Iron-based high-temperature composite powder, and preparation method and application of iron-based high-temperature composite powder

Abstract

The invention belongs to the technical field of metal material preparation and processing, and particularly relates to iron-based high-temperature composite powder and a preparation method and application of the iron-based high-temperature composite powder. The method comprises the following steps that S1, 0.5%-2.5% by mass of C, 4.0%-5.0% by mass of Cr, 0.3%-0.5% by mass of Mn, 1.0%-2% by mass of Mo, 0.1%-0.3% by mass of Ni, 0.5%-1.5% by mass of Si, 0.5%-1.5% by mass of V, 15%-30% by mass of W, 1%-2% by mass of graphite and the balance Fe are weighed, or 68%-84% by mass of 4Cr5MoSiV1, 15%-30% by mass of W and 1%-2% by mass of graphite are weighed; s2, putting the raw materials obtained in S1 and a polyvinyl alcohol solution into acoustic resonance equipment, and carrying out acoustic resonance mixing; s3, preparing spherical composite powder from the uniformly mixed composite powder obtained in S2 through a spray granulation process; s4, performing heat treatment on the spherical composite powder obtained in S3; s5, the high-temperature composite powder obtained in the S4 is subjected to particle size screening; according to the method, through the acoustic resonance mixing technology, the uniformity, sphericity and fluidity of the composite powder are improved, damage of mechanical stress to the original structure of the powder is avoided, and the self-lubricating performance of graphite is reserved.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation and processing technology, specifically relating to an iron-based high-temperature composite powder, a method for preparing the iron-based high-temperature composite powder, and its application. Background Technology

[0002] Hot work die steels are widely used in high-temperature forming processes such as die casting, forging, and extrusion. Their service environment is harsh, often facing challenges of high temperature, high pressure, and frequent thermal cycling. At room temperature, the hardness of hot work die steel is 55 HRC, at 400℃ it is 35 HRC, and at 600℃ it is 25 HRC. During long-term high-temperature operation, the die surface is in direct contact with high-temperature metal, which easily leads to thermal fatigue cracks and abrasive wear, resulting in surface performance degradation and a significantly shortened service life. Therefore, improving the high-temperature strength, thermal fatigue resistance, wear resistance, and corrosion resistance of hot work die steels has become a key focus of technological development in this field.

[0003] Laser cladding technology, as an advanced surface modification method, melts the coating material with a high-energy laser beam and achieves metallurgical bonding with the substrate. It boasts advantages such as a small heat-affected zone, low dilution rate, high bonding strength, and controllable composition and size, gradually becoming an effective method for preparing high-performance mold steel surface coatings. Iron-based composite powders are widely used in laser cladding coating materials due to their low cost and good compatibility with the substrate. However, traditional iron-based composite powder preparation often employs mechanical stirring or ball milling, which have significant limitations: firstly, due to the significant density difference between the reinforcing phase and the matrix powder, segregation and agglomeration easily occur during mechanical mixing, leading to uneven composition distribution; secondly, ball milling relies on high-intensity mechanical collision and shearing, which not only takes several hours to tens of hours but also easily damages the powder morphology and causes lattice distortion, especially harming the structural integrity of lubricating phases such as flake graphite, affecting their self-lubricating function.

[0004] Furthermore, the flowability, sphericity, and uniformity of the powder directly affect the powder feeding stability and molten pool behavior during laser cladding, thus impacting the coating's forming quality and performance consistency. Existing mixing technologies struggle to achieve efficient and uniform composite powder preparation while ensuring powder characteristics, limiting further improvements in the overall coating performance. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides an iron-based high-temperature composite powder, a method for preparing the iron-based high-temperature composite powder, and its application, which solves the problems of reinforcing phase segregation, uneven mixing, and low mixing efficiency caused by density differences in existing mechanical mixing and ball milling technologies.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing iron-based high-temperature composite powder is provided, comprising the following steps: S1: Weigh out 0.5~2.5% C, 4.0~5.0% Cr, 0.3~0.5% Mn, 1.0~2% Mo, 0.1~0.3% Ni, 0.5~1.5% Si, 0.5~1.5% V, 15~30% W, 1~2% graphite and balance Fe by mass fraction, or weigh out 68~84% 4Cr5MoSiV1, 15~30% W and 1~2% graphite by mass fraction; S2: The raw material obtained in S1 is placed together with the polyvinyl alcohol solution in an acoustic resonance device for acoustic resonance mixing to obtain a uniformly mixed composite powder. S3: Prepare spherical composite powder by spray granulation process using the uniformly mixed composite powder obtained in S2; S4: Heat-treat the spherical composite powder obtained in S3 to obtain high-temperature composite powder; S5: Perform particle size sieving on the high-temperature composite powder obtained in S4.

[0007] The beneficial effects of adopting the above technical solution are as follows: This method for preparing iron-based high-temperature composite powder effectively solves the problems of segregation of reinforcing phases (such as graphite and tungsten powder) and uneven mixing caused by density differences during traditional mechanical mixing or ball milling by introducing acoustic resonance mixing technology, which significantly improves the uniformity, sphericity and flowability of the composite powder; at the same time, it avoids the damage of mechanical stress to the original structure of the powder, protects the lamellar structure of graphite and preserves its self-lubricating properties; combined with spray granulation and subsequent heat treatment processes, the physical properties of the powder are further optimized. Step S1, through precise weighing of each component raw material, ensures the accuracy and consistency of the chemical composition of the composite powder, laying the foundation for the preparation of high-performance iron-based high-temperature composite powder. It also provides two different component options, allowing the composite powder to balance self-lubricating properties and carbide strengthening effects, meeting the needs of different operating conditions. Step S2 employs acoustic resonance technology for mixing, using high-frequency vibration to rapidly achieve uniform dispersion of powders of different densities in a chaotic state, avoiding segregation caused by density differences in traditional mechanical mixing. Simultaneously, the weak shearing action protects the integrity of the graphite structure, improving mixing efficiency and quality. Step S3 uses a spray granulation process to transfer the mixed powder... The powder is spherical, which effectively improves its flowability and bulk density, thus benefiting the powder feeding stability and coating quality during subsequent laser cladding. It also enhances the wettability between the powder and the substrate. Step S4 removes residual organic binders introduced during spray granulation through heat treatment, purifies the surface of the composite powder, and avoids the generation of pores and impurities during subsequent laser cladding, further improving the density and metallurgical bonding quality of the coating. The sieving in step S5 controls the particle size of the composite powder, ensuring that the composite powder has good flowability and uniformity, which is beneficial for powder transportation and stable formation of the molten pool during laser cladding, and improves the uniformity and consistency of the coating.

[0008] Furthermore, in S1, the graphite is flake graphite.

[0009] The beneficial effects of adopting the above technical solution are as follows: flake graphite has a unique layered structure and anisotropy, which can more effectively play the role of solid lubricant in composite coatings. It can reduce the coefficient of friction by generating slip, thereby improving the lubrication performance of hot work die steel surfaces and reducing friction and wear under high temperature and heavy load conditions. At the same time, compared with other forms of graphite, the flake structure is more likely to achieve uniform physical adsorption and dispersion with metal powder during the acoustic resonance mixing process, avoiding the attenuation of lubrication performance caused by structural breakage, and ensuring that the final cladding coating has durable and stable self-lubricating properties.

[0010] Furthermore, the degree of alcoholysis of the polyvinyl alcohol solution is 98.0~99.0 mol%, the viscosity is 20.0~30.0 mPa·s, and the mass fraction is 10%.

[0011] The beneficial effects of adopting the above technical solution are as follows: using a polyvinyl alcohol solution with a degree of hydrolysis of 98.0~99.0 mol%, a viscosity of 20.0~30.0 mPa•s, and a mass fraction of 10%, can form a uniform and stable temporary bonding network during the acoustic resonance mixing process through its moderate molecular chain length and viscoelastic properties. This effectively prevents the floating and segregation of light phases such as graphite, and avoids particle agglomeration caused by high viscosity. Moreover, the polyvinyl alcohol solution can be completely decomposed in subsequent heat treatment without leaving any carbides. At the same time, through the synergistic effect with the acoustic resonance cavitation effect, the compositional uniformity and flowability of the composite powder are improved, so as to obtain a high-quality premixed powder with high sphericity and no density segregation.

[0012] Furthermore, in S2, the mixing parameters of the acoustic resonance device are: vibration frequency 60-80Hz, acceleration 60-90G, and vibration time 10-30 min.

[0013] The beneficial effects of adopting the above technical solution are as follows: the acoustic resonance equipment, through the synergistic effect of a vibration frequency of 60-80Hz and an acceleration of 60-90G, enables the composite powder particles to form a three-dimensional chaotic motion state within the resonance cavity of the acoustic resonance equipment, which counteracts the sedimentation and segregation caused by the density difference between heterogeneous phases such as graphite and carbides and iron-based powder. At the same time, the short vibration cycle of 10-30 minutes improves the processing efficiency compared with the traditional ball milling process. Furthermore, by directly exciting high-frequency collisions and uniform diffusion between particles through acoustic energy, the peeling and breakage of graphite sheets caused by mechanical stirring are avoided, thus obtaining composite powder with highly uniform composition and well-preserved sphericity.

[0014] Furthermore, in S3, the parameters of the spray granulation process are: rotation speed 5000~8000rpm, inlet temperature 320℃, and outlet temperature 180℃.

[0015] The beneficial effects of adopting the above technical solution are as follows: the high rotation speed of 5000~8000rpm can achieve sufficient refinement and uniform dispersion of droplets. Combined with the gradient heating of 320℃ inlet temperature and 180℃ outlet temperature, the polyvinyl alcohol binder can quickly form a uniform coating layer on the droplet surface while avoiding internal overheating and agglomeration. Finally, composite powder particles with concentrated particle size distribution and high sphericity are obtained, thus solving the density segregation problem caused by traditional mechanical mixing and ensuring the uniform spatial distribution of graphite and carbide reinforcing phase in iron-based powder.

[0016] Furthermore, in S4, the heat treatment parameters are: the heat treatment temperature is 300℃, and the holding time is 10~20 min.

[0017] The beneficial effects of adopting the above technical solution are as follows: by setting the heat treatment temperature to 300℃ and the holding time to 10~20 min, the residual polyvinyl alcohol binder in the composite powder can be effectively removed. At the same time, the agglomeration and coarsening of composite powder particles caused by excessive temperature or time are avoided, ensuring the purity and dispersibility of the composite powder. It also ensures the full decomposition and volatilization of the binder, maintaining the uniform component distribution and high sphericity structure formed by acoustic resonance mixing.

[0018] Furthermore, in S5, the particle size of the sieved composite powder is 50~150 μm, the flowability is 15~25 s / 50g, and the sphericity is ≥90%.

[0019] The beneficial effects of adopting the above technical solution are as follows: the particle size range of 50~150μm ensures that the composite powder can be smoothly transported and uniformly melted during the laser cladding process, forming a dense metallurgical bond; the flowability of 15~25s / 50g ensures the flow stability of the composite powder, avoiding uneven coating caused by clogging and discontinuous powder feeding; and the sphericity ≥90% reduces the frictional resistance between powder particles to enhance flowability, thereby ensuring the smoothness and uniformity of the final coating surface and excellent high-temperature wear resistance and self-lubricating properties.

[0020] Based on the above-mentioned method for preparing iron-based high-temperature composite powder, the present invention provides an iron-based high-temperature composite powder.

[0021] Based on the above-mentioned iron-based high-temperature composite powder, the present invention provides an iron-based high-temperature composite powder coating, the preparation method of which is as follows: the iron-based high-temperature composite powder is formed on the surface of hot work abrasive steel by laser cladding process, wherein the parameters of the laser cladding process are: laser power 4000~6000 W, spot size 6*19 mm, powder feeding rate 4~6 kg / h, scanning rate 7 mm / s, overlap rate 50%, and cladding layer thickness 1~2 mm.

[0022] Laser cladding technology is used to clad composite powder onto the surface of hot-work die steel, forming a composite coating with high hardness, high wear resistance, and self-lubricating properties. This significantly improves the wear resistance and service life of the die at high temperatures. Simultaneously, a good metallurgical bond is formed between the coating and the substrate, free from defects such as pores and cracks. The use of a laser power of 4000~6000 W ensures that the composite powder is fully melted and forms a good metallurgical bond with the substrate, while avoiding coarsening of the microstructure caused by overheating. The 6*19 mm spot size, combined with a powder feed rate of 4~6 kg / h, enables precise control of the coating thickness and ensures uniform composition. Furthermore, the scanning rate is 7... The synergistic effect of mm / s and 50% overlap rate can eliminate defects between cladding tracks, forming a continuous and dense composite coating. This improves the spatial distribution rationality of carbides (such as Cr7C3 and Fe3W3C) and self-lubricating phases (graphite) in the coating, thereby obtaining a gradient functional coating with high hardness, low friction coefficient and excellent wear resistance on the surface of hot work die steel. This effectively solves the problem of coating performance fluctuation caused by uneven mixing in traditional processes.

[0023] Based on the above-mentioned iron-based high-temperature composite powder coating, the present invention provides the application of iron-based high-temperature composite powder in the preparation of wear-resistant and self-lubricating coatings by laser cladding on the surface of hot work die steel.

[0024] Iron-based high-temperature composite powder is applied to hot work die steel via laser cladding to form a composite coating with high hardness, high temperature resistance, and wear resistance.

[0025] In summary, the iron-based high-temperature composite powder, the method for preparing the iron-based high-temperature composite powder, and its applications provided by this invention have the following beneficial effects: (1) This invention solves the problems of reinforcing phase segregation, uneven mixing and low efficiency caused by density differences in traditional mechanical mixing and ball milling technology by the synergistic effect of acoustic resonance mixing, spray granulation and heat treatment. Acoustic resonance mixing achieves efficient homogenization of composite powder, spray granulation optimizes powder morphology and flowability, heat treatment removes binder residue and maintains the characteristics of composite powder. In addition, a high-temperature composite coating with good metallurgical bonding, no defects and high hardness, excellent wear resistance and self-lubricating function can be obtained by laser cladding on the surface of hot work die steel, which significantly improves the service life and reliability of the die under high temperature and heavy load conditions.

[0026] (2) The acoustic resonance mixing in this invention can compensate for the defects caused by uneven powder mixing. By placing the powder into the resonance cavity of the acoustic resonance instrument, the acoustic resonance device generates vibration energy of a specific frequency and vertical upward. The powder particles are in a high-speed flow state under the multiple effects of sound and force, thereby enhancing the mass transfer and heat transfer of the powder. At the same time, the entire powder enters the resonance state, and the powder particles obtain uniform vibration energy, which effectively offsets the density difference of heterogeneous iron-based powders such as graphite and carbide, and avoids the segregation phenomenon caused by the floating of light phase and the sinking of heavy phase during the traditional mechanical mixing and ball milling process. At the same time, the acoustic resonance mixing can complete the homogenization process in only 10 to 30 minutes, which is dozens of times more efficient than the ball milling process. It also avoids the peeling and breakage of graphite sheets caused by mechanical stirring and maintains the original characteristics of the reinforcing phase.

[0027] (3) This invention can transform a uniformly mixed slurry into a spherical powder with high sphericity and excellent flowability through spray granulation and heat treatment processes. This not only improves the powder's conveying and cladding stability, but also completely removes organic residues, avoids coating defects, and ultimately enables the composite powder to form a uniform and dense cladding layer during laser cladding, thereby improving the coating's forming quality and performance consistency.

[0028] (4) The composite powder prepared by this invention can form a high-performance composite coating on the surface of a substrate (such as hot work die steel) by laser cladding. The coating not only exhibits excellent metallurgical bonding with the substrate, but also has no defects such as pores and cracks. It significantly improves the surface hardness, wear resistance and other comprehensive properties of hot work die steel. In addition, it can generate a variety of high-hardness carbide reinforcing phases in situ, giving full play to the self-lubricating properties of graphite. The coating exhibits hardness, wear resistance and friction reduction properties far exceeding those of the substrate at both room temperature and high temperature, thereby extending the service life of the die and solving the problem of coating performance fluctuation caused by uneven mixing in traditional processes. Attached Figure Description

[0029] Figure 1 Image of micro-alloy powder prepared by acoustic resonance in Example 1 of this invention; Figure 2 Image of micro-alloy powder prepared by ball milling for Comparative Example 1 provided by the present invention; Figure 3 Microscopic images of the coating surface after a friction experiment, obtained by laser cladding of alloy powder obtained after acoustic resonance mixing in Example 2 of this invention; Figure 4 Microscopic images of the coating surface after a friction experiment of the alloy powder obtained by ball milling and mixing and laser cladding to prepare the coating, which is provided for the present invention; Figure 5The image provided in Example 3 of this invention is a microscopic image of the coating surface after a friction experiment, prepared by laser cladding of alloy powder obtained by acoustic resonance mixing. Detailed Implementation

[0030] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0031] The method for preparing iron-based high-temperature composite powder provided by this invention includes the following steps: S1: Weigh out 0.5~2.5% C, 4.0~5.0% Cr, 0.3~0.5% Mn, 1.0~2% Mo, 0.1~0.3% Ni, 0.5~1.5% Si, 0.5~1.5% V, 15~30% W, 1~2% graphite and balance Fe by mass fraction, or weigh out 68~84% 4Cr5MoSiV1, 15~30% W and 1~2% graphite by mass fraction; S2: The raw material obtained in S1 is placed together with the polyvinyl alcohol solution in an acoustic resonance device for acoustic resonance mixing to obtain a uniformly mixed composite powder. S3: Prepare spherical composite powder by spray granulation process using the uniformly mixed composite powder obtained in S2; S4: Heat-treat the spherical composite powder obtained in S3 to obtain high-temperature composite powder; S5: Perform particle size sieving on the high-temperature composite powder obtained in S4.

[0032] This method for preparing iron-based high-temperature composite powder effectively solves the problems of segregation of reinforcing phases (such as graphite and tungsten powder) and uneven mixing caused by density differences during traditional mechanical mixing or ball milling by introducing acoustic resonance mixing technology. This significantly improves the uniformity, sphericity, and flowability of the composite powder. Simultaneously, it avoids the damage to the original powder structure caused by mechanical stress, protects the lamellar structure of graphite, and preserves its self-lubricating properties. Combined with spray granulation and subsequent heat treatment processes, the physical properties of the powder are further optimized. Specifically, step S1 ensures the accuracy and consistency of the chemical composition of the composite powder by accurately weighing each component, laying the foundation for preparing high-performance iron-based high-temperature composite powder and providing two different composition options, allowing the composite powder to balance self-lubricating properties and carbide strengthening effects to meet the needs of different working conditions. Step S2 uses acoustic resonance mixing technology, which uses high-frequency vibration to quickly achieve uniform dispersion of powders of different densities in a chaotic state, avoiding segregation caused by density differences in traditional mechanical mixing. At the same time, the weak shearing action protects the integrity of the graphite structure, improving mixing efficiency and quality. Step S3 uses a spray granulation process to transfer the mixed powder... The powder is spherical, which effectively improves its flowability and bulk density, thus benefiting the powder feeding stability and coating quality during subsequent laser cladding. It also enhances the wettability between the powder and the substrate. Step S4 removes residual organic binders introduced during spray granulation through heat treatment, purifies the surface of the composite powder, and avoids the generation of pores and impurities during subsequent laser cladding, further improving the density and metallurgical bonding quality of the coating. The sieving in step S5 controls the particle size of the composite powder, ensuring that the composite powder has good flowability and uniformity, which is beneficial for powder transportation and stable formation of the molten pool during laser cladding, and improves the uniformity and consistency of the coating.

[0033] To illustrate the improvement effect of the composite coating prepared in this invention on the performance of hot work die steel, wear and friction tests were conducted on the untreated hot work die steel substrate. The results showed that at room temperature, the wear amounts of the hot work die steel substrate after 30 min and 60 min were 0.007 g and 0.018 g, respectively; at 400℃, the wear amounts after 30 min and 60 min were 0.009 g and 0.022 g, respectively; and at 600℃, the wear amounts after 30 min and 60 min were 0.01 g and 0.033 g, respectively. Meanwhile, the coefficient of friction of the hot work die steel at room temperature was 0.4~0.6, and the coefficients of friction of the hot work die steel at 400℃ and 600℃ were 0.6~0.8. In subsequent embodiments, all coating performance data were based on the above-mentioned hot work die steel substrate performance.

[0034] Example 1 A method for preparing iron-based high-temperature composite powder includes the following steps: S1: Weigh out 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 15% W, 1% graphite and 74.9% Fe by mass fraction; S2: 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 15% W, 1% graphite, 74.9% Fe and 10% polyvinyl alcohol by mass fraction are placed together in an acoustic resonance device. The parameters of the acoustic resonance device are set as follows: vibration frequency 60-80 Hz, acceleration 60-90 G, vibration time 10-30 min. After thorough mixing, a composite powder is obtained. S3: Prepare spherical composite powder by spray granulation process of uniformly mixed composite powder. The parameters of spray granulation process are: rotation speed 5000~8000rpm, inlet temperature 320℃, and outlet temperature 180℃. S4: Heat treatment of spherical composite powder yields iron-based high-temperature composite powder. The heat treatment parameters are: heat treatment temperature of 300℃ and holding time of 10~20 min, to remove residual polyvinyl alcohol. S5: The iron-based high-temperature composite powder is sieved, and the sieved powder is weighed to obtain a powder particle size of 50~150μm, a flowability of 19s / 50g, a sphericity of 95%, and a powder utilization rate of 92%. S6: The powder prepared above is laser clad onto hot work die steel to obtain a composite coating, which is a self-lubricating and highly wear-resistant composite coating. The parameters of the laser cladding process are: laser power 4000~6000 W, spot size 6*19 mm, powder feeding rate 4~6 kg / h, scanning rate 7 mm / s, overlap rate 50%, and cladding layer thickness 1~2 mm. S7: The hardness of the laser-clad coating was tested at room temperature, 400℃, and 600℃, and friction and wear tests were conducted at 30 min and 60 min.

[0035] Microscopic images of the composite powder prepared by the above-mentioned iron-based high-temperature composite powder preparation method are shown below. Figure 1 As shown in Table 1, its characteristics and coating performance results are as follows.

[0036] Table 1 Powder properties and coating performance of Example 1

[0037] Depend on Figure 1As shown in Table 1, at room temperature, the coating hardness increased from 55 HRC to 70 HRC compared to the hot work die steel, an increase of 27%. The wear amount of the coating decreased from 0.007 g and 0.018 g to 0.0052 g and 0.0013 g at 30 min and 60 min, respectively, representing reductions of 25.7% and 27.7%. The coefficient of friction of the hot work die steel decreased from 0.4–0.6 to 0.1–0.2 after the coating was applied. At 400℃, the coating hardness increased from 35 HRC to 45 HRC compared to the hot work die steel, an increase of 28.6%. The wear amount of the coating decreased from 0.007 g and 0.018 g to 0.0052 g and 0.0013 g at 30 min and 60 min, respectively. The wear amount decreased from 0.009g and 0.022g to 0.0064g and 0.015g, respectively, representing a reduction of 40% and 31.8%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.3~0.5 after the coating was applied. At 600℃, the hardness of the coating increased from 25HRC to 31HRC compared to the hot work die steel, an increase of 24%. The wear amount of the coating decreased from 0.01g and 0.033g to 0.0076g and 0.023g at 30min and 60min, respectively, representing a reduction of 24% and 30.3%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.3~0.5 after the coating was applied.

[0038] Example 2 A method for preparing iron-based high-temperature composite powder includes the following steps: S1: Weigh out 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 20% W, 1.5% graphite and 69.4% Fe by mass fraction; S2: 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 20% W, 1.5% graphite, 69.4% Fe, and 10% polyvinyl alcohol by mass fraction are placed together in an acoustic resonance device. The parameters of the acoustic resonance device are set as follows: vibration frequency 60-80 Hz, acceleration 60-90 G, and vibration time 10-30 min. After thorough mixing, a composite powder is obtained. S3: Prepare spherical composite powder by spray granulation process of uniformly mixed composite powder. The parameters of spray granulation process are: rotation speed 5000~8000rpm, inlet temperature 320℃, and outlet temperature 180℃. S4: Heat treatment of spherical composite powder yields iron-based high-temperature composite powder. The heat treatment parameters are: heat treatment temperature of 300℃ and holding time of 10~20 min, to remove residual polyvinyl alcohol. S5: The iron-based high-temperature composite powder is sieved, and the sieved powder is weighed to obtain a powder particle size of 50~150μm, a flowability of 19s / 50g, a sphericity of 94%, and a powder utilization rate of 94%. S6: The powder prepared above is laser clad onto hot work die steel to obtain a composite coating, which is a self-lubricating and highly wear-resistant composite coating. The parameters of the laser cladding process are: laser power 4000~6000 W, spot size 6*19 mm, powder feeding rate 4~6 kg / h, scanning rate 7 mm / s, overlap rate 50%, and cladding layer thickness 1~2 mm. S7: The hardness of the laser-clad coating was tested at room temperature, 400℃, and 600℃, and friction and wear tests were conducted at 30 min and 60 min.

[0039] Microscopic images of the composite powder prepared by the above-mentioned iron-based high-temperature composite powder preparation method are shown below. Figure 3 As shown in Table 2, its characteristics and coating performance results are as follows.

[0040] Table 2 Powder properties and coating performance of Example 2

[0041] Depend on Figure 3As shown in Table 2, at room temperature, the coating hardness increased from 55 HRC to 71 HRC compared to the hot work die steel, an increase of 29%. The wear amount of the coating decreased from 0.007 g and 0.018 g at 30 min and 60 min to 0.0045 g and 0.0011 g respectively, representing reductions of 35.7% and 38.8%. The coefficient of friction of the hot work die steel decreased from 0.4–0.6 to 0.1–0.2 after the coating was applied. At 400℃, the coating hardness increased from 35 HRC to 44 HRC compared to the hot work die steel, an increase of 25.7%. The wear amount of the coating decreased from 0.007 g and 0.018 g at 30 min and 60 min to 0.0045 g and 0.0011 g respectively, representing reductions of 35.7% and 38.8%. The wear amount decreased from 0.009g and 0.022g to 0.0053g and 0.016g, respectively, representing a reduction of 41.1% and 27.3%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.3~0.5 after the coating was applied. At 600℃, the hardness of the coating increased from 25HRC to 34HRC compared to the hot work die steel, an increase of 36%. The wear amount of the coating decreased from 0.01g and 0.033g to 0.0074g and 0.025g at 30min and 60min, respectively, representing a reduction of 26% and 24.2%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.3~0.5 after the coating was applied.

[0042] Example 3 A method for preparing iron-based high-temperature composite powder includes the following steps: S1: Weigh out 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 25% W, 2% graphite and 63.9% Fe by mass fraction; S2: 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 25% W, 2% graphite, 63.9% Fe, and 10% polyvinyl alcohol by mass fraction are placed together in an acoustic resonance device. The parameters of the acoustic resonance device are set as follows: vibration frequency 60-80 Hz, acceleration 60-90 G, and vibration time 10-30 min. After thorough mixing, a composite powder is obtained. S3: Prepare spherical composite powder by spray granulation process of uniformly mixed composite powder. The parameters of spray granulation process are: rotation speed 5000~8000rpm, inlet temperature 320℃, and outlet temperature 180℃. S4: Heat treatment of spherical composite powder yields iron-based high-temperature composite powder. The heat treatment parameters are: heat treatment temperature of 300℃ and holding time of 10~20 min, to remove residual polyvinyl alcohol. S5: The iron-based high-temperature composite powder is sieved, and the sieved powder is weighed to obtain a powder particle size of 50~150μm, a flowability of 19s / 50g, a sphericity of 91%, and a powder utilization rate of 93%. S6: The powder prepared above is laser clad onto hot work die steel to obtain a composite coating, which is a self-lubricating and highly wear-resistant composite coating. The parameters of the laser cladding process are: laser power 4000~6000 W, spot size 6*19 mm, powder feeding rate 4~6 kg / h, scanning rate 7 mm / s, overlap rate 50%, and cladding layer thickness 1~2 mm. S7: The hardness of the laser-clad coating was tested at room temperature, 400℃, and 600℃, and friction and wear tests were conducted at 30 min and 60 min.

[0043] Microscopic images of the composite powder prepared by the above-mentioned iron-based high-temperature composite powder preparation method are shown below. Figure 5 As shown in Table 3, its characteristics and coating performance results are as follows.

[0044] Table 3 Powder properties and coating performance of Example 3

[0045] Depend on Figure 5As shown in Table 3, at room temperature, the coating hardness increased from 55 HRC to 69 HRC compared to the hot work die steel, an increase of 25.5%. The wear amount of the coating decreased from 0.007 g and 0.018 g at 30 min and 60 min to 0.0045 g and 0.012 g respectively, representing reductions of 35.7% and 33.3%. The coefficient of friction of the hot work die steel decreased from 0.4–0.6 to 0.1–0.2 after the coating was applied. At 400℃, the coating hardness increased from 35 HRC to 46 HRC compared to the hot work die steel, an increase of 31.4%. The wear amount of the coating decreased from 0.007 g and 0.018 g at 30 min and 60 min to 0.0045 g and 0.012 g respectively, representing reductions of 35.7% and 33.3%. The wear amount decreased from 0.009g and 0.022g to 0.0061g and 0.014g, respectively, representing a reduction of 32.2% and 36.4%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.3~0.5 after the coating was applied. At 600℃, the hardness of the coating increased from 25HRC to 33HRC compared to the hot work die steel, an increase of 32%. The wear amount of the coating decreased from 0.01g and 0.033g to 0.007g and 0.022g at 30min and 60min, respectively, representing a reduction of 30% and 33.3%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.3~0.5 after the coating was applied.

[0046] Comparative Example 1 A method for preparing iron-based high-temperature composite powder includes the following steps: S1: Weigh out 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 25% W, 2% graphite and 63.9% Fe by mass fraction; S2: 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 25% W, 2% graphite, 63.9% Fe, and 10% polyvinyl alcohol by mass fraction are placed together in a ball mill. The parameters of the ball mill are set as follows: ball-to-material ratio: 5:1, rotation speed: 400~500 rpm, and ball milling time: 16~32 h. After thorough mixing, a composite powder is obtained. S3: Prepare spherical composite powder by spray granulation process of uniformly mixed composite powder. The parameters of spray granulation process are: rotation speed 5000~8000rpm, inlet temperature 320℃, and outlet temperature 180℃. S4: Heat treatment of spherical composite powder yields iron-based high-temperature composite powder. The heat treatment parameters are: heat treatment temperature of 300℃ and holding time of 10~20 min, to remove residual polyvinyl alcohol. S5: The iron-based high-temperature composite powder is subjected to particle size sieving, and the sieved powder is weighed to obtain a powder particle size of 50~150μm, a flowability of 19s / 50g, a sphericity of 75%, and a powder utilization rate of 80%. S6: The powder prepared above is laser clad onto hot work die steel to obtain a composite coating, which is a self-lubricating and highly wear-resistant composite coating. The parameters of the laser cladding process are: laser power 4000~6000 W, spot size 6*19 mm, powder feeding rate 4~6 kg / h, scanning rate 7 mm / s, overlap rate 50%, and cladding layer thickness 1~2 mm. S7: The hardness of the laser-clad coating was tested at room temperature, 400℃, and 600℃, and friction and wear tests were conducted at 30 min and 60 min.

[0047] Microscopic images of the composite powder prepared by the above-mentioned iron-based high-temperature composite powder preparation method are shown below. Figure 2 As shown in Table 4, its characteristics and coating performance results are as follows.

[0048] Table 4 Comparative Example 1 Powder Properties and Coating Performance

[0049] Depend on Figure 2As shown in Table 4, at room temperature, the coating hardness increased from 55 HRC to 62.1 HRC compared to the hot work die steel, representing a 12.9% increase. The wear amount of the coating decreased from 0.007 g and 0.018 g to 0.006 g and 0.016 g at 30 min and 60 min, respectively, representing reductions of 14.2% and 11.1%. The coefficient of friction of the hot work die steel decreased from 0.4–0.6 to 0.3–0.5 after the coating was applied. At 400℃, the coating hardness increased from 35 HRC to 41 HRC compared to the hot work die steel, representing a 17.1% increase. The wear amount of the coating decreased from 30 min to 62.1 HRC compared to the hot work die steel at 30 min and 60 min, respectively. The wear amount decreased from 0.009g and 0.022g to 0.008g and 0.02g, respectively, representing a reduction of 11.1% and 9%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.4~0.6 after the coating was applied. At 600℃, the hardness of the coating increased from 25HRC to 31HRC compared to the hot work die steel, an increase of 24%. The wear amount of the coating decreased from 0.01g and 0.033g to 0.0093g and 0.03g at 30min and 60min, respectively, representing a reduction of 7% and 9%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.4~0.6 after the coating was applied.

[0050] Comparative Example 2 A method for preparing iron-based high-temperature composite powder includes the following steps: S1: Weigh out 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 20% W, 1.5% graphite and 69.4% Fe by mass fraction; S2: 0.5% C, 4.5% Cr, 0.4% Mn, 1.5% Mo, 0.2% Ni, 1.2% Si, 0.8% V, 20% W, 1.5% graphite, 69.4% Fe, and 10% polyvinyl alcohol by mass fraction were placed together in a planetary ball mill. The parameters of the planetary ball mill were set as follows: ball-to-material ratio: 5:1, rotation speed: 400~500 rpm, and milling time: 16~32 h. After thorough mixing, a composite powder was obtained. S3: Prepare spherical composite powder by spray granulation process of uniformly mixed composite powder. The parameters of spray granulation process are: rotation speed 5000~8000rpm, inlet temperature 320℃, and outlet temperature 180℃. S4: Heat treatment of spherical composite powder yields iron-based high-temperature composite powder. The heat treatment parameters are: heat treatment temperature of 300℃ and holding time of 10~20 min, to remove residual polyvinyl alcohol. S5: The iron-based high-temperature composite powder is subjected to particle size sieving, and the sieved powder is weighed to obtain a powder particle size of 50~150μm, a flowability of 19s / 50g, a sphericity of 80%, and a powder utilization rate of 84%. S6: The powder prepared above is laser clad onto hot work die steel to obtain a composite coating, which is a self-lubricating and highly wear-resistant composite coating. The parameters of the laser cladding process are: laser power 4000~6000 W, spot size 6*19 mm, powder feeding rate 4~6 kg / h, scanning rate 7 mm / s, overlap rate 50%, and cladding layer thickness 1~2 mm. S7: The hardness of the laser-clad coating was tested at room temperature, 400℃, and 600℃, and friction and wear tests were conducted at 30 min and 60 min.

[0051] Microscopic images of the composite powder prepared by the above-mentioned iron-based high-temperature composite powder preparation method are shown below. Figure 4 As shown in Table 5, its characteristics and coating performance results are as follows.

[0052] Table 5 Comparative Example 2 Powder Properties and Coating Performance

[0053] Depend on Figure 4As shown in Table 5, at room temperature, the coating hardness increased from 55 HRC to 61.3 HRC compared to the hot work die steel, an increase of 11.5%. The wear amount of the coating decreased from 0.007 g and 0.018 g at 30 min and 60 min to 0.0059 g and 0.016 g respectively, representing reductions of 15.7% and 14.6%. The coefficient of friction of the hot work die steel decreased from 0.4–0.6 to 0.3–0.5 after the coating was applied. At 400℃, the coating hardness increased from 35 HRC to 43 HRC compared to the hot work die steel, an increase of 22.8%. The wear amount of the coating decreased from 0.007 g and 0.018 g at 30 min and 60 min to 0.0059 g and 0.016 g respectively, representing reductions of 15.7% and 14.6%. The wear amount decreased from 0.009g and 0.022g to 0.0085g and 0.018g, respectively, representing a reduction of 16.6% and 18.2%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.4~0.6 after the coating was applied. At 600℃, the hardness of the coating increased from 25HRC to 30HRC compared to the hot work die steel, a 20% increase. The wear amount of the coating decreased from 0.01g and 0.033g to 0.0086g and 0.027g at 30min and 60min, respectively, representing a reduction of 14% and 18.1%. The coefficient of friction of the hot work die steel decreased from 0.6~0.8 to 0.4~0.6 after the coating was applied.

[0054] In summary, the iron-based high-temperature composite powder preparation method provided by this invention solves the problems of reinforcing phase segregation, uneven mixing, and low efficiency caused by density differences in traditional mechanical mixing and ball milling techniques through the synergistic effect of acoustic resonance mixing, spray granulation, heat treatment, and laser cladding. Among them, acoustic resonance mixing achieves efficient homogenization of composite powder, spray granulation optimizes powder morphology and flowability, heat treatment removes binder residues and maintains the characteristics of composite powder, and then laser cladding is used to obtain a high-temperature composite coating with good metallurgical bonding, no defects, high hardness, excellent wear resistance, and self-lubricating function on the surface of hot work die steel, which significantly improves the service life and reliability of the die under high temperature and heavy load conditions.

Claims

1. A method for preparing iron-based high-temperature composite powder, characterized in that, Includes the following steps: S1: Weigh out 0.5~2.5% C, 4.0~5.0% Cr, 0.3~0.5% Mn, 1.0~2% Mo, 0.1~0.3% Ni, 0.5~1.5% Si, 0.5~1.5% V, 15~30% W, 1~2% graphite and balance Fe by mass fraction, or weigh out 68~84% 4Cr5MoSiV1, 15~30% W and 1~2% graphite by mass fraction; S2: The raw material obtained in S1 is placed together with the polyvinyl alcohol solution in an acoustic resonance device for acoustic resonance mixing to obtain a uniformly mixed composite powder. S3: Prepare spherical composite powder by spray granulation process using the uniformly mixed composite powder obtained in S2; S4: Heat-treat the spherical composite powder obtained in S3 to obtain high-temperature composite powder; S5: Perform particle size sieving on the high-temperature composite powder obtained in S4.

2. The method for preparing iron-based high-temperature composite powder according to claim 1, characterized in that: In S1, the graphite is flake graphite.

3. The method for preparing iron-based high-temperature composite powder according to claim 1, characterized in that: In step S2, the polyvinyl alcohol solution has a degree of alcoholysis of 98.0~99.0 mol%, a viscosity of 20.0~30.0 mPa·s, and a mass fraction of 10%.

4. The method for preparing iron-based high-temperature composite powder according to claim 2, characterized in that: In S2, the mixing parameters of the acoustic resonance device are: vibration frequency 60-80Hz, acceleration 60-90G, and vibration time 10-30 min.

5. The method for preparing iron-based high-temperature composite powder according to claim 1, characterized in that: In step S3, the parameters of the spray granulation process are: rotation speed 5000~8000rpm, inlet temperature 320℃, and outlet temperature 180℃.

6. The method for preparing iron-based high-temperature composite powder according to claim 1, characterized in that: In step S4, the parameters for the heat treatment are: the heat treatment temperature is 300℃, and the holding time is 10~20 min.

7. The method for preparing iron-based high-temperature composite powder according to claim 1, characterized in that: In step S5, the particle size of the sieved composite powder is 50~150 μm, the flowability is 15~25 s / 50g, and the sphericity is ≥90%.

8. An iron-based high-temperature composite powder, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. A high-temperature composite powder coating based on iron, characterized in that: The iron-based high-temperature composite powder coating according to claim 8 is formed on the surface of hot work die steel by laser cladding process. The parameters of the laser cladding process are: laser power 4000~6000 W, spot size 6*19 mm, powder feeding rate 4~6 kg / h, scanning rate 7 mm / s, overlap rate 50%, and cladding layer thickness 1~2 mm.

10. The application of the iron-based high-temperature composite powder coating according to claim 9 in the preparation of wear-resistant and self-lubricating coatings by laser cladding on the surface of hot work die steel.

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