Preparation method of carbide-reinforced nickel-cobalt alloy charging barrel inner wall

Abstract

The invention provides a preparation method of a carbide-reinforced nickel-cobalt alloy charging barrel inner wall, and belongs to the technical field of metal material surface engineering and additive manufacturing. An inner hole laser cladding gun and synchronous preheating are integrated to form a synergistic system, and an alloy strengthening layer with uniform carbide distribution, high hardness and excellent wear resistance and corrosion resistance is formed on the inner surface of a charging barrel base body, so that the problems of cracking of a high-carbide alloy cladding layer, composition segregation and deep hole machining are solved; the method can be widely applied to inner surface strengthening and repairing of key components in the engineering plastic field such as injection molding machine charging barrels and splayed sleeves.

Description

Technical Field

[0001] This invention relates to the fields of surface engineering and additive manufacturing of metallic materials, and in particular to a method for preparing a carbide-reinforced nickel-cobalt alloy barrel inner wall. Background Technology

[0002] High-performance injection molding machine barrels are critical and vulnerable components, requiring extremely high wear resistance, corrosion resistance, and high-temperature resistance for their inner walls. Currently, the industry primarily employs bimetallic composite technology to manufacture these components, combining high-performance wear-resistant materials with a strong and tough steel matrix to balance overall mechanical properties and the service requirements of the working surface. Current mainstream manufacturing processes include centrifugal casting, hot isostatic pressing, and the promising laser cladding technology, each with its own distinct technical characteristics and limitations.

[0003] Centrifugal casting is currently the most widely used and mature traditional process. This process involves pouring molten wear-resistant alloys (such as cobalt-based and nickel-based alloys) into a high-speed rotating steel pipe, forming a composite layer using centrifugal force. It boasts advantages such as high production efficiency and suitability for mass production. To improve wear resistance, high-carbon components are often added to the alloy or carbide particles (such as tungsten carbide) are directly introduced. However, this process has inherent drawbacks: during the centrifugal force field and slow solidification process, the higher-density carbide phase inevitably migrates to the outer side of the pipe wall, leading to severe macroscopic compositional segregation. This results in uneven hardness and a radial gradient distribution of properties in the wear-resistant layer. Simultaneously, the open melting environment requires the addition of fluxes (such as boron oxide), which may introduce brittle phases that damage the matrix strength. The thermal dilution effect of the molten base material on the added phases also weakens the interfacial bonding strength, affecting the alloy composition. Furthermore, to correct dimensional problems caused by segregation and "settling," extensive subsequent machining is required, leading to low material utilization and increased overall costs.

[0004] Hot isostatic pressing (HIP) is an advanced powder metallurgy bonding process that theoretically can prepare nearly fully dense bimetallic composite materials with no macroscopic segregation. This process encapsulates different metal powders in a cladding and holds them at ultra-high temperatures (>1000℃) and isotropic ultra-high pressures (100-200 MPa) for extended periods, achieving metallurgical bonding through diffusion. While it yields excellent material homogeneity, it suffers from significant drawbacks: the equipment is extremely expensive, the process is lengthy (tens of hours), and the cost per unit is high; the complex cladding design, preparation, and removal processes increase process complexity and cost; and, especially for pipes with large aspect ratios, it is prone to bending deformation, limiting its application in large-scale production.

[0005] Laser cladding technology, as an additive manufacturing method, boasts extremely high heating and cooling rates (10⁻⁶ m / s). 3 ~10 6The laser cladding technology (K / s) provides a new approach for preparing composite coatings with fine microstructure and uniform composition on substrate surfaces. Theoretically, it can overcome the segregation problem of centrifugal casting and the cost and efficiency bottlenecks of hot isostatic pressing. However, when directly applying laser cladding technology to strengthen the deep inner walls of barrels, a series of process control challenges remain: the stability and accessibility of deep hole inner wall machining, the crack sensitivity of high-carbon alloy cladding layers due to high stress, and the precise control of carbide dissolution and precipitation behavior during rapid solidification of the molten pool. These challenges prevent this technology from stably and reliably replacing traditional processes.

[0006] In summary, existing technologies all have significant shortcomings: centrifugal casting is limited by compositional segregation and inefficiency; hot isostatic pressing is limited by extremely high costs and process complexity; and conventional laser cladding is limited by the stability of deep hole processing and coating quality control. Therefore, developing a novel barrel preparation process that can fundamentally avoid macroscopic segregation, significantly improve material utilization, effectively control the coating quality of deep hole inner walls, and possess good economic efficiency is of crucial technical value and market significance for breaking through industry technical bottlenecks and achieving a synergy between high performance and high efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a carbide-reinforced nickel-cobalt alloy barrel inner wall. By forming an alloy reinforcement layer with uniform carbide distribution, high hardness and excellent wear and corrosion resistance on the inner surface of the barrel matrix, it can be widely used for the inner surface reinforcement and repair of key components in the field of engineering plastics such as injection molding machine barrels and figure-eight sleeves.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a carbide-reinforced nickel-cobalt alloy barrel inner wall, comprising the following steps: After pretreatment of the inner wall of the barrel, the cladding area is preheated, laser cladding is performed under synchronous preheating conditions, followed by annealing to form a nickel-cobalt carbide composite coating on the inner wall of the barrel. By mass percentage, the cladding material used in the laser cladding comprises the following raw materials: 65-80% nickel-cobalt alloy powder and 20-35% carbide-reinforced powder; The composition of the nickel-cobalt alloy powder is: Co 30~45%, Cr 5~10%, B 2~4%, Si 2~4%, Mo 2~5%, Fe≤0.5%, Ni balance; The laser cladding gun used for laser cladding is equipped with a coaxial powder-feeding laser cladding head, and a medium-frequency heating coil is integrated in front of the laser cladding gun. The material cylinder is fixed to the spindle machine tool and rotates at a constant speed; the laser cladding gun moves at a constant speed in a straight line along the axis of the material cylinder.

[0009] Preferably, the preheating is to maintain the temperature of the substrate cladding area at 500~800℃.

[0010] Preferably, the conditions for laser cladding include: The laser power is 1500~3000 W, the scanning speed is 300~500 mm / min, the powder feeding rate is 7~12 g / min, and the overlap rate is 30~60%.

[0011] Preferably, the protective gas used for laser cladding is argon, and the flow rate of the protective gas is 15~25 L / min.

[0012] Preferably, the annealing temperature is 400~600℃ and the holding time is 2~4h.

[0013] Preferably, the carbide-reinforced powder comprises one or more of tungsten carbide, chromium carbide, and titanium carbide.

[0014] Preferably, when the carbide-reinforced powder is tungsten carbide, the laser power is 1800~2000 W and the scanning speed is 300~400 mm / min; When the carbide-reinforced powder is chromium carbide, the laser power is 1600~1800 W and the scanning speed is 400~500 mm / min; When the carbide-reinforced powder is titanium carbide, the laser power is 1800~2000 W and the scanning speed is 300~400 mm / min.

[0015] Preferably, the particle size of the nickel-cobalt alloy powder and the carbide-reinforced powder is independently 45~106 μm.

[0016] Based on the inherent defects of centrifugal casting in terms of composition control and economic efficiency, this invention provides a method for preparing the inner wall of a carbide-reinforced nickel-cobalt alloy barrel. It integrates an internal laser cladding gun with synchronous preheating to form a synergistic system, solving the problems of cracking, compositional segregation, and deep hole machining in high-carbide alloy cladding layers, fundamentally overcoming the bottlenecks of traditional technologies. 1) Solving the problem of macroscopic component segregation and interface dilution in wear-resistant layers: By employing laser cladding technology, utilizing its extremely high heating and cooling rates (up to 10... 3 -10 6(K / s), significantly shortening the molten pool existence time. This not only effectively inhibits the migration and aggregation of high-density carbide phases, achieving their uniform dispersion distribution in the matrix, but also greatly reduces the thermal dilution effect of the matrix on the carbide reinforcement phase, ensuring that the designed high-carbon, effective alloy composition is accurately retained in the cladding layer, thereby obtaining a wear-resistant layer with consistent composition and uniform performance, eliminating the risk of early wear or brittle cracking caused by compositional segregation and dilution from the root.

[0017] 2) Achieve grain refinement and comprehensive performance optimization of wear-resistant layer structure: By leveraging the rapid solidification characteristics of laser cladding, and based on solving the composition problem, a dense microstructure with fine grains and controllable carbide size and distribution is obtained, which simultaneously and significantly improves the hardness, wear resistance and corrosion resistance of the cladding layer, breaking through the upper limit of material properties caused by slow solidification and coarse structure in centrifugal casting.

[0018] 3) Significantly improves material utilization and reduces overall production energy consumption: Abandoning the traditional model of "integral casting and mass processing", high-performance alloys and carbide materials are precisely deposited on the key areas requiring reinforcement on the inner wall of the barrel through laser cladding. This avoids the subsequent overall machining that is necessary for centrifugal casting due to the settling of hard phases, which causes serious waste, thereby significantly reducing the overall energy consumption and material costs of the entire production cycle.

[0019] 4) Establishing a stable and controllable laser cladding process system for deep-hole inner walls: Addressing the structural characteristics of barrels with large aspect ratios, a system integrating synchronous preheating and a dedicated laser inner-hole cladding gun was developed, enabling stable operation within the barrel's bore. Specifically, by optimizing the gun's body structure, vibration-free operation is ensured during prolonged use in the narrow space of deep holes, guaranteeing the stability of the optical path and powder feeding path, thereby achieving stable deep-hole inner-wall processing. Synchronous preheating reduces the temperature gradient between the cladding layer and the substrate, controlling the cooling rate and thus suppressing excessive carbide precipitation or coarsening, promoting uniform distribution. Therefore, this invention solves the core technological challenges encountered in laser cladding of deep-hole inner walls, such as cladding layer uniformity, interpass metallurgical bonding, and high-carbon alloy layer crack control, ensuring the stable and reliable application of this technology in actual production. Thus, this invention provides a high-performance barrel manufacturing solution that can replace traditional centrifugal casting, offering superior performance, greater manufacturing precision, and higher economic efficiency.

[0020] The beneficial effects of the laser cladding strengthening method for the nickel-cobalt carbide composite coating on the inner wall of the barrel provided by this invention are specifically reflected in three aspects: coating quality, service performance, and production efficiency. 1) Fundamental improvement in coating quality: By using a synchronous preheating method, the cracking problem of high-carbon alloy cladding layers is completely solved, achieving macroscopic crack-free coatings. The preheating process effectively reduces thermal stress and promotes the wetting of carbide particles in the molten pool, enabling the carbides to be evenly distributed in the matrix and forming a dense, defect-free metallurgical bonding layer in one go.

[0021] 2) Improved service performance: Thanks to the fine-grained structure formed by rapid solidification and the uniformly distributed hard phase, the overall performance of the cladding layer is significantly better than that of traditional centrifugal castings. Abrasion resistance: By optimizing the type and ratio of carbides, the coating hardness can reach 58-62 HRC.

[0022] Corrosion resistance: The dense nickel-cobalt alloy matrix and uniform structure enhance the corrosion resistance of the coating in acidic media (such as 85% phosphoric acid and 10% hydrofluoric acid) to more than 5 times that of centrifugally cast parts.

[0023] 3) Significantly optimized production economy: It eliminates the need for extensive machining and subsequent heat treatment required to remedy segregation and defects. Combined with material savings, reduced energy consumption, and lower scrap rates, the production process is environmentally friendly, resulting in competitive overall manufacturing costs and reduced total lifecycle costs for users.

[0024] In summary, this invention, through a reproducible process, solves the core problems of "component segregation" and "high energy consumption" while simultaneously improving product performance and manufacturing efficiency. Attached Figure Description

[0025] Figure 1 Metallographic image of the nickel-cobalt alloy layer in the inner wall of the barrel prepared in Example 1; Figure 2 This is a schematic diagram of the laser cladding apparatus used in the preparation method of the inner wall of the nickel-cobalt alloy barrel of the present invention. Figure 3 This is a schematic diagram of the cladding gun in a laser cladding device. Figure 4 This is a schematic diagram of the gun tail assembly of a laser cladding device; Figure 5 A schematic diagram of the main body of the laser cladding device's gun head; Figure 6 This is a schematic diagram of the laser cladding device's gun head assembly; The components are as follows: 1-Spindle machine tool; 2-Chuck; 3-Integrated heating device; 4-Clad gun; 5-Slide rail; 6-Roller assembly; 7-Base; 8-Center frame; 9-Control panel; 10-Three-axis transmission table; 11-Gun tail assembly; 1101-Optical lens mount; 1102-Focusing structure; 1103-Protection module; 12-Gun body assembly; 13-Gun head assembly; 1301-Gun head body; 1302-Powder feeding pipe; 1303-Conical light outlet; 1304-Copper mirror; Figure 7 The test report for the tungsten carbide powder used in Example 1; Figure 8 The test report for the chromium carbide powder used in Example 2; Figure 9 This is the test report for the titanium carbide powder used in Example 3. Detailed Implementation

[0026] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0027] This invention provides a method for preparing a carbide-reinforced nickel-cobalt alloy barrel inner wall, comprising the following steps: After pretreatment of the inner wall of the barrel, the cladding area is preheated, laser cladding is performed under synchronous preheating conditions, followed by annealing to form a nickel-cobalt carbide composite coating on the inner wall of the barrel. By mass percentage, the cladding material used in the laser cladding comprises the following raw materials: 65-80% nickel-cobalt alloy powder and 20-35% carbide-reinforced powder; The composition of the nickel-cobalt alloy powder is: Co 30~45%, Cr 5~10%, B 2~4%, Si 2~4%, Mo 2~5%, Fe≤0.5%, Ni balance; The laser cladding gun used for laser cladding is equipped with a coaxial powder-feeding laser cladding head, and a medium-frequency heating coil is integrated in front of the laser cladding gun. The material cylinder is fixed to the spindle machine tool and rotates at a constant speed; the laser cladding gun moves at a constant speed in a straight line along the axis of the material cylinder.

[0028] In this invention, the material of the barrel is preferably non-quenched and tempered steel, more preferably 45MnSiV; the specifications of the barrel are not specifically limited and can be adjusted according to requirements. In embodiments of this invention, the preferred specification is the outer diameter. 90-100 mm, inner diameter 40-50 mm, length 900-2000 mm, more preferably 100 mm, inner diameter 50 mm, length 1400 mm or 2000 mm.

[0029] In this invention, the pretreatment preferably involves turning the inner wall of the barrel to ensure its rotational concentricity and straightness, while removing the surface oxide layer. Subsequently, it is cleaned with anhydrous ethanol to remove oil and cutting residue, and then dried to obtain a barrel with a clean inner surface, high geometric accuracy, and good activity. The treated barrel is then clamped onto a machine tool. This invention does not impose any specific limitations on the specific operation process of the pretreatment; any process well-known in the art can be followed.

[0030] In this invention, the preheating involves maintaining the temperature of the substrate cladding area at 500~800℃, more preferably 600~700℃. Under this preheating condition, laser cladding is performed, achieving simultaneous preheating and laser cladding.

[0031] In this invention, the laser cladding conditions preferably include: a laser power of 1500~3000 W, more preferably 1700~1800 W, a scanning speed of 300~500 mm / min, more preferably 350~400 mm / min, a powder feeding rate of 7~12 g / min, more preferably 8~10 g / min, and an overlap rate of 30~60%, more preferably 40~50%.

[0032] In this invention, the protective gas and the powder feeding gas used for laser cladding are preferably high-purity argon (99.999% purity), the flow rate of the protective gas is preferably 15~25 L / min, more preferably 18~20 L / min, and the flow rate of the powder feeding gas is preferably 3~5 L / min, more preferably 4~5 L / min.

[0033] The present invention preferably determines the laser power based on the powder feeding rate and the scanning speed; and determines the scanning speed based on the linear velocity of the rotating barrel.

[0034] This invention significantly reduces the thermal stress gradient during laser cladding by synchronous preheating, preventing cracks from forming in the coating during rapid cooling. Simultaneously, the high-temperature environment promotes powder wetting and spreading, as well as metallurgical reactions, improving powder utilization, facilitating uniform distribution of carbide particles, and effectively suppressing porosity. This achieves "one-time forming" of the coating, eliminating the need for intermediate stress-relief treatment.

[0035] like Figures 2-6 As shown, the laser cladding device used in the laser cladding process of the present invention includes a base 7, a spindle machine tool 1, a three-axis transmission table 10, a cladding gun 4, an integrated heating device 3, a control panel 9, a roller assembly 6, and a center frame 8.

[0036] A slide rail 5 is installed on the base 7 along its length. The spindle machine tool 1 is fixed to one end of the base 7 by bolts. A chuck 2 is driven and connected to the spindle machine tool 1 to hold the workpiece to be processed.

[0037] The three-axis drive table 10 is mounted on the slider of the slide rail 5 and can move along the length direction of the slide rail 5 (X-axis), moving closer to or away from the main spindle machine tool 1. A vertical guide rail (Z-axis) is mounted on the three-axis drive table 10, and a horizontal guide rail is fixed on the slider of the vertical guide rail. A cladding gun 4 is mounted on the slider of the horizontal guide rail (Y-axis).

[0038] Specifically, the cladding gun 4 includes: a gun head assembly 13, a gun body assembly 12, and a gun tail assembly 11.

[0039] The tail assembly 11 includes an optical lens mount 1101, a focusing structure 1102, and a protection module 1103 connected in sequence. The optical lens mount 1101 is connected to an optical fiber and mounted on a slider of a horizontal guide rail. The focusing structure 1102 contains an optical element box adjustment ring. By driving the adjustment ring, the optical element can be slightly displaced along the optical axis, thereby achieving precise adjustment of the emitted laser spot size. The protection module 1103 contains a protective lens to protect the optical lens mount 1101 and the focusing structure 1102. The body assembly 12 is made of a metal tube, which is mounted on the protection module 1103. Multiple focusing lenses are arranged inside the metal tube along the laser transmission direction. The head assembly 13 includes a head body 1301, on which a copper mirror 1304 and a conical light-emitting nozzle 1303 are arranged. Powder feeding tubes 1302 are arranged on both sides of the conical light-emitting nozzle 1303. The powder feeding pipe 1302 is connected to a powder feeding system via a powder feeding pipeline. The powder feeding system can deliver alloy powder to the powder feeding pipe 1302 in a dry, uniform, and continuous state and then eject it. The conical light-emitting nozzle 1303 is connected to a gas supply system via a gas supply pipeline. The conical light-emitting nozzle 1303 guides inert protective gas (such as argon) along the conical surface to the molten pool area. This not only effectively suppresses alloy powder splashing and protects the copper mirror 1304, but also creates a local high-concentration inert gas environment above the molten pool, thereby preventing alloy oxidation.

[0040] Specifically, the 1304 copper mirror integrates a high-efficiency water-cooling channel to ensure minimal thermal deformation during long-term operation and prevent focus drift.

[0041] Specifically, the gun body assembly 12 is composed of multiple coaxially arranged high-temperature and corrosion-resistant metal tubes connected in sequence. Each metal tube is inlaid with a focusing lens, forming an independent optical functional segment, which facilitates quick replacement or maintenance for different inner hole depths.

[0042] In this embodiment, a support rod parallel to the cladding gun 4 is also provided on the horizontal guide rail, and an integrated heating device 3 is provided at the other end of the support rod. The integrated heating device 3 includes an induction heating coil and an infrared thermometer. The outside of the induction heating coil is wrapped with a heat insulation layer, and the induction heating coil is connected to a heating power supply. The integrated heating device 3 can achieve precise "thermal control" of the cladding area from preheating, heat tracing to slow cooling. This active thermal management strategy can effectively reduce the cooling rate, homogenize the temperature gradient, and release residual stress, ensuring that even for high-hardness and high-brittle materials such as nickel-based tungsten carbide, a completely crack-free alloy layer with good metallurgical bonding can be obtained, and the hardness of the alloy layer can be stably reached HRC55-65.

[0043] The control panel 9 is installed on the side of the base 7. It adopts a PLC control system and is equipped with a touch screen. It can display and set parameters such as spindle speed, three-axis transmission table 10 movement speed, laser power, powder feeding amount, air supply pressure, and heating temperature in real time. The control panel 9 is electrically connected to the spindle machine tool 1, three-axis transmission table 10, cladding gun 4, laser emitter, focusing structure 1102, air supply system, powder feeding system, and the heating power supply and infrared thermometer of the integrated heating device 3 to achieve coordinated control.

[0044] In this invention, the laser cladding device used in the laser cladding process includes: Internal Hole Laser Cladding Gun: Employs a coaxial powder-feeding laser cladding head suitable for operation within deep holes in the barrel. This cladding gun integrates laser transmission, powder delivery, and protective gas path, enabling annular cladding under compact radial dimensions.

[0045] The preheating system (including an induction heating coil and an integrated heating device 3; the heating device controls the heating power, and the heating coil achieves preheating): A medium-frequency heating coil is integrated in front of the cladding gun 4. While the laser cladding is being performed, the substrate in the cladding area is precisely and continuously preheated, which fundamentally reduces the thermal stress in the cladding process and inhibits coating cracking.

[0046] Motion control system (spindle machine tool 1 and three-axis transmission table 10): The barrel is fixed to the spindle machine tool and rotates at a constant speed; the inner hole cladding gun moves at a constant speed in a straight line along the axis of the barrel through a precision slide table, and the two combine to form a spiral cladding trajectory.

[0047] In this invention, the cladding material used in the laser cladding comprises the following raw materials by mass percentage: 65-80% nickel-cobalt alloy powder and 20-35% carbide-reinforced powder; The composition of the nickel-cobalt alloy powder is: Co 30~45%, Cr 5~10%, B 2~4%, Si 2~4%, Mo 2~5%, Fe≤0.5%, Ni balance.

[0048] In this invention, the cladding material comprises 65-80% nickel-cobalt alloy powder, more preferably 70-75%; the cladding material comprises 20-35% carbide-reinforced powder, more preferably 25-30%.

[0049] The present invention does not have any special limitation on the source of the nickel-cobalt alloy powder, and any commercially available product with the above composition known in the art is acceptable. In the embodiments of the present invention, it is specifically sourced from Shanghai Xuanyi Industrial Co., Ltd.

[0050] The nickel-cobalt alloy powder of the present invention provides corrosion resistance, high-temperature strength, and good wettability to carbide particles in the alloy layer.

[0051] In this invention, the carbide-reinforcing powder includes one or more of tungsten carbide (WC), chromium carbide (Cr3C2), and titanium carbide (TiC). When the carbide-reinforcing powder comprises two or more of the above, this invention does not have a specific limitation on the ratio of different types of carbide-reinforcing powders, and any ratio is acceptable. The carbide-reinforcing powder of this invention provides extremely high hardness and wear resistance as a hard phase. The carbide-reinforcing powders of this invention are all commercially available products well-known in the art.

[0052] In this invention, the particle size of the nickel-cobalt alloy powder and the carbide-reinforced powder is preferably 45-106 μm. This particle size limitation ensures good flowability and stability during the cladding process.

[0053] This invention preferably involves mechanically mixing nickel-cobalt alloy powder and carbide-reinforced powder in a mixing device (such as a V-type mixer or ball mill), followed by drying, to obtain a laser cladding material with uniform composition and good flowability. This invention does not specify particular parameters for the mechanical mixing; the materials can be mixed uniformly according to a process well-known in the art. In embodiments of this invention, mechanical mixing specifically involves adding stainless steel grinding balls (the volume ratio of grinding balls to mixed powder is 1:1) to the mixed powder of nickel-cobalt alloy powder and carbide-reinforced powder, and continuously mixing at 30 rpm for 2 hours. The drying temperature is preferably 210°C, and the drying time is preferably 30 minutes. This invention thoroughly removes moisture adsorbed on the powder surface through drying, preventing the formation of pores during the cladding process.

[0054] The cladding material system described in this invention provides the material basis for the preparation process, and its composition range ensures that the cladding layer can simultaneously possess excellent high corrosion resistance, high wear resistance, and good metallurgical bonding strength.

[0055] The present invention preferably adjusts the core process parameters of laser cladding according to the different types and proportions of carbides in the cladding material in order to achieve the optimal cladding layer structure and performance. All adjustments are carried out under the guarantee of synchronous preheating (500~800℃).

[0056] In this invention, when the carbide-reinforced powder is tungsten carbide, the laser power is 1800~2000 W, more preferably 1800 W, and the scanning speed is 300~400 mm / min, more preferably 350 mm / min. Tungsten carbide (WC) has extremely high hardness and high density (approximately 15.6 g / cm³). 3 WC particles tend to settle in the molten pool. To ensure sufficient melting of the matrix and the generation of enough kinetic energy to suspend the WC particles and prevent their aggregation and settling, a combination of relatively high laser power and relatively low scanning speed is employed. Higher linear energy input helps maintain a molten pool with a certain degree of fluidity and duration, promoting the uniform distribution of WC particles.

[0057] When the carbide-reinforced powder is titanium carbide, the laser power is 1800~2000 W, and the scanning speed is 300~400 mm / min. Titanium carbide (TiC) has a high melting point (approximately 3160℃) and good chemical stability, but it also suffers from distribution uniformity issues due to density differences. Its parameter adjustment strategy is similar to that of WC, focusing on ensuring sufficient melting. Using the aforementioned relatively high laser power and relatively low scanning speed, the high heat input is crucial for melting a portion of TiC, promoting its metallurgical bonding with the matrix, and obtaining a uniform composite microstructure.

[0058] When the carbide-reinforced powder is chromium carbide, the laser power is 1600~1800 W, more preferably 1700 W, and the scanning speed is 400~500 mm / min, more preferably 400 mm / min. Chromium carbide (Cr3C2) has a relatively low melting point (approximately 1890℃), and is prone to decomposition and burn-off under excessively high heat input, leading to a decrease in the retention rate of the hard phase and weakening the strengthening effect. By employing the aforementioned moderate laser power combined with the aforementioned relatively high scanning speed, sufficient energy is provided to form a good cladding layer while reducing the high-temperature residence time in the molten pool, thereby maximizing the retention of the Cr3C2 hard phase.

[0059] In the carbide-reinforced powder of this invention, tungsten carbide exhibits excellent wear resistance, particularly suitable for abrasive wear, and extremely high WC hardness. As the main reinforcing phase, it significantly improves the macroscopic hardness of the coating surface. However, its corrosion resistance is generally poor, its high-temperature performance is insufficient, and its impact resistance is inadequate. This invention combines nickel-cobalt alloy powder with tungsten carbide, which solves both the wear resistance problem of using nickel-cobalt alloy powder alone and the problems of poor high-temperature resistance and corrosion resistance caused by using tungsten carbide alone. Chromium carbide possesses excellent corrosion resistance and good high-temperature oxidation resistance. During the cladding process, the Cr element in Cr3C2 dissolves extensively in the nickel-cobalt matrix, greatly improving the passivation ability of the matrix and forming a dense and stable Cr2O3 protective film on the surface, effectively resisting acid and alkali media and high-temperature oxidation. Titanium carbide has high hardness, high thermal stability, and a significant grain refinement strengthening effect. TiC particles are effective heterogeneous nucleation sites, which can refine the solidification structure of the nickel-cobalt alloy, simultaneously improving the strength and toughness of the coating through grain refinement strengthening. TiC has an extremely high melting point and dissolves very little in a laser molten pool, effectively pinning grain boundaries and inhibiting grain growth during thermal cycling, thus maintaining the stability of the coating structure at high temperatures. This invention, through precise control of heat input and adaptation to the physical and metallurgical properties of different carbides, ultimately optimizes the distribution and retention rate of carbides while ensuring the coating remains crack-free, thereby achieving optimal performance in key areas such as wear resistance.

[0060] After laser cladding is completed, the workpiece is preferably placed in a heating furnace for annealing and then cooled to room temperature in the furnace. Subsequently, the inner wall of the cladding layer can be bored and honed according to the dimensional accuracy requirements, with a machining allowance of 0.3-0.5 mm, to obtain a reinforced layer with uniform thickness and a smooth surface.

[0061] In this invention, the annealing temperature is 400~600℃, more preferably 400~500℃, the holding time is 2~4h, more preferably 3h, and the heating rate to the annealing temperature is ≤150℃ / h, more preferably 100℃ / h. After laser cladding and before finishing, heat treatment eliminates residual thermal stress accumulated inside the cladding layer, stabilizes the microstructure, and prevents the coating from cracking or deforming due to stress release during subsequent processing or use.

[0062] After the annealing process is completed, the present invention is preferably cooled to room temperature in the furnace, and the cooling rate is preferably ≤80℃ / h, more preferably 60℃ / h.

[0063] As an independent heat treatment process after cladding, annealing can systematically reduce and homogenize the high internal stress caused by rapid laser heating and cooling, further improving the dimensional stability of the coating and the reliability of its bonding with the substrate, and providing a stable workpiece condition for subsequent precision machining.

[0064] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0065] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0066] Example 1

[0067] I) Preparation of composite powder

[0068] Preparation of cladding materials for laser cladding: 1. Raw material preparation: Select spherical nickel-cobalt alloy powder and spherical tungsten carbide (WC) powder with a particle size range of 45~106 μm (see...). Figure 7 ); The composition of the nickel-cobalt alloy powder is as follows: Co 39.65%, Cr 7.91%, B 2.58%, Si 3.95%, Mo 3.07%, Fe 0.15%, Ni balance; The nickel-cobalt alloy powder is sourced from Shanghai Xuanyi Industrial Co., Ltd., and its grade is NC56.

[0069] 2. Weighing and mixing ratio: Accurately weigh 75% nickel-cobalt alloy powder and 25% WC powder by mass percentage; 3. Mechanical mixing: Pour the weighed mixed powder into a ball mill, add stainless steel grinding balls (the volume ratio of grinding balls to mixed powder is 1:1), and mix continuously at 30 rpm for 2 hours to obtain a mixture; 4. Drying treatment: Place the mixture in a drying oven, heat it to 210°C, and keep it at that temperature for 30 minutes to obtain nickel-cobalt alloy / WC composite powder, which is ready for laser cladding.

[0070] II) Pretreatment of the barrel substrate

[0071] Objective: To provide a clean, rough, and dimensionally accurate inner surface of the substrate for laser cladding, ensuring coating adhesion strength and uniformity.

[0072] step: Material preparation: Select specifications as follows 100 mm, inner diameter A 50 mm long, 2000 mm long non-quenched and tempered steel (45MnSiV) barrel is used as the base material.

[0073] Internal bore precision turning: The inner wall of the barrel is machined to ensure the straightness of the inner wall and the concentricity of the inner and outer diameters. After machining, the inner wall has a uniform silver-gray fresh metal surface.

[0074] Cleaning: After turning, the inner wall of the barrel is cleaned with anhydrous ethanol and then dried to obtain the barrel substrate.

[0075] III) Laser Cladding Strengthening Process

[0076] Objective: To prepare a composite reinforcement layer with no macroscopic cracks, high density, and uniform carbide distribution by one-time cladding on the inner wall of the pretreated barrel.

[0077] Equipment and core process parameters: Laser system: laser; Cladding system: Internal hole laser cladding gun, with a medium frequency induction heating coil integrated at the front end for synchronous preheating; Motion system: Spindle machine tool (capable of machining 1-4 meter inner holes and 1-8 meter outer holes).

[0078] The laser cladding process parameters are shown in Table 1: Table 1 Laser Cladding Parameters

[0079] step: 1. Clamping and Calibration: Clamp the pretreated barrel onto the spindle machine tool. Start the spindle rotation and use a dial indicator to measure the radial runout of the inner wall, ensuring that the runout does not exceed 0.1 mm to meet the requirements for uniform cladding.

[0080] 2. Equipment alignment: Insert the laser cladding gun into one end of the material cylinder, adjust the laser focal length to 3~4mm, and accurately position the relative axial distance between the induction heating coil and the laser cladding focal point (the laser cladding focal point is at the midpoint of the line segment of the heating coil) so that the preheating area matches the cladding area.

[0081] 3. Simultaneous preheating and cladding: Turn on the induction heating system to heat the barrel base until the infrared thermometer displays that the temperature of the target area has stabilized at 600℃.

[0082] The laser, powder feeder, and protective gas system are started simultaneously.

[0083] Start the machine tool program, the barrel rotates at a constant speed, and the cladding gun feeds at a constant speed along the axis. The two combine to form a spiral scanning path and start automatic cladding.

[0084] 4. Process execution: The system runs continuously until it covers the entire inner wall length of the target (1600mm).

[0085] 5. Gradient slow cooling: After the cladding process is completed, turn off the laser and powder feeder, keep the high-purity argon gas flowing, and control the induction heating system to slowly cool to 200°C. Then, turn off all systems and allow the workpiece to cool naturally to room temperature in the heat preservation environment.

[0086] Results: A bright, uniform, macroscopically crack-free cladding layer was obtained on the inner wall of the barrel. Measurements showed that the thickness of the cladding layer in a single molding process was 1-2 mm, with a machining allowance of 0.5 mm reserved.

[0087] IV) Intermediate stress-relief annealing

[0088] step: After the laser cladding strengthening process is completed, the workpiece in the cylinder, which has been slowly cooled to room temperature, is transferred to a holding furnace.

[0089] 1. Heating: The furnace temperature is uniformly increased to 500℃ at a rate of 100℃ / h.

[0090] 2. Heat preservation: Keep the workpiece at this temperature for 3 hours to ensure uniform temperature throughout the workpiece and to complete the stress relaxation and structural stabilization process.

[0091] 3. Slow cooling: After the heat preservation is completed, cut off the heating power supply and allow the workpiece to cool to room temperature with the furnace at a cooling rate of 80℃ / h.

[0092] V) Post-processing (finishing)

[0093] Objective: To obtain a finished reinforced barrel with precise final dimensions and a high surface finish.

[0094] Steps: The workpiece, which has been slowly cooled to room temperature, is clamped on a precision CNC internal grinding machine. The inner wall of the cladding layer is finely ground according to the preset program to remove the reserved machining allowance. Finally, the dimensional tolerances and surface roughness required by the drawing are achieved, resulting in a high wear-resistant and long-life injection molding machine barrel with a high-performance nickel-cobalt alloy tungsten carbide composite coating on the inner wall.

[0095] Example 2

[0096] I) Preparation of composite powder

[0097] Prepare laser cladding materials with uniform composition and good flowability.

[0098] step: 1. Raw material preparation: Select spherical nickel-cobalt alloy powder and spherical chromium carbide powder with a particle size range of 45~106 μm (see... Figure 8 ); The nickel-cobalt alloy powder used is the same as in Example 1.

[0099] 2. Weighing and mixing ratio: Weigh precisely 75% nickel-cobalt alloy powder and 25% Cr3C2 powder by mass percentage.

[0100] 3. Mechanical mixing: Pour the weighed mixed powder into a ball mill mixer, add stainless steel grinding balls (the volume ratio of grinding balls to mixed powder is 1:1), and mix continuously at 30 rpm for 2 hours to obtain a mixture; 4. Drying treatment: Place the mixture in a drying oven, heat it to 210℃, and keep it at that temperature for 30 minutes to obtain nickel-cobalt alloy / Cr3C2 composite powder, which is ready for laser cladding.

[0101] II) Pretreatment of the barrel substrate

[0102] Objective: To provide a clean, rough, and dimensionally accurate inner surface of the substrate for laser cladding, ensuring coating adhesion strength and uniformity.

[0103] step: Material preparation: Select specifications based on outer diameter 90mm, inner diameter A 40 mm long, 1400 mm long non-quenched and tempered steel (45MnSiV) barrel is used as the base material.

[0104] Internal bore precision turning: The inner wall of the barrel is machined to ensure the straightness of the inner wall and the concentricity of the inner and outer diameters. After machining, the inner wall has a uniform silver-gray fresh metal surface.

[0105] Cleaning: After turning, the inner wall of the barrel is cleaned with anhydrous ethanol and then dried to obtain the barrel substrate.

[0106] III) Laser Cladding Strengthening

[0107] The difference from Example 1 is that the laser cladding process parameters are shown in Table 2: Table 2 Laser Cladding Parameters

[0108] step: 1. Clamping and calibration: Same as in Example 1.

[0109] 2. Equipment alignment: Same as in Example 1.

[0110] 3. Simultaneous preheating and cladding: Turn on the induction heating system to heat the barrel base until the infrared thermometer displays that the temperature of the target area has stabilized at 700℃.

[0111] The laser, powder feeder, and protective gas system are started simultaneously.

[0112] Start the machine tool program, the barrel rotates at a constant speed, and the cladding gun feeds at a constant speed along the axis. The two combine to form a spiral scanning path and start automatic cladding.

[0113] 4. Process execution: The system runs continuously until it covers the entire inner wall length of the target (1400mm).

[0114] 5. Gradient slow cooling: After the cladding process is completed, turn off the laser and powder feeder, keep the high-purity argon gas flowing, and control the induction heating system to slowly cool to 200°C. Turn off all systems and let the workpiece cool naturally to room temperature in the heat preservation environment.

[0115] Results: A bright, uniform, macroscopically crack-free cladding layer was obtained on the inner wall of the barrel. Measurements showed that the thickness of the cladding layer in a single molding process was 1-2 mm, with a machining allowance of 0.5 mm reserved.

[0116] IV) Intermediate stress-relief annealing

[0117] step: After the laser cladding strengthening process is completed, the workpiece in the cylinder, which has been slowly cooled to room temperature, is transferred to a holding furnace.

[0118] 1. Heating: The furnace temperature is uniformly increased to 500℃ at a rate of 100℃ / h.

[0119] 2. Heat preservation: Keep the workpiece at this temperature for 3 hours to ensure uniform temperature throughout the workpiece and to complete the stress relaxation and structural stabilization process.

[0120] 3. Slow cooling: After the heat preservation is completed, cut off the heating power supply and allow the workpiece to cool to room temperature with the furnace at a cooling rate of 80℃ / h.

[0121] V) Post-processing (finishing)

[0122] Objective: To obtain a finished reinforced barrel with precise final dimensions and a high surface finish.

[0123] Steps: The workpiece, which has been slowly cooled to room temperature, is clamped in a precision CNC internal grinding machine. The inner wall of the cladding layer is finely ground according to the preset program to remove the reserved machining allowance and achieve the dimensional tolerances and surface roughness required by the drawing. This results in a high-wear-resistant and long-life injection molding machine barrel with a high-performance nickel-cobalt alloy tungsten carbide composite coating on the inner wall.

[0124] Example 3

[0125] The only difference from Example 1 is that titanium carbide powder is used (see Example 1). Figure 9 Replace tungsten carbide powder.

[0126] Characterization and performance testing

[0127] 1) Figure 1 The image shows a metallographic image of the nickel-cobalt alloy layer in the inner wall of the barrel prepared in Example 1. Figure 1 It can be seen that the carbides are evenly distributed in the lower part of the alloy layer. Even after turning, most of the hard phase can still be retained, which can improve the wear resistance of the alloy layer.

[0128] 2) The wear resistance of the nickel-cobalt alloy layer on the inner wall of the barrel in Examples 1 and 2 was tested using the GB / T 12444-2006 method and compared with commercially available iron-based alloy (iron-based Fe60, Shanghai Zhuyu Materials Technology Co., Ltd.). The results are shown in Tables 2 and 3.

[0129] Table 2 shows the frictional wear loss of the tungsten carbide nickel-cobalt alloy layer in Example 1.

[0130] As shown in Table 2, the nickel-cobalt alloy layer exhibits good wear resistance under a 150N load, and long-term wear does not lead to a significant increase in weight loss.

[0131] Table 3 shows the frictional wear loss of the chromium carbide nickel-cobalt alloy layer in Example 2.

[0132] As shown in Table 3, the nickel-cobalt alloy layer in Example 2 exhibits good wear resistance under a load of 150N, and long-term wear does not lead to a significant increase in weight loss.

[0133] 3) Using the same cladding process as in Example 1, commercially available nickel-based alloys (Ni255F, Shanghai Zhongzhou Special Alloy) and commercially available iron-based alloys (Fe60, Shanghai Zhuyu Materials Technology Co., Ltd.) were used to replace the nickel-cobalt alloy powder in Example 1. After cladding onto the inner wall of the barrel, the inner walls of the different barrels were wire-cut to separate the alloy layer from the substrate. The alloy layer was then immersed in 85% phosphoric acid in an 85°C water bath for 16 hours. The weight before and after immersion was tested, and the results are shown in Table 4.

[0134] Table 4 Results of phosphoric acid corrosion resistance of different alloy layers

[0135] Table 4 shows that the nickel-cobalt alloy used in Example 1 exhibits the best corrosion resistance and the smallest weight loss (0.3463), indicating that it has the lowest corrosion rate in a high-temperature concentrated phosphoric acid environment. The iron-based alloy is second, with a weight loss of 0.4442, showing better corrosion resistance than the nickel-based alloy but not as good as the nickel-cobalt alloy. The nickel-based alloy has relatively poor corrosion resistance: a weight loss of 0.4903, and exhibits the most significant corrosion among the three alloys. In summary, under the same experimental conditions, the corrosion resistance of the three alloys, from highest to lowest, is: nickel-cobalt alloy > iron-based alloy > nickel-based alloy.

[0136] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a carbide-reinforced nickel-cobalt alloy barrel inner wall, characterized in that, Includes the following steps: After pretreatment of the inner wall of the barrel, the cladding area is preheated, laser cladding is performed under synchronous preheating conditions, followed by annealing to form a nickel-cobalt carbide composite coating on the inner wall of the barrel. By mass percentage, the cladding material used in the laser cladding comprises the following raw materials: 65-80% nickel-cobalt alloy powder and 20-35% carbide-reinforced powder; The composition of the nickel-cobalt alloy powder is: Co 30~45%, Cr 5~10%, B 2~4%, Si 2~4%, Mo 2~5%, Fe≤0.5%, Ni balance; The laser cladding gun used for laser cladding is equipped with a coaxial powder-feeding laser cladding head, and a medium-frequency heating coil is integrated in front of the laser cladding gun. The material cylinder is fixed to the spindle machine tool and rotates at a constant speed; the laser cladding gun moves at a constant speed in a straight line along the axis of the material cylinder.

2. The preparation method according to claim 1, characterized in that, The preheating process involves maintaining the temperature of the substrate cladding area at 500~800℃.

3. The preparation method according to claim 1, characterized in that, The conditions for laser cladding include: The laser power is 1500~3000 W, the scanning speed is 300~500 mm / min, the powder feeding rate is 7~12 g / min, and the overlap rate is 30~60%.

4. The preparation method according to claim 1, characterized in that, The protective gas used in the laser cladding is argon, and the flow rate of the protective gas is 15~25 L / min.

5. The preparation method according to claim 1, characterized in that, The annealing process is carried out at a temperature of 400~600℃ and a holding time of 2~4h.

6. The preparation method according to claim 1, characterized in that, The carbide-reinforced powder includes one or more of tungsten carbide, chromium carbide, and titanium carbide.

7. The preparation method according to claim 6, characterized in that, When the carbide-reinforced powder is tungsten carbide, the laser power is 1800~2000 W and the scanning speed is 300~400 mm / min; When the carbide-reinforced powder is chromium carbide, the laser power is 1600~1800 W and the scanning speed is 400~500 mm / min; When the carbide-reinforced powder is titanium carbide, the laser power is 1800~2000 W and the scanning speed is 300~400 mm / min.

8. The preparation method according to claim 1, characterized in that, The particle size of the nickel-cobalt alloy powder and the carbide-reinforced powder is independently 45~106 μm.

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