Plasma spraying additive manufacturing iron cultural relic defect matching method

Abstract

The invention belongs to the technical field of cultural relic repair and protection, and discloses a plasma spraying additive manufacturing iron cultural relic defect repairing method, which comprises the following steps of: spraying gray cast iron powder to a to-be-repaired area of an iron cultural relic through a plasma spraying method, and then polishing to obtain a to-be-repaired area of the iron cultural relic; the geometrical shape and the size of the plasma spraying coating deposition restoration body are matched with the shape and the size of the to-be-matched area of the iron cultural relic, and matching is completed; the plasma spraying parameters comprise that the spraying distance is 100-130 mm, the current is 300-450 A, the voltage is 110-130 V, mixed carrier gas of inert gas and hydrogen is adopted, the flow of the inert gas is 140-160 L / min, and the flow of the hydrogen is 3-5 L / min. The gray cast iron powder is used as the raw material, the plasma spraying technology is adopted for repairing the defect area on the surface of the iron cultural relic, deposition of a high-quality metal coating can be achieved under the condition of low heat influence, the original form of the cultural relic is effectively recovered, and the composition, the structure and the physical property are highly compatible with an iron object base body.

Description

Technical Field

[0001] This invention belongs to the field of cultural relic restoration and protection technology, specifically relating to a method for repairing and replacing defects in iron cultural relics using plasma spraying additive manufacturing. Background Technology

[0002] Iron artifacts are an important part of cultural heritage, encompassing weapons, ritual objects, agricultural tools, and architectural components, possessing historical, artistic, and scientific value. Due to long-term burial or exposure to complex environments, iron artifacts commonly suffer from accelerated corrosion, surface peeling, and structural defects, resulting in compromised morphological integrity and degraded mechanical properties. The protection and restoration of these artifacts is therefore urgently needed. Among these, the repair and replacement of damaged parts is a core step in restoring the original form and structural stability of the artifact; the rationality of the technical approach directly determines the authenticity, durability, and ethical compliance of the restoration results.

[0003] Currently, traditional restoration methods mainly employ welding and epoxy resin filling to repair damaged areas. While welding provides strong connections, its high-temperature process can easily lead to thermal deformation and structural deterioration of the artifact, even causing secondary damage. Organic fillers, on the other hand, suffer from rapid aging and poor durability, failing to meet the requirements for long-term preservation. In recent years, advanced surface engineering technologies such as cold spraying, laser cladding, and plasma spraying have been gradually introduced into the field of cultural relic preservation. Among these, plasma spraying technology, due to its high deposition efficiency, good bonding strength, and wide applicability, shows promising application prospects in metal coating preparation. However, for the specific needs of iron artifact restoration, there is a lack of systematic research on using gray cast iron powder as a spraying material to achieve a high degree of matching with the original material's composition and properties. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a method for repairing defects in iron cultural relics using plasma spraying additive manufacturing. This invention uses gray cast iron powder as raw material and employs plasma spraying technology to repair defective areas on the surface of iron cultural relics. This invention can achieve the deposition of a high-quality metal coating under relatively low heat-affected conditions, effectively restoring the original form of the cultural relic while maintaining high compatibility with the original substrate in terms of composition, structure, and physical properties. This improves the stability and reversibility of the repair effect, providing a new technical path for the scientific restoration of iron cultural relics.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for repairing defects in iron artifacts manufactured using plasma spraying additive manufacturing includes the following steps: Gray cast iron powder is sprayed onto the area of ​​the iron artifact to be repaired using a plasma spraying method, forming a plasma sprayed coating deposition restoration body in the area of ​​the iron artifact to be repaired; The plasma-sprayed coating deposit restoration body is polished to match the geometry and size of the plasma-sprayed coating deposit restoration body with the shape and size of the area to be repaired on the iron cultural relic, thus completing the repair of the missing parts of the iron cultural relic. The plasma spraying parameters include: The spraying distance is 110–120 mm, the current is 385–388 A, the voltage is 115–125 V, and the carrier gas is a mixture of argon and hydrogen, with an argon flow rate of 150–153 L / min and a hydrogen flow rate of 3–3.5 L / min.

[0006] Preferably, the chemical composition of the gray cast iron powder, by mass percentage, includes: C 3.0 wt.%, Si 0.54 wt.%, Mn 0.54 wt.%, S ≤0.12 wt.%, P<0.15 wt.%, with the balance being Fe and unavoidable impurities, and the inert gas is argon or nitrogen.

[0007] Preferably, the gray cast iron powder has a particle size distribution range of about 10-55 μm and an average particle size of 30 μm.

[0008] Preferably, the gray cast iron powder is prepared by water atomization.

[0009] Preferably, before spraying, the gray cast iron powder is dried under vacuum to remove moisture.

[0010] Preferably, the thickness of the plasma-sprayed coating deposited repair is not less than 1 mm.

[0011] Preferably, before applying gray cast iron powder to the area of ​​the iron artifact to be repaired using a plasma spraying method, the process further includes: Surface pretreatment: Laser cleaning and sandblasting are performed on the iron artifacts to be repaired to remove the oxide and corrosion layer on the surface of the iron artifacts to be repaired. Then, gray cast iron powder is sprayed onto the iron artifacts to be repaired using plasma spraying.

[0012] Preferably, during surface pretreatment, a laser cleaning machine is used for cleaning and rust removal, with a laser power of 195-205W, and the number of rust removal cycles is 1-5, depending on the degree of rust corrosion.

[0013] Preferably, when performing sandblasting, the abrasive is brown corundum, the abrasive particle size is 400 µm-700 µm, and the sandblasting pressure is 0.5 MPa-0.7 MPa.

[0014] Preferably, after polishing the plasma-sprayed coating deposit repair body, an aging treatment is also included: The plasma-sprayed coating restoration is polished and shaped to ensure that it is consistent with the original surface of the iron artifact.

[0015] The present invention has the following beneficial effects: This invention relates to a method for repairing defects in iron cultural relics using plasma spraying additive manufacturing. Using gray cast iron powder as the spraying material, and employing precise process parameters—110–120 mm spraying distance, 385–388 A current, 115–125 V voltage, and 150–153 L / min argon and 3–3.5 L / min hydrogen—the method completes the repair through plasma spraying deposition and subsequent polishing, effectively solving many drawbacks of traditional restoration techniques. The gray cast iron powder is naturally homologous to the matrix of the iron cultural relic, and the repaired body prepared by this method contains only Fe, FeO, and Fe3O4, essentially identical to the composition of the corroded relic. This avoids compositional conflicts caused by organic fillers or dissimilar metals. Furthermore, the matching of electrochemical, thermal, and mechanical properties effectively prevents galvanic corrosion and stress cracking caused by temperature and humidity changes, adhering to the principle of restoration without altering the original state of the relic. Meanwhile, plasma spraying itself has a small heat-affected zone on the substrate. With the plasma spraying parameters provided by this invention, heat input can be further controlled, and the iron artifact substrate will not suffer secondary damage such as thermal deformation and tissue deterioration, achieving the effect of minimally invasive repair. The high flow rate of argon gas of 150–153 L / min can form a stable inert atmosphere. Combined with hydrogen to regulate the arc flame, it can suppress oxidation during powder flight. The spraying distance of 110–120 mm balances the powder kinetic energy and enthalpy, ensuring that the coating is dense (porosity as low as 0.54%) and firmly bonded. The bonding strength between the repaired body and the substrate is stable at 17.5–18.5 MPa, which can provide reliable mechanical support for iron artifacts and block external erosion, solving the problem of rapid aging of organic materials. Furthermore, the plasma spraying layer-by-layer deposition combined with polishing method can precisely match defect areas of different shapes and sizes, while controlling the surface roughness after repair. Moreover, the coating and the substrate are a composite form of mechanical interlocking and metallurgical bonding, and the repair can be removed in a minimally invasive manner, which has good reversibility. It is suitable for diverse scenarios such as fine restoration of museum collections and emergency reinforcement in the field, providing a safe, reliable and highly adaptable new path for the restoration of iron cultural relics. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the method for repairing defects in iron cultural relics using plasma spraying additive manufacturing, as described in this embodiment of the invention. Figure 2 This is a diagram illustrating the principle and scanning path of laser rust removal in an embodiment of the present invention. Figure 3 This is a morphology diagram of the gray cast iron powder used in the embodiments of the present invention; Figure 4 This is a particle size distribution diagram of the gray cast iron powder used in the embodiments of the present invention; Figure 5 The XRD pattern of the gray cast iron powder used in the embodiments of the present invention is shown below. Figure 6 This is a cross-sectional view of the cast iron coating (i.e., the plasma-sprayed coating deposition repair body) in Embodiment 1 of the present invention; Figure 7 This is the XRD phase diagram of the cast iron coating surface in Embodiment 1 of the present invention. Detailed Implementation

[0017] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0018] See Figure 1 The present invention provides a method for repairing defects in iron artifacts using plasma spraying additive manufacturing, comprising the following steps: Step 1: Selection of plasma additive manufacturing spray deposition materials: Gray cast iron powder with a composition similar to that of the iron artifact matrix is ​​selected as the spray material to ensure that the supplementary material has good compatibility with the iron artifact body in terms of chemical composition, physical properties and microstructure. Specifically, the material used for the replacement of iron cultural relics can be gray cast iron powder produced by water atomization, and the chemical composition (wt.%) of the powder is shown in Table 1.

[0019] Table 1

[0020] The gray cast iron powder used for replenishment has a particle size distribution range of approximately 10-55 μm, with an average particle size of 30 μm.

[0021] Before spraying, the cast iron powder is dried in a vacuum drying oven at 80±5℃ (wherein, the temperature control deviation of the drying equipment is ±5℃, and 80℃ is the set value of the drying temperature of the drying equipment; in the following embodiments, only the set value is given. It can be understood that the technical solution of the present invention is feasible within the range determined by the set value and the deviation range) for 3-4 hours to remove moisture from the powder.

[0022] Step 2: Surface pretreatment of iron artifacts: Laser cleaning and sandblasting are performed on the parts of the iron artifacts to be repaired to remove corrosion products, surface oxides and contaminants, expose the iron artifact body, and improve the bonding strength between the sprayed coating and the iron artifact substrate. The cleaning and rust removal process uses a laser cleaning machine, which is a portable handheld laser cleaning machine with a laser power of 200±5W (wherein, the output power deviation of the laser cleaning machine is ±5W, and 200W is the set value of the output power of the laser cleaning machine; in the following embodiments, only its set value is given. It can be understood that the technical solution of the present invention is feasible within the range determined by this set value and deviation range). The number of rust removal cycles is 1-5, and the number of rust removal cycles can be determined according to the degree of rust corrosion.

[0023] The sandblasting process uses brown corundum as the abrasive, with a particle size of 400 µm-700 µm and a sandblasting pressure of 0.5 MPa-0.7 MPa.

[0024] Step 3: The gray cast iron powder material from Step 2 is plasma additively sprayed and deposited onto the area of ​​the iron artifact to be repaired, forming a cast iron coating with a thickness of not less than 1 mm.

[0025] The plasma additive manufacturing spraying deposition process parameters are as follows: a high-efficiency supersonic atmospheric plasma spraying equipment (HEPJet) is used to carry out the spraying operation under the protective atmosphere of an inert gas (such as argon or nitrogen). The flow rate of argon or nitrogen is controlled at 150–153 L / min, the flow rate of hydrogen is 3–3.5 L / min, the spraying distance is 110–120 mm, the current is 385–388 A, and the voltage is 115–125 V.

[0026] Step four involves precision grinding of the plasma-sprayed cast iron coating restoration to ensure its geometry and dimensions precisely match the area of ​​the iron artifact to be repaired.

[0027] Step 5: Antiquing treatment. If necessary, lightly polish and reshape the repaired area to make it consistent with the original surface of the artifact.

[0028] Example 1 The method for repairing defects in iron artifacts using plasma spraying additive manufacturing in this embodiment includes the following steps: Step 1: Select a damaged iron artifact.

[0029] Step 2: Take 200g of micron-sized gray cast iron powder produced by irregular water atomization and dry it in an 80℃ drying oven for 3 hours. (See also...) Figures 3-5 The micron-sized gray cast iron powder of the present invention is composed of irregularly shaped particles. The particle size distribution range of the gray cast iron powder is 10-55µm, the average particle size is 30µm, and the XRD phase spectrum shows that only the Fe phase exists in the gray cast iron powder, and no oxide or other impurity phases are detected, making it suitable for cultural relic restoration.

[0030] Step 3: Before plasma spraying additive manufacturing deposition, the areas of the iron artifact to be repaired undergo laser cleaning and sandblasting to remove surface rust and contaminants. The laser scanning path during laser cleaning is as follows: Figure 2 The laser rust removal equipment is a portable handheld laser cleaning machine, model YJY-200, with a laser power setting of 200W and a rust removal cycle of 3 times. During sandblasting, brown corundum is used as the abrasive, with a particle size of 400µm and a sandblasting pressure of 0.5MPa, to improve coating adhesion.

[0031] Step 4: The powder material used to prepare cast iron is plasma additively sprayed and deposited layer by layer onto the surface of the iron artifact to be repaired, forming the cast iron restoration body, as described above. Figure 5 The plasma spraying process utilizes a high-efficiency supersonic atmospheric plasma spraying device (HEPJet), which operates under an argon protective atmosphere. The argon flow rate is 150 L / min, the hydrogen flow rate is 3.3 L / min, the spraying distance is 110 mm, the current is 385 A, and the voltage is 115 V.

[0032] Step 5: Perform cross-sectional metallographic observation on the prepared gray cast iron repair body (see...). Figure 6 The coating appears dense with a porosity of 0.62%, exhibiting no obvious cracks and good interlayer bonding. Phase composition results are as follows... Figure 7 As shown, the cast iron coating restoration contains only Fe, FeO and Fe3O4, which is consistent with the composition of iron artifacts, indicating that the restoration has good environmental compatibility in terms of chemical composition.

[0033] Step 6: The obtained cast iron coating deposition repair body is subjected to a bonding strength test. The bonding strength is 18 MPa, which proves that the coating and the substrate are well bonded.

[0034] Step 7: Antiquing the replacement area to ensure consistency with other areas of the iron artifact, with the surface roughness Ra controlled within 3 µm.

[0035] Step 8: Finally, apply a layer of microcrystalline wax as a protective coating to enhance environmental stability and durability.

[0036] Example 2 The method for repairing defects in iron artifacts using plasma spraying additive manufacturing in this embodiment includes the following steps: Step 1: Select a damaged iron artifact.

[0037] Step 2: Use the same micron-sized gray cast iron powder as in Step 2 of Example 1.

[0038] Step 3: Before plasma additive manufacturing deposition, the areas of the iron artifact to be repaired undergo laser rust removal and sandblasting to remove surface rust and contaminants. The laser scanning path during laser cleaning is as follows: Figure 2 The laser rust removal equipment is a portable handheld laser cleaning machine, model YJY-200, with a laser power of 200W and a cleaning cycle of 3 times. During sandblasting, brown corundum is used as the abrasive, with a particle size of 600µm and a sandblasting pressure of 0.6MPa, to improve coating adhesion.

[0039] Step 4: The powder material used to prepare the cast iron restoration is plasma-sprayed onto the area of ​​the iron artifact to be repaired to form the cast iron coating deposition restoration. The plasma spraying process uses a high-efficiency supersonic atmospheric plasma spraying device (HEPJet), and the spraying operation is carried out under an argon protective atmosphere. The argon flow rate is 151.8 L / min, the hydrogen flow rate is 3.5 L / min, the spraying distance is 115 mm, the current is 386 A, and the voltage is 120 V.

[0040] Step 5: The prepared cast iron coating deposition restoration body was characterized, and it was found that the coating porosity was 0.54%, the coating density was good, and the cast iron coating contained only Fe, FeO and Fe3O4, which was consistent with the composition of iron cultural relics.

[0041] Step 6: The bonding strength of the prepared cast iron deposition repair coating was tested, and the bonding strength was 17.5 MPa, which proved that the coating and the substrate were well bonded.

[0042] Step 7: Antiquing the replacement area to ensure consistency with other areas of the iron artifact, with the surface roughness Ra controlled within 3 µm.

[0043] Step 8: Finally, apply a layer of microcrystalline wax as a protective coating to enhance environmental stability and durability.

[0044] Example 3 See Figure 1 The method for repairing defects in iron artifacts using plasma spraying additive manufacturing in this embodiment includes the following steps: Step 1: Select a damaged iron artifact.

[0045] Step 2: Use the same micron-sized gray cast iron powder as in Step 2 of Example 1.

[0046] Step 3: Before plasma additive manufacturing deposition, the areas of the iron artifact to be repaired undergo laser rust removal and sandblasting to remove surface rust and contaminants. The laser scanning path during laser cleaning is as follows: Figure 2The laser rust removal equipment is a portable handheld laser cleaning machine, model YJY-200, with a laser power of 200W and a cleaning cycle of 4 times. During sandblasting, brown corundum is used as the abrasive, with a particle size of 700µm and a sandblasting pressure of 0.7MPa, to improve coating adhesion.

[0047] Step 4: The powder material used to prepare the cast iron restoration is plasma-sprayed onto the area of ​​the iron artifact to be repaired to form the cast iron coating deposition restoration. The plasma spraying process uses a high-efficiency supersonic atmospheric plasma spraying device (HEPJet), and the spraying operation is carried out under a nitrogen protective atmosphere. The argon flow rate is 153 L / min, the hydrogen flow rate is 3 L / min, the spraying distance is 120 mm, the current is 388 A, and the voltage is 125 V.

[0048] Step 5: The prepared cast iron coating deposition restoration body was characterized and it was found that the coating porosity was 0.59%, the coating density was good, and the cast iron coating contained only Fe, FeO and Fe3O4, which was consistent with the composition of iron cultural relics.

[0049] Step 6: The bonding strength of the prepared cast iron deposition repair coating was tested, and the bonding strength was 18.5 MPa, which proved that the coating and the substrate were well bonded.

[0050] Step 7: Antiquing the replacement area to ensure consistency with other areas of the iron artifact, with the surface roughness Ra controlled within 3 µm.

[0051] Step 8: Finally, apply a layer of microcrystalline wax as a protective coating to enhance environmental stability and durability.

[0052] In summary, this invention employs plasma spraying additive manufacturing technology to deposit a gray cast iron coating under relatively low-temperature conditions. The powder composition used is similar to that of the iron artifact substrate, significantly improving the compatibility and structural matching between the restoration material and the artifact. The resulting coating is dense and uniform with high bonding strength, possessing excellent mechanical support and corrosion resistance, which helps extend the service life of the artifact. The process is simple to operate, highly adaptable, and applicable to various shapes and sizes of damaged parts. Furthermore, the restoration process is reversible, facilitating subsequent maintenance and treatment.

[0053] This invention relies on the interdisciplinary integration of materials science, surface engineering, and cultural relic conservation, fully leveraging the respective technological advantages of each discipline to achieve an organic combination of scientific rigor and practicality. It provides a systematic and controllable technical approach for the restoration of iron cultural relics. This method not only demonstrates the application value of modern materials preparation technology in the field of cultural heritage protection but also offers new ideas for the modernization and upgrading of traditional restoration techniques.

[0054] In summary, this invention provides a safe, reliable, and highly adaptable new method for repairing the surface of iron cultural relics, which has good engineering application prospects and promotional value.

[0055] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for repairing defects in iron cultural relics using plasma spraying additive manufacturing, characterized in that, The process includes the following: Gray cast iron powder is sprayed onto the area of ​​the iron artifact to be repaired using a plasma spraying method, forming a plasma sprayed coating deposition restoration body in the area of ​​the iron artifact to be repaired; The plasma-sprayed coating deposit restoration body is polished to match the geometry and size of the plasma-sprayed coating deposit restoration body with the shape and size of the area to be repaired on the iron cultural relic, thus completing the repair of the missing parts of the iron cultural relic. The plasma spraying parameters include: The spraying distance is 110–120 mm, the current is 385–388 A, the voltage is 115–125 V, and the carrier gas is a mixture of argon and hydrogen, with an argon flow rate of 150–153 L / min and a hydrogen flow rate of 3–3.5 L / min.

2. The method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 1, characterized in that, The chemical composition of the gray cast iron powder, by mass percentage, includes: C 3.0 wt.%, Si 0.54 wt.%, Mn 0.54 wt.%, S ≤0.12 wt.%, P <0.15 wt.%, with the balance being Fe and unavoidable impurities.

3. The method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 1, characterized in that, The particle size distribution of gray cast iron powder ranges from approximately 10 to 55 μm, with an average particle size of 30 μm.

4. The method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 1, characterized in that, The gray cast iron powder is prepared by water atomization, and the inert gas is argon or nitrogen.

5. The method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 1, characterized in that, Before spraying, the gray cast iron powder is dried under vacuum to remove moisture.

6. The method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 1, characterized in that, The thickness of the plasma spray coating deposited repair is not less than 1 mm.

7. The method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 1, characterized in that, Before applying gray cast iron powder to the area of ​​the iron artifact to be repaired using plasma spraying, the process also includes: Surface pretreatment: Laser cleaning and sandblasting are performed on the iron artifacts to be repaired to remove the oxide and corrosion layer on the surface of the iron artifacts to be repaired. Then, gray cast iron powder is sprayed onto the iron artifacts to be repaired using plasma spraying.

8. The method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 7, characterized in that, When performing surface pretreatment, a laser cleaning machine is used for cleaning and rust removal. The laser power is 195-205W, and the number of rust removals is 1-5 times, depending on the degree of rust.

9. A method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 7, characterized in that, When performing sandblasting, the abrasive used is brown corundum, the abrasive particle size is 400 µm-700 µm, and the sandblasting pressure is 0.5 MPa-0.7 MPa.

10. A method for repairing defects in iron cultural relics using plasma spraying additive manufacturing according to claim 7, characterized in that, After polishing the plasma-sprayed coating deposit repair, an aging process is also included: The plasma-sprayed coating restoration is polished and shaped to ensure that it is consistent with the original surface of the iron artifact.

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