Cobalt-based laser cladding high-temperature-corrosion-resistant composite coating containing Ti3SiC2 and preparation method of cobalt-based laser cladding high-temperature-corrosion-resistant composite coating

Abstract

The invention discloses a Ti3SiC2-containing cobalt-based laser cladding high-temperature-corrosion-resistant composite coating and a preparation method thereof, the Ti3SiC2-containing cobalt-based laser cladding high-temperature-corrosion-resistant composite coating comprises cobalt-based powder and Ti3SiC2 powder, and the Ti3SiC2 powder accounts for 2-10wt% of the cobalt-based powder by mass. In the laser cladding process, grains of the cobalt-based coating are refined through Ti3SiC2, the grain boundary area is increased, the Cr element is more easily diffused to the surface of the coating with the grain boundary as a channel to form Cr2O3 with the protective effect, after corrosion is conducted for 168 hours, the corrosion weight increment is minimum, the thickness of an oxidation film is 10 microns, and the internal corrosion depth does not exceed 20 microns.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional coatings, and in particular relates to a cobalt-based laser-cladding high-temperature corrosion-resistant composite coating containing Ti3SiC2 and a preparation method thereof. Background Art

[0002] Waste-to-energy incineration not only quickly disposes of accumulated garbage but also transforms waste into energy, converting it into electricity and achieving resource recycling, achieving multiple goals at one stroke. However, waste-to-energy incineration also has its drawbacks. The incineration process produces corrosive gases such as SO2 and Cl2. Furthermore, molten salts in domestic waste (such as NaCl, KCl, and Na2SO4) react with elements in boiler pipes at high temperatures, severely corroding and damaging the pipes, causing them to fail or even burst. Therefore, to extend the service life of boiler pipes and the efficiency of waste-to-energy plants, research on how to improve the corrosion resistance of boiler pipes in harsh, high-temperature environments has become a key issue that needs to be addressed in the field of boiler pipe performance.

[0003] To address the corrosion problem of waste incineration boiler pipes, experts have specifically researched various materials and technologies. Common boiler pipe materials include carbon steel, austenitic stainless steel, and nickel-based superalloys. Common boiler pipe surface modification technologies include thermal spraying, cladding, and embedded diffusion. Nickel-based alloys offer excellent corrosion and high-temperature oxidation resistance, but their cost is relatively high. While carbon steel and austenitic stainless steel are relatively inexpensive, boiler pipes made from these materials can corrode and fail over time in high-temperature corrosive environments, reducing boiler efficiency and even causing safety incidents. Technically, thermal spray coatings have poor adhesion to the substrate and low porosity; cladding coatings have a high dilution rate and are therefore more expensive; and embedded diffusion coatings have a long cycle and demanding equipment requirements.

[0004] Therefore, it is necessary to develop new materials and technologies to meet the performance requirements of boiler pipes. The commonly used boiler pipe materials on the market can no longer meet the future development requirements of high temperature and high pressure, and cobalt-based alloys have good high-temperature corrosion resistance, so they have become the focus of research. However, the cost of cobalt materials is relatively high, so it is not economically suitable as a base material for boiler pipes. In order to balance cost and performance, researchers proposed laser cladding a thin and dense high-temperature corrosion-resistant alloy coating on the surface of commonly used boiler pipe materials. This method can not only improve the high-temperature corrosion resistance of the pipeline, but also effectively reduce the cost of the material.

[0005] Currently, the addition of TiC particles to cobalt-based coatings to improve performance results in poor results due to slow oxidation rates and low brittleness. Common high-temperature oxidation-resistant materials currently on the market typically incorporate small amounts of Ti3SiC2 and Co powders into hard phase powders such as tungsten carbide during laser cladding. The resulting coatings offer high hardness and wear resistance, but their high-temperature corrosion resistance needs improvement. Summary of the Invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and to briefly introduce some preferred embodiments.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a cobalt-based laser cladding high-temperature corrosion-resistant composite coating containing Ti3SiC2.

[0009] To solve the above technical problems, the present invention provides the following technical solution: a cobalt-based laser cladding high-temperature corrosion-resistant composite coating containing Ti3SiC2, characterized in that it includes cobalt-based powder and Ti3SiC2 powder, wherein the mass percentage of Ti3SiC2 powder in the cobalt-based powder is 2~10wt.%.

[0010] As a preferred solution of the cobalt-based laser cladding high-temperature corrosion-resistant composite coating of the present invention, the mass percentage of the Ti3SiC2 powder in the cobalt-based powder is 2wt.%, 4wt.%, 6wt.%, 8wt.%, and 10wt.%, respectively.

[0011] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a cobalt-based laser cladding high-temperature corrosion-resistant composite coating, comprising: Ti3SiC2 powder is added to the cobalt-based powder, and the mixture is subjected to ball milling to obtain a mixed powder; 304 stainless steel was selected as the laser cladding substrate, and the surface of the substrate was brushed to reduce the reflection of the laser on the substrate surface to obtain the treated substrate; The treated substrate is ultrasonically cleaned with anhydrous ethanol and then dried to obtain a cleaned and dried substrate; The cleaned and dried substrate is placed on a constant temperature heating table and heated to 300° C. to obtain a heated substrate; The mixed powder is clad on the heated substrate surface using a laser cladding process to form a coating.

[0012] As a preferred embodiment of the preparation method of the present invention, the ball milling treatment is performed at a ball milling speed of 300 r / min and a ball milling time of 3 h.

[0013] As a preferred embodiment of the preparation method of the present invention, the cobalt-based powder comprises spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh, and the particle size of the Ti3SiC2 powder is 200 mesh.

[0014] As a preferred embodiment of the preparation method of the present invention, the laser cladding parameters are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, and overlap rate 50%.

[0015] As a preferred embodiment of the preparation method of the present invention, the size of the laser cladding substrate is 100 mm × 100 mm × 20 mm. Beneficial effects of the present invention: (1) During the laser cladding process of the present invention, Ti3SiC2 refines the grains of the cobalt-based coating and increases the grain boundary area. The Cr element is more likely to diffuse to the coating surface through the grain boundary as a channel to form Cr2O3 with a protective effect. After 168 hours of corrosion, the corrosion weight gain is minimal, the oxide film thickness is 10 μm, and the internal corrosion depth does not exceed 20 μm.

[0016] (2) The cost control of the present invention is feasible and suitable for large-scale industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them: Figure 1 This is a diagram of the corrosion reaction mechanism of the cobalt-based coating after adding Ti3SiC2 in the present invention; Figure 2 These are cross-sectional SEM-EDS images of the coatings of Control Example 1 and Examples 1-5 of the present invention after corrosion at 600°C for 168 h, wherein (a) is the SEM-EDS image of Control Example 1, (b) is the SEM-EDS image of Example 1, (c) is the SEM-EDS image of Example 2, (d) is the SEM-EDS image of Example 3, (e) is the SEM-EDS image of Example 4, and (f) is the SEM-EDS image of Example 5.

[0018] Figure 3 This is the cross-sectional SEM-EDS image of control example 2 after corrosion at 600℃ for 168 h; Figure 4These are the cross-sectional micromorphologies of the coatings of Control Example 1 and Examples 1-5 of the present invention, wherein (a) is Control Example 1, (b) is Example 1, (c) is Example 2, (d) is Example 3, (e) is Example 4, and (f) is Example 5.

[0019] Figure 5 Corrosion kinetics curves obtained by weighing the coatings of Control Example 1 and Examples 1-5 every 24 hours in a high-temperature corrosion resistance test according to the present invention; Figure 6 This is an EDS scan image of the cross section of the coating of Example 2 of the present invention after being corroded at 600°C for 168 h; Figure 7 The XRD patterns of the coating surfaces of Control Example 1 and Examples 1-5 of the present invention are shown. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0021] The test materials used in this invention are all common materials purchased on the market. The laser cladding system used is composed of an RFL-C3000 fiber laser, an HR-PFS-STBN06 powder feeder, a CWFL*3000ANS water chiller, and an SBW-50KVA stabilized power supply. The system is equipped with an LH-ZRS-1020-02 cladding head, a CC-0715-01 annular nozzle, and a HUIRUI automatic powder feeder with two independent powder feeding bins. The tube furnace model used in the oxidation cycle is GSL-1100X-S; The tissue morphology of the samples was observed using a BX53MRF-S optical microscope; A Gemini SEM 300 field emission scanning electron microscope with energy spectrum analysis function was used to observe the surface and cross-sectional morphology of the original cobalt-based coating and the coating after high-temperature corrosion and cyclic oxidation treatment, and to perform elemental analysis. The sample composition was determined using a Bruker-AXS D8 Advance X-ray diffractometer.

[0022] High temperature corrosion test conditions of the present invention: A mixed salt solution of KCl and Na2SO4 in a mass ratio of 3:1 was evenly sprayed on the sample surface using a salt spray gun, and the salt deposition amount was controlled to be 5±0.1 mg / cm 2The crucible containing the sample was placed in a tube furnace at 600°C, and a mixture of SO2, O2 and water vapor with a gas pressure ratio of 140:10:11 was introduced; the SO2 and O2 pressures were set to 0.14 MPa and 0.01 MPa respectively by adjusting the pressure reducing valve, and the water vapor pressure was 0.011 MPa; a NaOH washing bottle was connected to the outlet of the tube furnace to absorb Cl2 and residual SO2; the corrosion test lasted for 168 hours; a cycle operation was carried out every 24 hours, including cooling, immersion, drying, weighing and re-spraying of mixed salt.

[0023] Example 1 A cobalt-based high-temperature corrosion-resistant composite coating containing 2 wt.% Ti3SiC2 and a preparation method thereof, comprising the following steps: (1) Prepare the raw materials by adding 2 wt.% Ti3SiC2 powder to the cobalt-based powder and milling the mixture in a ball mill at 300 r / min for 3 h. (2) 304 stainless steel was selected as the laser cladding substrate with a size of 100 mm × 100 mm × 20 mm.

[0024] (3) ultrasonically cleaning the 304 stainless steel substrate in step (2) with anhydrous ethanol and then drying; (4) placing the substrate described in step (3) on a 300°C constant temperature heating table and heating it to 300°C; (5) Using a laser cladding process, the mixed powder (1) is clad on the surface of the substrate (4) to form a coating.

[0025] Wherein, step (1) uses spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh and Ti3SiC2 powder with a particle size of 200 mesh.

[0026] The laser cladding parameters used in step (5) are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, overlap rate 50%, and energy density formula E = P / (v × D) = 56.82 J / mm 2 , where E, P, V, and D represent energy density, laser power, scanning speed, and spot diameter, respectively.

[0027] Example 2 A cobalt-based high-temperature corrosion-resistant composite coating containing 4 wt.% Ti3SiC2 and a preparation method thereof, comprising the following steps: (1) Prepare the raw materials by adding 4 wt.% Ti3SiC2 powder to the cobalt-based powder and milling the mixture in a ball mill at 300 r / min for 3 h. (2) 304 stainless steel was selected as the laser cladding substrate with a size of 100 mm × 100 mm × 20 mm.

[0028] (3) ultrasonically cleaning the 304 stainless steel substrate in step (2) with anhydrous ethanol and then drying; (4) placing the substrate described in step (3) on a 300°C constant temperature heating table and heating it to 300°C; (5) Using a laser cladding process, the mixed powder (1) is clad on the surface of the substrate (4) to form a coating.

[0029] Wherein, step (1) uses spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh and Ti3SiC2 powder with a particle size of 200 mesh.

[0030] The laser cladding parameters used in step (5) are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, overlap rate 50%, and energy density formula E = P / (v × D) = 56.82 J / mm 2 , where E, P, V, and D represent energy density, laser power, scanning speed, and spot diameter, respectively.

[0031] Example 3 A cobalt-based high-temperature corrosion-resistant composite coating containing 6 wt.% Ti3SiC2 and a preparation method thereof, comprising the following steps: (1) Prepare the raw materials by adding 6 wt.% Ti3SiC2 powder to the cobalt-based powder and milling the mixture in a ball mill at 300 r / min for 3 h. (2) 304 stainless steel was selected as the laser cladding substrate with a size of 100 mm × 100 mm × 20 mm.

[0032] (3) ultrasonically cleaning the 304 stainless steel substrate in step (2) with anhydrous ethanol and then drying; (4) placing the substrate described in step (3) on a 300°C constant temperature heating table and heating it to 300°C; (5) Using a laser cladding process, the mixed powder (1) is clad on the surface of the substrate (4) to form a coating.

[0033] Wherein, step (1) uses spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh and Ti3SiC2 powder with a particle size of 200 mesh.

[0034] The laser cladding parameters used in step (5) are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, overlap rate 50%, and energy density formula E = P / (v × D) = 56.82 J / mm 2 , where E, P, V, and D represent energy density, laser power, scanning speed, and spot diameter, respectively.

[0035] Example 4 A cobalt-based high-temperature corrosion-resistant composite coating containing 8 wt.% Ti3SiC2 and a preparation method thereof, comprising the following steps: (1) Prepare the raw materials by adding 8 wt.% Ti3SiC2 powder to the cobalt-based powder and milling the mixture in a ball mill at 300 r / min for 3 h. (2) 304 stainless steel was selected as the laser cladding substrate with a size of 100 mm × 100 mm × 20 mm.

[0036] (3) ultrasonically cleaning the 304 stainless steel substrate in step (2) with anhydrous ethanol and then drying; (4) placing the substrate described in step (3) on a 300°C constant temperature heating table and heating it to 300°C; (5) Using a laser cladding process, the mixed powder (1) is clad on the surface of the substrate (4) to form a coating.

[0037] Wherein, step (1) uses spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh and Ti3SiC2 powder with a particle size of 200 mesh.

[0038] The laser cladding parameters used in step (5) are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, overlap rate 50%, and energy density formula E = P / (v × D) = 56.82 J / mm 2 , where E, P, V, and D represent energy density, laser power, scanning speed, and spot diameter, respectively.

[0039] Example 5 A cobalt-based high-temperature corrosion-resistant composite coating containing 10 wt.% Ti3SiC2 and a preparation method thereof, comprising the following steps: (1) Prepare the raw materials by adding 10 wt.% Ti3SiC2 powder to the cobalt-based powder and milling the mixture in a ball mill at 300 r / min for 3 h. (2) 304 stainless steel was selected as the laser cladding substrate with a size of 100 mm × 100 mm × 20 mm.

[0040] (3) ultrasonically cleaning the 304 stainless steel substrate in step (2) with anhydrous ethanol and then drying; (4) placing the substrate described in step (3) on a 300°C constant temperature heating table and heating it to 300°C; (5) Using a laser cladding process, the mixed powder (1) is clad on the surface of the substrate (4) to form a coating.

[0041] Wherein, step (1) uses spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh and Ti3SiC2 powder with a particle size of 200 mesh.

[0042] The laser cladding parameters used in step (5) are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, overlap rate 50%, and energy density formula E = P / (v × D) = 56.82 J / mm 2 , where E, P, V, and D represent energy density, laser power, scanning speed, and spot diameter, respectively.

[0043] Comparative Example 1 The preparation method of the Co-based powder doped with different fractions of Ti3SiC2 in Example 2 is replaced by pure Co powder, comprising the following steps: (1) Prepare the raw materials by using spherical Stellite 6 cobalt-based powder and ball milling it at 300 r / min for 3 h; (2) 304 stainless steel is selected as the laser cladding substrate with a size of 100 mm × 100 mm × 20 mm. The surface of the substrate needs to be brushed to reduce the reflection of the laser on the substrate surface; (3) ultrasonically cleaning the 304 stainless steel substrate in step (2) with anhydrous ethanol and then drying; (4) placing the substrate described in step (3) on a 300°C constant temperature heating table and heating it to 300°C; (5) Using a laser cladding process, the mixed powder (1) is clad on the surface of the substrate (4) to form a coating.

[0044] Wherein, step (1) uses spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh.

[0045] The laser cladding parameters used in step (5) are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, and overlap rate 50%. The energy density formula E = P / (v × D) = 56.82 J / mm is satisfied. 2 , where E, P, V, and D represent energy density, laser power, scanning speed, and spot diameter, respectively.

[0046] Comparative Example 2 The 304 stainless steel substrate used in Example 2 was replaced with the existing commonly used high-temperature corrosion-resistant material TP347H steel.

[0047] The corrosion reaction mechanism of cobalt-based coating after adding Ti3SiC2 is shown in the figure Figure 1 shown.

[0048] Depend on Figure 2 As can be seen, all coatings exhibit surface corrosion oxide layers and internal intergranular corrosion. However, varying the Ti₃SiC₂ addition significantly affects the coatings' high-temperature corrosion resistance. The results of high-temperature corrosion tests on each coating are shown in Table 1.

[0049] Table 1. Corrosion results after 168 h at 600℃ The results show that the thickness of the oxide film formed on the surface of the coating after corrosion first decreases and then increases with the increase in the amount of Ti3SiC2 added. The corrosion resistance of the cobalt-based coating is better than that of TP347H steel. The surface corrosion products of the cobalt-based coating are mainly composed of dense Cr2O3 and a small amount of CoO, and have excellent corrosion resistance. After adding Ti3SiC2, the thickness of the oxide film on the coating surface and the degree of internal corrosion first decrease and then increase. Among them, the coating with 4 wt.% Ti3SiC2 added in Example 2 has the best corrosion resistance.

[0050] like Figure 4 As shown in the figure, the cobalt-based coating without Ti3SiC2 addition exhibits coarse columnar crystals, a small number of grains and a small grain boundary area. As the Ti3SiC2 addition increases, the content and size of columnar crystals continue to decrease, the proportion of equiaxed crystals and cellular crystals increases significantly, the grains become refined, and the grain boundary area expands.

[0051] like Figure 5 As shown in the figure, the cobalt-based coating with different Ti3SiC2 contents has the least weight gain and the best high-temperature corrosion resistance when the Ti3SiC2 content is 4%. When the addition amount exceeds 4%, the weight gain becomes larger and the high-temperature corrosion resistance weakens.

[0052] Figure 6In order to obtain the best high-temperature corrosion resistance, a cross-sectional EDS surface scan image of the coating (prepared in Example 2) was obtained. It can be seen from the image that the generated oxide components are mostly Cr2O3 and a small amount of Co, Ni and Fe oxides, but the thickness of the oxide is reduced, and no C layer is scanned between the coating and the substrate, indicating that the coating has excellent corrosion resistance and the interior of the substrate is not severely corroded. Therefore, less oxide is generated, so the oxide on the coating surface is thinner.

[0053] like Figure 7 As shown in the figure, the phase composition of the cobalt-based coating changes significantly with the addition of Ti3SiC2, with new TiC and Cr7C3 phases being generated. This indicates that Ti3SiC2 partially retains its original structure during the laser cladding process. Ti3SiC2 also decomposes at high temperatures to form TiC and some free C. C reacts with Cr to form Cr7C3. TiC and Cr7C3 can refine the microstructure grains, increase the grain boundary area, and promote the diffusion of Cr to form a protective Cr2O3 oxide film.

[0054] Figure 3 The TP347H steel of Comparative Example 2 is shown Figure 2 In comparison, under the same corrosion conditions, its high-temperature corrosion resistance is lower than that of the cobalt-based coating containing Ti3SiC2 in Examples 1-5 and the pure cobalt-based coating in Comparative Example 1.

[0055] The present invention adds a small amount of Ti3SiC2 powder to pure Co powder, which improves the coating's lubricity, reduces the likelihood of cracking, and significantly enhances the coating's high-temperature corrosion resistance. While Ti3SiC2's improvement in wear resistance is predictable in the prior art, its impact on high-temperature corrosion resistance is unpredictable, and whether performance improves or deteriorates is unpredictable. Research conducted by the present invention shows that as the Ti3SiC2 content increases, high-temperature corrosion resistance initially improves and then weakens.

[0056] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A cobalt-based laser cladding high-temperature corrosion-resistant composite coating containing Ti3SiC2, characterized by: The invention comprises cobalt-based powder and Ti3SiC2 powder, wherein the mass percentage of Ti3SiC2 powder in the cobalt-based powder is 2-10wt.%.

2. The cobalt-based laser cladding high-temperature corrosion-resistant composite coating according to claim 1, characterized in that: The mass percentages of Ti3SiC2 powder in the cobalt-based powder were 2wt.%, 4wt.%, 6wt.%, 8wt.%, and 10wt.%, respectively.

3. The method for preparing the cobalt-based laser cladding high-temperature corrosion-resistant composite coating according to claim 1 or 2, characterized in that: include, Ti3SiC2 powder is added to the cobalt-based powder, and the mixture is subjected to ball milling to obtain a mixed powder; 304 stainless steel was selected as the laser cladding substrate, and the surface of the substrate was brushed to reduce the reflection of the laser on the substrate surface to obtain the treated substrate; The treated substrate is ultrasonically cleaned with anhydrous ethanol and then dried to obtain a cleaned and dried substrate; The cleaned and dried substrate is placed on a constant temperature heating table and heated to 300° C. to obtain a heated substrate; The mixed powder is clad on the heated substrate surface using a laser cladding process to form a coating.

4. The preparation method according to claim 3, wherein: The ball milling process is performed at a speed of 300 r / min and a time of 3 h.

5. The preparation method according to claim 3, wherein: The cobalt-based powder includes spherical Stellite 6 cobalt-based powder with a particle size range of 100-270 mesh, and the particle size of the Ti3SiC2 powder is 200 mesh.

6. The preparation method according to claim 4 or 5, characterized in that: The laser cladding parameters are: laser power 2000 W, spot diameter 3.2 mm, scanning speed 660 mm / min, powder feeding rate 1.1 r / min, and overlap rate 50%.

7. The preparation method according to claim 6, wherein: The size of the laser cladding substrate is 100 mm×100 mm×20 mm.

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