforced FeCrB-based composite material are TiC and TiB2, and the total integral of TiC and TiB2 in the composite material is 1.0-2.0%.

[0013] As one embodiment of the present invention, the in-situ nanoparticle-reinforced FeCrB-based composite material comprises the following components in the following mass percentages: C 0.35-0.5%, B 3.5-4.0%, Cr 12.0-16.0%, Si 1.5-3.0%, Ni 0.5-1.0%, Ti 0.8-1.6%, with the balance being iron.

[0014] The pre-oxidation temperature specified in this invention is 600-800℃. If the pre-oxidation temperature is below 600℃, it is insufficient to form a continuous and dense oxide film, resulting in pores and uncovered areas. If the pre-oxidation temperature is above 800℃, the formed oxide film will peel off and cracks will form, weakening the protective effect on the in-situ nanoparticle-reinforced FeCrB-based composite material.

[0015] The pre-oxidation treatment time specified in this invention is 5 to 30 hours. If the pre-oxidation treatment time is less than 5 hours, a continuous oxide film will not be formed on the surface of the in-situ nanoparticle-reinforced FeCrB matrix matrix due to the short time. If the pre-oxidation treatment time is greater than 30 hours, the formed oxide film will peel off and crack, which will become a channel for accelerated diffusion of aluminum atoms. In addition, it will also lead to intensified oxidation of the nanoparticle-reinforced FeCrB matrix, and the oxidization and volatilization of borates in the matrix will form many pores.

[0016] The oxidizing gas specified in this invention is air. Other types of gases (such as water vapor) can alter the type and state of the oxide film, which is detrimental to the corrosion resistance of FeCrB-based composite materials reinforced by in-situ nanoparticles.

[0017] The heating rate specified in this invention is 5-10°C / min. Too fast a heating rate will result in uneven temperature, while too slow a heating rate will result in prolonged oxidation time.

[0018] The cooling method specified in this invention is air cooling. Under air cooling conditions, the state of the oxide film at the end of oxidation can be preserved, and the microstructure of the in-situ nanoparticle-reinforced FeCrB-based composite material will not change.

[0019] The thickness of the multilayer oxide film defined in this invention is 0.5 to 2 μm. If the thickness of the oxide film is less than 0.5 μm, the protective effect on the substrate is weakened. Oxide films with a thickness greater than 2 μm are not easy to obtain. Extending the oxidation temperature and oxidation time will cause the oxide film to peel off and will not increase the thickness of the oxide film. Therefore, the maximum thickness of the oxide film is limited to 2 μm.

[0020] The nanoparticles specified in this invention are TiC and TiB2, wherein the total volume fraction of TiC and TiB2 is 1.0-2.0%. TiC and TiB2 are generated in situ after the addition of Ti. If the total volume fraction of TiC and TiB2 is less than 1.0%, the promoting effect of the nanoparticles on the oxide film and the improvement effect on the corrosion resistance of molten aluminum are weakened; if the total volume fraction of TiC and TiB2 is greater than 2.0%, the size of the in-situ generated nanoparticles will be in the micrometer range, and agglomeration will occur, thus the effect of the nanoparticles will still be limited.

[0021] The in-situ nanoparticle-reinforced FeCrB-based composite material specified in this invention has the following mass percentage composition: C 0.35-0.5%, B 3.5-4.0%, Cr 12.0-16.0%, Si 1.5-3.0%, Ni 0.5-1.0%, Ti 0.8-1.6%, with the balance being iron. Deviating from this composition will alter the total volume fraction of nanoparticles formed by the alloy, thereby affecting the formation of the oxide film and the improvement of resistance to molten aluminum corrosion.

[0022] As one embodiment of the present invention, the pretreatment process parameters are: pre-oxidation temperature 700℃, pre-oxidation treatment time 10h, oxidizing gas is air, heating rate is 8℃ / min, and cooling method is air cooling.

[0023] As one embodiment of the present invention, the method includes the following steps:

[0024] S1. Grind and polish the in-situ nanoparticle-reinforced FeCrB-based composite material;

[0025] S2. The in-situ nanoparticle-reinforced FeCrB-based composite material that has been polished and then heated and kept at a constant temperature.

[0026] S3. Cool the in-situ nanoparticle-reinforced FeCrB-based composite material after heat preservation in air to obtain the in-situ nanoparticle-reinforced FeCrB-based composite material after oxidation treatment.

[0027] As one embodiment of the present invention, in step S1, grinding and polishing are conventional techniques in the art.

[0028] In one embodiment of the present invention, in step S2, the heating is carried out in a resistance furnace. The holding time is the pre-oxidation treatment time.

[0029] In one embodiment of the present invention, in step S3, the cooling method is air cooling.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention generates a uniform, continuous, and dense multilayer oxide film on the substrate surface through pre-oxidation treatment. The innermost layer is Cr2O3, the middle layer is B2O3-Si2O3 silicate glass, and the outermost layer is Cr2O3. The oxide film has excellent adhesion to the substrate and is not easily peeled off.

[0032] 2. The multilayer oxide film of this invention, on the one hand, exhibits poor wettability between molten aluminum and Cr2O3, which can inhibit direct contact between the substrate and molten aluminum in the initial stage of corrosion, thus prolonging the corrosion resistance time; on the other hand, the oxide film can act as a barrier to the diffusion of Al atoms into the substrate, weakening the diffusion of aluminum atoms towards the substrate. Simultaneously, the reaction between the oxide film and the molten Al also delays the corrosion of the substrate by the molten aluminum. Therefore, pre-oxidation treatment can improve the corrosion resistance of nanoparticle-reinforced FeCrB alloys to molten aluminum corrosion.

[0033] 3. Compared with the corrosion rate of the traditional Cr2O3 oxide film (0.425 μm / min), the three-layer oxide film of the present invention (i.e., Cr2O3-B2O3-Si2O3-Cr2O3) has a lower corrosion rate (0.327 μm / min), which is only 76.9% of the original, that is, the corrosion resistance of aluminum liquid is improved by 1.3 times. Attached Figure Description

[0034] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0035] Figure 1 The matrix thickness loss curves and corrosion rate curves of the in-situ nanoparticle-reinforced FeCrB matrix composites obtained by oxidation treatment in Example 1 and Comparative Examples 1-4 are shown for different immersion times in molten aluminum at 750°C.

[0036] Figure 2 Cross-sectional views of the corrosion interface of the in-situ nanoparticle-reinforced FeCrB-based composite materials obtained by oxidation treatment in Example 1 and Comparative Examples 1-4 after immersion in aluminum liquid at 750°C for 1 hour, where (a) Example 1, (b) Comparative Example 1, (c) Comparative Example 2, (d) Comparative Example 3, and (e) Comparative Example 4.

[0037] Figure 3 The images show cross-sectional views of the multilayer oxide film formed by the in-situ nanoparticle-reinforced FeCrB-based composite material in Example 1, including (a) SEM image and (b) TEM image. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the invention in any way. Several modifications and improvements can be made without departing from the concept of the present invention, and all of these fall within the scope of protection of the present invention.

[0039] The mechanism by which the pre-oxidation treatment improves the resistance of in-situ nanoparticle-reinforced FeCrB-based composite materials to aluminum melt corrosion in this invention is mainly as follows:

[0040] In the in-situ nanoparticle-reinforced FeCrB-based composite melt, TiB2 and TiC nanoparticles can be generated in situ. After oxidation in air at 750℃ for 10 hours, a multilayer oxide film is obtained, consisting of an inner Cr2O3 layer, a middle B2O3-SiO2 amorphous layer, and an outer Cr2O3 layer. During static aluminum melt corrosion, the Cr2O3 oxide film exhibits poor wettability with the aluminum melt, inhibiting direct contact between the matrix and molten aluminum in the initial corrosion stage. Furthermore, the oxide film prevents the interdiffusion of aluminum and iron atoms, delaying the reaction and diffusion between the aluminum melt and the matrix, and reducing the thickness of the intermetallic compound layer. This improves the aluminum melt corrosion resistance of the in-situ nanoparticle-reinforced FeCrB-based composite.

[0041] The following examples and comparative examples were all carried out according to the relevant processes, and static aluminum liquid corrosion performance tests can be performed subsequently.

[0042] Example 1

[0043] The metal used in this embodiment is an in-situ nanoparticle-reinforced FeCrB-based composite material, comprising the following components by mass percentage: C 0.35%, B 3.5%, Cr 12.0%, Si 2.0%, Ni 0.5%, Ti 1.4%, with the balance being iron. It undergoes a pre-oxidation treatment, with the following process parameters:

[0044] Process parameters: Pre-oxidation temperature 700℃, pre-oxidation treatment time 10h. Oxidizing gas is air, heating rate is 8℃ / min, and cooling method is air cooling.

[0045] The pre-oxidation treatment process steps are as follows:

[0046] (1) Grind and polish the in-situ nanoparticle-reinforced FeCrB-based composite material;

[0047] (2) The FeCrB-based composite material reinforced by in-situ nanoparticles was placed in a resistance furnace, heated to 700°C, and then kept at that temperature for 10 hours.

[0048] (3) After the specified heat preservation time is reached, the in-situ nanoparticle-reinforced FeCrB-based composite material is taken out of the resistance furnace and cooled in the air to obtain the in-situ nanoparticle-reinforced FeCrB-based composite material after oxidation treatment. Figure 3 The images show cross-sectional views of the multilayer oxide film formed by the composite material, where (a) is a SEM image and (b) is a TEM image.

[0049] Comparative Example 1

[0050] The alloy used in Comparative Example 1 is the same as that in Example 1, both being in-situ nanoparticle-reinforced FeCrB-based composite materials, the difference being that no pre-oxidation treatment was performed.

[0051] The chemical composition (mass fraction) of the nanoparticle-reinforced FeCrB alloy in this comparative example is as follows:

[0052] C 0.35%, B 3.5%, Cr 12.0%, Si 2.0%, Ni 0.5%, Ti 1.4%, balance iron.

[0053] Comparative Example 2

[0054] The alloy used in Comparative Example 2 has the following composition (mass fraction):

[0055] Cr 4.96%, Mn 0.28%, V 1.15%, Mo 1.42wt%, Si 0.92%, C 0.36%, Fe balance.

[0056] Comparative Example 2 alloy was not pre-oxidized.

[0057] Comparative Example 3

[0058] The alloy used in Comparative Example 3 has the following composition (mass fraction):

[0059] Cr 9.48%, V 0.55%, Mo 2.86%, W 5.49%, Co 10.66%, Si 0.19%, C 0.27%, Fe balance.

[0060] Comparative Example 3 alloy was not pre-oxidized.

[0061] Comparative Example 4

[0062] The alloy used in Comparative Example 4 is the same as that in Example 1, both being in-situ nanoparticle-reinforced FeCrB-based composite materials. The difference lies in the pre-oxidation treatment parameters: the pre-oxidation temperature is 750°C, and the oxidation time is 200 h. Other parameters, such as the oxidizing gas, heating rate, and cooling method, are the same as in the example.

[0063] The chemical composition of the nanoparticle-reinforced FeCrB alloy in this comparative example is as follows:

[0064] C 0.35%, B 3.5%, Cr 12.0%, Si 2.0%, Ni 0.5%, Ti 1.4%, balance iron.

[0065] Static aluminum melt corrosion test

[0066] Test conditions: The alloys in the examples and comparative examples were placed in molten aluminum at 750°C and left to stand for 0.25h, 0.5h, 1h, 2h and 4h respectively. The thickness of the samples before and after corrosion was measured to obtain the matrix thickness loss of the alloy in the molten aluminum.

[0067] The corrosion rate of the matrix in molten aluminum was calculated by measuring the matrix thickness loss of the alloy.

[0068] The results of static aluminum melt corrosion resistance tests in the examples and comparative examples are as follows: Figure 1 and Figure 2 As shown, Figure 1 The matrix thickness loss curves are obtained by immersing the alloys of Example 1 and Comparative Examples 1-4 in molten aluminum at 750°C for different times. Figure 2 Here are cross-sectional views of the corrosion interface of alloys in Examples 1 and 4 after corrosion in molten aluminum at 750°C for 1 hour: (a) Example 1; (b) Comparative Example 1; (c) Comparative Example 2; (d) Comparative Example 3; (e) Comparative Example 4

[0069] Depend on Figure 1 It can be seen that the thickness loss of the matrix in the examples is significantly lower than that in the comparative examples, and the corrosion rate of the alloy in the examples is also significantly lower than that in the comparative examples. This indicates that the static aluminum melt corrosion resistance of the examples is significantly improved compared to the in-situ nanoparticle-reinforced FeCrB-based composite material without pre-oxidation (Comparative Example 1) and traditional mold steel materials (Comparative Examples 2 and 3). Figure 2It can be seen that after immersion in molten aluminum for 1 hour, the interface of the substrate in the example remained intact and was not corroded by the molten aluminum. This indicates that the generated oxide film can inhibit the contact between the molten aluminum and the substrate in the early stage of corrosion and delay the reaction between the molten aluminum and the substrate. In contrast, a distinct intermetallic compound intermediate layer was formed in Comparative Example 4. After immersion in molten aluminum for 4 hours, the corrosion rate of the example was 0.327 μm / min, which was 50.3% of the corrosion rate of Comparative Example 1 (0.65 μm / min), an increase of 1.99 times. The static aluminum corrosion resistance of the example was 10.66 times that of Comparative Example 2, 4.06 times that of Comparative Example 3, and 1.3 times that of Comparative Example 4. Compared with the in-situ nanoparticle-reinforced FeCrB-based composite material without pre-oxidation treatment, the pre-oxidation treatment in this invention can form a uniform, continuous, and dense oxide film on the substrate surface, inhibiting the direct contact between the substrate and the molten aluminum in the initial stage of corrosion. Subsequently, it can reduce the diffusion of Al atoms into the substrate and inhibit the reaction with the molten aluminum. The oxide film can react with the molten aluminum, delaying the corrosion of the substrate by the molten aluminum. It improves the resistance to aluminum liquid corrosion and has broad application prospects in the field of liquid metal corrosion and wear technology.

[0070] The above description is merely of specific embodiments of the present invention. It should be noted that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications and variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for improving the corrosion resistance of in-situ nanoparticle-reinforced FeCrB-based composite materials to molten aluminum, characterized in that, The method includes: pre-oxidizing the in-situ nanoparticle-reinforced FeCrB-based composite material to generate a multilayer oxide film; the pre-oxidation temperature of the pre-oxidation treatment is 600~800 ℃, and the pre-oxidation treatment time is 5~30 h. The oxidizing gas used in the pre-oxidation treatment is air, and the heating rate is 5~10 ℃ / min; The multilayer oxide film consists of an inner Cr2O3 layer, a middle B2O3-SiO2 amorphous layer, and an outer Cr2O3 layer. The nanoparticles in the in-situ nanoparticle-reinforced FeCrB-based composite material include TiC and TiB2, wherein the total integral of TiC and TiB2 in the composite material is 1.0-2.0%. The in-situ nanoparticle-reinforced FeCrB-based composite material comprises the following components in the following mass percentages: C 0.35-0.5%, B 3.5-4.0%, Cr 12.0-16.0%, Si 1.5-3.0%, Ni 0.5-1.0%, Ti 0.8-1.6%, with the balance being iron.

2. The method according to claim 1, characterized in that, The pre-oxidation treatment was carried out at a pre-oxidation temperature of 700 °C for 10 h.

3. The method according to claim 1, characterized in that, The heating rate for the pre-oxidation treatment is 8 °C / min.

4. The method according to claim 1, characterized in that, The cooling method for the pre-oxidation treatment is air cooling.

5. The method according to claim 1, characterized in that, The thickness of the multilayer oxide film is 0.5 ~ 2 μm.

6. The method according to claim 1, characterized in that, The pre-oxidation treatment specifically includes the following steps: S1. Grind and polish the in-situ nanoparticle-reinforced FeCrB-based composite material; S2. The in-situ nanoparticle-reinforced FeCrB-based composite material that has been polished and ground is heated and then kept at a constant temperature. S3. Cool the in-situ nanoparticle-reinforced FeCrB-based composite material after heat preservation in air to obtain the in-situ nanoparticle-reinforced FeCrB-based composite material after oxidation treatment.

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