A grate bar for a baking car and a method of manufacturing the same

Abstract

This invention discloses a grate bar for a roasting trolley, comprising a chromium-nickel alloy substrate and a thermally sprayed composite coating deposited on its surface after a sealing treatment. The thermally sprayed composite coating comprises a CoNiCrAlY base layer and a CoCrAlYTa-based high-temperature gradient surface layer. The CoCrAlYTa-based high-temperature gradient surface layer comprises CoCrAlYTa and heat-resistant oxides, with the content of the heat-resistant oxides distributed in a gradient along the coating. This invention, using a chromium-nickel alloy substrate combined with a thermally sprayed composite coating, achieves a good balance of high-temperature wear resistance, resistance to impurity adhesion, high-temperature oxidation resistance, and erosion resistance, effectively extending its service life in belt-type roasting trolley operating systems and offering wide applicability.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical pelletizing technology, specifically relating to a grate bar for a steel belt roasting unit trolley and its preparation method. Background Technology

[0002] In the sintering process of iron and steel smelting pellets, the belt roaster mainly operates within the roasting equipment. The roasting equipment includes drying, preheating, roasting, homogenization, and cooling zones. The processing temperature in each section is gradually increased from room temperature to approximately 1300℃. The heat is supplied to the corresponding drying, preheating, and roasting zones via the waste heat hot air system of different cooling sections. The highest hot air temperature is approximately 1250℃. The hot air flows from the trolley upwards through the gaps between the grate bars, heating the pellet material carried on the trolley's grate bars. The belt roasting trolley's running system is a stepping, reciprocating structure, powered by a main shaft gear chain. The pellets and grate bars move at a uniform speed with the trolley within the roasting equipment. The belt roasting unit has approximately 160 trolleys, each equipped with approximately 320 grates.

[0003] The grate bars of the trolley are a key piece of equipment for carrying pellet materials and are among the most vulnerable components of the trolley, making them a critical factor in trolley failure. The main failure modes of the grate bars are wear from unloading the pellets and erosion from flue gas containing metal particles, which increases the gap between adjacent grate bars, leading to pellet leakage. While the erosion effect from flue gas containing metal particles is relatively minor, the primary cause is sliding scouring wear during pellet unloading. Typically, the trolley grate bars used in pellet belt roasters are made of high-alloy cast steel. However, due to the high operating temperature, periodic rapid temperature rise and fall, and wide temperature range, coupled with repeated high-temperature erosion from hot air flue gas and the presence of dust of varying particle sizes in the flue gas, the grate bars are prone to oxidation during service, resulting in a porous surface structure. Furthermore, after the roasting process, the trolley unloads the pellets by tilting its body. The finished pellets have high strength and hardness, resulting in significant impact and sliding wear on the upper edge of the grate bars, making them prone to gradual wear and failure during the reciprocating process and unloading. Summary of the Invention

[0004] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a grate bar for a pellet belt roasting trolley. The grate bar uses a chromium-nickel alloy substrate combined with a thermal spray composite coating, which can achieve good high-temperature wear resistance, resistance to impurity adhesion, high-temperature oxidation resistance, and erosion resistance, effectively extending its service life in the belt roasting trolley operating system.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A grating bar for a roasting trolley includes a chromium-nickel alloy substrate and a thermally sprayed composite coating deposited on its surface after a sealing treatment; the thermally sprayed composite coating comprises a CoNiCrAlY base layer and a CoCrAlYTa-based high-temperature resistant gradient surface layer, wherein the CoCrAlYTa-based high-temperature resistant gradient surface layer comprises CoCrAlYTa and heat-resistant oxides, and the content of heat-resistant oxides is distributed in a gradient from the surface to the interior of the coating.

[0007] Furthermore, in the CoCrAlYTa-based high-temperature gradient surface layer, the content of heat-resistant oxides decreases in a gradient from the surface to the interior along the coating thickness direction.

[0008] Furthermore, the content of heat-resistant oxides in the CoCrAlYTa-based high-temperature gradient surface layer is 5-15 wt%.

[0009] In the above scheme, the stoichiometric formula of CoCrAlYTa is shown in Formula I;

[0010] Co a Cr b Al c Y d Ta e (I);

[0011] Specifically, based on atomic percentages, 50% ≤ a ≤ 65%, 15% ≤ b ≤ 25%, 8% ≤ c ≤ 12%, 0.3% ≤ d ≤ 0.8%, and 0.5% ≤ e ≤ 5%.

[0012] In the above scheme, the heat-resistant oxide may be selected from one or more of the following: aluminum oxide (Al2O3), chromium oxide (Cr2O3), zirconium oxide (ZrO2), yttrium oxide (Y2O3), and lanthanum oxide (La2O3).

[0013] Furthermore, the CoCrAlYTa-based high-temperature gradient surface layer is obtained by plasma spraying using CoCrAlYTa powder (stoichiometric formula shown in Formula I) and heat-resistant oxide powder as the main raw materials and a dual powder feeding process.

[0014] Furthermore, the CoCrAlYTa powder is fed vertically, while the heat-resistant oxide powder is fed obliquely.

[0015] Furthermore, the particle size of the CoCrAlYTa raw material powder is 15–45 μm, and the particle size of the heat-resistant oxide powder is 30–55 μm.

[0016] Furthermore, the heat-resistant oxide powder is Al2O3 powder, which has high hardness and excellent oxidation resistance, and can significantly improve the corrosion resistance and wear resistance of the coating.

[0017] Furthermore, the gradient coating of the CoCrAlYTa substrate layer is mainly prepared by adjusting the amount of Al2O3 powder fed at an angle to control the Al2O3 content of different thicknesses from 3% to 20%, thereby creating a coating structure with a gradient change in Al2O3 content.

[0018] In the above scheme, the stoichiometric formulas of the main components of the CoNiCrAlY substrate are shown in Formula II;

[0019] Co a Ni b Cr c Al d Y e (II)

[0020] Of these, based on atomic percentages, 40% ≤ a ≤ 60%, 20% ≤ b ≤ 40%, 10% ≤ c ≤ 20%, 5% ≤ d ≤ 15%, and 0.1% ≤ e ≤ 1%.

[0021] In the above scheme, the CoNiCrAlY substrate layer is obtained by supersonic flame spraying using CoNiCrAlY powder (stoichiometric formula shown in Formula II) as the main raw material.

[0022] Furthermore, the CoNiCrAlY powder is spherical CoNiCrAlY powder produced by atomization granulation.

[0023] Furthermore, the CoNiCrAlY powder is a spherical powder with a diameter of 15–45 μm and a loose packing density of 4.5–5.0 g / m³. 3 It has good fluidity, which helps to improve the heating uniformity during the spraying process and is not prone to over-oxidation, thus forming a uniform and dense coating.

[0024] In the above scheme, the stoichiometric formulas of the main components of the chromium-nickel alloy substrate are shown in formula (III).

[0025] Fe a C b Si c Mn d Cr e Ni f M g (III);

[0026] Where M represents trace elements and unavoidable impurity elements, and by atomic percentage, 54%≤a≤65%, 0.2%≤b≤0.5%, 0%≤c≤2%, d≤2%, 24%≤e≤28%, and 11%≤f≤14%.

[0027] In the above scheme, the two ends of the grate bars of the roasting trolley are provided with mechanical and physical connection notches to the trolley frame.

[0028] Furthermore, the inner side of the mating notch has an inclined structure with a matching trolley frame slot.

[0029] In the above scheme, both sides of the grating bar of the roasting trolley are provided with convex structures to isolate it from other adjacent grating bars, so that a gap is left between adjacent grating bars for hot air to pass through.

[0030] Furthermore, the convex structure has triangular structures on both sides that are larger at the bottom and smaller at the top, which are used to prevent the pellets from aggregating in the gaps between adjacent grate bars during the stacking process, and the middle part is an equilateral rhombus, scalene rhombus or triangular structure.

[0031] In the above scheme, the sealing treatment is to use a sealing agent to compensate for the microporous characteristics of the thermal spray coating.

[0032] Furthermore, the micropore characteristic refers to the phenomenon that during the use of thermally sprayed workpieces, high-temperature gas carrying some impurity elements penetrates into the coating through micropores, reacts with the substrate, and causes expansion, which damages the coating structure and produces phenomena such as pitting and corrosion, leading to coating failure.

[0033] Furthermore, the sealing agent used in the sealing treatment is a low-viscosity liquid resin; the components and their mass percentages include: sodium silicate 30%–50%, polyester resin 10%–25%, quartz powder 10%–30%, curing agent 2%–10%, sodium hydroxide 0.5%–3%, and calcium carbonate 5%–15%. The sealing agent used in this invention has a maximum heat resistance temperature of up to 1500℃. At high temperatures, the organic matter inside the sealing agent begins to transform into inorganic matter, filling the micropores of the coating and providing a certain strength support for the coating.

[0034] In the above scheme, the preparation steps of the sealing agent include: mixing the raw materials weighed according to the ratio; the curing conditions after coating are: heating to 200-250℃ for rapid curing (2-3h).

[0035] Furthermore, the sealing agent can be mixed with various pigments and fillers and applied to the substrate through various construction methods such as troweling, dipping, spraying, brushing, and roller coating. The substrates include, but are not limited to, metals, alloys, glass, ceramics, paint films, fiberglass, and polymer materials.

[0036] The present invention also provides a method for preparing the above-mentioned grating bar for a roasting trolley, comprising the following steps:

[0037] 1) Chromium-nickel alloy is used to form grate bars by static precision casting according to the designed structural features, and the cast grate bars are then cleaned and roughened.

[0038] 2) A CoNiCrAlY substrate layer is prepared on the surface of the workpiece obtained in step 1) using a supersonic flame spraying process;

[0039] 3) A CoCrAlYTa-based high-temperature resistant gradient surface layer is prepared on the surface of the workpiece obtained in step 2) using a plasma thermal spraying process;

[0040] 4) Coat the surface of the workpiece obtained in step 3) with a sealing agent and heat it to cure it quickly, thus obtaining the grating bar for the calcining trolley.

[0041] In the above scheme, the cleaning step 1) uses an organic solvent, specifically acetone, isopropanol, ethyl acetate or citric acid, etc.

[0042] In the above scheme, in step 1), the roughening treatment is carried out until the surface roughness of the workpiece is Ra 4 to 6 and the sprayed surface is non-reflective; its main purpose is to increase the adhesion of the workpiece surface and lay a good foundation for the subsequent thermal spraying process.

[0043] In the above scheme, during the workpiece spraying process in step 2), the workpiece needs to be fixed in the clamping chuck, and the clamping part of the workpiece is protected with high-temperature tape and copper sheet pads.

[0044] Furthermore, in step 2), during spraying, the workpiece is divided into equal left and right sections, and sprayed in sections. The workpiece rotates at a constant speed during the spraying process, and the spray gun is controlled by an ABB robotic arm.

[0045] Furthermore, the composite coating substrate is treated with a supersonic flame spraying process, and the process parameters include: spraying distance 300-400mm, oxygen flow rate 1800-2000scfh, fuel flow rate 4.5-5.5gph, auxiliary gas flow rate 23-27scfh, and powder feeding speed 40-50g / min.

[0046] Furthermore, in the supersonic flame spraying process, powder raw materials (CoNiCrAlY) prepared by atomization granulation process are used. The raw materials prepared by this process have high purity, uniform particle size and good flowability, which is more conducive to forming a uniform coating.

[0047] Furthermore, the thickness of the CoNiCrAlY substrate layer is 20–35 μm.

[0048] In the above scheme, the CoCrAlYTa-based high-temperature gradient surface layer is treated with plasma thermal spraying process, wherein CoCrAlYTa is the coating substrate and contains gradient-distributed heat-resistant oxides.

[0049] Furthermore, in the CoCrAlYTa-based high-temperature gradient surface layer, the content of heat-resistant oxides in the upper surface layer is 13-20 wt%, and the content of heat-resistant oxides in the lower surface layer is 3-5.5 wt%.

[0050] The coating employs a dual powder feeding process. During the spraying process, the gradient distribution of heat-resistant oxides in the coating is controlled by adjusting the powder feeding rates of heat-resistant oxide powder and CoCrAlYTa powder.

[0051] Furthermore, the plasma thermal spraying process parameters include: spray gun distance 100-300mm, argon flow rate 45-65NLPM, hydrogen flow rate 9-15NLPM, current 520-580A, powder feeding speed 25.5-28.5g / min (CoCrAlYTa), 1.45-4.5g / min (heat-resistant oxide powder).

[0052] Furthermore, the average thickness of each spray coating during the spraying process is 8–18 μm, and the amount of heat-resistant oxide in the powder feed material is increased proportionally after every 2–10 spray coatings.

[0053] Furthermore, after every 2 to 10 coats, the amount of heat-resistant oxide powder is adjusted by adding 4 to 6% (absolute value, the absolute percentage content of heat-resistant oxide powder in the mixed powder) to increase the amount of heat-resistant oxide powder.

[0054] Furthermore, the thickness of the CoCrAlYTa basal layer is 100–250 μm.

[0055] In the above scheme, in order to prevent the workpiece from being overheated and deformed, spraying must be stopped after each coat of paint, and a high-pressure air gun must be used to cool the workpiece. Spraying can only be carried out after the temperature drops below 50°C. After the spraying is completed, the workpiece should be placed in an open environment to cool down naturally.

[0056] In the above scheme, the coating formed by plasma thermal spraying has microporous characteristics. During the use of the workpiece, high-temperature gas will carry some impurity elements into the coating through the micropores, react with the substrate, and thus expand, destroying the coating structure and causing pitting and corrosion, ultimately leading to coating failure. It is necessary to seal the coating. The sealing agent used in this invention is a low-viscosity liquid resin, specially designed for thermal spraying systems. It can be cured quickly between 200 and 250°C. It can be applied to various types of substrates through various construction methods such as smearing, soaking, brushing, and roller coating, and can remain stable below 1500°C.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] 1) High-temperature wear resistance; the grate bar obtained by this invention maintains a low wear amount even after reciprocating heating and cooling wear during service;

[0059] 2) Mineral materials resistant to impurity adhesion will melt at high temperatures, easily forming solid solutions that react chemically with the substrate and adhere to the workpiece surface. The CoNiCrAlY substrate layer introduced in this invention has a similar coefficient of thermal expansion to the workpiece substrate material. On the one hand, it can alleviate the internal tension between the substrate and the gradient coating caused by the difference in coefficients of thermal expansion. On the other hand, it has good bonding strength with both the substrate and the gradient coating, ensuring good overall performance and preventing peeling during use.

[0060] 3) High-temperature oxidation resistance; CoCrAlYTa and Al2O3 and other heat-resistant oxides have good resistance to high-temperature oxidation and thermal shock, but their coefficients of thermal expansion are significantly different from those of the substrate. This invention further adopts a gradient heat-resistant oxide content coating construction, using heat-resistant oxides as a gradient phase. By layering, the internal tensile force generated when the heat-resistant oxide phase shrinks is reduced, thereby reducing the impact of the high coefficient of thermal expansion on the coating. In addition, a CoNiCrAlY layer is set between the gradient coating and the substrate, which can further reduce the impact of its internal tensile force and further improve the overall performance.

[0061] 4) Good physical properties; The surface layer of the coated grate bar described in this invention is a gradient coating composed of CoCrAlYTa and heat-resistant oxide phase. CoCrAlYTa has good resistance to high-temperature gas erosion and corrosion, while the reinforcing phase heat-resistant oxide has a high melting point and strong chemical corrosion resistance. In this gradient ceramic matrix coating, the content of heat-resistant oxide phase is higher closer to the outer surface. The high content of heat-resistant oxide phase can effectively prevent problems such as high-temperature oxidation and chemical gas corrosion. Attached Figure Description

[0062] Figure 1 This is a front view of the grate structure according to an embodiment of the present invention;

[0063] Figure 2 This is a top view of the grating structure according to an embodiment of the present invention;

[0064] Figure 3 This is a side view of the grate structure according to an embodiment of the present invention;

[0065] Figure 4 This is a three-dimensional view of the comb structure according to an embodiment of the present invention;

[0066] In the diagram, 1 represents a notch, and 2 represents a convex structure.

[0067] Figure 5 The images show the wear surface morphology of the sample before and after the grate wear test in one embodiment, with the left image showing the wear before wear and the right image showing the wear after wear. Detailed Implementation

[0068] To more clearly and comprehensively demonstrate the advantages of the present invention, the invention is further described in detail through the following specific embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of the invention. After reading this invention, any modifications of the invention by those skilled in the art in various equivalent forms fall within the scope defined by the appended claims.

[0069] In the following embodiments, a chromium-nickel alloy substrate and a CoNiCrAlY substrate layer, a CoCrAlYTa substrate surface layer, and a sealing layer are sequentially deposited on its surface. A schematic diagram of the structure is shown below. Figure 1-4 .

[0070] Example 1

[0071] A grating bar for a roasting trolley, the preparation method of which includes the following steps:

[0072] 1) The grate bar substrate is formed by static precision casting of chromium-nickel alloy (see structural diagram). Figure 1-4 The main chemical components used are based on the formula Fe. a C b Si c Mn d Cr e Ni f M g The ingredients are mixed, where a, b, c, d, e, f, and g represent the atomic percentages of the corresponding components: a 58%, b 0.35%, c 1%, d 0.5%, e 26%, f 13.5%, and g 0.65%.

[0073] 2) Clean the surface of the workpiece obtained in step 1) with acetone, and then roughen the surface of the workpiece with 46# white corundum (operated by hand-held air gun) until the surface roughness Ra of the workpiece is 4~6 and the sprayed surface is not reflective.

[0074] 3) A CoNiCrAlY substrate layer is prepared on the surface of the workpiece obtained in step 2) using a supersonic flame spraying process. The main chemical composition is determined according to the formula Co. a Ni b Cr c Al d Y e The ingredients were prepared as follows: a 52%, b 25.5%, c 12%, d 10%, and e 0.5%, with an average substrate thickness of approximately 20 μm. The supersonic flame spraying process parameters included a spraying distance of 350 mm, an oxygen flow rate of 1900 scfh, a fuel flow rate of 5.0 gph, an auxiliary gas flow rate of 25 scfh, and a powder feeding rate of 44 g / min.

[0075] 4) The main chemical components are adopted according to the component flow formula Co. a Cr b Al c Y d Ta e The ingredients were prepared as follows: a 62%, b 23%, c 11%, d 0.5%, e 3.5%. Using CoCrAlYTa powder and heat-resistant oxide powder Al2O3 as the main raw materials, a CoCrAlYTa-based high-temperature gradient surface layer was prepared by plasma spraying using a dual-powder feeding process. The average thickness was approximately 180 μm. The plasma spraying process parameters included: spray gun distance 200 mm, argon flow rate 52 NLPM, hydrogen flow rate 13 NLPM, and current 550 A. The first layer (first pass) of the gradient coating, i.e., the 5 wt% Al2O3 layer, used a powder feeding rate of 1.45–1.8 g / min (Al2O3) and 27.5–28.5 g / min (CoCrAlYTa). The first layer of gradient coating (Al2O3) was applied in three coats, with an average coating thickness of 10 μm per coat. The second layer, a 10 wt% Al2O3 layer, was applied in six coats at a powder feed rate of 2.5–2.9 g / min (Al2O3) and 22.5–26.5 g / min (CoCrAl2O3), with an average coating thickness of 15 μm per coat. The third layer, a 15 wt% Al2O3 layer, was applied in four coats at a powder feed rate of 3.5–4.5 g / min (Al2O3) and 19.8–25.5 g / min (CoCrAl2O3), with an average coating thickness of 15 μm per coat.

[0076] 5) The surface of the workpiece obtained in step 4) is sealed with a low-viscosity sealing resin. The raw materials and their weight proportions of the low-viscosity sealing resin are as follows: sodium silicate 40%, maleic anhydride polyester resin 18%, quartz powder 20%, dihydroxyphthalimide epoxy resin curing agent 5%, sodium hydroxide 2%, and calcium carbonate 15%. The weighed raw materials are mixed evenly and then coated on the surface of the obtained CoCrAlYTa-based high-temperature gradient surface layer. The surface is then heated to 230°C for rapid curing to obtain the grating bar for the calcining trolley.

[0077] Example 2

[0078] A grating bar for a roasting trolley, the preparation method of which includes the following steps:

[0079] 1) The grate bar substrate is formed by static precision casting of chromium-nickel alloy (see structural diagram). Figure 1-4 The main chemical components used are based on the formula Fe. a C b Si c Mn d Cr e Ni f Mg The ingredients are mixed, where a, b, c, d, e, f, and g represent the atomic percentages of the corresponding components: a 58%, b 0.35%, c 1%, d 0.5%, e 26%, f 13.5%, and g 0.65%.

[0080] 2) Clean the surface of the workpiece obtained in step 1) with acetone, and then roughen the surface of the workpiece with 46# white corundum (operated by hand-held air gun) until the surface roughness Ra of the workpiece is 4~6 and the sprayed surface is not reflective.

[0081] 3) A CoNiCrAlY substrate layer is prepared on the surface of the workpiece obtained in step 2) using a supersonic flame spraying process. The main chemical composition is determined according to the formula Co. a Ni b Cr c Al d Y e The ingredients were prepared as follows: a 52%, b 25.5%, c 12%, d 10%, and e 0.5%, with an average substrate thickness of approximately 30 μm. The supersonic flame spraying process parameters included a spraying distance of 350 mm, an oxygen flow rate of 1900 scfh, a fuel flow rate of 5.0 gph, an auxiliary gas flow rate of 25 scfh, and a powder feeding rate of 46 g / min.

[0082] 4) The main chemical components are adopted according to the component flow formula Co. a Cr b Al c Y d Ta eThe ingredients were prepared as follows: a 62%, b 23%, c 11%, d 0.5%, e 3.5%. Using CoCrAlYTa powder and heat-resistant oxide powder Al2O3 as the main raw materials, a CoCrAlYTa-based high-temperature gradient surface layer was prepared by plasma spraying using a dual-powder feeding process. The average thickness was approximately 170 μm. The plasma spraying process parameters included: spray gun distance 200 mm, argon flow rate 52 NLPM, hydrogen flow rate 13 NLPM, and current 550 A. The first layer (first pass) of the gradient coating, i.e., the 5 wt% Al2O3 layer, used a powder feeding rate of 1.45–1.8 g / min (Al2O3) and 27.5–28.5 g / min (CoCrAlYTa). The first layer of gradient coating (Al2O3) was applied in three coats, with an average coating thickness of 10 μm per coat. The second layer, 10 wt% Al2O3, was applied in eight coats at a powder feed rate of 2.5–2.9 g / min (Al2O3) and 22.5–26.5 g / min (CoCrAl2O3), with an average coating thickness of 10 μm per coat. The third layer, 15 wt% Al2O3, was applied in four coats at a powder feed rate of 3.5–4.5 g / min (Al2O3) and 19.8–25.5 g / min (CoCrAl2O3), with an average coating thickness of 15 μm per coat.

[0083] 5) The surface of the workpiece obtained in step 4) is sealed with a low-viscosity sealing resin. The raw materials and their weight proportions of the low-viscosity sealing resin are as follows: sodium silicate 40%, maleic anhydride polyester resin 18%, quartz powder 20%, dihydroxyphthalimide epoxy resin curing agent 5%, sodium hydroxide 2%, and calcium carbonate 15%. The weighed raw materials are mixed evenly and then coated on the surface of the obtained CoCrAlYTa-based high-temperature gradient surface layer. The surface is then heated to 230°C for rapid curing to obtain the grating bar for the calcining trolley.

[0084] Example 3

[0085] A grating bar for a roasting trolley, the preparation method of which includes the following steps:

[0086] 1) The grate bar substrate is formed by static precision casting of chromium-nickel alloy (see structural diagram). Figure 1-4 The main chemical components used are based on the formula Fe. a C b Si c Mn d Cr e Ni f M gThe ingredients are mixed, where a, b, c, d, e, f, and g represent the atomic percentages of the corresponding components: a 58%, b 0.35%, c 1%, d 0.5%, e 26%, f 13.5%, and g 0.65%.

[0087] 2) Clean the surface of the workpiece obtained in step 1) with acetone, and then roughen the surface of the workpiece with 46# white corundum (operated by hand-held air gun) until the surface roughness Ra of the workpiece is 4~6 and the sprayed surface is not reflective.

[0088] 3) A CoNiCrAlY substrate layer is prepared on the surface of the workpiece obtained in step 2) using a supersonic flame spraying process. The main chemical composition is determined according to the formula Co. a Ni b Cr c Al d Y e The ingredients were prepared as follows: a 52%, b 25.5%, c 12%, d 10%, and e 0.5%, with an average substrate thickness of approximately 35 μm. The supersonic flame spraying process parameters included a spraying distance of 350 mm, an oxygen flow rate of 1900 scfh, a fuel flow rate of 5.0 gph, an auxiliary gas flow rate of 25 scfh, and a powder feeding rate of 47 g / min.

[0089] 4) The main chemical components are adopted according to the component flow formula Co. a Cr b Al c Y d Ta eThe following ingredients were prepared: a 62%, b 23%, c 11%, d 0.5%, e 3.5%. Using CoCrAlYTa powder and heat-resistant oxide powder Al2O3 as the main raw materials, a CoCrAlYTa-based high-temperature gradient surface layer was prepared by plasma spraying using a dual-powder feeding process. The average thickness was approximately 165 μm. The plasma spraying process parameters included: spray gun distance 200 mm, argon flow rate 52 NLPM, hydrogen flow rate 13 NLPM, and current 550 A. The first layer of the gradient coating, the 5 wt% Al2O3 layer, was fed at a powder feeding rate of 1.45–1.8 g / min (Al2O3) and 27.5–28.5 g / min (CoCrAlYTa). The first layer of the gradient coating (Al₂O₃) was applied in three coats, with an average coating thickness of 10 μm per coat. The second layer, the 10 wt% Al₂O₃ layer, was applied in six coats at a powder feed rate of 2.5–2.9 g / min (Al₂O₃) and 22.5–26.5 g / min (CoCrAlYTa), with an average coating thickness of 15 μm per coat. The third layer, the 15 wt% Al₂O₃ layer, was applied in three coats at a powder feed rate of 3.5–4.5 g / min (Al₂O₃) and 19.8–25.5 g / min (CoCrAlYTa), with an average coating thickness of 15 μm per coat.

[0090] 5) The surface of the workpiece obtained in step 4) is sealed with a low-viscosity sealing resin. The raw materials and their weight proportions of the low-viscosity sealing resin are as follows: sodium silicate 40%, maleic anhydride polyester resin 18%, quartz powder 20%, dihydroxyphthalimide epoxy resin curing agent 5%, sodium hydroxide 2%, and calcium carbonate 15%. The weighed raw materials are mixed evenly and then coated on the surface of the obtained CoCrAlYTa-based high-temperature gradient surface layer. The surface is then heated to 230°C for rapid curing to obtain the grating bar for the calcining trolley.

[0091] Comparative Example 1

[0092] A grating bar for a roasting trolley, the preparation method of which includes the following steps:

[0093] 1) The grate bar substrate is formed by static precision casting of chromium-nickel alloy (see structural diagram). Figure 1-4 The main chemical components used are based on the formula Fe. a C b Si c Mn d Cr e Ni f M g The ingredients are mixed, where a, b, c, d, e, f, and g represent the atomic percentages of the corresponding components: a 58%, b 0.35%, c 1%, d 0.5%, e 26%, f 13.5%, and g 0.65%.

[0094] 2) Clean the surface of the workpiece obtained in step 1) with acetone, and then roughen the surface of the workpiece with 46# white corundum (operated by hand-held air gun) until the surface roughness Ra of the workpiece is 4~6 and the sprayed surface is not reflective.

[0095] 3) No spraying treatment is used.

[0096] Comparative Example 2

[0097] A grating bar for a roasting trolley, the preparation method of which includes the following steps:

[0098] 1) The grate bar substrate is formed by static precision casting of chromium-nickel alloy (see structural diagram). Figure 1-4 The main chemical components used are based on the formula Fe. a C b Si c Mn d Cr e Ni f M g The ingredients are mixed, where a, b, c, d, e, f, and g represent the atomic percentages of the corresponding components: a 58%, b 0.35%, c 1%, d 0.5%, e 26%, f 13.5%, and g 0.65%.

[0099] 2) Clean the surface of the workpiece obtained in step 1) with acetone, and then roughen the surface of the workpiece with 46# white corundum (operated by hand-held air gun) until the surface roughness Ra of the workpiece is 4~6 and the sprayed surface is not reflective.

[0100] 3) A CoNiCrAlY substrate layer is prepared on the surface of the workpiece obtained in step 2) using a supersonic flame spraying process. The main chemical composition is determined according to the formula Co. a Ni b Cr c Al d Y e The ingredients were prepared as follows: a 52%, b 25.5%, c 12%, d 10%, and e 0.5%, with an average substrate thickness of approximately 20 μm. The supersonic flame spraying process parameters included a spraying distance of 350 mm, an oxygen flow rate of 1900 scfh, a fuel flow rate of 5.0 gph, an auxiliary gas flow rate of 25 scfh, and a powder feeding rate of 44 g / min.

[0101] 4) The main chemical components are adopted according to the component flow formula Co. a Cr b Al c Y d Ta eThe ingredients were prepared as follows: a 62%, b 23%, c 11%, d 0.5%, e 3.5%. CoCrAlYTa powder and heat-resistant oxide powder Al2O3 were used as the main raw materials. A CoCrAlYTa-based high-temperature resistant, gradient-free surface layer was prepared by plasma spraying using a dual powder feeding process. The average thickness was approximately 165 μm. The plasma spraying process parameters included: spray gun distance 200 mm, argon flow rate 52 NLPM, hydrogen flow rate 13 NLPM, and current 550 A. The coating was applied in 13 passes with a powder feeding rate of 1.45–1.8 g / min (Al2O3) and 27.5–28.5 g / min (CoCrAlYTa) for a 5 wt% Al2O3 layer. The first 7 passes were each coated with a thickness of 15 μm, and the last 6 passes were each coated with a thickness of 10 μm.

[0102] 5) The surface of the workpiece obtained in step 4) is sealed with a low-viscosity sealing resin. The raw materials and their weight proportions of the low-viscosity sealing resin are as follows: sodium silicate 40%, maleic anhydride polyester resin 18%, quartz powder 20%, dihydroxyphthalimide epoxy resin curing agent 5%, sodium hydroxide 2%, and calcium carbonate 15%. The weighed raw materials are mixed evenly and then coated on the surface of the obtained CoCrAlYTa-based high-temperature gradient surface layer. The surface is then heated to 230°C for rapid curing to obtain the grating bar for the calcining trolley.

[0103] Comparative Example 3

[0104] A grating bar for a roasting trolley, the preparation method of which includes the following steps:

[0105] 1) The grate bar substrate is formed by static precision casting of chromium-nickel alloy (see structural diagram). Figure 1-4 The main chemical components used are based on the formula Fe. a C b Si c Mn d Cr e Ni f M g The ingredients are mixed, where a, b, c, d, e, f, and g represent the atomic percentages of the corresponding components: a 58%, b 0.35%, c 1%, d 0.5%, e 26%, f 13.5%, and g 0.65%.

[0106] 2) Clean the surface of the workpiece obtained in step 1) with acetone, and then roughen the surface of the workpiece with 46# white corundum (operated by hand-held air gun) until the surface roughness of the workpiece is Ra4~6 and the sprayed surface is not reflective.

[0107] 3) A CoNiCrAlY substrate layer is prepared on the surface of the workpiece obtained in step 2) using a supersonic flame spraying process. The main chemical composition is determined according to the formula Co. a Ni b Cr c Al d Y e The ingredients were prepared as follows: a 52%, b 25.5%, c 12%, d 10%, and e 0.5%, with an average substrate thickness of approximately 20 μm. The supersonic flame spraying process parameters included a spraying distance of 350 mm, an oxygen flow rate of 1900 scfh, a fuel flow rate of 5.0 gph, an auxiliary gas flow rate of 25 scfh, and a powder feeding rate of 44 g / min.

[0108] 4) The main chemical components are adopted according to the component flow formula Co. a Cr b Al c Y d Ta e The following ingredients were prepared: a 62%, b 23%, c 11%, d 0.5%, e 3.5%. Using CoCrAlYTa powder and heat-resistant oxide powder Al2O3 as the main raw materials, a CoCrAlYTa-based high-temperature gradient surface layer was prepared by plasma spraying using a dual-powder feeding process. The average thickness was approximately 180 μm. The plasma spraying process parameters included: spray gun distance 200 mm, argon flow rate 52 NLPM, hydrogen flow rate 13 NLPM, and current 550 A. The first layer of the gradient coating, the 5 wt% Al2O3 layer, was fed at a powder feeding rate of 1.45–1.8 g / min (Al2O3) and 27.5–28.5 g / min (CoCrAlYTa). a) Three coats of spraying were applied, with an average coating thickness of 10 μm per coat. The second gradient coating layer, namely the 10 wt% Al2O3 layer, was applied in six coats at a powder feed rate of 2.55–2.9 g / min (Al2O3) and 22.5–26.5 g / min (CoCrAlYTa), with an average coating thickness of 15 μm per coat. The third gradient coating layer, namely the 15 wt% Al2O3 layer, was applied in four coats at a powder feed rate of 3.5–4.5 g / min (Al2O3) and 19.8–25.5 g / min (CoCrAlYTa), with an average coating thickness of 15 μm per coat.

[0109] 5) Apply an organic sealing agent to the surface of the workpiece obtained in step 4), consisting of 55% acrylic emulsion and 45% dibutyl phthalate plasticizer.

[0110] Table 1 compares the performance of the workpieces obtained in Examples 1-3 and Comparative Examples 1-3 under 20-cycle simulated wear tests.

[0111] Group Coating substrate layer μm Coating base top layer μm Wear thickness μm Example 1 20 180 99 Example 2 30 170 108 Example 3 35 165 135 Comparative Example 1 0 0 355 Comparative Example 2 20 165 196 Comparative Example 3 20 180 138

[0112] This invention is not limited to the above-described embodiments. For those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention. These improvements and modifications are also considered to be within the protection scope of this invention. Contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A grate bar for a roasting trolley, characterized in that, It includes a chromium-nickel alloy substrate and a thermally sprayed composite coating deposited on its surface after a sealing treatment; the thermally sprayed composite coating includes a CoNiCrAlY base layer and a CoCrAlYTa-based high-temperature gradient surface layer, wherein the CoCrAlYTa-based high-temperature gradient surface layer includes CoCrAlYTa and heat-resistant oxides, and the content of heat-resistant oxides is gradient-distributed along the coating thickness direction. In the CoCrAlYTa-based high-temperature gradient surface layer, the content of heat-resistant oxides is 3~20 wt%, and the content of heat-resistant oxides decreases gradually from the surface to the inside along the coating thickness direction. The stoichiometric formula of CoCrAlYTa is shown in Formula I; Co a Cr b Al c Y d Dad e (I); Among them, based on atomic percentage, 62%≤a≤65%, 23%≤b≤25%, 8%≤c≤12%, 0.3%≤d≤0.8%, and 0.5%≤e≤5%; The sealing agent used in the sealing treatment is a low-viscosity liquid resin; the components and their mass percentages include: sodium silicate 30%~50%, polyester resin 10%~25%, quartz powder 10%~30%, curing agent 2%~10%, sodium hydroxide 0.5%~3%, and calcium carbonate 5%~15%.

2. The grating bar for a roasting trolley according to claim 1, characterized in that, The heat-resistant oxide is one or more of aluminum oxide, chromium oxide, zirconium oxide, yttrium oxide, and lanthanum oxide.

3. The grating bar for a roasting trolley according to claim 1, characterized in that, The CoCrAlYTa-based high-temperature gradient surface layer is obtained by plasma spraying using CoCrAlYTa powder and heat-resistant oxide powder as the main raw materials and a dual powder feeding process.

4. The grating bar for a roasting trolley according to claim 1, characterized in that, The stoichiometric formulas of the main components of the CoNiCrAlY substrate are shown in Formula II; Co a Ni b Cr c Al d Y e (II) Among them, in terms of atomic percentage, 40%≤a≤60%, 20%≤b≤40%, 10%≤c≤20%, 5%≤d≤15%, and 0.1%≤e≤1%.

5. The grating bar for a roasting trolley according to claim 1, characterized in that, The CoNiCrAlY substrate layer is obtained by supersonic flame spraying using CoNiCrAlY powder as the main raw material.

6. The grating bar for a roasting trolley according to claim 1, characterized in that, The stoichiometric formulas of the main components of the chromium-nickel alloy substrate are shown in formula (III); Feb a C b Si c Mr d Cr e Ni f M g (III); Where M represents trace elements and unavoidable impurity elements, and by atomic percentage, 54%≤a≤58%, 0.2%≤b≤0.5%, 0%≤c≤2%, d≤2%, 24%≤e≤28%, and 11%≤f≤14%.

7. The method for preparing the grating bar for the roasting trolley according to any one of claims 1 to 6, characterized in that, Includes the following steps: 1) The chromium-nickel alloy is precision cast into grate bars according to the designed structure, and the cast grate bars are then cleaned and roughened. 2) A CoNiCrAlY substrate layer is prepared on the surface of the workpiece obtained in step 1) using a supersonic flame spraying process; 3) A CoCrAlYTa-based high-temperature resistant gradient surface layer is prepared on the surface of the workpiece obtained in step 2) using a plasma thermal spraying process; 4) Coat the surface of the workpiece obtained in step 3) with a sealing agent and heat to cure, thereby obtaining the grating bar for the calcining trolley.

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