Preparation process and application of corrosion-resistant stainless steel composite material

Abstract

The invention belongs to the technical field of material metallurgy, and relates to a corrosion-resistant stainless steel composite material and a preparation process and application thereof. Copper alloy powder and titanium carbide are doped in stainless steel components for alloying treatment, the uppermost layer and the lowermost layer are stainless steel layers, the middle of the stainless steel layers is filled with ceramic powder, spark plasma sintering is adopted, a blank is prepared, the outer layer of the blank is plated with a nano TiO2 film, and the nano TiO2 film is formed. The stainless steel composite material with good corrosion resistance, high temperature resistance and impact resistance is obtained, the service life of a pipeline can be prolonged, blockage is prevented, the corrosion risk is reduced, and the material is applied to preparation of elbows and other pipe fittings in a heating system.

Description

Technical Field

[0001] This invention belongs to the field of materials metallurgy technology, and particularly relates to a preparation process and application of a corrosion-resistant stainless steel composite material. Background Technology

[0002] In heating systems, pipes need to transport high-temperature hot water or steam for extended periods. To ensure that the pipes do not deform or become damaged under long-term high-temperature conditions, the materials used for the pipe fittings must have good high-temperature resistance, corrosion resistance, as well as a certain level of strength and sealing.

[0003] Traditional stainless steel has a lower hardness than carbon steel and alloys, but better corrosion resistance. Therefore, stainless steel is often used to manufacture various conveying pipes and connecting fittings. Stainless steel is prone to creep during long-term service at high temperatures, and brittle fracture can occur in low-temperature environments due to decreased toughness. Furthermore, its forming process is quite limited. Cold forming is prone to cracking due to insufficient plasticity, while hot forming requires temperature control and can easily lead to coarse grains, affecting subsequent performance.

[0004] Chinese patent application CN120155568 A discloses a stainless steel composite material and its preparation method and application. This material involves doping stainless steel components with Cr2AlC ceramic components as a reinforcing phase. During sintering, Cr2AlC decomposes into Cr7C3, which possesses excellent strength and interfacial compatibility. The resulting stainless steel composite material exhibits excellent mechanical strength, toughness, and wear resistance, thus enabling the manufactured turbine to have excellent service life and energy conversion efficiency. However, in reality, the thermal expansion coefficients of ordinary stainless steel and ceramic fillers differ significantly, easily generating interfacial thermal stress during cooling. Furthermore, stainless steel has low surface activity and poor wettability with ceramics, leading to ceramic particle agglomeration or interfacial voids, affecting dispersion uniformity and ultimately causing cracks or bonding failure.

[0005] Alloyed stainless steel can have its thermal expansion coefficient adjusted by adding elements, thus reducing the difference between it and ceramics. Therefore, the performance of alloyed stainless steel doped with ceramic fillers can be significantly improved through the dual strengthening of the alloy matrix and ceramics. Summary of the Invention

[0006] This invention aims to provide a preparation process and application of a corrosion-resistant stainless steel composite material. The corrosion-resistant stainless steel composite material is prepared by alloying stainless steel components with copper alloy powder and titanium carbide, filling with ceramic powder, and sintering with spark plasma to obtain a billet. A nano-titanium dioxide film is then deposited on the outer layer of the billet to obtain a stainless steel composite material with good corrosion resistance, high temperature resistance and impact resistance, which can be used in the preparation of pipe fittings for heating systems.

[0007] To achieve the above objectives, the present invention provides a process for preparing a corrosion-resistant stainless steel composite material, comprising:

[0008] Step S1: Mix the stainless steel component, copper alloy powder and titanium carbide, grind and sieve, fill a mold with a layer of the above mixed powder, a layer of ceramic filler, and then fill another layer of the above mixed powder. Under inert gas protection, use spark plasma sintering to obtain the billet.

[0009] Step S2: Tetrabutyl titanate is dispersed in an aqueous ethanol solution, a catalyst is added, and the mixture is stirred to obtain a TiO2 sol. The billet is completely immersed in the TiO2 sol, dried, and annealed to obtain a corrosion-resistant stainless steel composite material.

[0010] Preferably, the ceramic filler is any one or more of hexagonal boron nitride, ceramic micro powder, and mullite.

[0011] Preferably, the mass ratio of the stainless steel component, copper alloy powder, and titanium carbide is 1:(0.25-0.4):(0.15-0.25).

[0012] Preferably, the stainless steel composition is any one or more of 06Cr17Ni12Mo2 and 022Cr17Ni12Mo2.

[0013] This invention also provides a process for preparing a corrosion-resistant stainless steel composite material, comprising:

[0014] Preferably, in step S1, the filling thickness of the mixed powder is 3-5 mm.

[0015] Preferably, in step S1, the filling thickness of the ceramic filler is 1 to 2 mm.

[0016] Preferably, in step S1, the process parameters for the spark plasma sintering are: sintering pressure of 50-100 MPa, heating rate of 100-200 °C / min, sintering temperature of 1350-1500 °C, and holding time of 5-10 min; the operation of the spark plasma sintering is as follows: after sintering, heating is stopped, pressure is maintained until the temperature drops below 200 °C, and the pressure is released and the blank is removed.

[0017] Preferably, in step S2, the mass ratio of ethanol to water in the ethanol-water solution is 1:(0.3-0.5).

[0018] Preferably, in step S2, the catalyst is any one or more of dilute hydrochloric acid, dilute nitric acid, and dilute sulfuric acid.

[0019] Preferably, in step S2, the mass ratio of tetrabutyl titanate, aqueous ethanol solution and catalyst is 1:(5-10):(0.01-0.05).

[0020] Preferably, in step S2, the time for the billet to be completely immersed in the TiO2 sol is 3 to 5 minutes.

[0021] Preferably, in step S2, the drying temperature is 50-80°C and the drying time is 1-2 hours.

[0022] Preferably, in step S2, the annealing temperature is 600–800°C and the annealing time is 2–4 hours.

[0023] This invention also provides an application of corrosion-resistant stainless steel composite material in the manufacture of elbows.

[0024] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0025] (1) This invention uses copper alloy powder and titanium carbide doping to alloy stainless steel materials, resulting in a hard alloy material with stainless steel as the base. The top and bottom layers are both alloyed hard alloy materials, and the middle is filled with ceramic filler. Through the synergistic effect of each component, the performance shortcomings of stainless steel are optimized, and its wear resistance, tensile strength, yield strength, corrosion resistance and other properties are improved. Stainless steel itself has excellent corrosion resistance, and as a matrix, it can ensure the stability of composite materials in humid and acidic / alkaline environments. TiC has an extremely high melting point, which can compensate for the problem of strength reduction of stainless steel at high temperatures. Copper alloy has a low melting point and can be used as a liquid phase sintering aid in the spark plasma sintering process to promote particle diffusion and densification, thereby improving the overall hardness of the alloy.

[0026] (2) In order to improve the corrosion resistance and self-cleaning performance of the composite material, the present invention covers the surface of the composite material with a dense nano-TiO2 film, which can give the material self-cleaning performance, reduce manual cleaning, block the penetration of corrosive media, and improve the corrosion resistance of the material. Under ultraviolet light irradiation, the photogenerated electron-hole pairs generated by TiO2 further oxidize bacteria and other organic substances, which can prevent microorganisms from settling in the sanitary dead corners of the pipeline. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the preparation process of a corrosion-resistant stainless steel composite material.

[0028] Figure 2 The image shows an actual elbow made using the corrosion-resistant stainless steel composite material from Example 3. Detailed Implementation

[0029] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0030] Unless otherwise specified, all reagents and equipment used in the following examples were purchased from commercial channels.

[0031] Example 1

[0032] A corrosion-resistant stainless steel composite material, comprising:

[0033] Step S1: Mix 1000g of 06Cr17Ni12Mo2 component, 250g of copper alloy powder and 150g of titanium carbide, grind and sieve through a 400-mesh sieve. Fill a mold with a 3mm layer of mixed powder, a 1mm layer of hexagonal boron nitride, and then fill another 3mm layer of mixed powder. Under argon protection, use spark plasma sintering, set the pressure to 50MPa, the heating rate to 100℃ / min, the sintering temperature to 1350℃, hold for 10min, stop heating, maintain pressure until the temperature drops below 200℃, and obtain the billet.

[0034] Step S2: Disperse 100g of tetrabutyl titanate in 500g of ethanol aqueous solution (384.6g of ethanol and 115.4g of water), add 1g of dilute hydrochloric acid, stir to obtain a sol, completely immerse the billet in the sol for 3min, dry at 50℃ for 2h, and anneal at 600℃ for 4h to obtain corrosion-resistant stainless steel composite material.

[0035] Example 2

[0036] A corrosion-resistant stainless steel composite material, comprising:

[0037] Step S1: Mix 1000g of 022Cr17Ni12Mo2 component, 300g of copper alloy powder and 200g of titanium carbide, grind and sieve, fill a mold with a 4mm layer of mixed powder, a 1.5mm layer of ceramic micro powder, and then fill another 4mm layer of mixed powder. Under argon protection, use spark plasma sintering, set the pressure to 75MPa, the heating rate to 150℃ / min, the sintering temperature to 1400℃, hold for 8min, stop heating, maintain pressure until the temperature drops below 200℃, and obtain the billet.

[0038] Step S2: Disperse 100g of tetrabutyl titanate in 750g of ethanol aqueous solution (535g of ethanol and 215g of water), add 3g of dilute nitric acid, stir to obtain a sol, completely immerse the billet in the sol for 4min, dry at 60℃ for 1.5h, and anneal at 700℃ for 3h to obtain corrosion-resistant stainless steel composite material.

[0039] Example 3

[0040] A corrosion-resistant stainless steel composite material, comprising:

[0041] Step S1: Mix 1000g of 022Cr17Ni12Mo2 component, 400g of copper alloy powder and 250g of titanium carbide, grind and sieve, fill a mold with a 5mm layer of mixed powder, a 2mm layer of mullite, and then fill another 5mm layer of mixed powder. Under argon protection, use spark plasma sintering, set the pressure to 100MPa, the heating rate to 200℃ / min, the sintering temperature to 1500℃, hold for 5min, stop heating, maintain pressure until the temperature drops below 200℃, and obtain the billet.

[0042] Step S2: Disperse 100g of tetrabutyl titanate in 1000g of ethanol aqueous solution (666g of ethanol and 334g of water), add 5g of dilute sulfuric acid, stir to obtain a sol, and completely immerse the blank in the sol for 5 minutes.

[0043] The corrosion-resistant stainless steel composite material was obtained by drying at 80℃ for 1 hour and annealing at 800℃ for 2 hours.

[0044] Comparative Example 1

[0045] A corrosion-resistant stainless steel composite material, the preparation method of which differs from that of Example 3 in that copper alloy powder is not added in step S1.

[0046] Comparative Example 2

[0047] A corrosion-resistant stainless steel composite material, the preparation method of which differs from that of Example 3 in that titanium carbide is not added in step S1.

[0048] Comparative Example 3

[0049] A corrosion-resistant stainless steel composite material, the preparation method of which differs from that of Example 3 in that no ceramic filler is added in step S2.

[0050] Comparative Example 4

[0051] A corrosion-resistant stainless steel composite material is prepared in a manner different from that in Example 2, in step S2, the blank is not immersed in an ethanol-water solution of tetrabutyl titanate for coating treatment.

[0052] The corrosion-resistant stainless steel composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were used to prepare corrosion-resistant stainless steel elbows using the following method:

[0053] The corrosion-resistant stainless steel composite material is fixed on the mandrel of the spinning machine. The spindle speed is set to 1000-1500 r / min, the spinning wheel feed speed is 0.5-2 mm / r, and the spinning force is 10-20 kN. The corrosion-resistant stainless steel elbow is obtained by spinning.

[0054] Performance testing:

[0055] (1) Mechanical properties

[0056] The tensile strength and yield strength of the elbow were tested using a metal material tensile strength testing device under the test conditions specified in GB / T 228.1-2021.

[0057] (2) Pressure resistance:

[0058] Static pressure test: Connect both ends of the elbow to the test pipeline through the sealing device, slowly fill the test system with water until the air in the system is completely expelled, start the pressurization pump, slowly increase the pressure to the specified test pressure (usually 1.5 times the working pressure), turn off the pressurization pump, maintain the pressure for 5 minutes, during the pressure holding period, observe whether there is any leakage or sweating on the surface of the elbow and the connection parts, reduce the pressure to normal pressure, remove the sample, and check for any deformation.

[0059] Bursting pressure test: Connect both ends of the elbow to the test pipeline through the sealing device, slowly fill the test system with water until the air in the system is completely expelled, start the pressurization pump, and continuously increase the pressure at ≥3 times the working pressure until the elbow bursts (the appearance of an irreparable leak is considered a burst), and record the moment of bursting.

[0060] (3) Corrosion resistance:

[0061] Neutral salt spray conditions: Prepare a sodium chloride solution with a mass fraction of 5% ± 1%, adjust the pH value of the solution to 6.5 to 7.2, fix the metal elbow on the sample rack inside the test chamber, maintain the temperature inside the chamber at 35 ± 2℃, start the test chamber, spray continuously according to the set parameters, take out the sample after 48 hours, gently rinse with running distilled water, dry for 1 to 2 hours, and observe the corrosion of the sample surface.

[0062] Media corrosion: Prepare 10% hydrochloric acid solution and sodium hydroxide solution respectively, and completely immerse the elbow in the container containing the corrosive medium. After 48 hours at 25±2℃, take out the sample, rinse it gently with running distilled water, dry it for 1-2 hours, and observe the corrosion on the sample surface.

[0063] (4) Self-cleaning performance test:

[0064] Degradation of organic pollutants: Coating with methylene blue solution (10 mg / L) or oleic acid film (1 μm). UV-A light source (365 nm, 1 mW / cm²). 2 Irradiation for 4 hours, and the change in absorbance was measured (λ=664nm).

[0065] Scale buildup: Circulating hard water (Ca 2+ 200 mg / L, 70℃ × 7 days), and weigh the sediment after drying.

[0066] Oil stain adhesion: Apply edible oil (0.1 mL / cm²) 2 After standing for 24 hours, rinse with warm water and assess the residual area.

[0067] Table 1. Test results of the mechanical properties of the elbow.

[0068] Sample number Tensile strength (MPa) Yield strength (MPa) Example 1 332 254 Example 2 348 263 Example 3 372 312 Comparative Example 1 286 213 Comparative Example 2 257 206 Comparative Example 3 242 218 Comparative Example 4 357 254

[0069] According to Table 1, the double-layer composite stainless steel elbows prepared in Examples 1 to 3 and Comparative Example 4 have good mechanical properties, with tensile strengths all above 300 MPa and yield strengths all above 250 MPa; while the elbows prepared in Comparative Examples 1 to 3 have tensile strengths below 300 MPa and yield strengths below 250 MPa.

[0070] Table 2 Test Results of Elbow Pressure Resistance Performance

[0071]

[0072] As shown in Table 2, the elbows prepared in Examples 1 to 3 did not show any deformation or leakage when held in a static pressure environment for 5 minutes. Although Comparative Examples 2 and 3 did not show any leakage under the same conditions, they did show slight deformation. In the burst pressure test, the elbows prepared in Examples 1 to 3 and Comparative Example 4 all had a pressure holding time greater than 60 seconds. The elbows prepared in Comparative Examples 1 to 3 had a pressure holding time significantly lower than the other groups, all below 40 seconds.

[0073] Table 3. Resistance of elbows to neutral salt spray and media corrosion.

[0074] Sample number neutral salt spray Acidic media corrosion Alkaline media corrosion Example 1 Rust-free Rust-free Rust-free Example 2 Rust-free Rust-free Rust-free Example 3 Rust-free Rust-free Rust-free Comparative Example 1 Rust-free Rust-free Rust-free Comparative Example 2 Rust-free Rust-free Rust-free Comparative Example 3 Rust-free Rust-free Rust-free Comparative Example 4 Slight rust Obvious rust Obvious rust

[0075] Table 4 Electrochemical Corrosion Resistance of Elbows

[0076]

[0077] According to Table 3, the elbows prepared in Examples 1 to 3 and Comparative Examples 1 to 3 showed no corrosion on their surface and inner layers in neutral salt spray environment, acidic medium and alkaline medium; the elbow prepared in Comparative Example 4 showed slight corrosion on its surface and inner layers in neutral salt spray environment, and obvious corrosion in acidic and alkaline medium.

[0078] As shown in Table 4, the elbows prepared in Examples 1-3 and Comparative Examples 1-3 did not show any corrosion after electrochemical corrosion testing, while the elbow prepared in Comparative Example 4 showed corrosion with a pitting density of 5 pits / cm². 2 The maximum pitting depth is 17.42 μm.

[0079] Table 5 Self-cleaning performance test data

[0080] Note: Excellent: No residue, clean metal surface; Good: Residue <10%, trace amounts of oil residue on metal surface; Medium: 10% ≤ Residue <30%, localized oil film buildup on metal surface; Poor: Residue ≥30%, large amounts of oil residue on metal surface.

[0081] As shown in Table 5, the elbows prepared in Examples 1-3 and Comparative Examples 1-3 all exhibited good degradation activity against methylene blue and oleic acid, with degradation rates exceeding 95% for methylene blue and over 90% for oleic acid. The elbow prepared in Comparative Example 4 showed degradation rates below 45% for methylene blue and below 35% for oleic acid, significantly lower than those prepared in Examples 1-3 and Comparative Examples 1-3.

[0082] The elbows prepared in Examples 1-3 and Comparative Examples 1-3 showed a scale deposition of 1 mg / cm³ after a 7-day test. 2 Below, the scale deposition in the elbow prepared in Comparative Example 4 was 2.56 mg / cm³. 2 The results were significantly higher than those of the elbows prepared in Examples 1-3 and Comparative Examples 1-3. The elbows prepared in Examples 1-3 and Comparative Examples 1-3 all showed no residual oil in the oil adhesion test, receiving an excellent rating. The elbow prepared in Comparative Example 4 had ≥30% residual oil on its surface, receiving a poor rating. The experiment demonstrates that depositing a dense TiO2 film on the surface can endow the inner and outer stainless steel materials of the stainless steel elbow with good organic matter degradation capabilities, reducing scale and oil residue. This allows for long-term self-cleaning without chemical cleaning, reducing maintenance costs and mitigating various risks.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A preparation process for a corrosion-resistant stainless steel composite material, characterized in that, include: Step S1: Mix stainless steel components, copper alloy powder and titanium carbide, grind and sieve to obtain mixed powder, fill a mold with a layer of mixed powder, a layer of ceramic filler, and then fill another layer of mixed powder, and sinter by spark plasma under inert gas protection to obtain a billet; Step S2: Tetrabutyl titanate is dispersed in an aqueous ethanol solution, a catalyst is added, and the mixture is stirred to obtain a TiO2 sol. The billet is completely immersed in the TiO2 sol, dried, and annealed to obtain a corrosion-resistant stainless steel composite material.

2. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, In step S1, the stainless steel composition is any one or more of 06Cr17Ni12Mo2 or 022Cr17Ni12Mo2.

3. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, The ceramic filler in step S1 is any one or more of hexagonal boron nitride, ceramic micro powder, and mullite.

4. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, In step S1, the mass ratio of the stainless steel component, copper alloy powder, and titanium carbide is 1:(0.25-0.4):(0.15-0.25).

5. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, In step S1, the filling thickness of the mixed powder is 3-5 mm; the filling thickness of the ceramic filler is 1-2 mm.

6. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, In step S1, the process parameters for the spark plasma sintering are: sintering pressure of 50-100 MPa, heating rate of 100-200 °C / min, sintering temperature of 1350-1500 °C, and holding time of 5-10 min. The operation of the spark plasma sintering is as follows: after sintering, heating is stopped, pressure is maintained until the temperature drops below 200 °C, and the pressure is released and the blank is removed.

7. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, In step S2, the mass ratio of ethanol to water in the ethanol-water solution is 1:(0.3-0.5); the catalyst is any one or more of dilute hydrochloric acid, dilute nitric acid, and dilute sulfuric acid.

8. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, In step S2, the mass ratio of tetrabutyl titanate, aqueous ethanol solution, and catalyst is 1:(5-10):(0.01-0.05).

9. The preparation process of a corrosion-resistant stainless steel composite material according to claim 1, characterized in that, In step S2, the blank is completely immersed in TiO2 sol for 3 to 5 minutes; the drying temperature is 50 to 80°C and the drying time is 1 to 2 hours; the annealing temperature is 600 to 800°C and the annealing time is 2 to 4 hours.

10. The application of a corrosion-resistant stainless steel composite material prepared according to any one of claims 1 to 9 in the manufacture of elbows.

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