A SiC / TiC ceramic-reinforced high-entropy alloy coating and its preparation method

Abstract

This invention relates to a SiC / TiC ceramic-reinforced high-entropy alloy coating and its preparation method. The coating comprises a high-entropy alloy coating and a ceramic-reinforced composite coating, formed by laser cladding and overlapping. The high-entropy alloy coating consists of Fe, Cr, Co, Si, Ti, and Nb metal powders mixed in a molar ratio of 1:1:1:1:0-0.5:0-0.5. The ceramic-reinforced composite coating consists of SiC and TiC ceramic phases added to the composition of the high-entropy alloy coating. The SiC and TiC reinforcing phases in this coating are intact and uniformly distributed, exhibiting high hardness and good wear resistance. Furthermore, the provided preparation method is mature, capable of obtaining coatings of various thicknesses without cracks or porosity, and has a long service life. This invention solves the problems of existing cladding coatings failing to achieve expected friction and wear performance, and having insufficient and unevenly distributed reinforcing phases.

Description

Technical Field

[0001] This invention relates to the field of laser cladding composite material technology, and in particular to a SiC / TiC ceramic-reinforced high-entropy alloy coating and its preparation method. Background Technology

[0002] Coaxial powder-fed laser cladding is a novel surface modification technology that uses a high-energy-density laser beam to melt synchronously fed powder, which then metallurgically bonds with the substrate to form a coating.

[0003] Typically, laser cladding for ceramic-reinforced composites utilizes iron-based, nickel-based, and cobalt-based binders. These binders have a large coefficient of linear expansion with the added ceramic phase, leading to a high tendency to crack and the formation of numerous pores during solidification. Currently, ceramic-reinforced composite coatings prepared by laser cladding mainly employ single-layer or double-layer cladding methods. Their thickness is often limited by porosity and cracking. Excessively thick single-layer cladding coatings are prone to porosity and cracking defects, which further exacerbates cracking in large-area, multi-layer cladding, limiting the application of ceramic particle composite powders in practical engineering. In summary, current methods for preparing ceramic-reinforced composite coatings suffer from problems such as mismatch between the alloy binder phase and the ceramic phase, cladding quality, and cladding thickness. Therefore, this invention is proposed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a SiC / TiC ceramic reinforced high-entropy alloy coating and its preparation method.

[0005] This invention is achieved through the following technical solution:

[0006] A SiC / TiC ceramic-reinforced high-entropy alloy coating comprises a high-entropy alloy coating and a ceramic-reinforced composite coating formed by laser cladding. The high-entropy alloy coating comprises Fe, Cr, Co, Si, Ti, and Nb metal powders mixed in a molar ratio of 1:1:1:1:0-0.5:0-0.5. The ceramic-reinforced composite coating comprises SiC and TiC ceramic phases added to the composition of the high-entropy alloy coating.

[0007] According to the above technical solution, preferably, the high-entropy alloy coating and the ceramic-reinforced composite coating are stacked in 6 layers, including 3 layers of high-entropy alloy coating and 3 layers of ceramic-reinforced composite coating, wherein the high-entropy alloy coating is located in the inner layer, that is, from the inside to the outside, the first, third and fifth layers are high-entropy alloy coatings as transition layers, and the second, fourth and sixth layers are ceramic-reinforced composite coatings.

[0008] According to the above technical solution, preferably, the thickness of the high-entropy alloy coating is 0.1-0.3 mm, and the thickness of the ceramic-reinforced composite coating is 0.5-1 mm.

[0009] According to the above technical solution, preferably, the ceramic-reinforced composite coating includes the following components: 5-40% SiC and 5-40% TiC ceramic phases are added to the composition of the high-entropy alloy coating by mass ratio.

[0010] This application also discloses a method for preparing a SiC / TiC ceramic-reinforced high-entropy alloy coating, which includes the following steps:

[0011] S1. Weigh out Fe, Cr, Co, Si, Ti and Nb metal powders in sequence at a molar ratio of 1:1:1:1:0-0.5:0-0.5, mix them to obtain mixed powder A, and dry it in a dryer at 150℃ for 1 hour;

[0012] S2. Add the dried mixed powder A to the left powder cylinder of the powder feeder;

[0013] S3. Weigh out Fe, Cr, Co, Si, Ti and Nb metal powders in sequence at a molar ratio of 1:1:1:1:0-0.5:0-0.5, and then weigh out SiC and TiC ceramic phases in sequence at a mass ratio of 20%, mix them to obtain mixed powder B, and dry it in a dryer at 150℃ for 1 hour.

[0014] S4. Add the dried mixed powder B to the right powder cylinder of the powder feeder;

[0015] S5. The mixed powder A and mixed powder B are overlapped and clad onto the substrate material by laser cladding to form the high-entropy alloy coating and the ceramic-reinforced composite coating, respectively.

[0016] According to the above technical solution, preferably, before step S1, the matrix material is polished and cleaned with anhydrous ethanol, and then dried for later use.

[0017] According to the above technical solution, preferably, in steps S1 and S3, the mixture is ball-milled under vacuum to obtain mixed powder A or mixed powder B, wherein the ball milling parameters are: ball milling speed of 50 r / min, ball-to-material ratio of 8:1, and ball milling time of 3 h.

[0018] According to the above technical solution, preferably, in steps S1 and S3, the particle size range of the Fe, Cr, Co, Si, Ti, and Nb metal powders is 70-125 μm, and the particle size range of the SiC and TiC ceramic phases is 50-150 μm.

[0019] According to the above technical solution, preferably, in step S2, the processing parameters of laser cladding are: laser power of 5kW, linear speed of 200mm / s, single-pass transverse movement of 1mm, powder feeding amount of 15g / min, spot diameter of 2.1mm, and argon flow rate of 15L / min.

[0020] According to the above technical solution, preferably, in step S4, the processing parameters of laser cladding are: laser power of 5kW, linear speed of 100mm / s, single-pass transverse movement of 1mm, powder feeding rate of 20g / min, spot diameter of 2.1mm, and argon flow rate of 15L / min.

[0021] The beneficial effects of this invention are:

[0022] The present invention provides an overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coating. The SiC and TiC reinforcing phases in the coating are intact and uniformly distributed, with high hardness and good wear resistance. This solves the problems of existing cladding coatings failing to meet expectations in terms of friction and wear performance, and having a small number and uneven distribution of reinforcing phases in the coating.

[0023] Specifically, during the cladding process, a small amount of SiC and TiC decomposes under high temperature. Carbon atoms further combine with Nb / Ti elements in the high-entropy alloy to form NbC / TiC precipitate phase. The in-situ synthesized NbC / TiC precipitate phase and the undecomposed SiC and TiC particles are both non-deformable hard phases, which both cause second-phase strengthening. When dislocations pass through, they can only bend and elongate to form dislocation loops. This process requires very high energy, making dislocation movement difficult and increasing the hardness of the coating.

[0024] The added SiC and TiC provide a large number of heterogeneous nuclei for the melt, which helps to promote alloy crystal nucleation and increase the nucleation rate. At the same time, ceramic phase particles can inhibit grain growth through grain boundary pinning, thereby refining the grains and intensifying the fine-grain strengthening effect inside the alloy.

[0025] Its high-entropy alloy exhibits good compatibility with SiC and TiC, and during the cladding process, it has a suitable molten pool life, which is beneficial for the discharge of pores and the release of residual stress. An overlapping transition multilayer structure is adopted. The first, third, and fifth layers use a 0.2 mm thick high-entropy alloy as a transition layer, while the second, fourth, and sixth layers use a 0.7 mm thick SiC / TiC reinforced high-entropy alloy composite coating. The target thickness is achieved through overlapping cladding, continuously utilizing the highly compatible high-entropy alloy coating as a transition. Furthermore, the relatively thin thickness of the ceramic phase-reinforced composite coating in each cladding layer discourages the formation of pores and cracks. Therefore, the overlapping transition multilayer SiC / TiC reinforced high-entropy alloy composite coating provided in this application is free from defects such as cracks and pores.

[0026] Meanwhile, another aspect of the present invention provides a method for preparing SiC / TiC ceramic-reinforced high-entropy alloy coatings. The preparation process is mature, can obtain coatings of various thicknesses, and has a high cladding line speed and high processing efficiency, making it suitable for large-scale promotion and use.

[0027] Specifically, by controlling the power of laser cladding, excessive decomposition of the ceramic phase and increased dilution rate caused by excessive laser power can be avoided, thus preventing the cladding layer efficiency from being affected. At the same time, by controlling the overlap ratio, spot diameter, linear velocity, and powder feed rate, it is possible to ensure the preparation of high-performance overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coatings. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the hierarchical structure of the present invention.

[0029] Figure 2 These are experimental data graphs of the composite coatings prepared in Examples 1-4 and Comparative Examples 1-2 of this invention.

[0030] Figure 3 These are scanning electron microscope (SEM) images of the composite coatings prepared in Examples 1-4 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0032] As shown in the figure, this invention discloses a SiC / TiC ceramic-reinforced high-entropy alloy coating, comprising a high-entropy alloy coating and a ceramic-reinforced composite coating formed by laser cladding. The high-entropy alloy coating comprises the following components: Fe, Cr, Co, Si, Ti, and Nb metal powders mixed in a molar ratio of 1:1:1:1:0-0.5:0-0.5. The ceramic-reinforced composite coating comprises the following components: 5-40% SiC and 5-40% TiC ceramic phases added by mass to the composition of the high-entropy alloy coating. In this example, it is preferred to add 20% SiC and 20% TiC ceramic phases by mass to the composition of the high-entropy alloy coating.

[0033] High-entropy alloys, also known as multi-principal-element alloys, exhibit a high-entropy effect thermodynamically, which is more conducive to the formation of stable solid solutions. They also exhibit a "cocktail effect" in terms of performance, meeting a wider range of performance requirements. Therefore, high-entropy alloys designed for the ceramic phase are more suitable for preparing the binder phase of ceramic-reinforced composite materials. Specifically, in this example, six layers of high-entropy alloy coating and ceramic-reinforced composite coating are overlapped, including three layers of high-entropy alloy coating (each with a thickness of 0.1-0.3 mm) and three layers of ceramic-reinforced composite coating (each with a thickness of 0.5-1 mm). The high-entropy alloy coating is located in the inner layer; that is, from the inside out, the first, third, and fifth layers are high-entropy alloy coatings as transition layers, and the second, fourth, and sixth layers are ceramic-reinforced composite coatings. In this example, the preferred thickness of the high-entropy alloy coating is 0.2 mm, and the thickness of the ceramic-reinforced composite coating is 0.7 mm.

[0034] This application also discloses a method for preparing a SiC / TiC ceramic-reinforced high-entropy alloy coating, which includes the following steps:

[0035] S1. Weigh out Fe, Cr, Co, Si, Ti and Nb metal powders in sequence at a molar ratio of 1:1:1:1:0-0.5:0-0.5, mix them to obtain mixed powder A, and dry it in a dryer at 150℃ for 1 hour;

[0036] S2. Add the dried mixed powder A to the left powder cylinder of the powder feeder;

[0037] S3. Weigh out Fe, Cr, Co, Si, Ti and Nb metal powders in sequence at a molar ratio of 1:1:1:1:0-0.5:0-0.5, and then weigh out SiC and TiC ceramic phases in sequence at a mass ratio of 20%, mix them to obtain mixed powder B, and dry it in a dryer at 150℃ for 1 hour.

[0038] S4. Add the dried mixed powder B to the right powder cylinder of the powder feeder;

[0039] S5. The mixed powder A and mixed powder B are overlapped and clad onto the substrate material by laser cladding to form the high-entropy alloy coating and the ceramic-reinforced composite coating, respectively.

[0040] It should also be noted that before step S1, the matrix material is polished and cleaned with anhydrous ethanol, and then dried for later use.

[0041] In steps S1 and S3, the mixture is ball-milled under vacuum to obtain mixed powder A or mixed powder B. The ball milling parameters are: ball milling speed of 50 r / min, ball-to-material ratio of 8:1, and ball milling time of 3 h.

[0042] In steps S1 and S3, the particle size range of the Fe, Cr, Co, Si, Ti, and Nb metal powders is 70-125 μm, and the particle size range of the SiC and TiC ceramic phases is 50-150 μm.

[0043] In step S2, the laser cladding process parameters are as follows: laser power is 5kW, linear speed is 200mm / s, single-pass transverse movement is 1mm, powder feed rate is 15g / min, spot diameter is 2.1mm, and argon flow rate is 15L / min.

[0044] In step S4, the processing parameters for laser cladding are as follows: laser power is 5kW, linear speed is 100mm / s, single-pass transverse movement is 1mm, powder feed rate is 20g / min, spot diameter is 2.1mm, and argon flow rate is 15L / min.

[0045] Example 1: (a) Weigh 500g of Co, Cr, Fe, Si, Ti and Nb metal powders with a molar ratio of 1:1:1:1:0:0 and mix them. The particle diameter of the powder is controlled between 70-125μm to obtain mixed powder A.

[0046] (b) Weigh 300g of Co, Cr, Fe, Si, Ti, and Nb metal powders with a molar ratio of 1:1:1:1:0:0, and control the particle diameter of the powders between 70-125μm. Then weigh 100g of SiC and 100g of TiC powders, with particle diameters controlled between 50-150μm. Mix the above powders to obtain mixed powder B.

[0047] (c) The two powders mentioned above were added to two planetary ball mills respectively. The ball milling speed was 50 r / min, the ball-to-material ratio was 3:1, and the ball milling time was 3 h.

[0048] (d) After ball milling, the powder is placed in a drying oven and dried at 150°C for 1 hour;

[0049] (e) Place the two dried powders into the left powder hopper and the right powder hopper respectively;

[0050] (f) Grind the shaft made of Q233 steel to remove surface rust and oil, and then clean it with alcohol.

[0051] (g) Laser cladding is performed on the shaft. The left powder cylinder of the powder feeder is connected. The processing parameters of laser cladding are: laser power of 5kW, linear speed of 200mm / s, single-pass transverse movement of 1mm, powder feeding amount of 15g / min, spot diameter of 2.1mm, argon flow rate of 15L / min, and the first layer of coating with a thickness of 0.2mm is formed by cladding.

[0052] (h) Then connect the right powder cylinder of the powder feeder. The processing parameters for laser cladding are set as follows: laser power is 5kW, linear speed is 100mm / s, single-pass transverse movement is 1mm, powder feeding rate is 20g / min, spot diameter is 2.1mm, argon flow rate is 15L / min, and a second coating with a thickness of 0.7mm is formed by cladding.

[0053] (i) Repeat step (g) to form the third coating layer, then repeat step (h) to form the fourth coating layer, then repeat step (g) again to form the fifth coating layer, and finally repeat step (h) to form the sixth coating layer with a thickness of 2.7 mm, thus obtaining an overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coating.

[0054] Example 2: This example provides an overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coating. Its preparation method is the same as that in Example 1, except that the molar ratio of high-entropy alloy powder Co, Cr, Fe, Si, Ti and Nb in the coating is 1:1:1:1:0.5:0.

[0055] Example 3: This example provides an overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coating. Its preparation method is the same as that in Example 1, except that the molar ratio of high-entropy alloy powder Co, Cr, Fe, Si, Ti and Nb in the coating is 1:1:1:1:0:0.5.

[0056] Example 4: This example provides an overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coating. Its preparation method is the same as that in Example 1, except that the molar ratio of high-entropy alloy powder Co, Cr, Fe, Si, Ti and Nb in the coating is 1:1:1:1:0.5:0.5.

[0057] Comparative Example 1: This comparative example provides an overlapping transitional multilayer SiC / TiC reinforced iron-based alloy composite coating, which is prepared in the same way as in Example 1, except that the alloy powder (Co, Cr, Fe, Si, Ti, Nb metal powder) in the coating is replaced with 316 stainless steel alloy powder.

[0058] Comparative Example 2: This comparative example provides a conventional single-layer SiC / TiC reinforced iron-based alloy coating, which is prepared using the same method as in Example 1, except that the alloy powder (Co, Cr, Fe, Si, Ti, Nb metal powder) in the coating is replaced with Ni60 nickel-based alloy powder. The preferred but not limited steps are as follows:

[0059] (a) Weigh 300g of Ni60 nickel-based alloy powder, with the particle diameter controlled between 70-125μm. Then weigh 100g of SiC and 100g of TiC powder, with the particle diameter controlled between 50-150μm, and mix the powders together.

[0060] (b) Add the above powder to a planetary ball mill, with a ball milling speed of 50 r / min, a ball-to-material ratio of 3:1, and a ball milling time of 3 h;

[0061] (d) After ball milling, the powder is placed in a drying oven and dried at 150°C for 1 hour;

[0062] (e) Place the two dried powders into clean powder containers respectively;

[0063] (f) Grind the shaft made of Q233 steel to remove surface rust and oil, and then clean it with alcohol.

[0064] (g) Laser cladding is performed on the shaft, and a powder feeder cylinder is connected. The processing parameters for laser cladding are: laser power of 3kW, linear velocity of 20mm / s, single-pass transverse movement of 1.5mm, powder feed rate of 30g / min, spot diameter of 2.1mm, and argon flow rate of 15L / min. A single-layer SiC / TiC reinforced iron-based alloy coating with a thickness of 2mm is formed by cladding.

[0065] The hardness, wear resistance, porosity, and crack state of the overlapping transitional multilayer SiC+TiC reinforced alloy composite coatings in Examples 1-4 and Comparative Examples 1 and 2 were tested respectively. The test methods and conditions are as follows: Hardness was tested using a Vickers hardness tester with a load of 0.2 kg and a holding time of 15 seconds. Ten points were randomly selected, and the lowest and highest values ​​were removed before taking the average value. Wear resistance was determined according to the national standard GB T12444-2006. Specific test results are as follows. Figure 2 .

[0066] Combination Figure 2 , 3 Experimental characterization revealed that Example 1 used CoCrFeSi as the transition layer and alloy binder phase, Example 2 used CoCrFeSiTi0.5, Example 3 used CoCrFeSiNb0.5, and Example 4 used CoCrFeSiTi0.5Nb0.5. The addition of Ti and Nb elements significantly improved the coating hardness and wear resistance. Example 4, containing both Ti and Nb, exhibited excellent hardness and wear resistance. Comparative Example 1 used 316 stainless steel alloy powder as the overlapping transition cladding layer and as the binder phase for the ceramic phase. Compared to Examples 1-4, the hardness and wear resistance were significantly reduced. Simultaneously, combined with… Figure 2 , 3It can be seen that the ceramic phase in Examples 1-4 is uniformly distributed and free of cracks and pore defects, while in Comparative Examples 1-2, pores and crack defects appeared.

[0067] This invention provides an overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coating. The SiC and TiC reinforcing phases in this coating are intact and uniformly distributed, resulting in high hardness and good wear resistance. This solves the problems of existing cladding coatings failing to meet expectations in terms of friction and wear performance, as well as the small number and uneven distribution of reinforcing phases in the coating.

[0068] Specifically, during the cladding process, a small amount of SiC and TiC decomposes under high temperature. Carbon atoms further combine with Nb / Ti elements in the high-entropy alloy to form NbC / TiC precipitate phase. The in-situ synthesized NbC / TiC precipitate phase and the undecomposed SiC and TiC particles are both non-deformable hard phases, which both cause second-phase strengthening. When dislocations pass through, they can only bend and elongate to form dislocation loops. This process requires very high energy, making dislocation movement difficult and increasing the hardness of the coating.

[0069] The added SiC and TiC provide a large number of heterogeneous nuclei for the melt, which helps to promote alloy crystal nucleation and increase the nucleation rate. At the same time, ceramic phase particles can inhibit grain growth through grain boundary pinning, thereby refining the grains and intensifying the fine-grain strengthening effect inside the alloy.

[0070] Its high-entropy alloy exhibits good compatibility with SiC and TiC, and during the cladding process, it has a suitable molten pool life, which is beneficial for the discharge of pores and the release of residual stress. An overlapping transition multilayer structure is adopted. The first, third, and fifth layers use a 0.2 mm thick high-entropy alloy as a transition layer, while the second, fourth, and sixth layers use a 0.7 mm thick SiC / TiC reinforced high-entropy alloy composite coating. The target thickness is achieved through overlapping cladding, continuously utilizing the highly compatible high-entropy alloy coating as a transition. Furthermore, the relatively thin thickness of the ceramic phase-reinforced composite coating in each cladding layer discourages the formation of pores and cracks. Therefore, the overlapping transition multilayer SiC / TiC reinforced high-entropy alloy composite coating provided in this application is free from defects such as cracks and pores.

[0071] Meanwhile, another aspect of the present invention provides a method for preparing SiC / TiC ceramic-reinforced high-entropy alloy coatings. The preparation process is mature, can obtain coatings of various thicknesses, and has a high cladding line speed and high processing efficiency, making it suitable for large-scale promotion and use.

[0072] Specifically, by controlling the power of laser cladding, excessive decomposition of the ceramic phase and increased dilution rate caused by excessive laser power can be avoided, thus preventing the cladding layer efficiency from being affected. At the same time, by controlling the overlap ratio, spot diameter, linear velocity, and powder feed rate, it is possible to ensure the preparation of high-performance overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coatings.

[0073] 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 principle 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 method for preparing a SiC / TiC ceramic-reinforced high-entropy alloy coating, characterized in that, Includes the following steps: (a) Weigh 500g of Co, Cr, Fe, Si, Ti and Nb metal powders with a molar ratio of 1:1:1:1:0.5:0.5 and mix them. The particle diameter of the powder is controlled between 70-125μm to obtain mixed powder A. (b) Weigh 300g of Co, Cr, Fe, Si, Ti and Nb metal powders with a molar ratio of 1:1:1:1:0.5:0.5, with the particle diameter controlled between 70-125μm. Weigh 100g of SiC and 100g of TiC powders with the particle diameter controlled between 50-150μm. Mix the above powders to obtain mixed powder B. (c) The two mixed powders mentioned above were added to two planetary ball mills respectively. The ball milling speed was 50 r / min, the ball-to-powder ratio was 3:1, and the ball milling time was 3 h. (d) After ball milling, the powder is placed in a drying oven and dried at 150°C for 1 hour; (e) Place the two dried powders into the left powder hopper and the right powder hopper respectively; (f) Grind the shaft made of Q233 steel to remove surface rust and oil, and then clean it with alcohol. (g) Laser cladding is performed on the shaft. The left powder cylinder of the powder feeder is connected. The processing parameters of laser cladding are: laser power of 5kW, linear speed of 200mm / s, single-pass transverse movement of 1mm, powder feeding amount of 15g / min, spot diameter of 2.1mm, argon flow rate of 15L / min, and the first layer of coating with a thickness of 0.2mm is formed by cladding. (h) Then connect the right powder cylinder of the powder feeder. The processing parameters for laser cladding are set as follows: laser power is 5kW, linear speed is 100mm / s, single-pass transverse movement is 1mm, powder feeding rate is 20g / min, spot diameter is 2.1mm, argon flow rate is 15L / min, and a second coating with a thickness of 0.7mm is formed by cladding. (i) Repeat step (g) to form the third coating layer, then repeat step (h) to form the fourth coating layer, then repeat step (g) again to form the fifth coating layer, and finally repeat step (h) to form the sixth coating layer with a thickness of 2.7 mm, thus obtaining an overlapping transitional multilayer SiC / TiC reinforced high-entropy alloy composite coating, wherein the first, third, and fifth coating layers are high-entropy alloy coatings, and the second, fourth, and sixth coating layers are ceramic reinforced composite coatings.

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