High-temperature molten salt corrosion-resistant FeCrAl composite coating based on ceramic phase proportion optimization and preparation method of high-temperature molten salt corrosion-resistant FeCrAl composite coating

Abstract

The invention discloses a method for enhancing high temperature resistance and molten salt corrosion resistance, and belongs to the technical field of material science and surface engineering. According to the preparation method, Al2O3 and TiC ceramic phases are added into the FeCrAl alloy, the ceramic reinforced FeCrAl composite coating is prepared by adopting a laser cladding method, and the proportion of the ceramic phases is optimized, so that diffusion of molten salt is blocked through a physical barrier effect, formation of an Al2O3-Cr2O3 composite oxide film is promoted, and the corrosion resistance of the FeCrAl alloy in the high-temperature molten salt is improved.

Description

Technical Field

[0001] The present invention belongs to the field of materials science and surface engineering technology, and specifically relates to a ceramic-reinforced FeCrAl composite coating prepared by laser cladding technology, which is suitable for corrosion protection in high-temperature molten salt environments. Background Art

[0002] In recent years, FeCrAl alloys have attracted widespread attention due to their ability to form a protective oxide film at high temperatures and their excellent corrosion resistance. However, in a high-temperature molten salt environment, the penetration of molten salt will destroy the stability of the oxide film, causing selective grain boundary corrosion of the material, which seriously restricts its engineering application. In the existing technology, although the corrosion resistance of FeCrAl coatings can be improved by element doping (such as Si, Cr / Al gradient design) or process parameter optimization (such as laser power control), there is a bottleneck in their long-term protection in high-temperature molten salts. Therefore, there is an urgent need to develop a FeCrAl composite coating that is resistant to high-temperature molten salt corrosion. Summary of the Invention

[0003] In view of some deficiencies in the prior art, the present invention provides a preparation process of a ceramic-reinforced FeCrAl composite coating with good high-temperature resistance and molten salt corrosion resistance.

[0004] The present invention provides a method for achieving good high-temperature and molten salt corrosion resistance, comprising: introducing Al2O3 and TiC ceramic phases, preparing a ceramic-reinforced FeCrAl composite coating by a laser cladding method, optimizing the proportion of the ceramic phases, and improving the corrosion resistance of the coating in high-temperature molten salt.

[0005] Furthermore, the composite coating comprises:

[0006] (1) Base material: 304, 316, 310S stainless steel, etc.

[0007] (2) Powder particle size: Al2O3 (particle size 20–80 μm), TiC (particle size 1–5 μm), FeCrAl alloy powder (particle size 20–150 μm);

[0008] (3) Ceramic phase content: the mass fraction of Al2O3 or TiC is 0, 20%, 40%, 60%, and 80%.

[0009] Furthermore, the method comprises the following steps:

[0010] Step 1: cutting the base material by wire electric discharge cutting, grinding, polishing and cleaning with anhydrous ethanol;

[0011] Step 2: Mechanically mix a series of ceramic powders with different contents with FeCrAl powder in proportion, and dry the mixed powders at 100° C. under vacuum for 1.5 hours;

[0012] Step 3: Under specific parameters, a ceramic-reinforced FeCrAl composite coating is prepared on the surface of the substrate by a laser cladding method;

[0013] Step 4: testing the high temperature molten salt corrosion resistance of the ceramic reinforced FeCrAl composite coating;

[0014] Furthermore, in step 3, the specific parameters include: laser power: 1400–2000 W (adjusted according to the ceramic phase content); scanning speed: 4-6 mm / s; spot diameter: 3-4 mm; powder feeding rate: 0.6-1.2 r / min; shielding gas: argon, flow rate 15 L / min.

[0015] Furthermore, in step 4, the high temperature molten salt corrosion resistance testing step includes:

[0016] Step A1: Cut the sample into appropriate sizes using wire-cut electrical discharge machining (WEDM), followed by grinding and polishing to obtain a smooth surface. The sample was then ultrasonically cleaned in ethanol and dried at room temperature.

[0017] Step A2: The dried sample was weighed three times using an electronic balance with an accuracy of 0.1 mg to obtain an average initial mass, thereby ensuring the reliability of the measurement.

[0018] Step A3: performing a hot corrosion test on the salt-coated sample in a muffle furnace;

[0019] Step A4: Allow the sample to cool naturally to ambient temperature at predetermined intervals. Boil the desalted sample in distilled water to remove residual salt. Weigh the sample three times using a high-precision electronic balance to determine the average mass after corrosion, eliminating errors caused by salt retention.

[0020] The beneficial effects of the present invention are:

[0021] The present invention uses laser cladding technology to add a ceramic phase to the FeCrAl alloy, optimizes the ceramic content, utilizes the physical barrier effect of the ceramic to block the diffusion of molten salt, promotes the formation of an Al2O3-Cr2O3 composite oxide film, and improves the corrosion resistance of the FeCrAl alloy in high-temperature molten salt.

[0022] In addition, excessive ceramic phase will lead to an increase in coating interface defects, prompting the rapid penetration of molten salt along the pores, resulting in a decrease in corrosion performance, revealing the nonlinear correlation mechanism between ceramic content and corrosion resistance.

[0023] The present invention utilizes laser cladding technology to add a ceramic phase into the FeCrAl alloy. Because the FeCrAl alloy has good corrosion resistance under high-temperature molten salt conditions, it has great application potential in high-temperature molten salt environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the corrosion kinetics curve of FeCrAl / Al2O3 composite coating;

[0025] Figure 2 It is the longitudinal section morphology of the FeCrAl / Al2O3 composite coating sample after different hot corrosion time;

[0026] in Figure 1 : S1 is a pure FeCrAl coating; S2 is a FeCrAl / Al2O3 (20%) composite coating; S3 is a FeCrAl / Al2O3 (40%) composite coating.

[0027] Figure 2 a, b, c represent the cross-sectional microstructures of pure FeCrAl coating, FeCrAl / Al2O3 (20%) composite coating, and FeCrAl / Al2O3 (40%) composite coating after hot corrosion for 20 h, respectively. a1, b1, c1 represent the cross-sectional microstructures of pure FeCrAl coating, FeCrAl / Al2O3 (20%) composite coating, and FeCrAl / Al2O3 (40%) composite coating after hot corrosion for 100 h, respectively. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] Example 1:

[0030] (1) Base material

[0031] 310S stainless steel is used as the base material;

[0032] Use wire EDM to cut the base material into 100×100×5mm 3 The size is then adjusted, ground, polished and cleaned with anhydrous ethanol.

[0033] (2) Powder preparation: Al2O3 ceramic powder was mechanically mixed with FeCrAl powder in proportions (0, 20%, 40%), and the mixed powder was dried under vacuum at 100°C for 1.5 hours.

[0034] (3) FeCrAl / Al2O3 composite coating was prepared by laser cladding technology. The laser parameters were as follows: laser power: 1800W; scanning speed: 6mm / s; spot diameter: 3.5mm; powder feeding rate: 0.8r / min; shielding gas: argon, flow rate 15L / min;

[0035] (4) Cut the prepared sample into 10×10×5mm pieces using an EDM wire. 3 The samples were then ultrasonically cleaned in ethanol and dried at room temperature.

[0036] (5) The dried sample was weighed three times with an electronic balance with an accuracy of 0.1 mg to obtain the average initial mass, which ensured the reliability of the measurement.

[0037] (6) Place the sample in a drying oven at 120°C and dry for 20 minutes. Apply a saturated salt solution (50 wt% NaCl + 50 wt% KCl) evenly on the coating surface and make it smooth. The salt density should be controlled at 2-3 mg / cm 2 .

[0038] (7) The salt-coated samples were subjected to a hot corrosion test in a muffle furnace at 650°C for 100 hours.

[0039] (8) At predetermined time intervals (20, 40, 60, 80, and 100 hours), the sample was allowed to cool naturally to ambient temperature. The desalted sample was boiled in distilled water for 30 minutes to remove residual salt. The sample was then weighed three times using a high-precision electronic balance (minimum resolution: 0.001 g) to determine the average mass after corrosion and eliminate errors caused by salt retention.

[0040] like Figure 1 As shown in Figure 2, after 100 hours of high temperature chloride corrosion test, the weight of the three composite coatings gradually increased. The total mass gains of the FeCrAl, FeCrAl / Al2O3 (20%) and FeCrAl / Al2O3 (40%) coatings were 17.32 mg / cm 2 、11.65mg / cm 2 and 18.12 mg / cm 2 Compared with the FeCrAl coating, the mass gain of the FeCrAl / Al2O3 (20%) coating is significantly reduced, and it has stronger corrosion resistance. However, the corrosion resistance of the FeCrAl / Al2O3 (40%) coating is slightly lower than that of the FeCrAl coating, which indicates that as the Al2O3 content increases, the excessive Al2O3 ceramic content will gradually reduce the high-temperature corrosion resistance of the coating.

[0041] like Figure 2Figure 2 shows the cross-sectional microstructures of the three composite coatings after exposure to hot corrosion for different times. Comparative analysis shows that as the hot corrosion time increases, an oxide layer forms within the exfoliated corrosion product layer. In the initial stage (20 h), the corrosion layer thickness of the pure FeCrAl coating reaches 21.11 μm, with a small amount of void defects in the oxide layer. In contrast, the corrosion layer thicknesses of the composite coatings containing 20% ​​Al2O3 and 40% Al2O3 are 17.78 μm and 21.34 μm, respectively. After long-term exposure (100 h), the corrosion layer thickness of the pure FeCrAl coating increases significantly to 44.45 μm, with obvious cracks and residual void defects appearing in the oxide layer. It is noteworthy that the coating containing 20% ​​Al2O3 forms a thin and dense oxide layer with a thickness of 30.56 μm, exhibiting excellent oxidation resistance. When the Al2O3 content is 40%, the thickness of the coating corrosion layer increases sharply (44.56μm). This is because the excessively high Al2O3 content leads to loose structure and local void defects, which ultimately aggravates corrosion degradation.

Claims

1. A method for enhancing high temperature and molten salt corrosion resistance, characterized in that: By introducing Al2O3 and TiC ceramic phases, a ceramic-reinforced FeCrAl composite coating was prepared by laser cladding method, the proportion of its ceramic phase was optimized, and the corrosion resistance of the coating in high-temperature molten salt was improved.

2. The composite coating composition according to claim 1 comprises: (1) Base material: 304, 316, 310S stainless steel, etc. (2) Powder particle size: Al2O3 (particle size 20–80 μm), TiC (particle size 1–5 μm), FeCrAl alloy powder (particle size 20–150 μm); (3) Ceramic phase content: the mass fraction of Al2O3 or TiC is 0, 20%, 40%, 60%, and 80%.

3. The method according to claim 1 comprises the following steps: Step 1: cutting the base material by wire electric discharge cutting, grinding, polishing and cleaning with anhydrous ethanol; Step 2: Mechanically mix a series of ceramic powders with different contents with FeCrAl powder in proportion, and dry the mixed powders at 100° C. under vacuum for 1.5 hours; Step 3: Under specific parameters, a ceramic-reinforced FeCrAl composite coating is prepared on the surface of the substrate by a laser cladding method; Step 4: Test the high-temperature molten salt corrosion resistance of the ceramic-reinforced FeCrAl composite coating.

4. The method for improving high temperature and molten salt corrosion resistance according to claim 3, characterized in that: In step 3, specific parameters Includes: Laser power: 1400–2000W (adjusted according to ceramic phase content); Scanning speed: 4-6mm / s; Spot diameter: 3-4mm; powder feeding rate: 0.6-1.2r / min; shielding gas: argon, flow rate 15L / min.

5. The method for improving high temperature and molten salt corrosion resistance according to claim 3, characterized in that: In step 4, the high temperature molten salt corrosion resistance testing step includes: Step A1: Cut the sample into appropriate sizes using wire-cut electrical discharge machining (WEDM), followed by grinding and polishing to obtain a smooth surface. The sample was then ultrasonically cleaned in ethanol and dried at room temperature. Step A2: The dried sample was weighed three times using an electronic balance with an accuracy of 0.1 mg to obtain an average initial mass, thereby ensuring the reliability of the measurement. Step A3: performing a hot corrosion test on the salt-coated sample in a muffle furnace; Step A4: Allow the sample to cool naturally to ambient temperature at predetermined intervals. Boil the desalted sample in distilled water to remove residual salt. Weigh the sample three times using a high-precision electronic balance to determine the average mass after corrosion, eliminating errors caused by salt retention.

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