Magnesium alloy carrying corrosion-resistant-conductive multifunctional gradient carbon film and preparation method thereof

Abstract

The present application belongs to the technical field of metal material surface treatment, and provides a magnesium alloy loaded with a corrosion-resistant and conductive multifunctional gradient carbon film and a preparation method thereof. The gradient carbon film is mainly composed of a mixed phase with diamond as a main phase and a mixed phase with graphite as a main phase. The thickness of the gradient carbon film is controllable. According to the composition of the substrate, the proportion of diamond and graphite in the carbon film is adjustable and controllable, and the gradient transition of the film layer material structure is realized through the synergistic control of laser and related parameters, so that a multifunctional composite gradient carbon film with an inner insulating layer, an outer conductive gradient structure, high adhesion, high mechanical properties and high corrosion resistance is obtained. The preparation method of the present application is relatively simple and cost-saving. The carbon film further expands the application field of the substrate magnesium alloy.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to magnesium alloys carrying corrosion-resistant and conductive multifunctional gradient carbon films and their preparation methods. Background Technology

[0002] Magnesium alloys, with their high specific strength and low density, are ideal materials for lightweight manufacturing in the automotive, electronics, and defense industries. However, magnesium alloys suffer from severe microgalvanic corrosion; their surface films are porous and prone to various types of corrosion, significantly impacting their structural strength and properties, and greatly reducing their service life. Therefore, a dense and robust coating is typically applied to the surface of magnesium alloys to improve their corrosion resistance. Furthermore, in many applications, the corrosion-resistant coating on the magnesium alloy surface must possess a certain degree of conductivity to eliminate static electricity buildup and protect other electronic components from interference or damage.

[0003] Currently, common corrosion-resistant protective coatings for magnesium alloy surfaces include micro-arc oxidation films, chemical conversion films, and LDH (layered dihydroxy composite metal hydroxide). These mainly work by chemically reacting a portion of the surface substrate material to form an oxide film, thereby inhibiting further corrosion of the substrate surface. However, this process damages the substrate surface. Furthermore, while existing films exhibit some corrosion resistance, they typically cannot guarantee simultaneous improvement in electrical or mechanical properties. Additionally, the films obtained using existing technologies are usually thin, as thicker films are prone to uneven deposition, delamination, or poor adhesion to the substrate. Therefore, developing multifunctional magnesium alloy coating materials with high corrosion resistance, high electrical conductivity, high mechanical properties, uniformity, adjustable and controllable thickness, and good adhesion to the substrate without damaging the substrate surface is a pressing technical challenge. Summary of the Invention

[0004] To address the aforementioned technical challenges, this invention provides a magnesium alloy carrying a corrosion-resistant and conductive multifunctional gradient carbon film, the preparation method of which includes the following steps:

[0005] Step 1: Place a transparent carrier on a stage, place a carbon source material underneath, and obtain a carrier with a transfer graphite coating under near-infrared laser irradiation; the laser irradiation time is 2-30s, the laser power is 5-100W, and the laser wavelength is 700-3000nm; the transparent carrier is a quartz sheet or glass sheet, and the carbon source is a graphite plate, graphite paper, graphene film, multi-walled carbon nanotube film, or polyimide film;

[0006] Step 2: Place a magnesium alloy under the carrier with the transfer graphite coating prepared in Step 1, and then irradiate it with a near-infrared laser to obtain a magnesium alloy with a diamond-graphite mixed phase coating 1. The diamond phase in the mixed phase coating 1 is 50-100% by mass percentage. The laser irradiation time is 5-30 seconds, the laser power is 10-100W, and the laser wavelength is 700-3000 nm. The magnesium alloy is AZ31, AZ91, Mg-Al-Ca, Mg-Zn-Ca, or Mg-Li alloy.

[0007] Step 3: Place the magnesium alloy with diamond-graphite mixed phase coating 1 obtained in Step 2 under the carrier with the transfer graphite coating prepared in Step 1. Then, after near-infrared laser irradiation, obtain a magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film. The gradient carbon film of the magnesium alloy with the corrosion-resistant and conductive multifunctional gradient carbon film is mainly composed of the obtained diamond-graphite mixed phase coating 1 and graphite-diamond mixed phase coating 2. The graphite-diamond mixed phase coating 2, by mass percentage, contains 51-98% graphite phase. The laser irradiation time is 5-30s, the laser power is 10-50W, and the laser wavelength is 700-3000nm.

[0008] The carbon film thickness in the magnesium alloy with the corrosion-resistant and conductive multifunctional gradient carbon film described in step 3 is 2-200 μm, the self-corrosion potential shifts positively by 300-600 mV, and the self-corrosion current density is ≤7×10⁻⁶ mV. -7 A cm -2 Surface contact resistance ≤7mΩcm -2 .

[0009] Furthermore, the laser irradiation in step 1 includes: a laser irradiation time of 10-20 seconds, a laser wavelength of 780-1100 nm, and a laser power of 20-80 W.

[0010] Further, in step 2, the diamond phase in the mixed phase coating 1, by mass percentage, is 52-80%.

[0011] Furthermore, in step 3, the graphite phase in the mixed phase coating 2, by mass percentage, is 55-90%.

[0012] Furthermore, the carbon film thickness in magnesium alloys carrying corrosion-resistant and conductive multifunctional gradient carbon films ranges from 5 to 160 μm.

[0013] Compared with the existing technology, the present invention has the following characteristics:

[0014] Compared with existing technologies, this invention, based on the composition and structure of the base alloy, achieves the following significant improvements through the synergistic control of the interactions between raw materials, their proportions, processes, and process parameters:

[0015] (1) This invention achieves a gradient distribution of diamond and graphite components and their structure by depositing a gradient carbon film on the surface of a magnesium alloy. This results in a composite gradient carbon film composed of alternating graphite-diamond / diamond-graphite mixed phase coatings. The synergistic effects of the interaction between diamond and graphite components, the control of their proportions, and the gradient distribution of their structure simultaneously improve the corrosion resistance, electrical conductivity, mechanical properties, and adhesion of the magnesium alloy coating material. The gradient carbon film obtained by this invention has a thickness of 2-160 μm, simultaneously achieving adjustable and controllable thickness, breaking through the technical bottleneck of achieving thick films in existing technologies. This is achieved by laser-induced partial carbon bond sp... 2 (Graphite phase) to sp 3 The transformation of the diamond phase can be effectively controlled without the need for high temperature or vacuum equipment, thus preparing a gradient carbon film with diamond phase as the main phase in the inner layer and graphite phase as the main phase in the outer layer.

[0016] (2) The gradient carbon film prepared by the present invention has strong bonding with the magnesium alloy substrate and has good mechanical, chemical stability, thermal stability, mechanical properties, corrosion resistance and electrical conductivity; and the process is simple and low cost, which meets the actual production needs and expands the application field of magnesium alloy.

[0017] (3) Compared with commercial magnesium alloys, the magnesium alloy with gradient carbon film obtained by this invention has better performance in all relevant aspects than the coated magnesium alloy obtained by the prior art. The self-corrosion potential of the magnesium alloy with gradient carbon film obtained by this invention is shifted positively by 300-600mV, and the self-corrosion current density is ≤7×10 -7 A cm -2 Surface contact resistance ≤7mΩcm -2 . Attached Figure Description

[0018] Figure 1 The Raman spectrum of the laser-induced deposited corrosion-resistant conductive gradient carbon film 1 on the surface of the magnesium alloy prepared in Example 1 is shown below.

[0019] Figure 2 This is a scanning electron microscope cross-sectional image of the laser-induced deposition of corrosion-resistant conductive gradient carbon film 3 on the surface of the magnesium alloy prepared in Example 3. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the embodiments.

[0021] Example 1

[0022] A magnesium alloy containing a corrosion-resistant and conductive multifunctional gradient carbon film 1 is prepared by the following method:

[0023] Step 1: Place a transparent glass slide on a stage, and place a graphite plate underneath the glass slide. Irradiate the slide with a near-infrared laser for 5-8 seconds to obtain a transparent glass slide with a transferred graphite coating. The laser irradiation has a power of 5-6W and a wavelength of 780-1100nm. The graphite coating is deposited in situ on the glass slide. The glass slide can effectively confine the vaporized graphite molecules and allow the graphite coating to be transferred and deposited on the glass slide, resulting in good adhesion.

[0024] Step 2: Place an AZ31B magnesium alloy under the transparent glass slide containing the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with the AZ31B magnesium alloy. Irradiate with a near-infrared laser for 25-30 seconds to obtain an AZ31B magnesium alloy with a diamond-graphite mixed phase coating I. The laser irradiation has a power of 26-30W and a wavelength of 780-1100nm. The diamond phase in the diamond-graphite mixed phase coating I has a mass ratio of 52-55%. The diamond phase in the diamond-graphite mixed phase coating I is formed by vaporized graphite molecules undergoing sp... 2 -sp 3 The diamond-graphite mixed phase coating I is formed by conversion deposition; it is uniformly deposited and covers the surface of the magnesium alloy substrate; the diamond-graphite mixed phase coating I has a strong adhesion to the magnesium alloy substrate, with a peel force of about 13 N / cm; the thickness of the diamond-graphite mixed phase coating I is about 20-50 μm.

[0025] Step 3: Place the AZ31B magnesium alloy with diamond-graphite mixed phase coating I obtained in Step 2 under the transparent glass slide with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with coating I. After irradiation with a near-infrared laser for 10-15 seconds, a magnesium alloy with a laser-induced deposition corrosion-resistant and conductive multifunctional composite gradient carbon film 1 on its surface is obtained. The corrosion-resistant and conductive multifunctional composite gradient carbon film 1 is composed of diamond-graphite mixed phase coating I and graphite-diamond mixed phase coating II. The laser irradiation has a laser power of 5-6W and a laser wavelength of 780-1100nm. The graphite phase component in the diamond-graphite mixed phase coating II accounts for 70-80% by mass. The diamond phase in coating II is formed by vaporized graphite molecules passing through sp... 2 -sp 3The coating II is formed by conversion deposition, uniformly deposited and completely covering the diamond-graphite mixed-phase coating I described in step 2; a strong adhesion is formed between coating II and coating I described in step 2, with a peel force of approximately 9 N / cm, and no delamination occurs between coating II and coating I. The thickness of the diamond-graphite mixed-phase coating II is approximately 70-80 μm; the Raman spectrum of the composite gradient carbon film 1 is shown below. Figure 1 As shown, the D band peak is at 1363 cm⁻¹. –1 , corresponding to sp in the ring 2 The breathing pattern of carbon atoms; the G-band peak at 1591 cm⁻¹ –1 The corresponding in-plane aromatic rings and sp in the carbon chain 2 The bond stretching of carbon atom pairs proves that the composite gradient carbon film 1 is a mixture of diamond and graphite phases.

[0026] The total thickness of the composite gradient carbon film 1 obtained in step 3 is 90-130 μm. Compared with commercial AZ31B magnesium alloy, the magnesium alloy with the laser-induced deposited corrosion-resistant and conductive multifunctional composite gradient carbon film 1 on its surface obtained in this invention exhibits a 600 mV positive shift in self-corrosion potential and a self-corrosion current density of 7 × 10⁻⁶ mV. -7 A cm -2 The surface film contact resistance is 3mΩcm -2 .

[0027] Example 2

[0028] A magnesium alloy containing a corrosion-resistant and conductive multifunctional gradient carbon film 2 is prepared by the following method:

[0029] Step 1: Place a transparent quartz sheet in a sealed container filled with nitrogen atmosphere, place a graphene film under the quartz sheet, and irradiate with a near-infrared laser for 7-10 seconds to obtain a quartz sheet with a transferred graphite coating; the laser irradiation: laser power of 8-9W, wavelength of 780-1100nm; the graphite coating is deposited in situ on the quartz sheet; the quartz sheet can effectively confine the vaporized graphite molecules and allow the graphite coating to be transferred and deposited on the quartz sheet, with good adhesion;

[0030] Step 2: Place an AZ91D magnesium alloy under the quartz plate with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with the AZ91D magnesium alloy. After irradiation with a near-infrared laser for 18-20 seconds, an AZ91D magnesium alloy with a diamond-graphite mixed phase coating III is obtained. The laser irradiation has a power of 46-50W and a wavelength of 780-1100nm. The diamond phase in the diamond-graphite mixed phase coating III has a mass ratio of 60-70%. The diamond phase in the diamond-graphite mixed phase coating III is formed by vaporized graphite molecules passing through sp... 2-sp 3 The diamond-graphite mixed phase coating III is formed by conversion deposition; it is uniformly deposited and covers the surface of the magnesium alloy substrate; the diamond-graphite mixed phase coating III forms a strong adhesion on the surface of the magnesium alloy substrate, with a peel force of about 14 N / cm; the thickness of the diamond-graphite mixed phase coating III is about 10-30 μm.

[0031] Step 3: Place the AZ91D magnesium alloy with diamond-graphite mixed-phase coating III obtained in Step 2 under the quartz plate with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with coating III. After irradiation with a near-infrared laser for 9-10 seconds, a magnesium alloy with a laser-induced deposition corrosion-resistant and conductive multifunctional composite gradient carbon film 2 on its surface is obtained. The laser irradiation has a laser power of 11-12W and a laser wavelength of 780-1100nm. The corrosion-resistant and conductive multifunctional composite gradient carbon film 2 is composed of diamond-graphite mixed-phase coating III and graphite-diamond mixed-phase coating IV. The graphite phase component in the graphite-diamond mixed-phase coating IV accounts for 65-70% by mass. The diamond phase in coating IV is formed by vaporized graphite molecules through sp... 2 -sp 3 The transformation deposition process forms the coating IV, which is uniformly deposited and completely covers the coating III described in step 2. The coating III and coating IV have strong adhesion, with a peel force of approximately 10 N / cm. Furthermore, there is no delamination between coating III and coating IV, and the thickness of the diamond-graphite mixed phase coating IV is approximately 50-60 μm.

[0032] The total thickness of the laser-induced corrosion-resistant and conductive multifunctional composite gradient carbon film 2 obtained in step 3 is 60-90 μm. Compared with commercial AZ91D magnesium alloy, the self-corrosion potential of the magnesium alloy with the laser-induced corrosion-resistant and conductive multifunctional composite gradient carbon film 2 on its surface shifts positively by 400 mV, and the self-corrosion current density is reduced to 5 × 10⁻⁶ mV. -7 A cm -2 The surface film contact resistance is 5 mΩcm -2 .

[0033] Example 3

[0034] A magnesium alloy loaded with a corrosion-resistant and conductive multifunctional gradient carbon film 3 is prepared by the following method:

[0035] Step 1: Place a transparent quartz sheet in a sealed container filled with nitrogen atmosphere, place a graphene film under the quartz sheet, and irradiate with a near-infrared laser for 3-5 seconds to obtain a quartz sheet with a transferred graphite coating; the laser irradiation: laser power is 8-10W, wavelength is 780-1100nm; the graphite coating is deposited in situ on the quartz sheet; the quartz sheet can effectively confine the vaporized graphite molecules and allow the graphite coating to be transferred and deposited on the quartz sheet, with good adhesion;

[0036] Step 2: Place a Mg-Al-Ca magnesium alloy under the quartz sheet with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with the Mg-Al-Ca magnesium alloy. After irradiation with a near-infrared laser for 18-20 seconds, a Mg-Al-Ca magnesium alloy with a diamond-graphite mixed phase coating V is obtained. The laser irradiation has a power of 60-70W and a wavelength of 780-1100nm. The diamond phase in the diamond-graphite mixed phase coating V has a mass ratio of 70-75%. The diamond phase in the diamond-graphite mixed phase coating V is formed by vaporized graphite molecules passing through sp... 2 -sp 3 The diamond-graphite mixed phase coating V is formed by conversion deposition; it is uniformly deposited and covers the surface of the magnesium alloy substrate; the diamond-graphite mixed phase coating V has a strong adhesion to the magnesium alloy substrate, with a peel force of about 16 N / cm; the thickness of the diamond-graphite mixed phase coating V is about 30-40 μm.

[0037] Step 3: Place the Mg-Al-Ca magnesium alloy with diamond-graphite mixed-phase coating V obtained in Step 2 under the quartz plate with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with coating V. After irradiation with a near-infrared laser for 10-12 s, a magnesium alloy with a laser-induced deposition corrosion-resistant and conductive multifunctional composite gradient carbon film 3 on its surface is obtained. The laser irradiation has a laser power of 13-14 W and a laser wavelength of 780-1100 nm. The corrosion-resistant and conductive multifunctional composite gradient carbon film 2 is composed of diamond-graphite mixed-phase coating V and graphite-diamond mixed-phase coating VI. The graphite phase component in the graphite-diamond mixed-phase coating VI accounts for 60-65% of the total mass. The diamond phase in coating VI is formed by vaporized graphite molecules passing through sp... 2 -sp 3 The process involves conversion deposition; coating VI is uniformly deposited and completely covers coating V from step 2; coating V and coating VI have strong adhesion, with a peel force of approximately 12 N / cm; the thickness of the diamond-graphite mixed-phase coating VI is approximately 60-70 μm; no obvious delamination is observed between the diamond-graphite mixed-phase coating VI and the diamond-graphite mixed-phase coating V from step 2 under a scanning electron microscope. Figure 2 As shown, the total thickness of the gradient carbon film 3 is approximately 90-110 μm; compared to the unmodified Mg-Al-Ca magnesium alloy, the magnesium alloy with the laser-induced deposited corrosion-resistant and conductive multifunctional composite gradient carbon film 3 on its surface exhibits a 500 mV positive shift in self-corrosion potential and a reduced self-corrosion current density of 3 × 10⁻⁶ mV. -7 A cm -2 The surface film contact resistance is 6 mΩcm -2 .

[0038] Example 4

[0039] The preparation method of a magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film 4 includes the following:

[0040] Step 1: Place a transparent quartz sheet in a sealed container filled with nitrogen atmosphere, place a polyimide film under the quartz sheet, and irradiate with a near-infrared laser for 10-15 seconds to obtain a quartz sheet with a transferred graphite coating; the laser irradiation: laser power is 10-20W, wavelength is 780-1100nm; the graphite coating is deposited in situ on the quartz sheet; the quartz sheet can effectively confine the vaporized graphite molecules and allow the graphite coating to be transferred and deposited on the quartz sheet, with good adhesion;

[0041] Step 2: Place an AZ91D magnesium alloy under the quartz plate with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with the AZ91D magnesium alloy. After irradiation with a near-infrared laser for 15-25 seconds, an AZ91D magnesium alloy with a diamond-graphite mixed phase coating VII is obtained. The laser irradiation has a power of 55-60W and a wavelength of 780-1100nm. The diamond phase in the diamond-graphite mixed phase coating VII has a mass ratio of 65-75%. The diamond phase in the diamond-graphite mixed phase coating VII is formed by vaporized graphite molecules passing through sp... 2 -sp 3 The diamond-graphite mixed phase coating VII is formed by conversion deposition; it is uniformly deposited and covers the surface of the magnesium alloy substrate; the diamond-graphite mixed phase coating VII has a strong adhesion to the magnesium alloy substrate, with a peel force of about 20 N / cm; the thickness of the diamond-graphite mixed phase coating VII is about 1-2 μm.

[0042] Step 3: Place the AZ91D magnesium alloy with diamond-graphite mixed phase coating VII obtained in Step 2 under the quartz plate with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with coating VII. After irradiation with a near-infrared laser for 10-15 seconds, a magnesium alloy with a laser-induced deposition corrosion-resistant and conductive multifunctional composite gradient carbon film 4 on its surface is obtained. The laser irradiation has a laser power of 15-20W and a laser wavelength of 780-1100nm. The corrosion-resistant and conductive multifunctional composite gradient carbon film 4 is composed of diamond-graphite mixed phase coating VII and graphite-diamond mixed phase coating VIII. The graphite phase component in the graphite-diamond mixed phase coating VIII accounts for 55-75% of the total mass. The diamond phase in coating VIII is formed by vaporized graphite molecules passing through sp... 2 -sp 3 The transformation deposition process forms the coating VIII, which is uniformly deposited and completely covers the coating VII described in step 2. The coating VII and coating VIII have strong adhesion with a peel force of approximately 15 N / cm. Furthermore, there is no delamination between coating VII and coating VIII. The thickness of the diamond-graphite mixed phase coating VIII is approximately 1-3 μm.

[0043] The total thickness of the laser-induced deposited corrosion-resistant and conductive multifunctional composite gradient carbon film 4 obtained in step 3 is 2-5 μm. Compared with commercial AZ91D magnesium alloy, the self-corrosion potential of the magnesium alloy with the laser-induced deposited corrosion-resistant and conductive multifunctional composite gradient carbon film 4 shifts positively by 300 mV, and the self-corrosion current density decreases to 6 × 10⁻⁶. -7 A cm -2 The surface film contact resistance is 4 mΩcm -2 .

[0044] Example 5

[0045] A magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film 5 is prepared by the following method:

[0046] Step 1: Place a transparent quartz sheet in a sealed container filled with nitrogen atmosphere, place a graphite plate under the quartz sheet, and irradiate with a near-infrared laser for 5-15 seconds to obtain a quartz sheet with a transferred graphite coating; the laser irradiation: laser power is 6-10W, wavelength is 780-1100nm; the graphite coating is deposited in situ on the quartz sheet; the quartz sheet can effectively confine the vaporized graphite molecules and allow the graphite coating to be transferred and deposited on the quartz sheet, with good adhesion;

[0047] Step 2: Place a Mg-Zn-Ca magnesium alloy under the quartz sheet with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with the Mg-Zn-Ca magnesium alloy. After irradiation with a near-infrared laser for 20-30 seconds, a Mg-Zn-Ca magnesium alloy with a diamond-graphite mixed phase coating IX is obtained. The laser irradiation has a power of 45-50W and a wavelength of 780-1100nm. The diamond phase in the diamond-graphite mixed phase coating IX has a mass ratio of 62-72%. The diamond phase in the diamond-graphite mixed phase coating IX is formed by vaporized graphite molecules passing through sp... 2 -sp 3 The diamond-graphite mixed phase coating IX is formed by conversion deposition; it is uniformly deposited and covers the surface of the magnesium alloy substrate; the diamond-graphite mixed phase coating IX has a strong adhesion to the magnesium alloy substrate, with a peel force of about 19 N / cm; the thickness of the diamond-graphite mixed phase coating IX is about 40-70 μm.

[0048] Step 3: Place the Mg-Zn-Ca magnesium alloy with diamond-graphite mixed phase coating IX obtained in Step 2 under the quartz plate with the transferred graphite coating prepared in Step 1, wherein the graphite coating is in direct contact with coating IX. After irradiation with a near-infrared laser for 10-16 s, a magnesium alloy with a laser-induced deposition corrosion-resistant and conductive multifunctional composite gradient carbon film 5 on its surface is obtained. The laser irradiation has a laser power of 16-17 W and a laser wavelength of 780-1100 nm. The corrosion-resistant and conductive multifunctional composite gradient carbon film 5 is composed of diamond-graphite mixed phase coating IX and graphite-diamond mixed phase coating X. The graphite phase component in the graphite-diamond mixed phase coating X accounts for 55-60% by mass. The diamond phase in coating X is formed by vaporized graphite molecules passing through sp... 2 -sp 3 The coating is formed by conversion deposition; the coating X is uniformly deposited and completely covers the coating IX described in step 2; the coating X and coating IX have strong adhesion, with a peel force of about 12 N / cm; and there is no delamination between coating X and coating IX, and the thickness of the diamond-graphite mixed phase coating X is about 60-90 μm.

[0049] The total thickness of the laser-induced corrosion-resistant and conductive multifunctional composite gradient carbon film 5 obtained in step 3 is 100-160 μm. Compared with the unmodified Mg-Zn-Ca magnesium alloy, the self-corrosion potential of the magnesium alloy with the laser-induced corrosion-resistant and conductive multifunctional composite gradient carbon film 5 shifts positively by 360 mV, and the self-corrosion current density decreases to 2 × 10⁻⁶ mV. -7 A cm -2 The surface film contact resistance is 7 mΩcm -2 .

[0050] Comparative Example 1

[0051] A publicly published SCI journal paper entitled "Preparation and corrosion resistance characterization of MAO coating on AZ31B magnesium alloy formed in the mixed silicate and phosphate electrolytes with pectin as an additive" (authors: Chunting Guo et al.; Surface and Coatings Technology 476(2024):130209) shows that, compared with AZ31B magnesium alloy, after passivation treatment with micro-arc oxide film, the corrosion potential of AZ31B magnesium alloy with micro-arc oxide film shifted positively by 100mV, and the self-corrosion current density was 1.3×10⁻⁶. -6 A cm -2 Compared to the AZ31B magnesium alloy coating material obtained in Example 1 of this invention, the AZ31B magnesium alloy coating material exhibits a 600mV positive shift in self-corrosion potential and a reduced self-corrosion current density of 7×10⁻⁶ mV. -7 A cm -2 The surface film contact resistance is 3mΩcm -2 Compared to Comparative Example 1, the coating material of Comparative Example 1 exhibits lower corrosion resistance than that of Example 1 of this invention. Furthermore, the coating material disclosed in Comparative Example 1 undergoes micro-arc oxidation on the substrate surface, which causes a partial reaction in the surface substrate material, thus damaging the substrate surface. In contrast, the laser-induced deposition gradient carbon film method used in this invention does not damage the substrate surface. While improving adhesion to the substrate, it forms a film material with a gradient distribution of mass and structure. This gradient film material has no layered structure and maintains good adhesion to the substrate, exhibiting strong corrosion resistance. Since the underlying coating material obtained in this invention is primarily composed of diamond, it possesses higher mechanical properties than films obtained using existing technologies. Moreover, Comparative Example 1 does not disclose a method for improving the conductivity of the coating. Compared to Comparative Example 1, this invention improves the corrosion resistance of the film while simultaneously improving the mechanical properties and conductivity of the film material.

[0052] Comparative Example 2

[0053] A publicly published SCI journal paper entitled "Designing for the chemical conversion coating with high corrosion resistance and low electrical contact resistance on AZ91D magnesium alloy" (authors: Guoqing Duan et al.; Corrosion Science 135(2018):197-206) describes the formation of a surface film material for AZ91D magnesium alloy using Na2HPO4, H3PO4, Ca(NO3)2, NH4VO3, and OP-10 surfactant. The main components of this film material are MgHPO4, CaHPO4, and MgO. Compared to the AZ91D magnesium alloy, the self-corrosion potential of the AZ91D magnesium alloy with the film material published in Comparative Example 2 shows almost no positive shift, and the self-corrosion current density is 1×10⁻⁶. -6 A cm -2 The contact resistance of the surface film is approximately 6 mΩcm. -2 Compared to the AZ91D magnesium alloy coating material obtained in Example 2 of this invention, the self-corrosion potential of Example 2 shifts positively by 400mV, and the self-corrosion current density decreases to 5×10⁻⁶ mV. -7 Acm -2 The surface film contact resistance is 5 mΩcm -2 Compared with the present invention, the AZ91D magnesium alloy coating material obtained in Example 4 (compared to AZ91D magnesium alloy, the self-corrosion potential of Example 4 shifts positively by 300mV, and the self-corrosion current density is reduced to 6×10) -7 A cm -2 The surface film contact resistance is 4 mΩcm -2In comparison, the film material obtained in the comparative example differs from that of the present invention. The corrosion resistance of the coating material disclosed in Comparative Example 2 is far lower than that of the coating of the present invention, and the conductivity of the surface film is also lower than that of the surface film of the present invention. Furthermore, the chemical conversion film used in the prior art forms a dense oxide film by reacting with a portion of the substrate magnesium alloy surface material, which damages the surface of the substrate material. This requires the design of various chemical solution formulations and complex multi-step processing, involving a large amount of organic solvents, which is environmentally unfriendly. In contrast, the laser-induced deposition method used in the present invention does not require the addition of organic solvents, is simple in process, and does not damage the surface of the substrate material. While improving adhesion to the substrate, it forms a film material with a gradient distribution of mass and structure. This gradient film material has no layered structure and maintains good adhesion to the substrate, exhibiting strong corrosion resistance and surface conductivity. In addition, the mechanical properties of the coating material obtained by the present invention are superior to those of the film materials obtained in the prior art. These excellent characteristics enable the film material to be applied to a wider range of applications in conjunction with the substrate material.

[0054] In summary, this invention achieves superior results compared to existing technologies by synergistically controlling the process and process parameters based on the type of matrix alloy. A detailed comparison is as follows:

[0055] Compared to existing technologies, existing coating materials typically require a reaction with the substrate surface to form an oxide film to inhibit further corrosion of the substrate. These technologies also fail to address improving conductivity and mechanical properties. In contrast, the gradient carbon film obtained in this invention does not damage the substrate material, requires no expensive raw materials, organic solvents, vacuum equipment, or complex chemical processing. Existing coating materials are primarily thin films, making it difficult to obtain thick films. This invention achieves better controllability of carbon film thickness, ranging from 5 μm and below to 100 μm and above. Appropriate film thickness can be selected based on different operating conditions, achieving high corrosion resistance and high conductivity for magnesium alloys in various scenarios. Furthermore, by effectively adjusting the ratio of diamond to graphite phases, the thickness of the mixed phase, and the gradient structure of the mixed phase in the gradient carbon film, this invention achieves a better simultaneous balance and control of the film's mechanical properties, corrosion resistance, and conductivity. Compared to existing technologies, this invention significantly improves the corrosion resistance of the film material while also significantly enhancing its mechanical and electrical properties, resulting in a multifunctional film material with high corrosion resistance, high conductivity, and high mechanical properties. This is mainly attributed to the ability to effectively confine and deposit vaporized graphite molecules into a film through the synergistic control of the process and process parameters, thereby achieving the sp-carbon bond structure in the coating material. 2 Convert to sp 3The controllable quantity of the diamond-graphite phase composition, its distribution, and the film thickness were effectively regulated, ultimately leading to the transfer and deposition of a gradient carbon film on the magnesium alloy surface. This film material possesses high mechanical and electrical properties, strong adhesion to the substrate material, and high corrosion resistance and conductivity. Compared to commercially available magnesium alloys, the magnesium alloy with the gradient carbon film obtained in this invention exhibits a 300-600mV positive shift in self-corrosion potential and a self-corrosion current density ≤7×10⁻⁶. -7 A cm -2 The surface contact resistance of the coating is ≤7mΩcm -2 Compared with existing technologies, this invention simplifies the process. It eliminates the need for high temperatures, organic solvents, vacuum equipment, or complex chemical treatments, and does not damage the substrate material surface, achieving high corrosion resistance, high electrical conductivity, and high mechanical properties on the magnesium alloy coating surface. Furthermore, as can be seen from the embodiments of this invention, different processes and parameters are used for processing different substrate materials. Even for the same substrate material, the process parameters vary, resulting in significantly different coating performances. Therefore, the superior coating effect obtained by this invention is not determined by a single process or parameter, but rather requires synergistic control of the interaction and proportion of raw materials, processes, and process parameters, based on the type of substrate alloy.

Claims

1. A magnesium alloy containing a corrosion-resistant and conductive multifunctional gradient carbon film, characterized in that: Its preparation method includes the following steps: Step 1: Place a transparent carrier on a stage, place a carbon source material underneath, and obtain a carrier with a transfer graphite coating under near-infrared laser irradiation; the laser irradiation time is 2-30 s, the laser power is 5-100 W, and the laser wavelength is 700-3000 nm; the transparent carrier is a quartz sheet or glass sheet, and the carbon source is a graphite plate, graphite paper, graphene film, multi-walled carbon nanotube film, or polyimide film; Step 2: Place a magnesium alloy under the carrier with the transfer graphite coating prepared in Step 1, and then irradiate it with a near-infrared laser to obtain a magnesium alloy with a diamond-graphite mixed phase coating 1. The diamond phase in the mixed phase coating 1 is 50-100% by mass percentage. The magnesium alloy is AZ31, AZ91, Mg-Al-Ca, Mg-Zn-Ca or Mg-Li alloy. Step 3: Place the magnesium alloy with diamond-graphite mixed phase coating 1 obtained in step 2 under the carrier with transfer graphite coating prepared in step 1, and then irradiate it with near-infrared laser to obtain a magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film. The gradient carbon film of the magnesium alloy with corrosion-resistant and conductive multifunctional gradient carbon film is mainly composed of diamond-graphite mixed phase coating 1 and graphite-diamond mixed phase coating 2. The graphite-diamond mixed phase coating 2, by mass percentage, contains 51-98% graphite phase. The carbon film thickness in the magnesium alloy with the corrosion-resistant and conductive multifunctional gradient carbon film described in step 3 is 2-200 μm, the self-corrosion potential shifts positively by 300-600 mV, and the self-corrosion current density is ≤7×10⁻⁶ mV. -7 A cm -2 Surface contact resistance ≤ 7 mΩ cm -2 ; The laser irradiation in step 2 has a duration of 25-30 s, a laser power of 26-30 W, and a laser wavelength of 780-1100 nm. The laser irradiation in step 3 has a duration of 10-15 s, a laser power of 5-6 W, and a laser wavelength of 780-1100 nm. Alternatively, the laser irradiation in step 2 has a duration of 18-20 s, a laser power of 46-50 W, and a laser wavelength of 780-1100 nm. The laser irradiation in step 3 has a duration of 9-10 s, a laser power of 11-12 W, and a laser wavelength of 780-1100 nm. Alternatively, the laser irradiation in step 2 has a duration of 18-20 s, a laser power of 60-70 W, and a laser wavelength of 780-1100 nm. The laser irradiation in step 3 has a duration of 10-12 s, a laser power of 13-14 W, and a laser wavelength of 780-1100 nm. nm; or the laser irradiation described in step 2: time 15-25 s, laser power 55-60 W, laser wavelength 780-1100 nm; the laser irradiation described in step 3: time 10-15 s, laser power 15-20 W, laser wavelength 780-1100 nm; or the laser irradiation described in step 2: time 20-30 s, laser power 45-50 W, laser wavelength 780-1100 nm; the laser irradiation described in step 3: time 10-16 s, laser power 16-17 W, laser wavelength 780-1100 nm.

2. The magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film according to claim 1, characterized in that: The laser irradiation in step 1 is as follows: the laser irradiation time is 10-20 s, the laser wavelength is 780-1100 nm, and the laser power is 20-80 W.

3. The magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film according to claim 1, characterized in that: The diamond phase in the mixed phase coating 1, as described in step 2, is 52-80% by mass percentage.

4. The magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film according to claim 1, characterized in that: The graphite phase in the mixed phase coating 2, as described in step 3, is 55-90% by mass percentage.

5. The magnesium alloy with a corrosion-resistant and conductive multifunctional gradient carbon film according to any one of claims 1-4, characterized in that: The carbon film thickness in magnesium alloys carrying corrosion-resistant and conductive multifunctional gradient carbon films ranges from 5 to 160 μm.

Images