Functional gradient laser cladding screw and preparation method thereof

Abstract

The invention provides a functional gradient laser cladding screw and a preparation method thereof, and belongs to the technical field of additive manufacturing. The preparation method comprises the following steps: firstly, sequentially carrying out laser cladding on a metal mandrel to form a base coat and a wear-resistant layer to obtain a composite blank; and turning, grinding and precisely turning the composite blank to obtain the functionally gradient laser cladding screw. The composite structure design of the low-cost base body and the high-performance functional layer is adopted, only a small amount of special alloy is used in a key functional area, and the production cost is remarkably reduced. High-strength and interface-free firm combination is achieved between the functional layer formed through laser cladding and the mandrel, the combination strength of the functional layer is even higher than that of base metal, the technical problem that a traditional surface coating or surfacing layer is prone to stripping and stripping is fundamentally solved, and a crucial guarantee is provided for material safety in an ultra-pure production environment.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a functionally graded laser cladding screw and its preparation method. Background Technology

[0002] In the injection molding or extrusion molding process of ultrapure fluoroplastic products (such as pipes, valves, and storage tanks for semiconductors), the screw, as the core component of the plasticizing and transporting system, rotates within the feed tube, undertaking the critical functions of solid material conveying, melting, homogenizing, and pumping. This precisely fitted pair operates under extreme conditions of high temperature, high pressure, and highly corrosive fluoroplastic melts for extended periods. Scratching problems between them caused by various factors have become a major cause of equipment failure, product contamination, and escalating costs. Existing screw technology faces severe challenges in this regard, mainly in the following aspects: Scratching can lead to the generation and shedding of metal particles, resulting in potentially fatal contamination. Under high temperature, high pressure, and high load conditions, the microscopic gap between the screw and the feed tube may disappear due to uneven thermal expansion, mechanical misalignment, or hard impurities mixed in the material, causing direct metal-to-metal contact and dry friction. If the screw surface is made of a soft base material (such as tempered steel) or a hard coating with weak adhesion, it is easily scratched. The micron- or even nano-sized metal shavings generated in this process, once mixed into the ultrapure fluoroplastic melt, become permanent impurities that cannot be filtered out, directly causing electrical failures in downstream semiconductor devices or safety risks to biopharmaceutical products, resulting in the scrapping of entire batches of expensive products.

[0003] Scratching damage compromises geometric precision and functional integrity. Continuous scraping creates grooves and scratches on the outer surface of the screw (especially at the thread crests and roots) and the inner wall of the feed tube, altering critical clearances: on one hand, it increases the radial clearance between the screw and the feed tube, severely weakening melt pumping efficiency, back pressure stability, and metering accuracy, leading to uneven plasticization, decreased output, and increased energy consumption; on the other hand, it creates "material trapping" dead zones, where scratches and pits become "traps" for material retention and thermal oxidation. Fluoroplastics trapped within these areas carbonize and decompose at prolonged high temperatures, producing defects such as black spots and crystal points. Their periodic shedding contaminates the product and releases corrosive decomposition products, exacerbating localized corrosion. Furthermore, the scraped area becomes a preferential pathway for corrosion propagation: once the original dense protective state of the surface (whether it's the passivation film of the substrate itself or the surface coating) is damaged, the exposed fresh metal or the weak bonding layer under the coating will be eroded by the highly corrosive fluoroplastic melt (often containing trace amounts of fluoride ions and high-temperature acidic decomposition products), causing the corrosion rate to increase exponentially. Scratches become the starting point for pitting and crevice corrosion. Corrosion spreads rapidly along the scratches in both depth and breadth, promoting mechanical wear and forming a failure mechanism that accelerates the process through wear and corrosion. This leads to perforation or breakage of the screw or tube at a time far below its expected lifespan.

[0004] For screws made of integral special alloys, although they possess good corrosion resistance, the material may be too soft or poorly matched with the tube material. After scratching, geometric accuracy is easily lost, making repair extremely difficult and costly. For screws with hard coatings (such as chrome plating or tungsten carbide spraying), scratching easily leads to localized peeling of the brittle coating. The peeled area not only exposes the corrosion-sensitive substrate, but its sharp edges further aggravate scratching of the tube's inner wall. The resulting hard coating particles become new abrasives, triggering a vicious cycle of "coating peeling → aggravated scratching → larger area peeling," ultimately rendering both the screw and tube unusable in a short period.

[0005] It is evident that existing technologies are insufficient to systematically address the cascading problems caused by scraping between the screw and the feed tube, including primary contamination (metal shavings), secondary contamination (carbides), loss of geometric precision, and wear-corrosion synergistic accelerated failure. Therefore, researching a functionally graded laser cladding screw and its fabrication method is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a functionally graded laser cladding screw and its preparation method, so as to solve the problems of primary contamination, secondary contamination and failure caused by screws in the prior art.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for fabricating a functionally graded laser cladding screw, comprising the following steps: (1) Laser cladding is performed on the metal mandrel in sequence to form an underlayer and a wear-resistant layer, resulting in a composite blank; (2) The composite blank is turned, ground and precision turned to obtain a functionally graded laser cladding screw.

[0008] Preferably, in step (1), the metal mandrel is preheated before laser cladding is performed; the preheating temperature is 300~500℃.

[0009] Preferably, in step (1), the raw material for the underlayment contains the following components: Co ≤2%, Cr 14.5~17%, Si ≤1%, Mo 15~17%, Fe ≤1%, C ≤0.15%, Mn ≤1%, W 3~5%, and the remainder is Ni, and the sum of the above components is 100%; the particle size of the raw material for the underlayment is 46~105μm.

[0010] Preferably, the laser cladding parameters for the underlayer include: laser power of 1000~2000W, scanning speed of 300~500mm / min, spot diameter of 2~3 mm, powder feeding gas flow rate of 2~5 L / min, and protective gas flow rate of 15~25 L / min.

[0011] Preferably, the thickness of the base layer is 2-5 mm.

[0012] Preferably, in step (1), the raw material of the wear-resistant layer contains the following components: Co ≤2%, Cr 14~16%, Si 1~3%, Mo 22~24%, Fe ≤1.25%, C ≤0.1%, Mn ≤0.5%, W 1~2%, and the remainder is Ni, and the sum of the above components is 100%.

[0013] Preferably, the wear-resistant layer is preheated before laser cladding; the temperature of the preheating treatment is 450~550℃.

[0014] Preferably, the laser cladding parameters of the wear-resistant layer include: laser power of 0.5~1kW, powder feeding rate of 0.1~0.3 r / min, scanning speed of 100~300 mm / min, spot diameter of 2~3 mm, powder feeding gas flow rate of 2~5 L / min, protective gas flow rate of 15~25 L / min, and cladding layers of 2~4 layers.

[0015] Preferably, the thickness of the wear-resistant layer is 2~4mm.

[0016] The present invention also provides a functionally graded laser cladding screw prepared by the above-described method.

[0017] The beneficial effects of this invention are: The functionally graded laser cladding screw prepared by this invention can significantly reduce production costs. It adopts a composite structure design of "low-cost substrate + high-performance functional layer", uses a small amount of special alloy only in key functional areas, and uses conventional high-strength steel for the mandrel. While ensuring excellent performance, it reduces material costs by 50-70% compared with screws that use special alloys throughout, resulting in outstanding economic benefits.

[0018] This invention achieves a high-strength, interface-free, and robust bond between the functional layer formed by laser cladding and the mandrel. The bond strength is even higher than that of the base material, fundamentally solving the technical problem of easy peeling and detachment of traditional surface coatings or weld overlays, and providing crucial protection for material safety in ultrapure production environments.

[0019] This invention utilizes laser cladding to form functional layers (underlayer and wear-resistant layer). A high-strength, interface-free bond is achieved between the functional layers and the mandrel, laying the foundation for customized performance design. Based on the design concept of functionally graded materials, materials can be precisely matched according to the service conditions (such as wear, corrosion, and stress) of different parts of the screw. For example, the thread top surface achieves extremely high hardness (HRC≥45) and wear resistance, while ensuring excellent toughness in the core and thread root. This "rigid-flexible" gradient structure results in overall service performance, especially fatigue resistance and wear life, far exceeding that of homogeneous material screws, with an expected improvement of 2-4 times.

[0020] This invention uses laser cladding technology to manufacture screws, which has high flexibility. Based on the same mandrel platform, by adjusting the cladding path and material combination, it can quickly respond to the customized needs of screws with different specifications and configurations.

[0021] The screw of this invention is manufactured in a single piece, resulting in a superior overall streamlined shape and avoiding the contamination traps such as gaps and threaded connections that may exist in traditional assembled screws. The screw has a smooth, dense working surface without weak interfaces, which not only reduces the risk of material residue and degradation but also makes it easier to thoroughly clean and maintain, fully meeting the extreme cleanliness requirements of equipment in fields such as semiconductors and biomedicine. Attached Figure Description

[0022] Figure 1 Metallographic structure diagram of the gradient alloy layer prepared in Example 1; Figure 2 This is a schematic diagram of a functionally graded laser cladding screw. Detailed Implementation

[0023] This invention provides a method for fabricating a functionally graded laser cladding screw, comprising the following steps: (1) Laser cladding is performed on the metal mandrel in sequence to form an underlayer and a wear-resistant layer, resulting in a composite blank; (2) The composite blank is turned, ground and precision turned to obtain a functionally graded laser cladding screw.

[0024] In this invention, the laser cladding is performed in a protective atmosphere.

[0025] In this invention, in step (1), the metal mandrel is preheated before laser cladding is performed; the preheating temperature is 300~500℃, specifically 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, and 500℃.

[0026] In this invention, in step (1), the raw material for the underlayment contains the following components: Co ≤2%, Cr 14.5~17%, Si ≤1%, Mo 15~17%, Fe ≤1%, C ≤0.15%, Mn ≤1%, W 3~5%, and the remainder is Ni, and the sum of the above components is 100%; the particle size of the raw material for the underlayment is 46~105μm.

[0027] In this invention, the laser cladding parameters for the underlayer include: laser power of 1000~2000W, specifically 1000W, 1200W, 1500W, 1600W, 1800W, and 2000W; scanning speed of 300~500mm / min, specifically 300mm / min, 320mm / min, 340mm / min, 360mm / min, 380mm / min, 400mm / min, 420mm / min, 440mm / min, 460mm / min, 480mm / min, and 500mm / min; spot diameter of 2~3mm, specifically 2mm or 3mm; and powder gas flow rate of 2~5. The flow rate can be L / min, specifically 2L / min, 3L / min, 4L / min, or 5L / min; the flow rate of the protective gas is 15~25L / min, specifically 16L / min, 18L / min, 20L / min, 22L / min, or 24L / min.

[0028] In this invention, the thickness of the base layer is 2-5mm, specifically 2mm, 3mm, or 4mm.

[0029] In this invention, in step (1), the raw material of the wear-resistant layer contains the following components: Co ≤2%, Cr 14~16%, Si 1~3%, Mo 22~24%, Fe ≤1.25%, C ≤0.1%, Mn ≤0.5%, W 1~2%, and the remainder is Ni. The sum of the above components is 100%.

[0030] In this invention, the wear-resistant layer is preheated before laser cladding; the temperature of the preheating treatment is 450~550℃, specifically 450℃, 480℃, 500℃, 520℃, or 530℃.

[0031] In this invention, if the preheating temperature is too low, the functional layer will crack, thus rendering it unusable.

[0032] In this invention, the laser cladding parameters of the wear-resistant layer include: laser power of 0.5~1kW, specifically 0.5kW, 0.6kW, 0.7kW, 0.8kW, and 0.9kW; powder feeding rate of 0.1~0.3 r / min, preferably 0.2r / min; scanning speed of 100~300 mm / min, specifically 120mm / min, 140mm / min, 160mm / min, 180mm / min, 200mm / min, 220mm / min, 240mm / min, 260mm / min, and 280mm / min; spot diameter of 2~3 mm; and powder feeding gas flow rate of 2~5. The flow rate can be L / min, specifically 2L / min, 3L / min, 4L / min, or 5L / min; the flow rate of the protective gas is 15~25L / min, specifically 16L / min, 18L / min, 20L / min, 22L / min, or 24L / min; and the number of cladding layers is 2~4 layers.

[0033] In this invention, the thickness of the wear-resistant layer is 2-4 mm, specifically 2 mm, 3 mm, or 4 mm.

[0034] In this invention, the grinding process is preferably followed by heat treatment, wherein the heat treatment temperature is 400~600℃, specifically 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, or 580℃, and the heat treatment time is 2~4 hours, preferably 3 hours.

[0035] The present invention also provides a functionally graded laser cladding screw prepared by the above-described method.

[0036] The screw manufactured according to this application has a threaded working surface made of a high-hardness, wear-resistant nickel-based alloy, while the core and the bottom layer are supported by a tough, corrosion-resistant nickel-based alloy and an alloy steel mandrel, achieving a functional gradient design. This screw exhibits excellent wear resistance and corrosion resistance in ultra-pure PFA injection molding production, effectively eliminating the risk of coating peeling and contamination, significantly extending its service life, and its overall manufacturing cost is significantly lower than that of integral special alloy screws.

[0037] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1

[0039] SKD61 hot work die steel was selected and machined to a size of Φ36 mm × 1000 mm to obtain a metal mandrel, which was then thoroughly cleaned.

[0040] The cleaned metal mandrel is clamped onto a precision rotating fixture and preheated to 400°C under an argon protective atmosphere. Then, the laser cladding system is activated, controlling the mandrel to rotate at a constant speed while the laser cladding head moves at a constant speed along the mandrel's axis for laser cladding. The raw material is nickel-based alloy powder with a particle size of 46~105μm (specifically, the content is Co 2%, Cr 15%, Si 1%, Mo 16%, Fe 0.8%, C 0.15%, Mn 1%, W...). 4% (the remainder being Ni), the spot diameter is 2mm, the flow rate of argon powder feed gas is 3L / min, the flow rate of argon protective gas is 20L / min, the laser power is 1500W, the scanning speed is 400mm / min, and the powder is fed coaxially to the surface of the metal mandrel for reciprocating cladding until a 3mm thick nickel-based alloy underlayer is formed. The underlayer is uniform and dense. The resulting composite is ground with a CBN grinding wheel at a linear speed of 40m / s, a workpiece rotation speed of 100r / min, a radial feed of 0.02mm, and an axial feed speed of 2m / min. Grinding fluid is used throughout the process until the surface is bright and the dimensions are consistent.

[0041] The composite material after grinding was preheated to 480℃ and held at that temperature. Using wear-resistant layer raw material powder (specific content: Co 2%, Cr 15%, Si 2%, Mo 23%, Fe 1%, C 0.1%, Mn 0.3%, W 1%, with the remainder being Ni), a 1kW fiber laser was used under an argon protective atmosphere. The interlayer temperature was controlled at 500℃. The cladding was performed on the area corresponding to the future thread working surface (including the top of the thread and the stress surfaces on both sides). The powder feeding rate was 0.2r / min, the scanning speed was 200mm / min, the spot diameter was 2mm, the argon powder feeding gas flow rate was 2L / min, the argon protective gas flow rate was 20L / min, and 3 cladding layers were formed until a wear-resistant layer with a thickness of 2mm was formed, thus obtaining the composite blank.

[0042] Using the center holes at both ends of the composite blank as a reference, the outer diameter of the blank is machined on a precision lathe to Φ=45.5 mm. Then, the outer diameter of the screw is ground using an external cylindrical grinder. According to the screw drawing program, the basic groove shape of the thread is ground and further precision ground to Φ=45.1 mm, ensuring good cylindricity. Then, it is heat-treated at 500℃ for 3 hours and cooled to room temperature in the furnace. Finally, it is precision turned on a turning-milling machining center using CBN (cubic boron nitride) inserts to machine all key dimensions to the final accuracy required by the drawing, ensuring that the major diameter of the screw is Φ45.0±0.015 mm and the surface roughness R of the thread working surface is achieved. a The value reaches 0.3 μm. After processing, the screw is cleaned and non-destructive tested to ensure that the cladding layer is dense and defect-free.

[0043] Figure 1 The image shows the metallographic structure of the gradient alloy layer prepared in Example 1. Figure 1 It can be seen that the gradient alloy layer consists of uniform and fine columnar crystals. The wear-resistant layer and the underlayer are metallurgically bonded, without defects such as cracks or pores.

[0044] Functionally graded laser cladding screws were prepared according to the method in Example 1. The hardness of the alloy layer (comprising the underlayer and wear-resistant layer) was tested five times, and the average value was calculated, as shown in Table 1. Table 1. Hardness test results of the alloy layer in functionally graded laser clad screws.

[0045] Table 2 Results of hydrofluoric acid corrosion resistance test

[0046] Example 2

[0047] SKD61 hot work die steel was selected and machined to a size of Φ36 mm × 1000 mm to obtain a metal mandrel, which was then thoroughly cleaned.

[0048] The cleaned metal mandrel is clamped onto a precision rotating fixture and preheated to 300°C under an argon protective atmosphere. Then, the laser cladding system is activated, controlling the mandrel to rotate at a constant speed while the laser cladding head moves at a constant speed along the mandrel's axis for laser cladding. The raw material is nickel-based alloy powder with a particle size of 46~105μm (specifically, the content is Co 1%, Cr 17%, Si 0.1%, Mo 15%, Fe 0.3%, C 0.1%, Mn 0.6%, W...). The laser beam has a 3% purity (the remainder being Ni), a 3mm spot diameter, an argon powder feed gas flow rate of 4L / min, an argon protective gas flow rate of 25L / min, a laser power of 2000W, and a scanning speed of 300mm / min. The powder is fed coaxially to the surface of the metal mandrel for reciprocating cladding until a 3mm thick nickel-based alloy underlayer is formed. The underlayer is uniform and dense. The resulting composite is then ground using a CBN grinding wheel with a linear speed of 50m / s, a workpiece rotation speed of 200r / min, a radial feed of 0.01mm, and an axial feed speed of 3m / min. Grinding fluid is used throughout the process until the surface is smooth and dimensionally consistent.

[0049] The composite material after grinding was preheated to 480℃ and held at that temperature. Using wear-resistant layer raw material powder (specific content: Co 2%, Cr 15%, Si 2%, Mo 23%, Fe 1%, C 0.1%, Mn 0.3%, W 1%, with the remainder being Ni), a 0.5kW fiber laser was used under an argon protective atmosphere. The interlayer temperature was controlled at 500℃. The cladding was performed on the area corresponding to the future thread working surface (including the top of the thread and the stress surfaces on both sides). The powder feeding rate was 0.2r / min, the scanning speed was 100mm / min, the spot diameter was 2mm, the argon powder feeding gas flow rate was 4L / min, the argon protective gas flow rate was 15L / min, and 4 cladding layers were formed until a wear-resistant layer with a thickness of 4mm was formed, thus obtaining the composite blank.

[0050] Using the center holes at both ends of the composite blank as a reference, the outer diameter of the blank is machined on a precision lathe to Φ=45.5 mm. Then, the outer diameter of the screw is ground using an external cylindrical grinder. According to the screw drawing program, the basic groove shape of the thread is ground and further precision ground to Φ=45.1 mm, ensuring good cylindricity. Then, it is heat-treated at 600℃ for 2 hours and cooled to room temperature in the furnace. Finally, it is precision machined on a turning-milling composite machining center using CBN (cubic boron nitride) inserts to machine all key dimensions to the final accuracy required by the drawing, ensuring that the major diameter of the screw is Φ45.0±0.015 mm and the surface roughness R of the thread working surface is achieved. a The value reaches 0.3 μm. After processing, the screw is cleaned and non-destructive tested to ensure that the cladding layer is dense and defect-free.

[0051] Example 3

[0052] SKD61 hot work die steel was selected and machined to a size of Φ36 mm × 1000 mm to obtain a metal mandrel, which was then thoroughly cleaned.

[0053] The cleaned metal mandrel is clamped onto a precision rotating fixture and preheated to 500°C under an argon protective atmosphere. Then, the laser cladding system is activated, controlling the mandrel to rotate at a constant speed while the laser cladding head moves at a constant speed along the mandrel's axis for laser cladding. The raw material is nickel-based alloy powder with a particle size of 46~105μm (specifically, the content is Co 0.5%, Cr 15.5%, Si 0.5%, Mo 17%, Fe 0.5%, C 0.1%, Mn 0.8%, W...). 5% (the remainder being Ni), with a spot diameter of 2 mm, an argon powder feed gas flow rate of 5 L / min, an argon protective gas flow rate of 15 L / min, a laser power of 1000 W, and a scanning speed of 500 mm / min. The powder is fed coaxially to the surface of the metal mandrel for reciprocating cladding until a 3 mm thick nickel-based alloy underlayer is formed. The underlayer is uniform and dense. The resulting composite is then ground using a CBN grinding wheel with a wheel linear speed of 30 m / s, a workpiece rotation speed of 100 r / min, a radial feed of 0.01 mm, and an axial feed speed of 0.5 m / min. Grinding fluid is used throughout the process until the surface is bright and the dimensions are consistent.

[0054] The composite material after grinding was preheated to 480℃ and held at that temperature. Using wear-resistant layer raw material powder (specific content: Co 0.5%, Cr 16%, Si 3%, Mo 24%, Fe 0.75%, C 0.05%, Mn 0.1%, W 2%, with the remainder being Ni), a 0.8kW fiber laser was used under an argon protective atmosphere. The interlayer temperature was controlled at 500℃. Cladding was performed on the area corresponding to the future thread working surface (including the top of the thread and the stress surfaces on both sides). The powder feeding rate was 0.2r / min, the scanning speed was 200mm / min, the spot diameter was 2mm, the argon powder feeding gas flow rate was 5L / min, the argon protective gas flow rate was 25L / min, and 3 cladding layers were formed until a wear-resistant layer with a thickness of 2mm was formed, thus obtaining the composite blank.

[0055] Using the center holes at both ends of the composite blank as a reference, the outer diameter of the blank is machined on a precision lathe to Φ=45.5 mm. Then, the outer diameter of the screw is ground using an external cylindrical grinder. According to the screw drawing program, the basic groove shape of the thread is ground, and it is further precision ground to Φ=45.1 mm, ensuring good cylindricity. Then, it is heat-treated at 400℃ for 4 hours, cooled to room temperature in the furnace, and finally precision turned on a turning-milling machining center using CBN (cubic boron nitride) inserts to machine all key dimensions to the final accuracy required by the drawing, ensuring that the major diameter of the screw is Φ45.0±0.015 mm and the surface roughness R of the thread working surface is achieved. a The value reaches 0.3 μm. After processing, the screw is cleaned and non-destructive tested to ensure that the cladding layer is dense and defect-free.

[0056] 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 fabricating a functionally graded laser cladding screw, characterized in that, Includes the following steps: (1) Laser cladding is performed on the metal mandrel in sequence to form an underlayer and a wear-resistant layer, resulting in a composite blank; (2) The composite blank is turned, ground and precision turned to obtain a functionally graded laser cladding screw.

2. The method for fabricating a functionally graded laser cladding screw according to claim 1, characterized in that, In step (1), the metal mandrel is preheated before laser cladding is performed; the preheating temperature is 300~500℃.

3. The method for fabricating a functionally graded laser cladding screw according to claim 1 or 2, characterized in that, In step (1), the raw material for the base layer contains the following components: Co ≤2%, Cr 14.5~17%, Si ≤1%, Mo 15~17%, Fe ≤1%, C ≤0.15%, Mn ≤1%, W 3~5%, and the remainder is Ni. The sum of the above components is 100%. The particle size of the raw material for the base layer is 46~105 μm.

4. The method for fabricating a functionally graded laser cladding screw according to claim 3, characterized in that, The laser cladding parameters for the underlayer include: laser power of 1000~2000W, scanning speed of 300~500mm / min, spot diameter of 2~3mm, powder feeding gas flow rate of 2~5 L / min, and protective gas flow rate of 15~25L / min.

5. The method for fabricating a functionally graded laser cladding screw according to claim 1, 2, or 4, characterized in that, The thickness of the base layer is 2~5mm.

6. The method for fabricating a functionally graded laser cladding screw according to claim 5, characterized in that, In step (1), the raw material of the wear-resistant layer contains the following components: Co ≤2%, Cr 14~16%, Si 1~3%, Mo 22~24%, Fe ≤1.25%, C≤0.1%, Mn ≤0.5%, W 1~2%, and the remainder is Ni. The sum of the above components is 100%.

7. The method for fabricating a functionally graded laser cladding screw according to claim 4 or 6, characterized in that, The wear-resistant layer is preheated before laser cladding; the temperature of the preheating treatment is 450~550℃.

8. The method for fabricating a functionally graded laser cladding screw according to claim 7, characterized in that, The laser cladding parameters of the wear-resistant layer include: laser power of 0.5~1kW, powder feeding rate of 0.1~0.3 r / min, scanning speed of 100~300 mm / min, spot diameter of 2~3 mm, powder feeding gas flow rate of 2~5 L / min, protective gas flow rate of 15~25 L / min, and cladding layers of 2~4 layers.

9. The method for fabricating a functionally graded laser cladding screw according to claim 6 or 8, characterized in that, The thickness of the wear-resistant layer is 2~4mm.

10. A functionally graded laser clad screw prepared by the method of any one of claims 1 to 9.

Images