A cerium fluoride modified laser cladding powder, a preparation method thereof and a cerium fluoride modified laser cladding composite coating and application thereof

Abstract

The application provides a cerium fluoride modified laser cladding powder, a preparation method of the cerium fluoride modified laser cladding powder and application of a cerium fluoride modified laser cladding composite coating, and relates to the fields of surface engineering and laser additive manufacturing technology. The cerium fluoride modified laser cladding powder comprises the following components in percentage by mass: 316L stainless steel powder 85-90%, Ti3SiC2 powder 8-12%, and CeF3 powder 1-3%. In the application, low-melting-point CeF3 is used as a modifier, CeF3 is completely decomposed in the laser cladding process, F ‑ is emitted to purify the molten pool, Ce 3+ is selectively adsorbed at the solid-liquid interface to inhibit grain growth, Ce 3+ is in-situ oxidized to form nano CeO2 particles under high oxygen activity to realize a multi-level synergistic mechanism of dispersion strengthening and grain boundary pinning, so that the microstructure of the coating and the structure of the passivation film are double-regulated. The coating formed from the cerium fluoride modified laser cladding powder has excellent corrosion resistance and mechanical properties.

Description

Technical Field

[0001] This invention relates to the fields of surface engineering and laser additive manufacturing technology, and in particular to a cerium fluoride modified laser cladding powder and its preparation method, and a cerium fluoride modified laser cladding composite coating and its application. Background Technology

[0002] Laser cladding technology, with its advantages of high forming precision, small heat-affected zone, controllable dilution rate, and metallurgical bonding between the coating and the substrate, has become an important means of surface protection and repair for marine engineering equipment. 316L stainless steel, due to its excellent corrosion resistance and good processing performance, is widely used as a laser cladding coating material. However, the marine atmospheric environment is characterized by high chlorine concentration, high humidity, and frequent condensation. A single 316L coating is prone to pitting corrosion failure during long-term service, and its corrosion resistance cannot meet the long-term service requirements of the harsh marine environment. Studies have shown that the substrate dilution effect during laser cladding leads to a reduction of approximately 2 wt.% in the chromium content of the 316L coating, significantly weakening its pitting potential in seawater. Therefore, how to improve the comprehensive protective performance of the coating through material design has become a current research hotspot.

[0003] To improve the performance of laser cladding coatings, researchers have introduced reinforcing phases to form composite coatings. Ti3SiC2, as a typical ternary layered MAX phase ceramic material, combines the high electrical and thermal conductivity of metals with the high-temperature oxidation resistance of ceramics, exhibiting high strength, high melting point, low coefficient of thermal expansion, and good wettability with metal substrates. Existing research shows that 316L-Ti3SiC2 composite coatings prepared by laser cladding on S355B substrates exhibit excellent wear and corrosion resistance. However, traditional Ti3SiC2 reinforced coatings are prone to microscopic defects during the rapid solidification process of laser cladding, leading to poor uniformity of the passivation film and the presence of weak areas, especially in Cl-containing substrates. - Longitudinal pitting corrosion still easily occurs in corrosive media, causing deep damage and reducing electrochemical protection performance. This problem is difficult to fundamentally solve by optimizing laser process parameters.

[0004] Adding rare earth oxides is an effective way to improve the defects and performance of laser cladding coatings. In existing technologies, rare earth oxides such as CeO2, La2O3, and Y2O3 are widely used in the modification research of laser cladding coatings. Among them, CeO2, due to its unique 4f electronic structure and chemical activity, is considered one of the most effective rare earth modifiers. Its mechanism of action mainly includes: refining grains, purifying the molten pool, improving interfacial bonding, and promoting passivation film formation. However, CeO2 has the following technical drawbacks in practical applications: (1) High melting point leads to poor decomposition and dispersion: CeO2 has a melting point as high as 2600℃, which is much higher than the temperature range of the laser molten pool (1600~2200℃). Therefore, CeO2 is difficult to thermally decompose during laser cladding and mainly exists in the molten pool in the form of original particles. According to the Stokes-Einstein equation, the diffusion coefficient of particles in the molten pool is inversely proportional to its radius. CeO2 particles are prone to agglomerate in the molten pool to form micron-sized agglomerates, which are difficult to achieve uniform dispersion. The resulting CeO2 modified coating often has the problem of local enrichment and uneven distribution of Ce elements, which seriously restricts the full play of its modification potential. (2) The regulation mechanism is singular and can only achieve physical regulation: Since CeO2 is difficult to decompose, its role in the molten pool is limited to the physical level—regulating the structure through heterogeneous nucleation and grain boundary pinning, and cannot exert the chemical activity of Ce. The high chemical activity endowed by Ce's unique 4f electron orbital structure is difficult to be effectively utilized, which limits its chemical effects on molten pool purification, interface regulation, etc., resulting in limited grain refinement effect of the formed CeO2 modified coating, and easy local grain coarsening and stress concentration due to uneven pinning of agglomerated particles; (3) Side reactions are prone to occur at high temperatures: In the local high-temperature hot spots of the laser molten pool, Ti3SiC2 decomposes and releases highly active elemental Si. Studies have shown that CeO2 easily reacts with active Si at high temperatures to form cerium silicate phases (such as Ce2Si2O7 and CeSiO3). These cerium silicate phases have low hardness and will reduce the mechanical properties of the coating. At the same time, the reaction between CeO2 and TiC may generate free C, which accumulates at grain boundaries and phase interfaces to form "soft areas", further weakening the hardness and wear resistance of the coating.

[0005] In summary, the corrosion resistance and mechanical properties (hardness and tribological properties) of the existing laser-clad 316L-Ti3SiC2 composite coating still need to be improved. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a cerium fluoride modified laser cladding powder, its preparation method, and a cerium fluoride modified laser cladding composite coating and its application. The laser cladding composite coating (modified 316L-Ti3SiC2 composite coating) formed by the cerium fluoride modified laser cladding powder provided by this invention has both excellent corrosion resistance and high mechanical properties (hardness and tribological properties).

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a cerium fluoride modified laser cladding powder, comprising the following components in weight percentage: 316L stainless steel powder 85~90%, Ti3SiC2 powder 8~12%, CeF3 powder 1~3%.

[0008] Preferably, the 316L stainless steel powder has a particle size of 200-325 mesh, the Ti3SiC2 powder has a particle size of 300-400 mesh, and the CeF3 powder has a particle size of 20-50 nm.

[0009] This invention provides a method for preparing the cerium fluoride modified laser cladding powder described above, comprising the following steps: The 316L stainless steel powder, Ti3SiC2 powder and CeF3 powder are mixed to obtain the cerium fluoride modified laser cladding powder.

[0010] This invention provides a cerium fluoride modified laser cladding composite coating, which is formed by laser cladding of cerium fluoride modified laser cladding powder on the surface of a substrate. The cerium fluoride modified laser cladding powder is the cerium fluoride modified laser cladding powder described in the above technical solution or the cerium fluoride modified laser cladding powder prepared by the preparation method described in the above technical solution.

[0011] Preferably, the parameters of the laser cladding include: laser power of 1000~1500W, scanning speed of 600~800mm / s, spot diameter of 2~4mm, overlap rate of 50~70%, and defocusing amount of +3~+7mm; the laser cladding is performed under an argon protective atmosphere.

[0012] Preferably, the phase composition of the cerium fluoride modified laser cladding composite coating includes BCC phase, FCC phase, TiC phase and residual Ti3SiC2 phase.

[0013] Preferably, the cerium fluoride modified laser cladding composite coating has an average grain size of 3~6μm, a large-angle grain boundary ratio of ≥45%, and a small-angle grain boundary ratio of ≤50%.

[0014] Preferably, the surface passivation film of the cerium fluoride modified laser cladding composite coating is a composite passivation film, and the chemical composition of the composite passivation film includes Fe2O3, Cr2O3, TiO2, SiO2 and CeO. x The CeO x Contains Ce 3+ and Ce 4+ Mixed valence state.

[0015] Preferably, the cerium fluoride-modified laser cladding composite coating has an average Vickers hardness of 400~460 HV. 0.3 .

[0016] This invention provides the application of the cerium fluoride modified laser cladding composite coating described above in the surface protection and repair of parts.

[0017] This invention provides a cerium fluoride-modified laser cladding powder, comprising the following components by weight percentage: 85-90% 316L stainless steel powder, 8-12% Ti3SiC2 powder, and 1-3% CeF3 powder. This invention uses the low-melting-point rare-earth fluoride CeF3 as a modifier. CeF3 completely decomposes during the laser cladding process, releasing fluoride (CeF3). - It combines with O, S, and P impurities in the molten pool to form volatile fluorides that escape, achieving deep purification of the molten pool; the released Ce 3+ Selective adsorption at the solid-liquid interface inhibits continuous grain growth; some Ce 3+ Under high oxygen activity conditions, in-situ oxidation generates 20-50 nm nano-CeO2 particles, which are uniformly dispersed within and around grain boundaries. Through heterogeneous nucleation and grain boundary pinning, the microstructure is refined, forming a multi-level synergistic regulatory mechanism of "thermal decomposition-melt pool purification-interfacial adsorption-in-situ oxidation-dispersion strengthening." This invention achieves a leap from the traditional single physical regulation of rare earth oxides to the synergistic physical-chemical regulation of CeF3, significantly improving the corrosion resistance and mechanical properties (hardness and tribological properties) of the coating. The resulting cerium fluoride-modified laser cladding composite coating is suitable for surface protection and repair of components in harsh corrosive environments such as marine engineering equipment and shipbuilding.

[0018] The results of the examples show that the cerium fluoride-modified laser cladding composite coating (316L-Ti3SiC2-CeF3 composite coating) formed by the cerium fluoride-modified laser cladding powder provided by the present invention, based on a multi-level synergistic regulation mechanism, possesses both excellent corrosion resistance and high mechanical properties. Specifically, regarding corrosion resistance: the cerium fluoride-modified laser cladding composite coating formed by the cerium fluoride-modified laser cladding powder described in the present invention has a corrosion potential of -0.098 to -0.112 V, a pitting potential of -0.896 to -0.912 V, and a charge transfer resistance ≥4.2 × 10⁻⁶ V in 3.5 wt.% NaCl solution. 4 Ω·cm 2 After corrosion, the surface exhibits a unique characteristic of increased diameter and shallower depth disc-shaped pitting corrosion, effectively confining the corrosion to the coating surface and preventing deep damage to the substrate. Regarding mechanical properties (hardness and tribological properties): the average hardness of the cerium fluoride modified laser cladding composite coating is 400~460 HV. 0.3 Compared with pure 316L coating and CeO2 modified coating, it can significantly improve the coating. Friction and wear test shows that the coating of the present invention has shallower furrows and fewer spalling pits. The wear mechanism is mainly abrasive wear and fatigue wear, but the degree is the least. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the laser cladding process in an embodiment of the present invention; Figure 2The images shown are SEM images of the cross-sectional morphology of the coatings prepared in Example 1 and Comparative Examples 1-3 of this invention. Figure 2 (a) corresponds to the coating prepared in Example 1, (b) corresponds to the coating prepared in Example 2, (c) corresponds to the coating prepared in Example 1, and (d) corresponds to the coating prepared in Example 3. Figure 3 This is a comparison of the XRD patterns of the coatings prepared in Example 1 and Comparative Examples 1-3; Figure 4 The images show the kernel mean orientation difference (KAM) and grain boundary distribution of the EBSD coatings prepared in Example 1 and Comparative Example 2. Figure 4 Within the dashed box at the top center, (a1) ~ (d1) are phase distribution diagrams, (a) ~ (d) are specific data on phase distribution, (a) and (a1) correspond to the upper region of the coating in Example 2, (b) and (b1) correspond to the middle region of the coating in Example 2, (c) and (c1) correspond to the upper region of the coating in Example 1, and (d) and (d1) correspond to the middle region of the coating in Example 1. Figure 4 Within the dashed box in the lower middle, (a2) ~ (d2) are the normal orientation inverse pole figures, (a) ~ (d) are grain size histograms, (a) and (a2) correspond to the upper region of the coating in Example 2, (b) and (b2) correspond to the middle region of the coating in Example 2, (c) and (c2) correspond to the upper region of the coating in Example 1, and (d) and (d2) correspond to the middle region of the coating in Example 1; Figure 5 XPS Ce 3d spectrum of the coating prepared in Example 1; Figure 6 The diagram shows the three-electrode electrochemical testing system (a), Tafel polarization curve (b), Nyquist plot (c), equivalent circuit diagram (d), Bode plot (impedance mode-frequency curve) (e), Bode plot (phase angle-frequency curve) (f), and Mott-Schottky curve (g). Figure 7 These are comparison images of the surface morphology of the coatings prepared in Example 1 and Comparative Examples 1-2 after electrochemical etching. Figure 7 In the figures, (a) shows the morphology of the coating in Comparative Example 1 before corrosion, (a1) and (a2) show the morphology of the coating in Comparative Example 1 after corrosion at different magnifications (SEM images), (b) shows the morphology of the coating in Comparative Example 2 after corrosion, (b1) and (b2) show the morphology of the coating in Comparative Example 2 after corrosion at different magnifications, (c) shows the morphology of the coating in Example 1 after corrosion, (c1) and (c2) show the morphology of the coating in Example 1 after corrosion at different magnifications; Figure 8 These are schematic diagrams and data comparison charts of the wear of the coatings prepared in Example 1 and Comparative Examples 1-3. Figure 8(a) is a schematic diagram of hardness testing, (b) is a schematic diagram of friction and wear testing, (c) is hardness data, (d) is average hardness, (e) is friction coefficient curve, and (f) is average friction coefficient and wear amount. Figure 9 Images (a) to (d) are SEM images of the wear morphology of the sample, and images (a1) to (d1) are white light interference morphology images of the sample. Figure 9 In the example, (c) and (c1) correspond to Example 1, (a) and (a1) correspond to Example 1, (b) and (b1) correspond to Example 2, and (d) and (d1) correspond to Example 3. Detailed Implementation

[0020] This invention provides a cerium fluoride modified laser cladding powder, comprising the following components in weight percentage: 316L stainless steel powder 85~90%, Ti3SiC2 powder 8~12%, CeF3 powder 1~3%.

[0021] Unless otherwise specified, all raw materials and equipment involved in this invention are commercially available products well known in the art.

[0022] The cerium fluoride-modified laser cladding powder provided by this invention comprises 85-90% 316L stainless steel powder, which can be 85%, 86%, 87%, 88%, 89%, and 90%. In this invention, the particle size of the 316L stainless steel powder is preferably 200-325 mesh; in the embodiments of this invention, the 316L stainless steel powder is spherical powder with a purity ≥99%.

[0023] The cerium fluoride modified laser cladding powder provided by the present invention comprises 8-12% Ti3SiC2 powder, which can be 8%, 9%, 10%, 11%, or 12%. In the present invention, the particle size of the Ti3SiC2 powder is preferably 300-400 mesh; in the embodiments of the present invention, the Ti3SiC2 powder is an irregular powder with a purity ≥99%.

[0024] The cerium fluoride modified laser cladding powder provided by the present invention comprises 1-3% CeF3 powder, which can be 1%, 2% or 3%. In the present invention, the particle size of the CeF3 powder is preferably 20-50 nm; in the embodiments of the present invention, the CeF3 powder is an irregular powder with a purity ≥99%.

[0025] CeO2, due to its high melting point (2600℃), is difficult to decompose in the laser cladding pool and can only exist as micron-sized unmelted particles. Its microstructure is controlled through physical methods such as heterogeneous nucleation and grain boundary pinning, failing to fully utilize the chemical activity of Ce. This invention, for the first time, uses the low-melting-point rare-earth fluoride CeF3 (melting point 1460℃) as a modifier for laser cladding of the 316L-Ti3SiC2 composite coating. Utilizing its low melting point, complete decomposition is achieved during the laser cladding process, realizing multi-level synergistic regulation of "thermal decomposition-melt pool purification-interfacial adsorption-in-situ oxidation-dispersion strengthening." Specifically, through F... - Evaporation purification of molten pool, Ce 3+ Selective adsorption at the solid-liquid interface inhibits grain growth and Ce 3+ In-situ oxidation generates nano-CeO2 particles, achieving a multi-level synergistic mechanism of dispersion strengthening and grain boundary pinning. This enables dual regulation of the coating microstructure and passivation film structure, resulting in a composite coating with both excellent corrosion resistance and high mechanical properties.

[0026] This invention provides a method for preparing the cerium fluoride modified laser cladding powder described above, comprising the following steps: The 316L stainless steel powder, Ti3SiC2 powder and CeF3 powder are mixed to obtain the cerium fluoride modified laser cladding powder.

[0027] In this invention, the mixing is preferably mechanical mixing, and the mechanical mixing time is preferably 2-4 hours. In an embodiment of this invention, the mechanical mixing is carried out in a planetary powder mixer, and the rotation speed of the planetary powder mixer is preferably 80 r / min. After the mixing, a uniform cladding powder is obtained.

[0028] The preparation process of this invention is simple, CeF3 raw material is widely available, the cost is controllable, and it is suitable for large-scale industrial production.

[0029] This invention provides a cerium fluoride modified laser cladding composite coating, which is formed by laser cladding of cerium fluoride modified laser cladding powder on the surface of a substrate. The cerium fluoride modified laser cladding powder is the cerium fluoride modified laser cladding powder described in the above technical solution or the cerium fluoride modified laser cladding powder prepared by the preparation method described in the above technical solution.

[0030] In this invention, the laser cladding parameters preferably include: laser power of 1000~1500W, which can be 1000, 1100, 1200, 1300, 1400 or 1500W; scanning speed of 600~800mm / s, which can be 600, 650, 700, 750 or 800mm / s; spot diameter of 2~4mm, which can be 2, 3 or 4mm; overlap rate of 50~70%, which can be 50%, 60% or 70%; and defocusing amount of +3~+7mm, which can be +3, +4, +5, +6 or +7mm. In this invention, the laser cladding is preferably performed under an argon protective atmosphere to prevent excessive oxidation of the molten pool. The argon is preferably high-purity argon (purity ≥99.99%), and the argon flow rate is preferably 5~10L / min. The laser cladding uses a coaxial powder feeding method, and the powder feeding rate is preferably 5~20g / min, which can be 8g / min. After the laser cladding is completed, the furnace is allowed to cool naturally to room temperature.

[0031] In this invention, the substrate is preferably carbon steel, stainless steel, or ordinary alloy steel, and the carbon steel can be S355 carbon steel. Before laser cladding, the substrate is preferably pretreated, which preferably includes grinding the substrate surface to a roughness Ra≤0.2μm, followed by cleaning and drying; the cleaning is preferably ultrasonic cleaning with anhydrous ethanol and acetone in sequence to remove surface oil and impurities; the drying temperature can be 60℃.

[0032] In this embodiment of the invention, the specific operation of laser cladding is as follows: the cerium fluoride modified laser cladding powder is laid (i.e., powder is laid) on the surface of the substrate to form a pre-coated layer; the pre-coated layer is then laser clad.

[0033] During the laser cladding process, CeF3 powder completely decomposes at the high temperature of laser cladding, releasing F... - It combines with impurities such as O, S, and P in the molten pool to form volatile fluorides (such as HF, SiF4 (Si comes from the thermal decomposition of Ti3SiC2 powder), and PF3) which escape, achieving deep purification of the molten pool; CeF3 decomposes to produce Ce 3+ Selective adsorption at the solid-liquid interface inhibits continuous grain growth by reducing interfacial energy; simultaneously, some Ce... 3+ Under the oxygen activity conditions of the molten pool, in-situ oxidation generates 20-50 nm nano-CeO2 particles, which are uniformly dispersed at grain boundaries and within the grains, further refining the microstructure through heterogeneous nucleation and grain boundary pinning. Simultaneously, during the laser cladding process, Ti3SiC2 undergoes partial decomposition at localized high-temperature hotspots, releasing Ti that reacts with free C diffused from the substrate to form a TiC reinforcing phase.

[0034] Figure 1This is a schematic diagram of the laser cladding process in an embodiment of the present invention. In this invention, conventional laser cladding equipment can be used for the laser cladding, requiring no special post-processing, and the process is stable and controllable. After laser cladding, the cladding layer and the substrate form a metallurgical bond.

[0035] In this invention, the cerium fluoride modified laser cladding composite coating is a CeF3 modified laser cladding 316L-Ti3SiC2 composite coating.

[0036] In this invention, the phase composition of the cerium fluoride modified laser cladding composite coating includes BCC phase, FCC phase, TiC phase (TiC phase is generated by the decomposition of Ti3SiC2 under local high temperature during laser cladding and its in-situ reaction with free C) and residual Ti3SiC2 phase.

[0037] In this invention, the average grain size of the cerium fluoride-modified laser cladding composite coating is 3~6μm, with large-angle grain boundaries (HAGB, orientation difference >15°) accounting for ≥45% and small-angle grain boundaries (LAGB, orientation difference 2°~10°) accounting for ≤50%. This invention achieves multi-scale optimization of the coating microstructure through the multi-level synergistic mechanism of CeF3. Compared with the 316L-Ti3SiC2 coating, the average grain size of the cerium fluoride-modified laser cladding composite coating of this invention is significantly refined; furthermore, the proportion of large-angle grain boundaries is significantly increased, while the proportion of small-angle grain boundaries is significantly decreased. This optimization of the grain boundary structure is of great significance: a high proportion of large-angle grain boundaries can effectively hinder dislocation movement and crack propagation, while reducing the number of short-range corrosion channels; while small-angle grain boundaries, as dislocation array structures, have lower energy but a looser structure, easily becoming Cl... - Rapid penetration pathways. Therefore, this invention simultaneously improves the mechanical properties and corrosion resistance of the coating through grain boundary optimization.

[0038] In this invention, the surface passivation film of the cerium fluoride modified laser cladding composite coating is a composite passivation film, and the chemical composition of the composite passivation film includes Fe2O3, Cr2O3, TiO2, SiO2 and CeO. x The CeO x Contains Ce 3+ and Ce 4+ Mixed valence state; that is, the surface of the cerium fluoride modified laser cladding composite coating forms a Ce-containing state. 3+ / Ce 4+ Fe2O3 / Cr2O3-TiO2-SiO2-CeO in mixed valence states x Composite passivation film. The passivation film of the CeO2 modified coating does not contain Ce, and the passivation film structure is a simple FeOOH / Cr2O3-TiO2-SiO2. This invention, through CeF3 modification, for the first time forms a Ce-containing layer on the surface of a laser cladding coating.3+ / Ce 4+ Fe2O3 / Cr2O3-TiO2-SiO2-CeO in mixed valence states x The composite passivation film has the following unique advantages: (1) Ce 3+ / Ce 4+ Mixed valence states endow the passivation film with redox buffering capacity: when oxidizing substances in the corrosive medium invade, Ce... 3+ It can be oxidized to Ce 4+ Consuming oxidants, playing a "self-repairing" or "corrosion-inhibiting" role; (2) Ce 4+ / Ce 3+ Redox effect on promoting Fe 2+ To Fe 3+ The transformation generates a denser Fe2O3, further improving the density and stability of the passivation film; (3) Ce 3+ Enhanced surface hydroxylation induced, improving resistance to Cl - The complexing ability of Ce in the passivation film of the coating of this invention. XPS analysis confirmed that Ce 4+ / Ce 3+ Mixed valence states exist stably, Fe 3+ The proportion has increased significantly.

[0039] In this invention, the average Vickers hardness of the cerium fluoride modified laser cladding composite coating is 400~460 HV. 0.3 Its performance is more than 100% higher than that of pure 316L laser cladding coating.

[0040] This invention provides the application of the cerium fluoride modified laser cladding composite coating described above in the surface protection and repair of parts.

[0041] The cerium fluoride modified laser cladding composite coating provided by this invention is suitable for surface protection and repair of parts in harsh corrosive environments in fields such as marine engineering equipment, shipbuilding, petrochemicals, and polar equipment.

[0042] To further illustrate the present invention, the following detailed descriptions, in conjunction with examples, illustrate the cerium fluoride modified laser cladding powder and its preparation method, as well as the cerium fluoride modified laser cladding composite coating and its application. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1 A cerium fluoride-modified laser cladding composite coating is prepared by the following method: (1) Matrix pretreatment S355 carbon steel was selected as the base material and wire-cut into samples with dimensions of 50mm × 50mm × 5mm. The sample surface was progressively polished using 240#, 400#, 600#, 800#, 1000#, 1500#, and 2000# sandpaper until the surface roughness Ra reached 0.1μm. The polished samples were then immersed in anhydrous ethanol and acetone, respectively, and ultrasonically cleaned for 15 minutes each to remove surface oil and impurities. Finally, they were dried in a drying oven at 60℃ for later use.

[0044] (2) Powder preparation and mixing Weigh the following raw material powders by mass percentage: 88 wt.% of 316L spherical stainless steel powder (particle size 270 mesh, purity ≥99.5%), 10 wt.% of Ti3SiC2 irregular powder (particle size 325 mesh, purity ≥99.5%), and 2 wt.% of CeF3 irregular powder (particle size 20~50 nm, purity ≥99.5%). Place the weighed powders in a planetary powder mixer and mechanically mix them at a speed of 80 r / min for 2 hours to obtain a uniformly mixed cladding powder.

[0045] (3) Laser cladding Laser cladding experiments were conducted using an XL-F2000W fiber continuous laser processing system. The laser cladding process parameters were as follows: laser power 1200W, scanning speed 700mm / s, spot diameter 3mm, overlap rate 60%, and defocusing distance +5mm. During cladding, a coaxial powder feeding method was used, with a powder feeding rate of 8g / min and a powder layer thickness of 1mm. High-purity argon gas (purity ≥99.99%) was simultaneously introduced as a protective gas at a flow rate of 10L / min to prevent oxidation of the molten pool. After laser cladding, the sample was allowed to cool naturally to room temperature with the furnace, resulting in a coating thickness of 0.7~0.8mm.

[0046] Example 2 This embodiment is basically the same as Embodiment 1, except for the ratio of raw material powder and some laser cladding process parameters.

[0047] Powder composition: 85 wt.% 316L spherical stainless steel powder, 12 wt.% Ti3SiC2 irregular powder, and 3 wt.% CeF3 irregular powder.

[0048] Laser cladding process: laser power 1300W, scanning speed 650mm / s, spot diameter 3mm, overlap rate 60%, defocusing amount +5mm.

[0049] Example 3 This embodiment is basically the same as Embodiment 1, except for the ratio of raw material powder and some laser cladding process parameters.

[0050] Powder composition: 90 wt.% 316L spherical stainless steel powder, 8 wt.% Ti3SiC2 irregular powder, and 2 wt.% CeF3 irregular powder.

[0051] Laser cladding process: laser power 1100W, scanning speed 750mm / s, spot diameter 3mm, overlap rate 60%, defocusing amount +5mm.

[0052] Example 4 This embodiment is basically the same as Embodiment 1, except for the laser cladding process parameters.

[0053] Laser cladding process: laser power 1200W, scanning speed 700mm / s, spot diameter 4mm, overlap rate 50%, defocusing amount +7mm.

[0054] Comparative Example 1 (Pure 316L coating) This comparative example is basically the same as Example 1, except that Ti3SiC2 and CeF3 are not added, and only 100wt.% 316L spherical stainless steel powder is used for laser cladding.

[0055] Comparative Example 2 (316L and Ti3SiC2 modified coatings) This comparative example is basically the same as Example 1, except that CeF3 powder is not added. The powder ratio is: 90 wt.% of 316L spherical stainless steel powder and 10 wt.% of Ti3SiC2 irregular powder.

[0056] Comparative Example 3 (CeO2 modified coatings of 316L and Ti3SiC2) This comparative example is basically the same as Example 1, except that CeF3 is not added, but CeO2 is added instead. The powder ratio is: 88 wt.% of 316L spherical stainless steel powder, 10 wt.% of Ti3SiC2 irregular powder, and 2 wt.% of CeO2 powder.

[0057] The laser cladding layers prepared in the examples and comparative examples were characterized and their performance was tested, as follows: (1) Sample preparation for characterization The clad samples were cut perpendicular to the laser scanning direction to obtain samples with dimensions of 10mm × 10mm × 5.6mm. Samples for microstructure observation were heat-mounted and then sequentially polished with 800#, 1200#, 2000#, 3000#, 4000#, and 5000# sandpaper. They were then mechanically polished to a mirror finish using 3.5μm, 1.5μm, and 0.5μm diamond polishing agents, respectively. After immersion in aqua regia (HCl:HNO3 = 3:1) for approximately 70 seconds, they were immediately rinsed with anhydrous ethanol and dried. Samples for electrochemical testing had copper wires soldered to the back, fixed with conductive silver paste, and then sealed with epoxy resin, leaving only a 10mm × 10mm working surface. Samples for hardness and friction / wear testing were directly heat-mounted and polished to a mirror finish without etching.

[0058] (2) Characterization of coating microstructure (2.1) Macroscopic morphology and microstructure The cross-section of the coating was observed using a scanning electron microscope (SEM).

[0059] Figure 2 The images show the cross-sectional SEM morphology of the coatings prepared in Example 1 and Comparative Examples 1-3. Figure 2 (a) corresponds to the coating prepared in Example 1, (b) corresponds to the coating prepared in Example 2, (c) corresponds to the coating prepared in Example 1, and (d) corresponds to the coating prepared in Example 3.

[0060] The results in the figure show that the interface between the coating and the substrate is smooth and arc-shaped, without macroscopic defects such as pores and cracks. The coating structure is dense, indicating that the coating and the substrate have formed a good metallurgical bond. The coating thicknesses prepared in Example 1 and Comparative Examples 1-3 are 0.7-0.85 mm.

[0061] (2.2) Phase composition Phase analysis of the coating surface was performed using X-ray diffraction (XRD).

[0062] Figure 3 This is a comparison of the XRD patterns of the coatings prepared in Example 1 and Comparative Examples 1-3. Figure 3 In the example, S2 corresponds to Example 1, S0 corresponds to Example 1, S1 corresponds to Example 2, and S3 corresponds to Example 3.

[0063] The results show that the coating in this embodiment mainly consists of BCC phase (α-Fe) and FCC phase (γ-Fe), while diffraction peaks of TiC phase and residual Ti3SiC2 phase were also detected. The TiC diffraction peak shows a slight right shift relative to the standard PDF card, indicating that the TiC lattice undergoes compression distortion.

[0064] (2.3) Grain size and grain boundary characteristics Electron backscatter diffraction (EBSD) was used to analyze the upper and middle regions of the coating.

[0065] Figure 4 The images show the kernel mean orientation difference (KAM) and grain boundary distribution of the EBSD coatings prepared in Example 1 and Comparative Example 2. Figure 4 Within the upper dashed box, (a1) to (d1) are phase distribution diagrams (red: face-centered cubic FCC phase, blue: body-centered cubic BCC phase), (a) to (d) are specific data on phase distribution, (a) and (a1) correspond to the upper region of the coating in Example 2, (b) and (b1) correspond to the middle region of the coating in Example 2, (c) and (c1) correspond to the upper region of the coating in Example 1, and (d) and (d1) correspond to the middle region of the coating in Example 1; Figure 4 Within the dashed box in the lower center, (a2) ~ (d2) are the normal orientation inverse pole figures, (a) ~ (d) are grain size histograms, (a) and (a2) correspond to the upper region of the coating in Example 2, (b) and (b2) correspond to the middle region of the coating in Example 2, (c) and (c2) correspond to the upper region of the coating in Example 1, and (d) and (d2) correspond to the middle region of the coating in Example 1.

[0066] The results show that the proportion of large-angle grain boundaries (black) in the coating of the present invention embodiment is significantly higher than that in Comparative Example 2. The average grain size of the coating of the present invention embodiment is 4.87 μm, the proportion of large-angle grain boundaries (HAGB, orientation difference > 15°) is 48.5%, and the proportion of small-angle grain boundaries (LAGB, orientation difference 2°~10°) is 47.8%. The local orientation difference (KAM) map shows that the overall KAM value of the coating is low, with only a few local small high-value areas at grain boundary intersections, indicating low lattice distortion and sufficient internal stress release.

[0067] (2.4) Chemical state of passivation film X-ray photoelectron spectroscopy (XPS) was used to analyze the passivation film on the coating surface before electrochemical testing.

[0068] Figure 5 The image shows the XPS Ce 3d spectrum of the coating prepared in Example 1.

[0069] The Ce 3d spectrum exhibits a complex multipeak structure, confirming that Ce 3+ and Ce 4+ Mixed valence states coexist in the passivation film.

[0070] High-resolution O 1s spectroscopy characterization revealed that the passivation film contains lattice oxygen O. 2- (approximately 530 eV), hydroxyl group OH - (Approximately 533 eV) and adsorbed water H2O (approximately 535 eV). The Fe 2p spectrum shows that Fe... 3+ The relative intensity of the peak is significantly higher than that of Fe.2+ The peaks are shifted towards higher binding energies. The Cr 2p spectrum shows that Cr... 3+ 2p 1 / 2 and Cr 3+ 2p 3 / 2 Characteristic peaks. The Ti 2p spectrum shows Ti... 4+ 2p 1 / 2 and Ti 4+ 2p 3 / 2 Characteristic peaks, corresponding to TiO2. The Si 2p spectrum shows Si... 4+ The characteristic peak (approximately 104 eV) corresponds to SiO2.

[0071] (3) Electrochemical performance The electrochemical performance of the coating in 3.5 wt.% NaCl solution was tested using an electrochemical workstation.

[0072] Figure 6 The diagram shows the three-electrode electrochemical testing system (a), Tafel polarization curve (b), Nyquist plot (c), equivalent circuit diagram (d), Bode plot (impedance mode-frequency curve) (e), Bode plot (phase angle-frequency curve) (f), and Mott-Schottky curve (g). Figure 6 In this context, S2 corresponds to Example 1, S0 corresponds to Example 1, S1 corresponds to Example 2, and S3 corresponds to Example 3.

[0073] Test results show that the corrosion potential (Ecorr) of the coating in Example 1 of this invention is -0.105V (vs. SCE), and the corrosion current density (icorr) is 0.00273A / cm². 2 The pitting potential (Epit) is -0.905V (vs. SCE), and the passivation current density (ip) is 0.01201A / cm. 2 Electrochemical impedance spectroscopy (EIS) results showed that Nyquist had the largest capacitive arc radius and a charge transfer resistance (Rct) of 4.97 × 10⁻⁶. 4 Ω·cm 2 The Mott-Schottky test results showed that the passivation film carrier concentration (ND) was 9.33 × 10⁻⁶. 20 / cm 3 The flat band potential (Efb) is -0.397V (n-type region); the maximum passivation film thickness is calculated to be 38.4nm (4.7 times greater than that of pure 316L).

[0074] After electrochemical testing of the samples in Example 1 and Comparative Examples 1-2, the surface corrosion morphology was observed using SEM.

[0075] Figure 7These are comparison images of the surface morphology of the coatings prepared in Example 1 and Comparative Examples 1-2 after electrochemical etching. Figure 7 In the figures, (a) shows the morphology of the coating in Comparative Example 1 before corrosion, (a1) and (a2) show the morphology of the coating in Comparative Example 1 after corrosion at different magnifications (SEM images), (b) shows the morphology of the coating in Comparative Example 2 after corrosion, (b1) and (b2) show the morphology of the coating in Comparative Example 2 after corrosion at different magnifications, (c) shows the morphology of the coating in Example 1 after corrosion, (c1) and (c2) show the morphology of the coating in Example 1 after corrosion at different magnifications. Comparative Example 1 (pure 316L coating) has a large number of deep, penetrating pits on its surface. The pit edges are cracked, and porous, honeycomb-like corrosion products accumulate inside the pits. Some pits have penetrated the entire coating, exposing the underlying substrate. Comparative Example 2 (316L and Ti3SiC2 modified coating) has pits confined to the coating surface, appearing bowl-shaped. The pit edges are smooth, without obvious cracks, and the corrosion products inside the pits are dense, exhibiting a characteristic of "consistent diameter and decreasing depth". Example 1 (Coating of the Invention): The surface shows only shallow, dish-shaped pits with smooth walls and almost no corrosion product accumulation. The pit diameter is approximately 40-50 μm, but the depth is extremely shallow, exhibiting a typical lateral expansion characteristic of "increasing diameter and decreasing depth." Corrosion is effectively confined to the coating surface, preventing deep erosion into the substrate. This transformation in corrosion behavior is due to: the increased HAGB content after CeF3 modification reduces short-path corrosion channels, while Ce... 3+ In-situ oxidation consumes the oxidant and blocks ion diffusion channels, forcing Cl... - It migrates laterally along the surface of the passivation film.

[0076] (4) Mechanical properties The cross-sectional hardness of the coating was tested using a micro Vickers hardness tester. Test conditions: The Lelot MHVS-1000Z touchscreen micro Vickers hardness tester was used, with parameters set as follows: load 200 gf, holding time 10 s. To improve data reliability, each test was repeated three times, and the average value was used to create an error bar as the final result. The tribological properties of the coating were tested using a reciprocating friction and wear tester. Test parameters: reciprocating friction mode, applied load 20 N, test duration 30 min, reciprocating frequency 300 r / min, reciprocating diameter 5 mm, and ZrO2 ceramic balls with a diameter of 5.0 mm were used for the friction pair.

[0077] Figure 8 These are schematic diagrams and data comparison charts of the wear of the coatings prepared in Example 1 and Comparative Examples 1-3. Figure 8 (a) is a schematic diagram of hardness testing, (b) is a schematic diagram of friction and wear testing, (c) is hardness data (HAZ represents the heat-affected zone), (d) is average hardness, (e) is the friction coefficient curve, and (f) is the average friction coefficient and wear amount. Figure 8In this context, S2 corresponds to Example 1, S0 corresponds to Example 1, S1 corresponds to Example 2, and S3 corresponds to Example 3.

[0078] The results showed that the average hardness of the coating in Example 1 of the present invention was 433.744 HV. 0.3 A purer 316L coating (194.339 HV) 0.3 The improvement is 123%, compared to the CeO2 modified coating (398.728 HV). 0.3 The hardness increased by 8.8%. The significant increase in hardness is due to the multi-level synergistic effect of grain refinement strengthening, dispersion strengthening, and grain boundary strengthening.

[0079] According to the friction and wear test, the average friction coefficient of the coating in Example 1 was 0.63, and the wear amount and friction coefficient were lower than those of the 316L and Ti3SiC2 modified coatings and the CeO2 modified coating.

[0080] After performing tribological tests on the samples of Example 1 and Comparative Examples 1-3, the surface morphology of the wear tracks was observed using SEM. The results are as follows: Figure 9 As shown, Figure 9 Images (a) to (d) are SEM images of the wear morphology of the sample, and images (a1) to (d1) are white light interference morphology images of the sample. Figure 9 In Comparative Example 1, (c) and (c1) correspond to Example 1, (a) and (a1) correspond to Example 1, (b) and (b1) correspond to Example 2, and (d) and (d1) correspond to Example 3. The results show that the wear surface of Comparative Example 1 (pure 316L coating) exhibits a periodic wavy "protrusion-recession" serrated morphology, with no continuous deep grooves, indicating primarily oxidative wear. In Comparative Example 2 (316L and Ti3SiC2 modified coating), the pitting is confined to the coating surface, appearing bowl-shaped. The pit edges are smooth, without obvious cracks. The wear surface within the pits contains numerous continuous furrows distributed along the sliding direction, arranged parallel to each other with uniform spacing. Irregularly shaped spalling pits are visible in some areas, indicating primarily abrasive and fatigue wear, with a relatively severe degree of wear. Although the wear surface of Example 1 (the coating of the present invention) also has furrows, the depth and width are significantly reduced, the spalling pits are sparse and small in size, and the wear is mainly abrasive wear and fatigue wear, but the wear degree is the lightest, which is consistent with the hardness test results. This result is consistent with the prediction of the Arcard wear model theory: high hardness materials have a stronger ability to resist abrasive cutting and furrowing.

[0081] Table 1 summarizes the main performance parameters of the above embodiments 1-4 and comparative examples 1-3 to more intuitively demonstrate the technical effects of the present invention.

[0082] Table 1 Comparison of coating performance between the examples and comparative examples.

[0083] As can be seen from Table 1: (1) Compared with Comparative Example 1 (pure 316L coating), the corrosion potential of the coatings in Examples 1 to 4 of the present invention increased by 0.38 to 0.39V, the pitting potential shifted positively by 0.13 to 0.14V, the charge transfer resistance increased by 36 to 42 times, and the average hardness increased by 2.0 to 2.3 times, indicating that CeF3 modification has a significant optimizing effect on the coating structure and properties.

[0084] (2) Compared with Comparative Example 2 (316L and Ti3SiC2 modified coatings), the grain size of Example 1 of the present invention is further refined (from 5.64 μm to 4.87 μm), the proportion of large-angle grain boundaries is further increased (from 40.5% to 48.5%), and the average hardness is increased from 399.978 HV. 0.3 Increased to 433.744 HV 0.3 ).

[0085] (3) Compared with Comparative Example 3 (CeO2 modified coating of 316L and Ti3SiC2), the hardness of Example 1 of the present invention is 398.728 HV. 0.3 Increased to 433.744 HV 0.3 The charge transfer resistance increased by about 2.1 times, indicating that the synergistic effect of Ti3SiC2 and CeF3 is of great significance in improving the overall performance of the coating.

[0086] (4) Through the comparison of Examples 1 to 4, it can be seen that within the range of raw material ratio and process parameters defined by the present invention, coatings with excellent performance can be obtained. Among them, the ratio (316L:Ti3SiC2:CeF3=88:10:2) and process parameters (laser power 1200W, scanning speed 700mm / s) of Example 1 are the optimal solutions.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 cerium fluoride-modified laser cladding powder, characterized in that, The components include the following components by mass percentage: 316L stainless steel powder 85~90%, Ti3SiC2 powder 8~12%, CeF3 powder 1~3%.

2. The cerium fluoride modified laser cladding powder according to claim 1, characterized in that, The 316L stainless steel powder has a particle size of 200-325 mesh, the Ti3SiC2 powder has a particle size of 300-400 mesh, and the CeF3 powder has a particle size of 20-50 nm.

3. The method for preparing the cerium fluoride modified laser cladding powder according to claim 1 or 2, characterized in that, Includes the following steps: The 316L stainless steel powder, Ti3SiC2 powder and CeF3 powder are mixed to obtain the cerium fluoride modified laser cladding powder.

4. A cerium fluoride-modified laser cladding composite coating, characterized in that, The cerium fluoride modified laser cladding powder is formed by laser cladding on the surface of a substrate. The cerium fluoride modified laser cladding powder is the cerium fluoride modified laser cladding powder according to claim 1 or 2, or the cerium fluoride modified laser cladding powder prepared by the preparation method according to claim 3.

5. The cerium fluoride-modified laser cladding composite coating according to claim 4, characterized in that, The parameters of the laser cladding include: laser power of 1000~1500W, scanning speed of 600~800mm / s, spot diameter of 2~4mm, overlap rate of 50~70%, and defocusing amount of +3~+7mm; the laser cladding is carried out under an argon protective atmosphere.

6. The cerium fluoride-modified laser cladding composite coating according to claim 4 or 5, characterized in that, The phase composition of the cerium fluoride modified laser cladding composite coating includes BCC phase, FCC phase, TiC phase and residual Ti3SiC2 phase.

7. The cerium fluoride-modified laser cladding composite coating according to claim 4 or 5, characterized in that, The average grain size of the cerium fluoride modified laser cladding composite coating is 3~6μm, with large-angle grain boundaries accounting for ≥45% and small-angle grain boundaries accounting for ≤50%.

8. The cerium fluoride-modified laser cladding composite coating according to claim 4 or 5, characterized in that, The surface passivation film of the cerium fluoride modified laser cladding composite coating is a composite passivation film, and the chemical composition of the composite passivation film includes Fe2O3, Cr2O3, TiO2, SiO2 and CeO. x The CeO x Contains Ce 3+ and Ce 4+ Mixed valence state.

9. The cerium fluoride-modified laser cladding composite coating according to claim 4 or 5, characterized in that, The average Vickers hardness of the cerium fluoride-modified laser cladding composite coating is 400~460 HV. 0.3 .

10. The application of the cerium fluoride modified laser cladding composite coating according to any one of claims 4 to 9 in the surface protection and repair of parts.

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