In-situ synthesis of multiphase composite carbide reinforced laser cladding coating and preparation method and application thereof

Abstract

The application provides in-situ synthesis of a multiphase composite carbide reinforced laser cladding coating, a preparation method and application thereof, and belongs to the technical field of metal material surface engineering technology. Nb powder and Mo2C powder are added as the precursors of the composite reinforcing phase, and the Mo2C has dual functions of "carbon source" and "alloy element source". Under the action of high-energy laser, the Mo2C is in-situ decomposed into free Mo atoms and C atoms, the C atoms in the molten pool rapidly react with the high-activity Nb, Cr and part of the Mo, and the NbC, Cr3C2 and (Nb, Mo)C solid solution carbides are synchronously generated in-situ. The carbides are in the form of fine dispersion in the nickel-based alloy melt, forming the composite reinforcing phase. The application realizes the multiphase composite reinforcement in one step, solves the problem of poor interface bonding of the added ceramic phase, and the obtained laser cladding coating has high hardness, excellent wear resistance and outstanding corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of surface engineering technology for metallic materials, specifically to an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating, its preparation method, and its application. Background Technology

[0002] In fields such as energy, transportation, and marine engineering, critical moving components (such as internal combustion engine cylinder liners, main shafts, and valves) are subjected to wear, corrosion, and their interaction over long periods, leading to premature failure and resulting in significant economic losses and safety hazards. For example, in the application of marine diesel engine cylinder liners, the coating needs to resist mechanical wear while withstanding high temperatures and marine conditions. - Corrosion in ionic environments.

[0003] Traditional methods such as electroplating and thermal spraying are widely used, but they have obvious limitations. For example, electroplated layers have limited bonding strength and are prone to peeling under alternating stress, and the electroplating solution pollutes the environment; thermal spraying (such as plasma spraying) coatings have better performance, but they have high porosity, the coating and the substrate are mainly mechanically bonded, they are prone to failure under impact or fatigue loads, and the equipment and process costs are high.

[0004] Laser cladding, an advanced surface modification method, uses a high-energy laser beam to form a molten pool on the substrate surface, simultaneously introducing or pre-placing alloy powder to achieve metallurgical bonding between the coating and the substrate. This method offers advantages such as low dilution rate, small heat-affected zone, dense coating structure, and high bonding strength. Currently, laser cladding is used to prepare nickel-based alloy coatings to improve the corrosion resistance of components. However, single nickel-based alloy coatings have limited hardness and insufficient wear resistance, making it difficult to meet the requirements of high wear-resistant operating conditions. To improve the hardness and wear resistance of laser cladding coatings, researchers typically add hard ceramic phases, such as WC, TiC, and Cr3C2, to the powder. There are two main methods of addition: Direct mixing method: Pre-synthesized ceramic particles are physically mixed with metal powder and then clad. This method is simple, but the ceramic particles have poor wettability with the metal matrix, which easily leads to pores or aggregation at the interface; moreover, the ceramic particles may dissolve or burn off under the high temperature of laser, and the phase structure is difficult to control precisely.

[0005] In-situ synthesis method: By adding reactive elements to the molten pool, an enhancing phase is generated in situ during the cladding process.

[0006] However, current research focuses on generating single or a few types of carbide reinforcing phases, which has a bottleneck effect on improving the overall performance of coatings (especially simultaneously improving wear resistance and corrosion resistance). To increase the types of carbide reinforcing phases, it is necessary to introduce multiple metal elements, and the complex reaction pathways make the products difficult to predict, making it difficult to promote. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating, its preparation method, and its application. The laser cladding coating prepared by this invention possesses high hardness, excellent wear resistance, and outstanding corrosion resistance, meeting the requirements of harsh friction-corrosion combined working conditions.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating, comprising the following steps: Ni-based alloy powder, Nb powder and Mo2C powder are mixed to obtain mixed raw material powder; The mixed raw material powder is laid on the surface of the substrate to form a pre-coated layer; The pre-formed coating is subjected to laser cladding to obtain an in-situ synthesized multiphase composite carbide-reinforced coating on the substrate surface.

[0009] Preferably, in the mixed raw material powder, the mass content of Ni-based alloy powder is 70-100%, and the total mass content of Nb powder and Mo2C powder is 0-30%, and not 0. The molar ratio of Nb to Mo2C is 1:(0.8~1.2).

[0010] Preferably, the composition of the Ni-based alloy powder, by mass percentage, includes Ni 70~75%, Cr 12~15%, Fe 6~9%, Si 1~3%, and C ≤10%.

[0011] Preferably, the particle size of the Ni-based alloy powder is 53~105 μm, and the particle size of the Nb powder and Mo2C powder is independently 15~53 μm.

[0012] Preferably, before laying, the mixture further includes mixing the raw material powder with the binder, wherein the mass ratio of the raw material powder to the binder is 90~97:3~10; The thickness of the pre-coated layer is 0.8~1.2 mm.

[0013] Preferably, the process parameters for the laser cladding process include: Laser power 1100~1300 W; Scanning speed 500~700 mm / min; Overlap rate 35%~45%; The diameter of the light spot is 1~3 mm; Defocusing amount: +3mm to +5mm.

[0014] Preferably, the substrate comprises stainless steel, gray cast iron, or 45 steel.

[0015] The present invention provides an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating prepared by the above preparation method. The laser cladding coating includes a Ni-based alloy matrix and a composite carbide reinforcing phase dispersed in the Ni-based alloy matrix. The composite carbide reinforcing phase includes NbC, Cr3C2 and (Nb, Mo)C.

[0016] This invention provides the application of the above-mentioned in-situ synthesized multiphase composite carbide-reinforced laser cladding coating in the preparation or repair of mechanical parts.

[0017] The present invention provides a mechanical component, including a component substrate and an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating disposed on the working surface of the component substrate.

[0018] This invention provides a method for preparing an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating, comprising the following steps: mixing Ni-based alloy powder, Nb powder, and Mo2C powder to obtain a mixed raw material powder; laying the mixed raw material powder on the surface of a substrate to form a pre-coating; and performing laser cladding treatment on the pre-coating to obtain an in-situ synthesized multiphase composite carbide-reinforced coating on the substrate surface. This invention adds Nb powder and Mo2C powder as precursors for the composite reinforcing phase, wherein Mo2C serves as both a "carbon source" and an "alloy element source." Under the action of a high-energy laser, Mo2C decomposes in-situ into free Mo and C atoms. The C atoms in the molten pool rapidly react with highly reactive Nb, Cr, and some Mo, simultaneously generating NbC, Cr3C2, and (Nb, Mo)C solid solution carbides in-situ. These carbides are distributed in a fine, dispersed form within the nickel-based alloy melt, forming a composite reinforcing phase. This invention achieves multiphase composite reinforcement in one step, solving the problem of poor bonding at the interface of the added ceramic phases. The resulting laser cladding coating possesses high hardness, excellent wear resistance, and outstanding corrosion resistance. Example results show that the average microhardness of the laser cladding coating obtained by this invention is not less than 650 HV; under conditions of a load of 30 N, a Si3N4 ball as the grinding workpiece, and a reciprocating frequency of 5 Hz, its wear is not higher than 0.015 mm. 3 In a 3.5 wt.% NaCl solution, its corrosion current density is no higher than 15 μA / cm. 2 It is particularly suitable for surface strengthening and repair of parts such as cylinder liners of marine diesel engines that are subjected to severe friction and corrosion conditions, effectively extending their service life.

[0019] Compared with the prior art, the present invention has the following significant advantages: (1) Achieving multiphase composite reinforcement in one step: This invention uses a sophisticated powder composition design (Nb+Mo2C) to generate multiple hard phases such as NbC, Cr3C2 and (Nb,Mo)C in situ simultaneously through a single laser cladding process. The process is simple and efficient.

[0020] (2) High bonding strength between the reinforcing phase and the matrix: The multiphase carbide generated in situ in this invention has good wettability with the metal melt and the interface is metallurgically bonded, which effectively avoids the common problems of poor interface compatibility and easy peeling of the added ceramic phase, and the coating has strong integrity.

[0021] (3) Comprehensive performance leap: The combined effect of multiple hard carbides in this invention increases the coating hardness by more than 30% compared to pure nickel-based coatings. The fine and dispersed hard phases can effectively resist abrasive cutting and adhesive wear, reducing wear by two orders of magnitude compared to the substrate. The dense coating structure, together with the contribution of Cr3C2 and other phases, constitutes an effective corrosion barrier, significantly reducing corrosion current.

[0022] (4) Strong process applicability: The laser cladding process adopted is green and efficient, with a wide parameter window and easy to automate. It is particularly suitable for the repair and strengthening of large, complex or on-site workpieces and has good prospects for engineering application. Attached Figure Description

[0023] Figure 1 The X-ray diffraction (XRD) pattern of the in-situ synthesized multiphase composite carbide-reinforced coating prepared in Example 1; Figure 2 Comparison of the microhardness distribution along the depth of the coating in Example 1 and Comparative Example 1. Figure 3 The bar chart shows the comparison of friction and wear volumes of the coating in Example 1, the coating in Comparative Example 1, and the HT250 substrate under the same conditions. Figure 4 The image shows a comparison of the potentiodynamic polarization curves of the coating in Example 1, the coating in Comparative Example 1, and the HT250 substrate in a 3.5 wt.% NaCl solution. Detailed Implementation

[0024] This invention provides a method for preparing an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating, comprising the following steps: Ni-based alloy powder, Nb powder and Mo2C powder are mixed to obtain mixed raw material powder; The mixed raw material powder is laid on the surface of the substrate to form a pre-coated layer; The pre-formed coating is subjected to laser cladding to obtain an in-situ synthesized multiphase composite carbide-reinforced coating on the substrate surface.

[0025] This invention involves mixing Ni-based alloy powder, Nb powder, and Mo2C powder to obtain a mixed raw material powder. In this invention, the Ni-based alloy is preferably a Ni-Cr-Fe alloy. Based on mass percentage, the composition of the Ni-based alloy powder preferably includes Ni 70-75%, more preferably 72-74%; Cr 12-15%, more preferably 13-14%; Fe 6-9%, more preferably 7-8%; Si 1-3%, more preferably 2%; and C ≤10%, more preferably 5-8%. As a specific embodiment of this invention, the Ni-based alloy powder is preferably Inconel 600 alloy powder.

[0026] In this invention, the particle size of the Ni-based alloy powder is preferably 53-105 μm, more preferably 60-90 μm, and even more preferably 70-80 μm; the particle sizes of the Nb powder and Mo2C powder are independently preferably 15-53 μm, more preferably 20-40 μm. In this invention, the mixing is preferably stirred, preferably carried out in a three-dimensional powder mixer, and the mixing time is preferably 2-4 h, more preferably 3-4 h.

[0027] In this invention, the mass content of Ni-based alloy powder in the mixed raw material powder is preferably 70-100%, more preferably 80-90%, specifically 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99%; the total mass content of Nb powder and Mo2C powder is preferably 0-30% and not 0, more preferably 10-20%, specifically 1%, 2%, 5%, 10%, 15%, 20%, 25%, or 30%. In this invention, the molar ratio of Nb to Mo2C is preferably 1:(0.8-1.2), more preferably 1:(0.9-1.1), and even more preferably 1:1.0. This invention, through ingenious composition design, ensures that the Ni-based content guarantees good wetting and metallurgical bonding between the cladding layer and the substrate, reducing crack sensitivity; when Nb and Mo2C are close to an equimolar ratio, a stable composite carbide reinforcing phase is formed; when the total content is controlled at 10-20%, segregation can be avoided and wear resistance can be improved. When the laser cladding parameters are adjusted (e.g., power 1.5~2.5 kW, scanning speed 6~10 mm / s), a higher power and lower speed are suitable when the proportion of reinforcing phase is low (10~15%) to obtain a dense, crack-free cladding layer. When the proportion of reinforcing phase is high (15~20%), the scanning speed needs to be increased (>8 mm / s) and the power reduced (<2.0kW) to prevent the reinforcing phase from coarsening, thereby achieving excellent forming quality and high performance in a coordinated manner.

[0028] This invention involves laying the mixed raw material powder onto the surface of a substrate to form a pre-coated layer. In this invention, the substrate preferably comprises stainless steel, gray cast iron, or 45 steel, more preferably HT250 gray cast iron. Before laying the raw material powder, this invention preferably cleans and roughens the substrate to enhance the coating adhesion. In this invention, the cleaning agent is preferably anhydrous ethanol, and the roughening treatment is preferably sandblasting or sandpaper polishing. In this invention, the surface roughness of the substrate is preferably 5~15 μm.

[0029] Before application, the present invention preferably mixes the mixed raw material powder with a binder to obtain a paste-like slurry, which is then applied to the surface of the substrate and dried to obtain a pre-coated layer. In the present invention, the binder is preferably a solution of polyvinyl alcohol, cellulose nitrate, and rosin alcohol; the mass ratio of the mixed raw material powder to the binder is preferably 90~97:3~10, more preferably 93~95:5~7. In the present invention, the drying temperature is preferably 80℃~100℃, and the drying time is preferably 1~2 hours.

[0030] In this invention, the thickness of the pre-coated layer is preferably 0.8~1.2 mm, more preferably 0.9~1.1 mm, and even more preferably 1.0 mm.

[0031] This invention involves laser cladding of the pre-formed coating to obtain an in-situ synthesized multiphase composite carbide-reinforced coating on the substrate surface. In this invention, the preferred process parameters for the laser cladding process include: The laser power is 1100~1300 W, more preferably 1200 W; The scanning speed is 500~700 mm / min, more preferably 600 mm / min; The overlap rate is 35%~45%, preferably 40%; The spot diameter is 1~3 mm, more preferably 2~3 mm; Defocusing amount: +3 mm to +5 mm.

[0032] In this invention, the laser cladding process is preferably performed under an argon protective atmosphere, and the argon gas flow rate is preferably 5~15 L / min, more preferably 10~15 L / min. In this invention, the laser cladding process is preferably single-channel laser scanning cladding.

[0033] Under the specific material system and laser cladding process parameters of this invention, the core in-situ synthesis reaction occurs as follows: Under the action of a high-energy laser, Mo2C decomposes into free Mo and C atoms. The C atoms in the molten pool rapidly react with highly reactive Nb, Cr, and some Mo, simultaneously generating NbC, Cr3C2, and (Nb, Mo)C solid solution carbides in situ. These carbides are distributed in a fine, dispersed form within the nickel-based alloy melt, forming a composite reinforcing phase.

[0034] This invention provides an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating prepared by the above-described method. In this invention, the laser cladding coating comprises a Ni-based alloy matrix and a composite carbide reinforcing phase dispersed within the Ni-based alloy matrix. Preferably, the Ni-based alloy matrix is ​​a Ni-Cr-Fe alloy. The composite carbide reinforcing phase is generated in-situ within the Ni-based alloy matrix and comprises NbC, Cr3C2, and (Nb, Mo)C. These reinforcing phases exhibit a clean metallurgical interface with the metal matrix, without significant porosity or aggregation.

[0035] In this invention, the size of the composite carbide reinforcing phase is preferably 1~3 μm; the mass ratio of the composite carbide reinforcing phases NbC, Cr3C2 and (Nb, Mo)C in the coating is preferably 10~30%, more preferably 20~25%.

[0036] This invention provides the application of the above-mentioned in-situ synthesized multiphase composite carbide-reinforced laser cladding coating in the preparation or repair of mechanical parts.

[0037] This invention provides a mechanical component, comprising a component substrate and an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating disposed on the working surface of the component substrate. In this invention, the component substrate preferably comprises a marine diesel engine cylinder liner, a marine stern shaft, or a marine propeller. In this invention, the thickness of the in-situ synthesized multiphase composite carbide-reinforced laser cladding coating is preferably 0.8~1.2 mm, more preferably 1 mm.

[0038] The following detailed description, in conjunction with embodiments, illustrates the in-situ synthesized multiphase composite carbide-reinforced laser cladding coating, its preparation method, and its applications provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0039] The raw materials, equipment, and testing and characterization methods used in the following embodiments are as follows: (1) Raw materials and equipment Base material: HT250 gray cast iron, with dimensions of 100 mm × 50 mm × 10 mm.

[0040] Metal powders: Inconel 600 alloy powder: particle size 53~105 μm, composition (wt.%): Ni 72.5%, Cr 15.0%, Fe 8.0%, Si 2.5%, C 0.1%. Nb powder: purity ≥99.8%, particle size 15~53 μm. Mo2C powder: purity ≥99.5%, particle size 15~53 μm.

[0041] Equipment: XL-F3000W fiber laser, KUKA robot-controlled laser head movement, coaxial powder feeder.

[0042] (2) Testing and characterization methods Phase analysis (XRD): The coating phase was analyzed using an XRD-7000 X-ray diffractometer.

[0043] Microhardness testing: An MHVD-1000AT Vickers hardness tester was used, with a load of 200 g and a holding time of 10 s. Tests were conducted at points every 0.1 mm from the coating surface to the substrate, and the average hardness value of the coating was recorded.

[0044] Wear performance testing: An SFT-2M tribology and wear testing machine was used, employing a ball-disc reciprocating mode. The grinding balls were Φ5mm Si3N4 balls, with a load of 30 N, a reciprocating frequency of 5 Hz, a stroke of 4 mm, and a total test time of 30 minutes. A white light interferometer was used to measure the wear track profile and calculate the wear volume.

[0045] Electrochemical corrosion performance testing: A CS350M electrochemical workstation was used with a standard three-electrode system (coated sample as working electrode, Pt sheet as auxiliary electrode, and saturated calomel electrode as reference electrode). The electrolyte was 3.5 wt.% NaCl solution. After the open-circuit potential stabilized, potentiodynamic polarization scanning was performed at a scan rate of 10 mV / s. The corrosion potential (E) was obtained by extrapolation from the Tafel region. corr ) and corrosion current density (I corr ).

[0046] Example 1 The method for preparing in-situ synthesized multiphase composite carbide-reinforced laser cladding coatings comprises the following steps: (1) Powder preparation and pretreatment: Weigh the powder according to the mass ratio of Inconel 600:(Nb+Mo2C) = 90:10, where the molar ratio of Nb powder to Mo2C powder is 1:1. Place the weighed powder in a three-dimensional powder mixer and mix for 4 hours to ensure uniform mixing. The HT250 substrate is ultrasonically cleaned with acetone and anhydrous ethanol in sequence, then roughened by sandblasting with 80-mesh alumina sand, and then cleaned again with anhydrous ethanol and dried.

[0047] (2) Pre-coating application: Mix the evenly mixed powder with 3% polyvinyl alcohol adhesive (PVA) solution to form a paste, apply it evenly to the surface of the pretreated substrate, and dry it in an 80℃ oven for 2 hours to form a pre-coating layer with a thickness of 1.0 mm.

[0048] (3) Laser cladding: The substrate with a pre-coated layer is fixed on the laser processing stage. The laser process parameters are set as follows: laser power 1200 W, scanning speed 600 mm / min, spot diameter 3 mm, overlap rate 40%, defocusing amount +5 mm. Single-pass laser scanning cladding is performed under an argon protective atmosphere (gas flow rate 15 L / min) to obtain an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating with a thickness of 1 mm.

[0049] (4) Coating characterization and performance testing: XRD analysis: XRD tests were performed on the coating surface, and the results are as follows: Figure 1 As shown. By Figure 1 As can be seen, in addition to the diffraction peaks of the matrix γ-Ni (Cr, Fe), the characteristic diffraction peaks of NbC, Cr3C2 and (Nb, Mo)C solid solution carbides are clearly visible in the spectrum, confirming that the designed multiphase composite carbides were successfully synthesized in situ during the laser cladding process.

[0050] Microhardness: The hardness distribution across the cross-section of the coating is as follows Figure 2 As shown, the average microhardness of the coating reaches 702±25 HV. 0.2 It is significantly higher than the substrate's HT250 (approximately 200 HV). 0.2 Furthermore, the smooth transition in hardness from the coating to the substrate indicates good bonding.

[0051] Wear resistance: The amount of wear after friction and wear test, such as Figure 3 As shown. The wear volume of the coating in this embodiment is 0.012 mm. 3 It exhibits excellent wear resistance.

[0052] Corrosion resistance: The potentiodynamic polarization curve in 3.5% NaCl solution is shown below. Figure 4 As shown. Based on Tafel extrapolation calculations, the corrosion potential (E) of the coating in this embodiment is... corr The corrosion current density (I) is -0.43 V (vs. SCE). corr The value is 8.7 × 10 - 6 A / cm 2 (8.7 μA / cm 2 It exhibits excellent resistance to chloride ion corrosion.

[0053] Example 2: Changing the ratio of reinforcing phases This example illustrates the effect of the total content of the reinforcing phase precursor (Nb+Mo2C) on the coating performance. The preparation method and process parameters are the same as in Example 1, only the powder ratio is changed: Inconel 600:(Nb+Mo2C)=85:15, and the molar ratio of Nb to Mo2C remains 1:1.

[0054] Performance test results: The average microhardness of the coating is 758±30 HV. 0.2 The wear volume is 0.009 mm. 3 The corrosion current density is 9.5 × 10⁻⁶. -6 A / cm 2 The results show that appropriately increasing the content of the reinforcing phase can further improve hardness and wear resistance, while corrosion resistance fluctuates slightly but still remains at an excellent level. This embodiment demonstrates the feasibility and effectiveness trend of the reinforcing phase content range of the present invention.

[0055] Example 3: Changing the molar ratio of Nb to Mo2C This example illustrates the effect of the molar ratio of Nb to Mo2C on the in-situ reaction products and their properties. The preparation method and process parameters are the same as in Example 1, and the total powder ratio is the same as in Example 1 (90:10), but the molar ratio of Nb to Mo2C is adjusted to 1:0.8.

[0056] Performance test results: The average microhardness of the coating is 665±28 HV. 0.2 The wear volume is 0.015 mm. 3 The corrosion current density is 11.2 × 10⁻⁶. -6 A / cm 2 XRD analysis showed a decrease in the characteristic peaks of the (Nb, Mo)C phase. Compared to Example 1, the overall performance was slightly lower, demonstrating the importance of controlling the Nb to Mo2C molar ratio within the range of 1:0.8 to 1.2 in this invention.

[0057] Comparative Example 1: Pure nickel-based coating without added reinforcing phase This comparative example serves to demonstrate the necessity of in-situ synthesis of composite carbide-reinforced phases. The preparation method and process parameters are the same as in Example 1, but only pure Inconel 600 powder is used, without the addition of any Nb and Mo2C powder.

[0058] Performance test results: The average microhardness of the coating is 498±20 HV. 0.2 The wear volume is 0.032 mm. 3 The corrosion current density is 52.4 × 10⁻⁶. -6 A / cm 2 .Depend on Figures 2-4It can be seen that its hardness, wear resistance, and corrosion resistance are significantly lower than those of Examples 1-3. This fully demonstrates that nickel-based alloys alone cannot meet the high-performance requirements. The key to performance improvement in this invention is the addition of Nb and Mo2C and the generation of composite carbides through in-situ reaction.

[0059] Comparative Example 2: Changing the ratio of the reinforcing phases This comparative example illustrates the effect of the total content of the reinforcing phase precursor (Nb+Mo2C) on the coating performance. The preparation method and process parameters are the same as in Example 1, only the powder ratio is changed: Inconel 600:(Nb+Mo2C)=70:30, and the molar ratio of Nb to Mo2C remains 1:1.

[0060] Performance test results: The average microhardness of the coating is 599±30 HV. 0.2 The wear volume is 0.024 mm. 3 The corrosion current density is 30.3 × 10⁻⁶. -6 A / cm 2 The results show that excessively increasing the reinforcing phase content reduces hardness, wear resistance, and corrosion resistance. This embodiment demonstrates the feasibility and effectiveness trend of the reinforcing phase content range of the present invention.

[0061] Comparative Example 3: Direct mixing using pre-synthesized NbC powder (addition of ceramic phase method) This comparative example is used to compare the differences between the two technical routes of "in-situ synthesis" and "direct mixing". The preparation method and process parameters are the same as in Example 1, but the powder used is: Inconel 600 powder and pre-synthesized NbC powder (particle size 1~3 μm) are directly physically mixed at a mass ratio of 90:10, and Mo2C is not added.

[0062] Performance test results: The average microhardness of the coating is 580±45 HV. 0.2 (Data fluctuates greatly), wear volume is 0.025 mm 3 The corrosion current density is 35.6 × 10⁻⁶. -6 A / cm 2 Metallographic observation revealed localized agglomeration of NbC particles with a clear interface to the matrix. While its performance was superior to Comparative Example 1, it was far inferior to Example 1. This indicates that directly added ceramic phases are difficult to achieve uniform dispersion and strong interfacial bonding, and cannot form a synergistic reinforcing effect of multiphases such as Cr3C2 and (Nb, Mo)C.

[0063] Comparative Example 4: Laser process parameters deviate from the optimized range This comparative example illustrates the importance of laser process parameters for achieving effective in-situ reaction and forming a good coating. The powder ratio is the same as in Example 1, except for the laser cladding parameters: laser power 800 W (too low), scanning speed 800 mm / min (too fast).

[0064] The results showed unmelted powder and pores on the coating surface, and defects at the interface with the substrate. Performance testing could not be performed effectively or the data were extremely poor. This comparative example demonstrates the necessity of a wide range of laser process parameters for ensuring cladding quality, promoting sufficient in-situ reaction, and obtaining high-performance coatings.

[0065] Table 1 shows a comparison of the performance of the coatings obtained in Examples 1-3 and Comparative Examples 1-4.

[0066] Table 1. Comparison of the performance of coatings obtained in Examples 1-3 and Comparative Examples 1-4

[0067] As can be seen from the above embodiments and comparative examples: Using the specific powder system (Inconel 600 + Nb + Mo2C) and optimized laser process provided by this invention, in-situ synthesized multiphase composite carbide-reinforced coatings (Examples 1-3) can be successfully prepared. The comprehensive performance (hardness, wear resistance, and corrosion resistance) of the coating of this invention (Example 1) is far superior to that of the pure nickel-based coating without reinforcing phase (Comparative Example 1), the nickel-based coating with an excess of reinforcing phase (Comparative Example 2), and the coating using the traditional method of adding ceramic phase (Comparative Example 3), demonstrating the inventiveness and superiority of the "in-situ synthesis of multiphase composite carbide" technical path of this invention. By adjusting the powder ratio (Examples 2 and 3), the performance of the coating can be controlled within a certain range to meet the requirements of different working conditions.

[0068] 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 an in-situ synthesized multiphase composite carbide-reinforced laser cladding coating, characterized in that, Includes the following steps: Ni-based alloy powder, Nb powder and Mo2C powder are mixed to obtain mixed raw material powder; The mixed raw material powder is laid on the surface of the substrate to form a pre-coated layer; The pre-formed coating is subjected to laser cladding to obtain an in-situ synthesized multiphase composite carbide-reinforced coating on the substrate surface.

2. The preparation method according to claim 1, characterized in that, In the mixed raw material powder, the mass content of Ni-based alloy powder is 70-100%, and the total mass content of Nb powder and Mo2C powder is 0-30%, and not 0. The molar ratio of Nb to Mo2C is 1:(0.8~1.2).

3. The preparation method according to claim 1 or 2, characterized in that, The composition of the Ni-based alloy powder, by mass percentage, includes Ni 70-75%, Cr 12-15%, Fe 6-9%, Si 1-3%, and C ≤10%.

4. The preparation method according to claim 1, characterized in that, The Ni-based alloy powder has a particle size of 53~105 μm, and the Nb powder and Mo2C powder have independent particle sizes of 15~53 μm.

5. The preparation method according to claim 1 or 4, characterized in that, Before laying, the process also includes mixing the mixed raw material powder with the binder, wherein the mass ratio of the mixed raw material powder to the binder is 90~97:3~10; The thickness of the pre-coated layer is 0.8~1.2 mm.

6. The preparation method according to claim 1, characterized in that, The process parameters for the laser cladding process include: Laser power 1100~1300 W; Scanning speed 500~700 mm / min; Overlap rate 35%~45%; The diameter of the light spot is 1~3 mm; Defocusing amount: +3 mm to +5 mm.

7. The preparation method according to claim 1, characterized in that, The substrate includes stainless steel, gray cast iron, or 45 steel.

8. The in-situ synthesized multiphase composite carbide-reinforced laser cladding coating prepared by any one of claims 1 to 7, characterized in that, The laser cladding coating comprises a Ni-based alloy matrix and a composite carbide reinforcing phase dispersed in the Ni-based alloy matrix; The composite carbide reinforcing phase includes NbC, Cr3C2 and (Nb, Mo)C.

9. The application of the in-situ synthesized multiphase composite carbide-enhanced laser cladding coating as described in claim 8 in the preparation or repair of mechanical parts.

10. A mechanical component, characterized in that, The component includes a component substrate and a laser cladding coating of claim 8, which is an in-situ synthesized multiphase composite carbide-reinforced coating disposed on the working surface of the component substrate.

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