A high salt spray resistant stainless steel material and its preparation method

Abstract

This invention discloses a high salt spray resistant stainless steel material and its preparation method, relating to the field of metal materials technology. In preparing the high salt spray resistant stainless steel material, the present invention involves weighing raw materials including Cr, Ni, Al, Si, Mn, Mo, Nb, C, Zr, Ti, and Fe according to specific mass percentages, and obtaining an alloy ingot through melting and casting; subjecting the alloy ingot to homogenization heat treatment and forging to obtain a stainless steel matrix; using the stainless steel matrix as the working electrode, surface modification is performed through cathodic polarization treatment in an electrolyte containing amidated carbon nanotube-boron nitride composite filler, thereby obtaining the high salt spray resistant stainless steel material. The high salt spray resistant stainless steel material prepared by this invention exhibits excellent salt spray corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, specifically to a high salt spray resistant stainless steel material and its preparation method. Background Technology

[0002] Stainless steel is one of the most widely used metallic materials, possessing high strength, good corrosion resistance, and processing properties, and is widely used in construction, automobile manufacturing, chemical equipment, and daily necessities. However, in salt spray environments, ordinary stainless steel is prone to localized corrosion, such as pitting and stress corrosion cracking, leading to a decline in material properties and a shortened service life, thereby causing safety risks and economic losses.

[0003] In recent years, with the rapid development of marine engineering, coastal infrastructure, and aerospace, the consumption of stainless steel has continued to grow, placing higher demands on the material's corrosion resistance in harsh environments. At the same time, the growing calls for resource conservation and environmental protection have prompted the development of highly salt-spray resistant stainless steel materials through methods such as composition optimization and surface modification to improve their reliability and sustainability. Summary of the Invention

[0004] The purpose of this invention is to provide a high salt spray resistant stainless steel material and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A high salt spray resistant stainless steel material, comprising a stainless steel matrix having the following chemical composition by mass percentage, and an amidated carbon nanotube-boron nitride composite nitriding modification layer laminated on the surface of the stainless steel matrix: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.4%~0.6%Nb, 0.004%~0.008%C, 0.002%~0.003%Zr, 0.002%~0.003%Ti, with the balance being Fe.

[0006] As an optimization, the stainless steel matrix is ​​obtained by melting and casting according to the element weight percentages described in claim 1, followed by homogenization heat treatment and forging.

[0007] As an optimization, the amidated carbon nanotube-boron nitride nitriding modified layer is prepared by using a stainless steel substrate as the working electrode, placing it in a composite nitriding electrolyte, and applying a cathode current for polarization treatment.

[0008] As an optimization, the composite nitrided electrolyte is prepared by adding amidated carbon nanotube-boron nitride composite filler to a basic electrolyte composed of potassium nitrate, nitric acid and deionized water, and then dispersing it by ultrasonication.

[0009] As an optimization, the amidated carbon nanotube-boron nitride composite filler is prepared by hydroxylating hexagonal boron nitride and then amidating it with γ-aminopropyltriethoxysilane and carboxylated multi-walled carbon nanotubes.

[0010] A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.4%~0.6%Nb, 0.004%~0.008%C, 0.002%~0.003%Zr, 0.002%~0.003%Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2 Pa, heat to 800~1000℃ until all the furnace charge melts, heat to 1570~1590℃, hold for 20~30min, pour the molten steel into a water-cooled mold preheated to 600~800℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1310~1330℃ at a rate of 9~11℃ / min under an argon atmosphere, hold for 3.5~4.5h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1250~1300℃, hold for 1~2h, forge to obtain a stainless steel matrix; (2) Add 3wt%~5wt% of hexagonal boron nitride to a 30% hydrogen peroxide solution, sonicate for 6~8h, stir at 25~30℃ and 200~400r / min for 48~72h, centrifuge, and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol, deionized water, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 3.5~4.5 with sulfuric acid, sonicate for 0.5~1.5h, and stir at 45~55℃ and 200~400r / min for 48~72h, centrifuge and dry to obtain hydroxylated boron nitride; weigh ...γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix Stir at 0~400 r / min for 1.5~2.5 h, add carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and continue stirring for 8~12 h to obtain amidated carbon nanotube-boron nitride composite filler; mix potassium nitrate, 65% nitric acid and deionized water at a mass ratio of 1:(0.14~0.17):(16~20) to dissolve and prepare electrolyte; add amidated carbon nanotube-boron nitride composite filler at 0.4wt%~0.6wt% to electrolyte, and sonicate for 6~8 h to obtain composite nitrided electrolyte; use stainless steel substrate as working electrode, place it together with platinum sheet counter electrode and calomel reference electrode in composite nitrided electrolyte, and cathodically polarize at a reduction current density of 3~7 mA / cm² for 2~4 h to obtain high salt spray resistant stainless steel material.

[0011] As an optimization, the stainless steel substrate obtained by forging in step (1) is a plate with a thickness of 2~4mm.

[0012] As an optimization, the hexagonal boron nitride particles in step (2) have a diameter of 100 nm and are manufactured by Shanghai McLean Biochemical Technology Co., Ltd.; the multi-walled carbon nanotubes have a diameter of 50 nm and a length of 0.5~2 μm and are manufactured by Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0013] As an optimization, before placing the stainless steel substrate as the working electrode in the composite nitriding electrolyte in step (2), the stainless steel substrate needs to be pretreated, including: cutting the stainless steel substrate into 12mm×12mm squares, polishing the surface with 400#, 800# and 1200# silicon carbide waterproof sandpaper in sequence, and then placing it in a mixed solution prepared by anhydrous ethanol and acetone at a volume ratio of 1:1 for ultrasonic cleaning for 20~30 minutes, rinsing with deionized water, and drying.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing high salt spray resistant stainless steel, the present invention weighs raw materials including Cr, Ni, Al, Si, Mn, Mo, Nb, C, Zr, Ti, and Fe according to specific mass percentages, and obtains alloy ingots through melting and casting; the alloy ingots are subjected to homogenization heat treatment and forging to obtain stainless steel plates; the stainless steel plates are used as working electrodes, and surface modification is carried out by cathodic polarization treatment in an electrolyte containing amidated carbon nanotube-boron nitride composite filler to obtain high salt spray resistant stainless steel.

[0015] First, a composite microalloying system was constructed by controlling the content of key alloying elements, in which the synergistic effect of niobium, titanium, and zirconium constitutes the core of the material's high salt spray resistance. Specifically, 0.4%~0.6% niobium, as a strong carbide-forming element, not only improves mechanical properties by refining grains, but also promotes the formation and repair of a protective alumina film through the "active element effect." 0.002%~0.003% zirconium and 0.002%~0.003% titanium form a composite deoxidation system, transforming the MnS inclusions in the steel that are prone to pitting corrosion into fine, highly chemically stable ZrO2 and TiN composite inclusions, inhibiting the origin of pitting corrosion, thereby fundamentally improving the material's pitting corrosion resistance. Based on this, 15%~16% chromium ensures the stability of the passivation film, 18.5%~19.5% nickel stabilizes the austenitic matrix, 1.85%~1.95% aluminum promotes the formation of the protective film, 2%~3% molybdenum enhances the resistance to pitting corrosion, and strictly controlling carbon at 0.004%~0.008% minimizes harmful precipitates, providing the material with excellent matrix corrosion resistance.

[0016] Secondly, an innovative surface modification technique combining nanocomposite fillers and cathodic polarization was employed. The prepared amidated carbon nanotube-boron nitride composite filler possesses unique structural advantages: the boron nitride sheets effectively isolate and prevent carbon nanotube aggregation, ensuring uniform dispersion of the filler in the electrolyte. More importantly, after chemical modification, the composite filler surface is rich in amide bonds and amino groups, becoming positively charged in the acidic composite nitride electrolyte. This allows it to efficiently migrate towards the negatively charged stainless steel cathode under an electric field, significantly promoting its electrochemical co-deposition efficiency on the surface nitride layer. Ultimately, the composite filler is firmly embedded in the material surface under a cathodic current of 3–7 mA / cm², forming a dense barrier. Boron nitride provides chemical inert isolation, while carbon nanotubes construct a three-dimensional anti-permeation network. These components work synergistically with the corrosion-resistant microstructure established by niobium, titanium, and zirconium in the matrix, collectively endowing the material with excellent and durable corrosion resistance in harsh salt spray environments. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] To more clearly illustrate the method provided by the present invention, the following embodiments will be described in detail.

[0019] Example 1: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15%Cr, 18.5%Ni, 1.85%Al, 1%Si, 1.4%Mn, 2%Mo, 0.4%Nb, 0.004%C, 0.002%Zr, 0.002%Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2 Pa, heat to 800℃ until all furnace charge melts, heat to 1570℃, hold for 20 min, pour the molten steel into a water-cooled mold preheated to 600℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1310℃ at a rate of 9℃ / min under argon atmosphere, hold for 3.5 h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1250℃, hold for 1 h, forge to obtain a stainless steel matrix; (2) Add 3 wt% of hexagonal boron nitride to 30% hydrogen peroxide solution, sonicate for 6 h, stir at 200 r / min for 48 h at 25 °C, centrifuge and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol, deionized water, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of 1:1.5:190:40:3:2.5:1, mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 3.5 with sulfuric acid, sonicate for 0.5 h, stir at 200 r / min for 1 h at 45 °C. After 5 hours, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added, and stirring was continued for 8 hours to obtain amidated carbon nanotube-boron nitride composite filler. Potassium nitrate, 65% nitric acid and deionized water were mixed and dissolved at a mass ratio of 1:0.14:16 to obtain electrolyte. The amidated carbon nanotube-boron nitride composite filler was added to the electrolyte at 0.4 wt%, and ultrasonic treatment was carried out for 6 hours to obtain composite nitrided electrolyte. The stainless steel substrate was used as the working electrode, and together with the platinum sheet counter electrode and the calomel reference electrode, it was placed in the composite nitrided electrolyte and cathodically polarized at a reduction current density of 3 mA / cm² for 2 hours to obtain high salt spray resistant stainless steel material.

[0020] Example 2: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15.5% Cr, 19% Ni, 1.9% Al, 1.3% Si, 1.46% Mn, 2.5% Mo, 0.5% Nb, 0.006% C, 0.0025% Zr, 0.0025% Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2 Pa, heat to 900℃ until all the furnace charge melts, heat to 1580℃, hold for 25 min, pour the molten steel into a water-cooled mold preheated to 700℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1320℃ at a rate of 10℃ / min under an argon atmosphere, hold for 4 h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1275℃, hold for 1.5 h, forge to obtain a stainless steel matrix; (2) Add 4 wt% hexagonal boron nitride to 30% hydrogen peroxide solution, sonicate for 7 h, stir at 27 °C and 300 r / min for 60 h, centrifuge, and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol, deionized water, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of 1:1.7:200:45:4:3:2, mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 4 with sulfuric acid, sonicate for 1 h, stir at 50 °C and 300 r / min for 2 h, and add Carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide were stirred for 10 hours to prepare an amidated carbon nanotube-boron nitride composite filler. Potassium nitrate, 65% nitric acid, and deionized water were mixed and dissolved at a mass ratio of 1:0.155:18 to prepare an electrolyte. The amidated carbon nanotube-boron nitride composite filler was added to the electrolyte at 0.5 wt% and ultrasonically treated for 7 hours to prepare a composite nitrided electrolyte. A stainless steel substrate was used as the working electrode and placed together with a platinum sheet counter electrode and a calomel reference electrode in the composite nitrided electrolyte. The substrate was cathodically polarized at a reduction current density of 5 mA / cm² for 3 hours to prepare a high salt spray resistant stainless steel material.

[0021] Example 3: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 16%Cr, 19.5%Ni, 1.95%Al, 1.5%Si, 1.5%Mn, 3%Mo, 0.6%Nb, 0.008%C, 0.003%Zr, 0.003%Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2 Pa, heat to 1000℃ until all furnace charge melts, heat to 1590℃, hold for 30 min, pour the molten steel into a water-cooled mold preheated to 800℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1330℃ at a rate of 11℃ / min under argon atmosphere, hold for 4.5 h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1300℃, hold for 2 h, forge to obtain a stainless steel matrix; (2) Add 5 wt% hexagonal boron nitride to 30% hydrogen peroxide solution, sonicate for 8 h, stir at 30℃ and 400 r / min for 72 h, centrifuge, and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol, deionized water, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of 1:2:210:50:5:3.5:3, mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 4.5 with sulfuric acid, sonicate for 1.5 h, and stir at 55℃ and 400 r / min for 2.5 h. Carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added, and the mixture was stirred for 12 hours to obtain an amidated carbon nanotube-boron nitride composite filler. Potassium nitrate, 65% nitric acid and deionized water were mixed and dissolved at a mass ratio of 1:0.17:20 to prepare an electrolyte. The amidated carbon nanotube-boron nitride composite filler was added to the electrolyte at 0.6 wt%, and the mixture was ultrasonically treated for 8 hours to obtain a composite nitrided electrolyte. A stainless steel substrate was used as the working electrode, and together with a platinum sheet counter electrode and a calomel reference electrode, it was placed in the composite nitrided electrolyte and cathodically polarized at a reduction current density of 7 mA / cm² for 4 hours to obtain a high salt spray resistant stainless steel material.

[0022] Comparative Example 1: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.004%~0.008%C, 0.002%~0.003%Zr, 0.002%~0.003%Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2 Pa, heat to 800~1000℃ until all the furnace charge melts, heat to 1570~1590℃, hold for 20~30min, pour the molten steel into a water-cooled mold preheated to 600~800℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1310~1330℃ at a rate of 9~11℃ / min under an argon atmosphere, hold for 3.5~4.5h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1250~1300℃, hold for 1~2h, forge to obtain a stainless steel matrix; (2) Add 3wt%~5wt% of hexagonal boron nitride to a 30% hydrogen peroxide solution, sonicate for 6~8h, stir at 25~30℃ and 200~400r / min for 48~72h, centrifuge, and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol, deionized water, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 3.5~4.5 with sulfuric acid, sonicate for 0.5~1.5h, and stir at 45~55℃ and 200~400r / min for 48~72h, centrifuge and dry to obtain hydroxylated boron nitride; weigh ...γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix Stir at 0~400 r / min for 1.5~2.5 h, add carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and continue stirring for 8~12 h to obtain amidated carbon nanotube-boron nitride composite filler; mix potassium nitrate, 65% nitric acid and deionized water at a mass ratio of 1:(0.14~0.17):(16~20) to dissolve and prepare electrolyte; add amidated carbon nanotube-boron nitride composite filler at 0.4wt%~0.6wt% to electrolyte, and sonicate for 6~8 h to obtain composite nitrided electrolyte; use stainless steel substrate as working electrode, place it together with platinum sheet counter electrode and calomel reference electrode in composite nitrided electrolyte, and cathodically polarize at a reduction current density of 3~7 mA / cm² for 2~4 h to obtain high salt spray resistant stainless steel material.

[0023] Comparative Example 2: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.4%~0.6%Nb, 0.004%~0.008%C, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2 Pa, heat to 800~1000℃ until all the furnace charge melts, heat to 1570~1590℃, hold for 20~30min, pour the molten steel into a water-cooled mold preheated to 600~800℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1310~1330℃ at a rate of 9~11℃ / min under an argon atmosphere, hold for 3.5~4.5h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1250~1300℃, hold for 1~2h, forge to obtain a stainless steel matrix; (2) Add 3wt%~5wt% of hexagonal boron nitride to a 30% hydrogen peroxide solution, sonicate for 6~8h, stir at 25~30℃ and 200~400r / min for 48~72h, centrifuge, and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol, deionized water, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 3.5~4.5 with sulfuric acid, sonicate for 0.5~1.5h, and stir at 45~55℃ and 200~400r / min for 48~72h, centrifuge and dry to obtain hydroxylated boron nitride; weigh ...γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix Stir at 0~400 r / min for 1.5~2.5 h, add carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and continue stirring for 8~12 h to obtain amidated carbon nanotube-boron nitride composite filler; mix potassium nitrate, 65% nitric acid and deionized water at a mass ratio of 1:(0.14~0.17):(16~20) to dissolve and prepare electrolyte; add amidated carbon nanotube-boron nitride composite filler at 0.4wt%~0.6wt% to electrolyte, and sonicate for 6~8 h to obtain composite nitrided electrolyte; use stainless steel substrate as working electrode, place it together with platinum sheet counter electrode and calomel reference electrode in composite nitrided electrolyte, and cathodically polarize at a reduction current density of 3~7 mA / cm² for 2~4 h to obtain high salt spray resistant stainless steel material.

[0024] Comparative Example 3: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.4%~0.6%Nb, 0.004%~0.008%C, 0.002%~0.003%Zr, 0.002%~0.003%Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2Pa, heat to 800~1000℃ until all the furnace charge melts, heat to 1570~1590℃, hold for 20~30min, pour the molten steel into a water-cooled mold preheated to 600~800℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1310~1330℃ at a rate of 9~11℃ / min under an argon atmosphere, hold for 3.5~4.5h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1250~1300℃, hold for 1~2h, forge to obtain a stainless steel matrix; (2) Add 3wt%~5wt% of hexagonal boron nitride to a 30% hydrogen peroxide solution, sonicate for 6~8h, stir at 25~30℃ and 200~400r / min for 48~72h, centrifuge, and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:(1.5~2):(190~210):(40~50), mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 3.5~4.5 with sulfuric acid, sonicate for 0.5~1.5h, and stir at 45~55℃. Aminated boron nitride filler was prepared by stirring at 200-400 r / min for 1.5-2.5 h; potassium nitrate, 65% nitric acid and deionized water were mixed and dissolved at a mass ratio of 1:(0.14-0.17):(16-20) to prepare electrolyte; aminated boron nitride filler was added to electrolyte at 0.4wt%-0.6wt% and ultrasonically treated for 6-8 h to prepare composite nitride electrolyte; stainless steel substrate was used as working electrode, and placed together with platinum sheet counter electrode and calomel reference electrode in composite nitride electrolyte, and cathodic polarization was performed at a reduction current density of 3-7 mA / cm² for 2-4 h to prepare high salt spray resistant stainless steel material.

[0025] Comparative Example 4: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.4%~0.6%Nb, 0.004%~0.008%C, 0.002%~0.003%Zr, 0.002%~0.003%Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2Pa, heat to 800~1000℃ until all the furnace charge melts, heat to 1570~1590℃, hold for 20~30min, pour the molten steel into a water-cooled mold preheated to 600~800℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1310~1330℃ at a rate of 9~11℃ / min under an argon atmosphere, hold for 3.5~4.5h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1250~1300℃, hold for 1~2h, forge to obtain a stainless steel matrix; (2) Weigh carboxylated multi-walled carbon nanotubes, γ-aminopropyltriethoxysilane, anhydrous ethanol, and deionized water in a mass ratio of 1:(1.5~2):(190~210):(40~50). Mix the carboxylated multi-walled carbon nanotubes, γ-aminopropyltriethoxysilane, anhydrous ethanol, and deionized water. Adjust the pH to 3.5~4.5 with sulfuric acid. Sonicate the mixture for 0.5~1.5 h and stir it at 45~55℃ and 200~400 r / min for 1.5~2.5 h to obtain aminated multi-walled carbon nanotubes. Potassium, 65% nitric acid, and deionized water were mixed and dissolved at a mass ratio of 1:(0.14~0.17):(16~20) to prepare an electrolyte. Aminated multi-walled carbon nanotubes were added to the electrolyte at a mass ratio of 0.4wt%~0.6wt%, and the mixture was ultrasonically treated for 6~8 hours to prepare a composite nitrided electrolyte. A stainless steel substrate was used as the working electrode, and together with a platinum sheet counter electrode and a calomel reference electrode, it was placed in the composite nitrided electrolyte and cathodically polarized at a reduction current density of 3~7mA / cm² for 2~4 hours to prepare a high salt spray resistant stainless steel material.

[0026] Comparative Example 5: A method for preparing a high salt spray resistant stainless steel material includes the following preparation steps: (1) Weigh the raw materials according to the following mass percentages: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.4%~0.6%Nb, 0.004%~0.008%C, 0.002%~0.003%Zr, 0.002%~0.003%Ti, with the balance being iron; place the raw materials in a vacuum induction melting furnace and evacuate to ≤5×10 -2Pa, heat to 800~1000℃ until all the furnace charge melts, heat to 1570~1590℃, hold for 20~30min, pour the molten steel into a water-cooled mold preheated to 600~800℃ to obtain an alloy ingot; place the alloy ingot in a box-type resistance furnace, heat to 1310~1330℃ at a rate of 9~11℃ / min under an argon atmosphere, hold for 3.5~4.5h, remove and air-cool to room temperature to obtain a homogenized ingot; heat the homogenized ingot to 1250~1300℃, hold for 1~2h, forge to obtain a stainless steel matrix; (2) Potassium nitrate, 65% nitric acid and deionized water are mixed and dissolved in a mass ratio of 1:(0.14~0.17):(16~20) to prepare an electrolyte; a stainless steel substrate is used as the working electrode, and together with a platinum sheet counter electrode and a calomel reference electrode, it is placed in the electrolyte and subjected to cathodic polarization treatment at a reduction current density of 3~7mA / cm² for 2~4h to obtain a high salt spray resistant stainless steel material.

[0027] Experimental Example 1: Salt spray corrosion resistance test: Salt spray corrosion resistance test method: The high salt spray resistant stainless steel materials obtained in each example and the materials of comparative examples 1-5 were subjected to neutral salt spray tests according to GB / T10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test". Before the test, the sample surface was cleaned with anhydrous ethanol. The sample was placed at an angle of about 20° to the vertical direction, avoiding the position where the salt spray was directly sprayed. The test temperature was 35℃, and the test was carried out for 72 hours.

[0028] The pitting potential of the high salt spray resistant stainless steel materials obtained in each embodiment and the materials of Comparative Examples 1 to 5 was determined according to GB / T17899-1999 "Method for Measurement of Pitting Potential of Stainless Steel".

[0029] The results are shown in Table 1; A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-5 in Table 1 reveals that the high salt spray resistant stainless steel material prepared by this invention exhibits excellent salt spray corrosion resistance.

[0030] A comparison of Examples 1-3 and Comparative Example 1 reveals that adding 0.4%-0.6% niobium during the stainless steel preparation process allows niobium, as a strong carbide-forming element, to preferentially combine with trace amounts of carbon in the steel to form stable carbides. This effectively prevents the precipitation of chromium carbides and ensures the full solid solution of 15%-16% chromium in the matrix, thereby significantly enhancing the stability and self-healing ability of the material's passivation film. Simultaneously, niobium promotes the selective oxidation of aluminum through the "active element effect," accelerating the formation and repair of a dense protective Al2O3 film, ultimately resulting in a substantial improvement in the material's resistance to salt spray corrosion.

[0031] A comparison of Examples 1-3 and Comparative Example 2 reveals that adding 0.002%-0.003% zirconium and 0.002%-0.003% titanium during the stainless steel preparation process creates a highly efficient composite deoxidation and inclusion modification system. This system preferentially combines with impurities such as oxygen and sulfur in the molten steel, transforming the plastic MnS inclusions, which are prone to pitting corrosion, into fine, chemically stable spherical ZrO2-TiN composite inclusions. This fundamentally eliminates the sensitive sites for pitting corrosion nucleation, significantly enhances the integrity and stability of the passivation film, and thus greatly improves the material's resistance to salt spray corrosion.

[0032] By comparing Examples 1-3 and Comparative Example 3, it can be found that the addition of carboxylated multi-walled carbon nanotubes and hydroxylated boron nitride to carry out an amidation reaction to construct a composite filler, the multi-walled carbon nanotubes, with their unique one-dimensional tubular structure, form a three-dimensional interconnected network between the boron nitride sheets, effectively blocking the longitudinal penetration path of the corrosive medium. Their high conductivity further promotes the uniformity of the electric field distribution during cathodic polarization, enabling the composite filler to migrate efficiently and be firmly embedded in the surface nitride layer, thereby significantly improving the salt spray corrosion resistance of the material.

[0033] By comparing Examples 1-3 and Comparative Example 4, it can be found that after adding hexagonal boron nitride and modifying it with hydroxylation, a composite filler is constructed with carbon nanotubes. Hexagonal boron nitride, with its unique layered structure, forms a dense physical barrier layer on the material surface, effectively blocking the penetration path of corrosive media. Its excellent chemical inertness provides a stable protective interface for the material. At the same time, the boron nitride sheets form a three-dimensional interconnected network structure through amidation reaction with carbon nanotubes, which significantly enhances the density and bonding strength of the surface modification layer, and together endows the material with excellent salt spray corrosion resistance.

[0034] By comparing Examples 1-3 and Comparative Example 5, it can be found that when only conventional nitriding treatment is performed without the addition of amidated carbon nanotube-boron nitride composite filler, although the cathodic polarization process can form a nitrided layer on the substrate surface to provide a certain degree of corrosion resistance, the lack of a synergistic protection system constructed by the composite filler makes it difficult for the surface modified layer to effectively block the continuous penetration of corrosive media. This results in a significant deficiency in the density and long-term stability of the surface modified layer, and its salt spray corrosion resistance is significantly inferior to that of the test group with the addition of composite filler.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A high salt spray resistant stainless steel material, characterized in that, The high salt spray resistant stainless steel material consists of a stainless steel matrix with the following chemical composition by mass percentage, and an amidated carbon nanotube-boron nitride composite nitriding modification layer laminated on the surface of the stainless steel matrix: 15%~16%Cr, 18.5%~19.5%Ni, 1.85%~1.95%Al, 1%~1.5%Si, 1.4%~1.5%Mn, 2%~3%Mo, 0.4%~0.6%Nb, 0.004%~0.008%C, 0.002%~0.003%Zr, 0.002%~0.003%Ti, with the balance being Fe.

2. The high salt spray resistant stainless steel material according to claim 1, characterized in that, The stainless steel matrix is ​​obtained by melting and casting according to the chemical composition described in claim 1, followed by homogenization heat treatment and forging.

3. The high salt spray resistant stainless steel material according to claim 1, characterized in that, The amidated carbon nanotube-boron nitride nitriding modified layer is prepared by using a stainless steel substrate as the working electrode, placing it in a composite nitriding electrolyte, and applying a cathode current for polarization treatment.

4. The high salt spray resistant stainless steel material according to claim 3, characterized in that, The composite nitrided electrolyte is prepared by adding amidated carbon nanotube-boron nitride composite filler to a base electrolyte composed of potassium nitrate, nitric acid and deionized water, and then dispersing it by ultrasonication.

5. The high salt spray resistant stainless steel material according to claim 4, characterized in that, The amidated carbon nanotube-boron nitride composite filler is prepared by hydroxylating hexagonal boron nitride and then amidating it with γ-aminopropyltriethoxysilane and carboxylated multi-walled carbon nanotubes.

6. A method for preparing a high salt spray resistant stainless steel material, characterized in that, The preparation steps include the following: (1) The raw materials are weighed according to the following mass percentages: 15% to 16% Cr, 18.5% to 19.5% Ni, 1.85% to 1.95% Al, 1% to 1.5% Si, 1.4% to 1.5% Mn, 2% to 3% Mo, 0.4% to 0.6% Nb, 0.004% to 0.008% C, 0.002% to 0.003% Zr, 0.002% to 0.003% Ti, and the balance of iron; the raw materials are placed in a vacuum induction melting furnace, vacuum is extracted to ≤5×10 -2 Pa, the temperature is raised to 800 to 1000 ℃ until the furnace charge is completely melted, the temperature is raised to 1570 to 1590 ℃, and the temperature is maintained for 20 to 30 min; the molten steel is poured into a water-cooled mold preheated to 600 to 800 ℃, and an alloy ingot is obtained; the alloy ingot is placed in a box-type resistance furnace, the temperature is raised to 1310 to 1330 ℃ at a rate of 9 to 11 ℃ / min under an argon atmosphere, the temperature is maintained for 3.5 to 4.5 h, and the alloy ingot is taken out and air-cooled to room temperature, and a homogenized ingot is prepared; the homogenized ingot is heated to 1250 to 1300 ℃, the temperature is maintained for 1 to 2 h, and the homogenized ingot is forged, and a stainless steel substrate is prepared. (2) Add 3wt%~5wt% of hexagonal boron nitride to a 30% hydrogen peroxide solution, sonicate for 6~8h, stir at 25~30℃ and 200~400r / min for 48~72h, centrifuge, and dry to obtain hydroxylated boron nitride; weigh hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol, deionized water, carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix hydroxylated boron nitride, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water, adjust the pH to 3.5~4.5 with sulfuric acid, sonicate for 0.5~1.5h, and stir at 45~55℃ and 200~400r / min for 48~72h, centrifuge and dry to obtain hydroxylated boron nitride; weigh ...γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:(1.5~2):(190~210):(40~50):(3~5):(2.5~3.5):(1~3), mix Stir at 0~400 r / min for 1.5~2.5 h, add carboxylated multi-walled carbon nanotubes, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and continue stirring for 8~12 h to obtain amidated carbon nanotube-boron nitride composite filler; mix potassium nitrate, 65% nitric acid and deionized water at a mass ratio of 1:(0.14~0.17):(16~20) to dissolve and prepare electrolyte; add amidated carbon nanotube-boron nitride composite filler at 0.4wt%~0.6wt% to electrolyte, and sonicate for 6~8 h to obtain composite nitrided electrolyte; use stainless steel substrate as working electrode, place it together with platinum sheet counter electrode and calomel reference electrode in composite nitrided electrolyte, and cathodically polarize at a reduction current density of 3~7 mA / cm² for 2~4 h to obtain high salt spray resistant stainless steel material.

7. The method for preparing a high salt spray resistant stainless steel material according to claim 6, characterized in that, The stainless steel substrate obtained by forging in step (1) is a plate with a thickness of 2~4mm.

8. The method for preparing a high salt spray resistant stainless steel material according to claim 6, characterized in that, The hexagonal boron nitride particles in step (2) have a diameter of 100 nm; the multi-walled carbon nanotubes have a diameter of 50 nm and a length of 0.5~2 μm.

9. The method for preparing a high salt spray resistant stainless steel material according to claim 6, characterized in that, Before placing the stainless steel substrate as the working electrode in the composite nitriding electrolyte in step (2), the stainless steel substrate needs to be pretreated, including: cutting the stainless steel substrate into 12mm×12mm squares, polishing the surface with 400#, 800# and 1200# silicon carbide waterproof sandpaper in sequence, and then placing it in a mixed solution prepared by anhydrous ethanol and acetone at a volume ratio of 1:1 for ultrasonic cleaning for 20~30 minutes, rinsing with deionized water, and drying.

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