Die surface machining process

Abstract

The invention relates to the technical field of metal surface strengthening, in particular to a mold surface processing technology which comprises the following steps: step 1, differentiated pretreatment based on curvature recognition; 2, gradient component dynamic plasma spraying is conducted, metal binding phase powder and ceramic reinforced phase powder are synchronously conveyed, the metal phase powder feeding rate is gradually increased while the ceramic phase is gradually increased from zero in the near-matrix interval, and the metal phase powder feeding rate is gradually decreased while the ceramic phase is gradually increased in the far-matrix interval; 3, energy self-adaptive functional layer strengthening is conducted, specifically, the motion parameters of a spray gun are adjusted according to a curvature sudden change area, dynamic remelting is conducted through an energy beam after each single channel is sprayed, and remelting energy is adjusted based on real-time temperature feedback; and 4, stress synergistic post-treatment is conducted, graded impact energy is applied according to coating thickness distribution, and aging treatment is conducted based on phase change characteristics. And through accurate curvature recognition, differential sand blasting, a gradient spraying technology, energy self-adaptive remelting and stress collaborative post-treatment, the overall performance of the surface of the mold is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal surface strengthening, in particular to a mold surface processing technology. BACKGROUND

[0002] In the field of automobile panel stamping die manufacturing, the die working surface has been subjected to continuous impact load of up to 800-1000 times per minute for a long time, and due to the complex curved surface design of the panel (the proportion of deep cavity, sharp angle and steep slope structure is ≥60%), the traditional plasma sprayed wear-resistant coating layer faces the following inherent defects: 1. Mechanism and harm of insufficient bonding strength on curved surface: Due to the difference of more than 100% in the thermal expansion coefficient between the metal die substrate (thermal expansion coefficient α≈12×10 -6 / K) and the ceramic coating (α≈6×10 -6 / K), interfacial shear stress is generated during the spraying and cooling process. Especially in the ridge line area with a curvature radius of ≤3mm (such as the door reinforcement groove), the bonding strength between the coating and the substrate is less than 200MPa, which is only 40%-50% of that in the flat area. This defect causes interlayer peeling under high temperature working conditions (mold surface temperature > 300℃), resulting in loss of control of the size tolerance of the stamped part, and the single repair downtime loss is as high as 200,000 yuan.

[0003] 2. Cause and influence of uncontrolled porosity: In the existing process, when spraying on a special-shaped surface, the angle of the molten particles colliding with the substrate is dispersed by more than 30° due to the influence of the curved surface on the flight trajectory of the powder particles, forming a large number of unspread stacked pores. Statistics show that the porosity in the concave corner area (aspect ratio ≥5) is as high as 5%-8%, which becomes a crack source under alternating load. When the pores are connected in a network structure (pore spacing < 50μm), the wear resistance of the coating is reduced to 1 / 3 of the normal value, resulting in the need for repair every 100,000 parts processed by the mold, which is much lower than the industry benchmark of 250,000 parts.

[0004] Therefore, there is an urgent need for a mold surface processing technology to solve the above problems. SUMMARY

[0005] Based on the above purpose, the present application provides a mold surface processing technology, comprising the following steps: Step 1: Differentiated pretreatment based on curvature recognition, scanning the die working surface and identifying the curvature mutation area, using a first sandblasting strategy for the mutation area according to the curvature distribution, and using a second sandblasting strategy for the non-mutation area, and generating an anchor-shaped structure with increased depth in the curvature mutation area; Step 2: Gradient component dynamic plasma spraying, synchronously delivering metal binder phase powder and ceramic reinforcing phase powder, increasing metal phase powder delivery rate from zero in the near-substrate zone and decreasing metal phase powder delivery rate in the far-substrate zone; Step 3: Energy self-adaptive functional layer strengthening, adjusting the spray gun motion parameters for the curvature mutation area, and using an energy beam for dynamic remelting after each spray single pass, and the remelting energy is adjusted based on real-time temperature feedback; Step 4: Stress synergistic post-processing, applying graded impact energy according to the coating thickness distribution, and implementing aging treatment based on phase change characteristics. Preferably, the implementation method of the first sandblasting strategy in step 1 comprises: The curvature radius of each area is calculated by three-dimensional point cloud data analysis, and the area with a curvature radius less than a predetermined threshold is defined as a curvature mutation area; The air pressure value of the first sandblasting strategy is determined by the ratio of the substrate material hardness to the abrasive hardness: when the ratio is in the first interval, 60%-70% of the standard air pressure is used, and when the ratio is in the second interval, 70%-80% of the standard air pressure is used; The selection of abrasive particle size is based on: for groove areas with a depth-width ratio greater than a predetermined value, an abrasive with a particle size of 50%-60% of the standard value of the flat area is selected; The dynamic adjustment method of the sandblasting incident angle is: according to the angle between the surface normal vector and the spray gun axis, the angle deviation is compensated in real time, so that the effective impact angle is kept within 85°-95°. Preferably, the control method of the powder delivery rate in step 2 specifically comprises: The thickness of the near-substrate zone is determined by: calculating the difference between the thermal expansion coefficients of the substrate material and the metal binder phase, and increasing the zone thickness when the difference exceeds a predetermined percentage; The increasing gradient of the metal phase powder delivery rate is determined according to the plasma jet temperature distribution: a steep increasing gradient is used in the high-temperature center of the jet, and a gentle increasing gradient is used in the low-temperature edge; The initial activation point of the ceramic phase powder delivery rate is located at a predetermined distance from the substrate surface, which is calculated by the residence time of the powder in the plasma jet, to ensure that the powder reaches the substrate in a molten state. Preferably, the operation method of dynamic remelting in step 3 comprises: The real-time temperature measurement data is collected at a position 2-3mm downstream of the remelting point, and the sampling frequency is not less than 1kHz; The remelting energy adjustment rule is: when the temperature value is lower than the target range, increase the unit area energy input value by each degree Celsius difference; when it is higher than the target range, increase the energy beam scanning speed by the same ratio; The target temperature range is calculated by the solidus temperature of the coating material: the lower limit is the solidus temperature x 0.85, and the upper limit is the solidus temperature x 0.92; The diameter of the energy beam focusing spot is adaptively adjusted according to the coating thickness: for every 50 μm increase in thickness, the spot diameter is expanded by a predetermined percentage. Preferably, the adjustment of the spray gun motion parameters in step 3 includes: The reduction ratio of the scanning speed is determined by the ratio of the curvature radius to the critical radius: when the curvature radius is less than the critical radius, the speed is reduced to 70%-80% of the speed in the planar region; The adjustment rule for the spray gun distance is: in the concave corner region, the distance is shortened to 80%-90% of the standard distance, and in the convex corner region, the distance is increased to 110%-120% of the standard distance; The value of the critical radius is determined according to the mold working load: for every predetermined increase in impact load, the critical radius is reduced by the same percentage. Preferably, the implementation method of the step 4 includes: The coating thickness distribution map is obtained by an eddy current thickness gauge, and the region with a thickness greater than the first threshold value is divided into a high-energy impact area, and the region with a thickness less than the second threshold value is divided into a low-energy impact area; The energy value of the high-energy impact area is 120%-130% of the reference energy, and the reference energy is calculated by the nanoindentation hardness value of the coating: for every predetermined increase in hardness, the reference energy is increased by the same percentage; The curvature radius of the impact needle is selected as follows: a needle with a radius ≤ 0.2 mm is used in the curvature mutation region, and a needle with a radius ≥ 0.5 mm is used in the planar region. Preferably, the step 2 includes: The metal binder phase powder is selected from a nickel-based alloy, and the particle size distribution is determined by Hall flow rate testing: a particle size combination with a flow rate in the optimal interval is selected; The ceramic reinforcing phase powder is an alumina-zirconia composite powder, and the content of zirconia is set according to the thermal shock resistance requirement of the coating: when the mold working temperature fluctuation exceeds a predetermined range, the content of zirconia is increased to a predetermined proportion. Preferably, the control method of the step 4 includes: The aging temperature is determined by differential scanning calorimetry after determining the phase transition point of the coating: 40%-50% of the phase transition point temperature is taken; The calculation logic of the holding time is: taking the maximum thickness value as the reference, 1 hour is calculated for every 10 mm of thickness, and when the cross-sectional thickness variation rate exceeds a predetermined value, the time is calculated based on 120% of the maximum thickness value; The cooling rate control is: a slow cooling rate of ≤ 30 ℃ / min is used in the temperature range below the phase transition point. Preferably, the calculation method of the residence time specifically comprises: Record the trajectory of the powder in the plasma jet by high-speed photography; Calculate the residence time according to the distance between the spray gun and the substrate and the average movement speed of the powder; When the residence time is less than the time required for complete melting of the powder, simultaneously increase the plasma power and reduce the powder feeding rate. Preferably, the determination logic of the unit area energy input value comprises: Establish a mapping relationship between the remelting depth and the energy density: measure the remelting depth under different energy densities by metallographic sectioning; Back-calculate the required energy density according to the target remelting depth, and set the target remelting depth to 10%-15% of the current coating thickness; When the coating porosity detection value exceeds the standard, increase the target remelting depth by the same proportion. Advantages of the present application: 1. By scanning the working profile of the mold, the curvature mutation area is accurately identified, and different sandblasting strategies are adopted. For the sharp corners and edge lines with small curvature, a sandblasting method with high air pressure and small particle size abrasive is used to form an anchor-shaped structure with increased depth, thereby enhancing the mechanical bonding force between the coating and the substrate. This strategy can effectively compensate for the insufficient bonding force of the coating in the traditional spraying process.

[0006] 2. By synchronously conveying metal binder phase powder and ceramic reinforcing phase powder, an increasing metal phase powder feeding rate and a decreasing ceramic phase powder feeding rate are adopted in the area close to the substrate, and the reverse adjustment is made in the area away from the substrate. This precise powder increasing and decreasing control ensures the uniformity and density of the coating. At the same time, dynamic remelting treatment is adopted during spraying, the coating temperature is monitored in real time, and energy adjustment is made, thereby effectively eliminating pores and reducing the porosity of the coating.

[0007] 3. By hierarchical impact energy treatment, appropriate impact energy is applied according to the coating thickness distribution, and combined with aging treatment, the microstructure of the coating is optimized, and the internal stress of the coating is reduced. The treatment is precisely controlled by eddy current thickness gauge, ensuring that the coating is fully strengthened in the high stress area.

[0008] 4. Through dynamic regulation of metal and ceramic powders, the composition and performance of the coating in different areas are designed differently, and the hardness, wear resistance and high temperature resistance of the coating are significantly improved. Especially the strengthening effect of the ceramic phase powder improves the wear resistance of the coating. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0010] Fig. 1 Flow chart of the step of the method of the present application; Fig. 2 Flow chart of the step of the implementation method of the graded impact energy in step 4 of the method of the present application; Fig. 3 Flow chart of the determination logic of the energy input value per unit area of the method of the present application. DETAILED DESCRIPTION

[0011] The present application will be described in detail below in conjunction with the drawings and specific embodiments. It should be noted here that, in order to make the embodiments more detailed, the following embodiments are the best, preferred embodiments, and other alternative ways can also be used by those skilled in the art to implement them; and the drawings are only used to more specifically describe the embodiments, and are not intended to specifically limit the present application.

[0012] Please refer to Figs. 1-3 The embodiment of the present application provides a mold surface processing technology. In step 1, a high-precision three-dimensional scanner is first used to measure the working profile of the mold in the whole domain, and the curvature change rate is calculated to identify the curvature mutation area (such as the edge line with a radius less than 3 mm, groove, etc.). In these areas, the first sandblasting strategy is selected, that is, corundum particles with a particle size of 80-100 mesh and a spraying pressure of 0.6-0.8 MPa are used to form an anchor-shaped roughening structure with a depth of 20-40 μm, so as to significantly improve the mechanical interlocking force between the ceramic coating and the substrate. For the curvature gentle area, the second sandblasting strategy with a particle size of 100-120 mesh and a lower air pressure (0.4 MPa) is used to avoid the influence of excessive roughening on the flatness.

[0013] In step 2, the plasma spraying process of gradient composition is implemented. During the spraying process, a double-channel powder feeding system is used to synchronously deliver metal (such as NiCr) and ceramic (such as Al2O3) powders. The near-substrate area (thickness of 10-20 μm) is mainly composed of metal phase, and the powder feeding rate is set to 30 g / min for metal phase and 5 g / min for ceramic phase, and the ceramic proportion is gradually increased. When spraying to the area far from the substrate, it is adjusted to 10 g / min for metal phase and 30 g / min for ceramic phase, so as to build a functional layer structure with gradient transition, thereby ensuring the bonding force while enhancing the wear resistance and thermal stability.

[0014] Step 3 uses an energy self-adaptive functional layer reinforcement process. The infrared temperature measuring device is used to monitor the surface temperature of the coating in real time, and the energy density of the laser or plasma remelting beam is dynamically adjusted according to the residual heat distribution after each spraying (range 1.5-3.5 J / mm 2 ). In the curvature mutation area, the spraying gun scanning speed is appropriately reduced and the remelting energy is increased to ensure that the coating inside is dense, crack-free and pore-free, and the material consistency and crack resistance are enhanced.

[0015] In step 4, a graded impact energy process is implemented according to the online coating thickness measurement results. In the thick coating area, the impact frequency is 20 Hz and the energy intensity is 4 J, while in the thin coating area, the impact parameters are 3 J. At the same time, the heating temperature is controlled in the range of 550-600℃ for two hours of aging treatment to release residual stress and induce microstructure phase transformation in the metal phase (such as metastable phase to stable phase transition), thereby improving the overall thermal shock resistance and structural stability of the coating.

[0016] The present application significantly enhances the bonding strength, density and thermal mechanical stability of the coating on the complex curved surface area of the mold, solves the problems of easy peeling, easy cracking, high porosity and short service life of traditional plasma spraying in special-shaped areas, and finally realizes a significant improvement in mold reliability and service life.

[0017] In one possible implementation, the present embodiment aims to solve the problem of non-uniform response of the mold complex curved surface in sandblasting treatment, and proposes a differentiated sandblasting strategy based on curvature driving, and designs an implementation method of the first sandblasting strategy to significantly improve the adhesion and structural uniformity of the subsequent coating.

[0018] Specifically, first, the point cloud data of the mold surface is obtained by a high-precision three-dimensional scanner, and the principal curvature of each sampling point is numerically analyzed by using a discrete curvature calculation algorithm. According to the set curvature radius threshold (such as 1.5mm), the area smaller than the threshold is defined as the curvature mutation area, which is mainly concentrated in the corners, edges and narrow grooves of the mold. These areas are usually high-risk areas of stress concentration and coating peeling due to the sharp change in curvature.

[0019] In terms of the setting of the sandblasting air pressure, a material response model is used to classify according to the hardness ratio of the base material (such as hot work die steel) and the abrasive used (such as brown corundum). For example, when the ratio is in the first interval of 1.0-1.5, to avoid causing micro-cracks or erosion to the base body, the sandblasting air pressure is set to 60%-70% of the standard value (0.6MPa); when the ratio is in the second interval of 1.5-2.0, the air pressure is increased to 70%-80% to obtain more effective roughening effect without damaging the surface integrity.

[0020] The selection of abrasive particle size is optimized for narrow and deep groove areas with a depth-to-width ratio greater than 2. To prevent large particle abrasives from accumulating, rebounding ineffectively, or damaging the microstructure in such areas, fine-grained abrasives (e.g., 120 mesh) with a particle size of 50-60% of the standard value (e.g., 80 mesh) are selected to improve the contact coverage of the groove bottom surface and the quality of micro-anchoring formation.

[0021] In terms of sandblasting angle control, a real-time angle compensation mechanism based on surface normal vectors is introduced. By calculating the included angle between the unit normal vector of the current sandblasting position and the spray axis of the spray gun, the incident direction of the spray gun is dynamically adjusted to ensure that the effective impact angle is always maintained between 85° and 95°. This angle range has been experimentally verified as the ideal interval that can ensure effective abrasive impact to form rough structures without causing surface micro-peeling or lateral damage.

[0022] This first sandblasting strategy not only improves the consistency of surface roughness and the stability of microstructure in high-curvature areas, but also effectively controls the damage risk of sandblasting to the substrate, significantly enhancing the adhesion strength and service stability of the subsequent coating, and is particularly suitable for high-complexity mold surface pretreatment processes.

[0023] In one possible implementation, the present embodiment addresses the problem of good bonding between the substrate surface and the metal binder phase and the formation of uniform coatings, and provides an innovation in the control of powder feed rate in mold surface processing technology, especially in high-temperature plasma spraying processes, providing a more precise and efficient control method for adjusting the powder feed rate.

[0024] Specifically, first, the thickness determination method for the near-substrate region adjusts by calculating the difference in thermal expansion coefficients between the substrate material and the metal binder phase. When the difference in thermal expansion coefficients is large, it means that the thermal stress difference of the material is large, which is easy to form cracks or delamination between the coating and the substrate. Therefore, when the difference in thermal expansion coefficients between the substrate material and the metal binder phase exceeds a certain threshold value, in order to avoid stress concentration and crack formation, the thickness of the near-substrate region needs to be increased to improve the thermal expansion capability and thermal stress dispersion performance of this region. This approach can improve the adhesion and durability of the metal coating, ensuring the stability and uniformity of the coating.

[0025] Second, the powder feed rate of the metal phase adopts a strategy of setting an incremental gradient based on the temperature distribution of the plasma jet. In the plasma spraying process, the center region of the plasma jet has the highest temperature, while the edge region has lower temperature. In order to ensure that the metal powder can be fully melted and form a firm bond with the substrate, a steeper incremental gradient is used in the high-temperature center region of the plasma jet to ensure that the powder feed rate increases rapidly, so that the powder reaches the melting state faster. In the low-temperature edge region of the plasma jet, a gentle incremental gradient is used to avoid the situation where too much powder is sent in without being fully melted, thereby improving the quality and uniformity of the metal coating.

[0026] The powder feeding rate control method of the ceramic phase is optimized based on the residence time of the powder in the plasma jet. At the initial design stage, by calculating the residence time of the ceramic powder in the plasma jet, the initial activation point of the ceramic phase powder feeding rate is determined, that is, the starting position of the powder entering the plasma jet. This position ensures that the ceramic powder has reached the molten state when it reaches the substrate surface, to ensure that the ceramic coating can uniformly cover and firmly bond with the substrate, thereby improving the wear resistance and corrosion resistance of the coating.

[0027] The present application solves the problems of poor adhesion and uneven coating between different phases during spraying by precisely controlling the powder feeding rate and the bonding process of the powder and the substrate. By timely adjusting the powder feeding rate gradient and activation point of the metal and ceramic powders, the overall quality of the coating can be ensured, and the durability and performance of the mold can be improved, especially the stability performance in high temperature and high pressure environments.

[0028] In one possible implementation, by controlling the real-time temperature and energy during the remelting process, the melting and solidification process of the coating is further optimized, thereby ensuring good bonding and uniformity of the coating and the substrate, and improving the wear resistance and corrosion resistance of the mold surface.

[0029] Specifically, first, the real-time temperature data collection position is set at 2-3 mm downstream of the remelting point, and the sampling frequency is not less than 1 kHz. This operation ensures high sensitivity and precise control of temperature changes during the remelting process. Since the coating will undergo different temperature changes during the remelting process, by collecting temperature data at a distance of 2-3 mm from the remelting point, the small changes in coating temperature can be reflected in time, avoiding control errors due to measurement lag. In addition, a sampling frequency of 1 kHz or more can capture the details of temperature changes, making temperature regulation more accurate, and thus ensuring the uniformity of the remelting process and the stability of the coating.

[0030] In terms of remelting energy regulation, when the temperature measurement value is lower than the target range, the energy input value per unit area is increased by each degree Celsius difference. This means that when the temperature is lower than the set target temperature range, the system will timely increase the energy input to speed up the melting process, to ensure that the coating reaches the ideal molten state. When the temperature is higher than the target range, the energy input is adjusted by increasing the energy beam scanning speed, to avoid overheating and prevent the coating from being excessively melted or evaporated, ensuring that the coating maintains in an ideal temperature range during the melting process, improving the coating quality.

[0031] The target temperature range is set based on the solidus temperature of the coating material, with the lower limit being 85% of the solidus temperature and the upper limit being 92% of the solidus temperature. The solidus temperature refers to the temperature range at which the coating material begins to transition from a solid state to a liquid state, so the set target temperature range is near the solidus temperature, which can ensure that the coating material is in an ideal temperature range during melting, thereby avoiding excessive melting or insufficient melting, and ensuring the adhesion and strength of the coating.

[0032] The diameter of the energy beam focusing spot is adaptively adjusted according to the coating thickness, and the spot diameter is expanded by a predetermined percentage for every 50 μm increase in coating thickness. This adjustment can ensure that the energy beam can uniformly cover the surface of the coating, and as the coating thickness increases, the spot diameter is appropriately expanded to avoid uneven melting of the coating due to excessive concentration of the energy beam, and to ensure that each layer of the coating is uniformly heated.

[0033] The dynamic remelting operation method of the present application solves the problems of uneven coating quality and poor adhesion caused by temperature fluctuations in traditional processing through precise temperature monitoring and intelligent energy adjustment. This method effectively improves the density, hardness and durability of the coating on the mold surface, and has significant technical advantages in improving the service life and performance of the mold.

[0034] In one possible implementation, first, the reduction ratio of the scanning speed is determined by the ratio of the curvature radius to the critical radius. When there is a change in curvature on the processing surface, if the curvature radius is less than the preset critical radius, it indicates that there is a large geometric curvature change in this area, such as sharp corners, concave structures, etc. Due to the complex topography of such areas, if sprayed at the conventional speed, problems such as uneven coating accumulation and poor adhesion are likely to occur. Therefore, the scanning speed is reduced to 70-80% of the speed on the flat area, on the one hand, to prolong the deposition time of the coating in this area and ensure sufficient material filling, and on the other hand, to reduce the heat input gradient change rate and reduce the thermal stress concentration caused by rapid movement, thereby improving the coating bonding quality and density.

[0035] Secondly, the distance between the spray gun and the processing surface is adjusted according to different geometric features: in the concave corner area, the distance between the spray gun and the processing surface is shortened to 80-90% of the standard distance, which can increase the deposition density of the coating material in the concave corner area and improve the thin coating phenomenon caused by the difficulty of covering the dead angle in the traditional process; while in the convex corner area, in order to prevent the coating from accumulating too thick and causing surface unevenness or peeling, the distance between the spray gun and the processing surface is appropriately increased to 110-120%, which reduces the energy density and particle kinetic energy to achieve the purpose of uniform coating. This differential distance adjustment enhances the consistency and adhesion strength of the coating on the non-flat surface.

[0036] The critical radius is dynamically determined according to the load condition of the mold in actual work. The greater the impact load borne by the mold, the higher the requirements for the strength and toughness of the surface structure, especially in the local microstructure area. According to the increasing trend of the impact load, the critical radius value is reasonably reduced, so as to identify the high-risk geometry in the high-load area in advance, and actively slow down and adjust the distance of the spray gun, thereby realizing the processing strengthening of the potential weak parts. The critical radius adjustment mechanism linked with the load response not only improves the coating consistency on the complex curved surface, but also strengthens the reliability and stability of the mold under extreme working conditions.

[0037] The dynamic adjustment method of the spray gun motion parameters can effectively cope with the deposition problems caused by the variable curvature surface, improve the spraying precision and process adaptability, and is especially suitable for surface strengthening treatment of high-precision molds and complex structural parts, and has significant engineering application value.

[0038] In a possible implementation, in the mold surface processing process of the present application, the implementation method of the graded impact energy is to accurately control the distribution of the impact energy in different areas to optimize the hardness and strength distribution of the coating. Specifically, the implementation steps include accurately measuring the thickness of the coating by using an eddy current thickness gauge, and dynamically adjusting the impact energy in combination with the nanoindentation hardness value of the coating, so as to accurately process different areas on the surface of the coating.

[0039] Specifically, first, the thickness distribution map of the coating is obtained by the eddy current thickness gauge, which divides the coating surface into multiple different areas. According to the size of the thickness value, the areas are divided into two categories: high-energy impact area and low-energy impact area. The area with a coating thickness greater than a first threshold value is classified as a high-energy impact area, and the area with a coating thickness less than a second threshold value is classified as a low-energy impact area. Through this grading method, different impact energies can be used for different thickness areas on the surface of the coating, thereby optimizing the uniformity and density of the coating.

[0040] In the high-energy impact area, the energy value used is 120%-130% of the reference energy, and the size of the reference energy is determined by the nanoindentation hardness value of the coating. Specifically, for every predetermined value increase in the hardness value of the coating, the reference energy is also increased accordingly. In this way, the area with a higher coating hardness value receives greater impact energy to strengthen its surface performance, and the area with a lower hardness value uses lower impact energy to avoid damage or excessive compaction of the coating due to excessive impact.

[0041] In addition, the selection rule of the curvature radius of the impact needle is also part of the technical features. When dealing with areas of different curvatures, it is crucial to select the appropriate impact needle radius. In areas with large curvature mutations, such as sharp corners or sharp turns, a needle with a radius ≤ 0.2 mm is used to ensure that the impact energy is effectively concentrated in a small range, strengthening the surface hardness of the area; while in flat areas with gentle curvature, a needle with a radius ≥ 0.5 mm is used, which can make the impact energy more evenly distributed, avoiding surface damage or uneven coating caused by excessive concentration.

[0042] Through the above method, the present application realizes the accurate impact energy distribution of different coating thickness and hardness areas, ensures the efficiency and uniformity of mold surface processing, and avoids coating defects or inconsistent performance caused by uneven energy. This regulation of graded impact energy not only improves the precision of mold surface treatment, but also significantly enhances the wear resistance and corrosion resistance of the coating, and improves the service life and working performance of the mold.

[0043] In one possible implementation, first, the selection of the metal binder phase powder is a nickel-based alloy, which has excellent high-temperature resistance and good binding ability, effectively enhancing the adhesion and stability of the coating. When determining the particle size distribution of the nickel-based alloy powder, the flow characteristics of the powder are accurately measured by Hall flow rate test. Hall flow rate test can determine the most suitable particle size interval according to the size, shape and distribution state of the powder particles. Generally, the particle size combination with optimal flow rate can ensure the uniformity and stability of the powder during transportation and deposition, thereby ensuring the uniform thickness and stable performance of the coating.

[0044] In the selection of ceramic reinforcing phase powder, aluminum oxide-zirconium oxide composite powder is used. Aluminum oxide has good hardness and wear resistance, while zirconium oxide has high thermal shock resistance and crack resistance, so the combination of the two can simultaneously improve the hardness and thermal stability of the coating. However, the content of zirconium oxide needs to be adjusted according to the temperature fluctuation of the mold working environment. When the working temperature of the mold fluctuates beyond the predetermined range, the content of zirconium oxide needs to be increased. By increasing the proportion of zirconium oxide, the thermal shock resistance of the coating can be significantly improved, preventing cracks or shedding caused by rapid temperature changes, and enhancing the stability and durability of the coating under extreme temperature changes.

[0045] By synchronously delivering metal binder phase powder and ceramic reinforcement phase powder, this combination ensures multiple properties of the coating in terms of high-temperature resistance, wear resistance, and thermal shock resistance. The selection of metal binder phase powder and the optimized ratio of ceramic reinforcement phase powder enable the coating to exhibit good adhesion, strength, and thermal stability under high temperature and complex working conditions. This technical feature can effectively prolong the service life of the mold and improve its performance in harsh environments, with significant practical value and economic benefits.

[0046] In one possible implementation, first, the aging temperature is selected based on the phase transition characteristics of the coating material. The phase transition temperature is accurately determined by differential scanning calorimetry (DSC), which can detect the phase transition temperature of the coating material during heating. To ensure the best performance of the coating, the aging temperature is selected to be 40%-50% of the phase transition point temperature. Within this temperature range, the microstructure of the material can be effectively transformed into a favorable state, thereby improving the hardness, wear resistance, and crack resistance of the coating.

[0047] Secondly, the holding time is calculated based on the geometric dimensions of the mold, especially the thickness of the thickest part of the cross section. Each increase of 10 mm in thickness corresponds to 1 hour of holding time. This design allows the coating to complete a uniform aging process at an appropriate temperature, ensuring that the microstructure within the material changes as expected. When the cross-sectional thickness variation rate of the mold exceeds the predetermined value, the maximum thickness value of 120% is used as the basis for calculating the holding time. This method avoids the impact of local thickness unevenness and ensures that all areas achieve the best aging effect.

[0048] Finally, the control of cooling rate is also an important part of the aging process. During the aging process, rapid changes in temperature can cause the coating to crack or lose its high-temperature resistance, so the cooling rate should be controlled to be no more than 30℃ / min below the phase transition point temperature range. This slow cooling process can prevent stress concentration caused by rapid temperature changes, effectively preventing the coating from cracking and maintaining its long-term stability.

[0049] By precisely controlling the aging temperature, holding time, and cooling rate, the coating can achieve a uniform microstructure during processing, improving the mechanical properties and thermal stability of the coating, prolonging the service life of the mold, and improving its reliability and durability in extreme working conditions. This control method achieves comprehensive optimization of the coating performance, with significant technical advantages.

[0050] In one possible implementation, first, the trajectory of the powder in the plasma jet is recorded by high-speed photography. This step employs high-speed photography technology to capture the specific movement path and time information of the powder in the plasma jet at an extremely high frame rate. Through this precise real-time recording, key data such as the movement trajectory of the powder in the plasma jet from the torch to the substrate surface and the speed change can be obtained, thereby providing accurate basis for subsequent residence time calculation.

[0051] Next, based on the distance between the torch and the substrate and the average movement speed of the powder, the residence time of the powder is calculated. The distance between the torch and the substrate directly affects the time for the powder to reach the substrate, while the average movement speed of the powder determines its residence time in the plasma jet. By combining the shooting distance of the torch with the movement speed of the powder, the actual residence time of the powder in the plasma jet can be accurately calculated, i.e. the time required for the powder to be shot out of the torch until it reaches the substrate surface.

[0052] When the calculated residence time is less than the time required for the powder to completely melt, the process parameters need to be adjusted. In this case, in order to ensure that the powder can completely melt and achieve the ideal coating quality, it is necessary to simultaneously increase the plasma power and reduce the powder feeding rate. Increasing the plasma power can increase the heat energy input, thereby prolonging the melting time of the powder in the plasma jet, ensuring that the powder can be fully melted and form a uniform coating. Reducing the powder feeding rate helps to reduce the flow of powder, so that each powder particle has a longer residence time in the plasma jet, further ensuring the sufficiency of the melting process.

[0053] By precisely controlling the residence time and adjusting the coordination of plasma power and powder feeding rate, it can be ensured that the powder coating reaches a completely melted state during processing, thereby obtaining a uniform and dense coating, improving the wear resistance and corrosion resistance of the mold surface. This technical method effectively avoids the instability of the coating quality caused by incomplete melting of the powder, thereby improving the service life and performance stability of the mold.

[0054] In one possible implementation, first, a mapping relationship between the remelt depth and the energy density is established. The remelt depth refers to the depth of the substrate surface that is heated and melted during the plasma spraying process, while the energy density refers to the heat energy applied per unit area. In order to obtain this mapping relationship, metallographic section technology is used, and experiments are conducted under different energy densities to measure the remelt depth under each condition. These experimental results provide basic data for further determination of processing parameters.

[0055] Then, the energy density required is back calculated according to the target remelt depth. In actual processing, the target remelt depth is set to 10%-15% of the current coating thickness. This range is set to ensure good bonding force between the coating and the substrate, while avoiding excessive melting that leads to overheating of the substrate or too thin coating. In this way, the corresponding energy density can be back calculated according to the target remelt depth, thereby providing guidance for power adjustment in actual operation.

[0056] When the coating porosity detection value exceeds the standard, the target remelt depth needs to be adjusted. If it is detected that the porosity of the coating is high, it means that the coating has not been completely melted or bonded firmly, which will affect the compactness and durability of the coating. Therefore, in this case, the target remelt depth needs to be increased proportionally to ensure that the melting effect of the coating can be improved and the porosity can be reduced. By appropriately increasing the target remelt depth, the melting degree of the coating can be improved, the porosity can be reduced, and the quality of the coating can meet the requirements.

[0057] Through precise control of energy density, the quality of the coating can be stabilized and controlled, especially for avoiding excessive melting or insufficient melting, which ensures the uniformity, compactness and durability of the coating on the mold surface. At the same time, timely adjustment of the target remelt depth helps to optimize the porosity of the coating, improve the performance of the mold surface, and prolong the service life.

[0058] The present application covers any substitutions, modifications, equivalent methods and solutions made on the essence and scope of the present application. In order to make the public have a thorough understanding of the present application, specific details are described in the following preferred embodiments of the present application, and the present application can also be fully understood without these details by those skilled in the art. In addition, in order to avoid unnecessary confusion to the essence of the present application, well-known methods, processes, procedures, elements and circuits, etc. are not described in detail.

[0059] The above is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

Claims

1. A mold surface processing technology, characterized in that, Includes the following steps: Step 1: Based on curvature recognition, differential preprocessing is performed to scan the working surface of the mold and identify curvature change areas. According to the curvature distribution, the first sandblasting strategy is applied to the change areas, and the second sandblasting strategy is applied to the non-change areas. An anchor-shaped structure with increased depth is generated in the curvature change areas. Step 2: Gradient component dynamic plasma spraying, synchronously delivering metal binder powder and ceramic reinforcing powder. In the near matrix region, the metal phase powder delivery rate increases while the ceramic phase delivery rate increases from zero. In the region far from the matrix, the metal phase powder delivery rate decreases while the ceramic phase delivery rate increases. Step 3: Enhance the energy adaptive functional layer by adjusting the spray gun motion parameters for areas with abrupt curvature changes. After each single coat, an energy beam is used for dynamic remelting, and the remelting energy is adjusted based on real-time temperature feedback. Step 4: Stress-coordinated post-treatment, applying graded impact energy according to the coating thickness distribution, and implementing aging treatment based on phase transformation characteristics.

2. The mold surface processing technology according to claim 1, characterized in that, The implementation method of the first sandblasting strategy in step 1 includes: The curvature radius of each region is calculated by analyzing 3D point cloud data, and regions with curvature radii less than a predetermined threshold are defined as curvature abrupt change regions. The air pressure value of the first sandblasting strategy is determined by the ratio of the hardness of the matrix material to the hardness of the abrasive: when the ratio is in the first range, 60%-70% of the standard air pressure is used, and when it is in the second range, 70%-80% is used. The selection criteria for abrasive grain size are as follows: for groove areas with a depth-to-width ratio greater than the predetermined value, abrasive grains with a grain size of 50%-60% of the standard value for planar areas should be selected. The dynamic adjustment method for the sandblasting incident angle is as follows: the angle deviation is compensated in real time according to the angle between the surface normal vector and the spray gun axis, so that the effective impact angle is kept within the range of 85°-95°.

3. The mold surface processing technology according to claim 1, characterized in that, The specific method for controlling the powder feeding rate in step 2 includes: The thickness of the near-matrix region is determined by calculating the difference in thermal expansion coefficients between the matrix material and the metal binder phase, and increasing the region thickness when the difference exceeds a predetermined percentage. The increasing gradient of the metal phase powder feeding rate is determined based on the temperature distribution of the plasma flow: a steep increasing gradient is used in the high-temperature region at the center of the flow, and a gentle increasing gradient is used in the low-temperature region at the edge. The initial activation point of the ceramic phase powder delivery rate is located at a predetermined distance from the substrate surface. This distance is calculated by the residence time of the powder in the plasma jet, ensuring that the powder reaches a molten state when it reaches the substrate.

4. The mold surface processing technology according to claim 1, characterized in that, The dynamic remelting operation method in step 3 includes: The real-time temperature data acquisition location is set 2-3 mm downstream of the remelting point, and the sampling frequency is not less than 1 kHz. The remelting energy adjustment rule is as follows: when the measured temperature is lower than the target range, the energy input value per unit area is increased by one degree Celsius; when it is higher than the target range, the energy beam scanning speed is increased proportionally. The target temperature range is calculated based on the solidus temperature of the coating material: the lower limit is solidus temperature × 0.85, and the upper limit is solidus temperature × 0.

92. The diameter of the focused energy beam spot is adaptively adjusted according to the coating thickness: for every 50μm increase in thickness, the spot diameter increases by a predetermined percentage.

5. The mold surface processing technology according to claim 1, characterized in that, Step 3, adjusting the spray gun motion parameters, includes: The reduction rate of scanning speed is determined by the ratio of the radius of curvature to the critical radius: when the radius of curvature is less than the critical radius, the speed is reduced to 70%-80% in the planar region; The rules for adjusting the spray gun distance are as follows: in concave areas, shorten it to 80%-90% of the standard distance; in convex areas, increase it to 110%-120%. The critical radius is determined based on the working load of the mold: for every increase of a predetermined value in the impact load, the critical radius decreases proportionally.

6. The mold surface processing technology according to claim 1, characterized in that, The implementation method of graded impact energy in step 4 includes: The coating thickness distribution map is obtained by using an eddy current thickness gauge. Areas with a thickness greater than the first threshold are classified as high-energy impact zones, and areas with a thickness less than the second threshold are classified as low-energy impact zones. The energy value of the high-energy impact zone is 120%-130% of the reference energy. The reference energy is calculated by the nano-indentation hardness value of the coating: for every increase in hardness by a predetermined value, the reference energy increases proportionally. The selection rule for the radius of curvature of the impact needle is as follows: use a needle with a radius ≤0.2mm in areas of abrupt curvature change, and use a needle with a radius ≥0.5mm in planar areas.

7. The mold surface processing technology according to claim 1, characterized in that, The simultaneous conveying of the metal binder phase powder and the ceramic reinforcing phase powder in step 2 also includes: The metallic binder phase powder is a nickel-based alloy, and its particle size distribution is determined by Hall flow rate testing: the particle size combination with the flow rate in the optimal range is selected. The ceramic reinforcing phase powder is an alumina-zirconia composite powder, wherein the zirconia content is set according to the coating's thermal shock resistance requirements: when the mold's working temperature fluctuates beyond a predetermined range, the zirconia content is increased to a predetermined ratio.

8. The mold surface processing technology according to claim 1, characterized in that, The control method for time-sensitive processing in step 4 includes: After determining the phase transition point of the coating using differential scanning calorimetry, the aging temperature is taken as 40%-50% of the phase transition point temperature. The calculation logic for heat preservation time is as follows: based on the thickest part of the mold cross section, 1 hour is corresponding to every 10mm of thickness. When the change rate of cross section thickness exceeds the predetermined value, the time is calculated as 120% of the maximum thickness value. The cooling rate is controlled as follows: a slow cooling rate of ≤30℃ / min is used in the temperature range below the phase transition point.

9. The mold surface processing technology according to claim 3, characterized in that, The method for calculating the dwell time specifically includes: The trajectory of powder in a plasma jet is recorded by high-speed photography. The residence time is calculated based on the distance between the spray gun and the substrate and the average speed of the powder movement. When the residence time is less than the time required for the powder to completely melt, the plasma power is increased and the powder feeding rate is reduced simultaneously.

10. The mold surface processing technology according to claim 4, characterized in that, The logic for determining the energy input value per unit area includes: Establish the mapping relationship between remelting depth and energy density: measure the remelting depth at different energy densities using metallographic sections; The required energy density is calculated by working backward from the target remelting depth, and the target remelting depth is set to 10%-15% of the current coating thickness; When the coating porosity exceeds the standard, the target remelting depth is increased year-on-year.

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