High-temperature-resistant and corrosion-resistant hydraulic rod and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant and corrosion-resistant hydraulic rod and a preparation method thereof, relates to the technical field of hydraulic element manufacturing, in particular to a high-temperature-resistant and corrosion-resistant hydraulic rod and a preparation method thereof, and is suitable for the fields of heavy-load machinery, aviation, metallurgical equipment and the like in a high-temperature and high-corrosion environment. The invention relates to a ceramic coating rod which comprises an inner core rod and an outer layer rod, the outer layer rod is in a sleeve shape, the inner core rod is fixedly inserted in an inner core of the outer layer rod, and a transition layer, a ceramic coating and a lubricating protective film layer are sequentially arranged on the outer layer of the outer layer rod. And the inner core rod and the outer layer rod are assembled by adopting a thermal process. The inner-layer structure and the outer-layer structure are connected in a high-strength mode, and the inner core rod serves as a bearing main core and can stably support the structure. The outer layer has high surface hardness and corrosion resistance, and the high-performance hydraulic rod is formed by combining the inner layer and the outer layer. The method has the advantages that the surface hardness is high, and adhesion is firm; the corrosion resistance is better than that of the traditional chromium-plated rod or nickel-plated rod; the device can stably work at high temperature (more than or equal to 400 DEG C) and in an acid-base environment; and the process flow is controllable and suitable for batch production.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic component manufacturing, and specifically to a hydraulic rod with excellent high-temperature resistance and corrosion resistance and a preparation method thereof, which is suitable for heavy-load machinery, aviation, metallurgical equipment and other fields under high-temperature and high-corrosion environments. Background Art

[0002] As the core transmission component in hydraulic systems, the performance of hydraulic rods directly impacts the stability and lifespan of equipment. Conventional hydraulic rods are susceptible to surface oxidation, corrosion, and even fracture in high-temperature or highly corrosive environments (such as salt spray, strong acids, alkalis, dust, and high heat). This is especially true under high loads and frequent reciprocating operation. Existing hydraulic rods often suffer from the following defects: weak adhesion and easy peeling of the surface protective layer; decreased mechanical strength at high temperatures, resulting in shortened fatigue life; insufficient corrosion resistance, making them susceptible to corrosion by chlorides or acidic media; and complex coating processes, high costs, and poor consistency during preparation.

[0003] Therefore, there is an urgent need for a new hydraulic rod structure with excellent high temperature resistance and corrosion resistance and an efficient preparation method thereof. Summary of the Invention

[0004] The purpose of the present invention is to address the defects and shortcomings of the existing technology and provide a high-temperature and corrosion-resistant hydraulic rod and a preparation method thereof, which has the following advantages: high surface hardness and firm adhesion; corrosion resistance is better than that of traditional chrome-plated rods or nickel-plated rods; it can operate stably at high temperatures (≥400°C) and in acidic and alkaline environments; the process flow is controllable and suitable for mass production.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a high-temperature resistant and corrosion-resistant hydraulic rod, which includes an inner core rod 1 and an outer layer rod 2. The outer layer rod 2 is sleeve-shaped, and the inner core rod 1 is fixedly inserted into the inner core of the outer layer rod 2. The outer layer of the outer layer rod 2 is sequentially provided with a transition layer 21, a ceramic coating 22, and a lubricating protective film layer 23.

[0006] The inner core rod 1 is made of AISI alloy steel or 42CrMo steel; the outer rod 2 is made of a Ni-based alloy, high-chromium martensitic stainless steel, or a Ni-Cr-Mo superalloy. AISI 4140 alloy steel offers high strength, good processability, and low cost, making it suitable for heavy-duty equipment. It also boasts high strength, high toughness, ease of processing, and affordability. Ni-based alloys offer excellent surface compatibility and strong coating adhesion, resist salt spray, acid and alkali corrosion, and are suitable for coating ceramic and metal layers. High-chromium martensitic stainless steel has a high surface hardness, making it suitable for use after surface strengthening and exhibiting excellent adhesion with ceramic coatings. Ni-Cr-Mo superalloys are extremely corrosion-resistant and suitable for chemically intensive environments.

[0007] The inner core rod 1 and outer layer rod 2 are assembled using a thermal process. Specifically, the outer layer rod 2 is heated with hot oil to increase its inner diameter. Simultaneously, the inner core rod 1 is cooled with liquid nitrogen. After cooling, the inner core rod 1 is inserted into the outer layer rod 2. After natural cooling, the outer layer rod 2 and the inner core rod 1 tightly fit together to form a single hydraulic rod. This inner and outer layer structure provides a high-strength connection. The inner core rod 1 serves as the main load-bearing core, providing a stable support structure. The outer layer has a high surface hardness and corrosion resistance. Together, the inner and outer layers form a high-performance hydraulic rod.

[0008] The transition layer 21 is made of a Ni-Cr alloy and is applied using thermal or cold spraying to form a bonding layer. Arc spraying is used with Ni-Cr alloy wire at a temperature of 2800-3000°C. Arc spraying offers advantages such as simplicity, high adhesion, and low cost. The transition layer 21 strengthens the bond between the ceramic coating and the metal substrate, mitigates differences in thermal expansion coefficients, and prevents flaking and cracking.

[0009] The ceramic coating 22 is made of zirconium oxide (ZrO2) or silicon nitride (Si3N4) and is applied using vacuum ion spraying. Vacuum ion spraying offers advantages such as high density, low oxidation resistance, and superiority over APS. The ceramic coating 22 provides high hardness, wear resistance, corrosion resistance, and high-temperature protection, and is the core functional layer on the surface of this hydraulic rod.

[0010] The thickness of the ceramic coating 22 is 50-150 μm, and the coating process of the ceramic coating 22 is as follows: 1. The outer rod 2 to which the transition layer 21 has been added is subjected to surface roughening, with the surface roughness Ra=1.6-3.2 μm; 2. The surface is sandblasted, the sandblasting material is Al2O3 particles (particle size 50-100 μm), the sandblasting pressure is 0.5-0.6 MPa; the target roughness is Ra≈3-5 μm, and the ceramic coating 22 is sprayed within 2 hours after borax; 3. Ceramic powder is prepared, and Al2O3+Y2O3-ZrO2 composite powder is selected; the powder needs to have high sphericity, be dry, and flowable Good properties; powder can be obtained by spray drying and stored in moisture-proof sealed containers; 4. Use a layered multi-pass spraying method: the thickness of each pass is controlled at 15-25μm; spray 3 to 6 times to form the target thickness (such as 100μm); the workpiece can use a rotary clamping device to make the spraying more uniform; the coating overlap rate is controlled at 30%-50% to avoid cracking of thick layers; the same coating area is not sprayed continuously for more than 2 minutes to prevent thermal accumulation cracking; 5. After cooling, inspection and necessary polishing or fine grinding are carried out: the surface roughness is polished to Ra≤0.2μm; ensure that the roundness and concentricity are controlled within the range of ±0.01mm. The sandblasting process can remove the surface oxide layer, oil stains, and improve the adhesion strength of the coating. Spraying must be completed within 2 hours after sandblasting to prevent oxidation recurrence;

[0011] The lubricating protective film 23 is made of either boron nitride (h-BN) or polytetrafluoroethylene (PTFE). This layer is applied using a solution coating and drying / curing process. Specifically, the lubricating protective film material is sprayed or dip-coated as a dispersion and then cured by drying at 180°C to 220°C. Boron nitride has the advantages of high thermal conductivity and electrical insulation, while polytetrafluoroethylene has the advantages of strong chemical resistance and a very low coefficient of friction.

[0012] After adopting the above technical solution, the beneficial effects of the present invention are:

[0013] Significantly improved high-temperature resistance: The present invention sprays an alumina-zirconia composite ceramic coating on the surface of the hydraulic rod, enabling it to work stably in an environment as high as 500°C or above, significantly expanding the application range of the hydraulic rod in high-temperature environments.

[0014] Excellent corrosion resistance: The ceramic coating is dense and continuous, which can effectively block the erosion of corrosive media such as acids, alkalis, and salts. It is suitable for highly corrosive scenes such as marine, chemical, and metallurgical industries, extending the product service life.

[0015] High hardness and strong wear resistance: The surface hardness of the coating can reach above Hv1200, with excellent impact and scratch resistance. It can effectively resist the wear caused by reciprocating motion and ensure the long-term stable operation of the hydraulic system.

[0016] The coating is firmly and reliably bonded: a transition metal layer is applied before the ceramic layer is sprayed, effectively enhancing the bonding between the coating and the metal substrate. The adhesion strength is ≥70MPa, avoiding problems such as easy shedding and cracking of traditional coatings.

[0017] Good lubricity and reduced friction resistance: Setting a lubricating protective film on the surface of the ceramic coating can effectively reduce the friction resistance between the hydraulic rod and the seal, reduce seal wear, and at the same time reduce operating temperature rise and energy consumption.

[0018] Strong structural maintainability: The present invention adopts a double-layer structure design of a central rod and an outer rod. The outer rod is a coating-bearing substrate. The outer rod can be replaced separately after wear and tear, which facilitates maintenance, reduces replacement costs, and extends the service life of core components.

[0019] Mature technology, suitable for mass production: Using industrially mature processes such as plasma spraying, the process parameters are controllable, the coating consistency is good, suitable for industrial mass production, and has good economic benefits and application prospects.

[0020] In summary, the present invention has significant improvements in high temperature resistance, corrosion resistance, wear resistance and structural reliability, can meet the high requirements of the hydraulic system on the performance of the hydraulic rod under harsh working conditions, and has wide promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 is a schematic diagram of the structure of the invention;

[0023] Figure 2 yes Figure 1 Magnified view of part A.

[0024] Explanation of the accompanying reference numerals: inner core rod 1, outer layer rod 2, outer layer rod 2, transition layer 21, ceramic coating 22, lubricating protective film layer 23. DETAILED DESCRIPTION

[0025] See Figure 1-2 As shown, the hydraulic rod of this specific embodiment includes an inner core rod 1 and an outer layer rod 2. The outer layer rod 2 is sleeve-shaped. The inner core rod 1 is fixedly inserted into the inner core of the outer layer rod 2. The outer layer of the outer layer rod 2 is sequentially provided with a transition layer 21, a ceramic coating 22, and a lubricating protective film layer 23.

[0026] The inner core rod 1 is made of AISI 4140 alloy steel or 42CrMo steel; the outer rod 2 is made of Ni-based alloy (such as Inconel625), high-chromium martensitic stainless steel (410, 420) or Ni-Cr-Mo superalloy (Hastelloy). AISI4140 alloy steel has the advantages of high strength, good processing performance and low cost, and is suitable for heavy-duty equipment; 42CrMo steel has the advantages of high strength, high toughness, easy processing and low price. Ni-based alloys (such as Inconel625) have good surface affinity and strong coating adhesion; they are resistant to salt spray and acid and alkali corrosion; and are suitable for coating ceramic and metal layers; high-chromium martensitic stainless steel (410, 420) has high surface hardness and is suitable for use after surface strengthening, and has good adhesion with ceramic coating; Ni-Cr-Mo superalloy (Hastelloy) is extremely corrosion-resistant and suitable for chemical medium-intensive environments (such as seawater and acid-base mixtures).

[0027] The inner core rod 1 and outer layer rod 2 are assembled using a thermal process. Specifically, the outer layer rod 2 is heated with hot oil to increase its inner diameter. Simultaneously, the inner core rod 1 is cooled with liquid nitrogen. After cooling, the inner core rod 1 is inserted into the outer layer rod 2. After natural cooling, the outer layer rod 2 and the inner core rod 1 tightly fit together to form a single hydraulic rod. This inner and outer layer structure provides a high-strength connection. The inner core rod 1 serves as the main load-bearing core, providing a stable support structure. The outer layer has a high surface hardness and corrosion resistance. Together, the inner and outer layers form a high-performance hydraulic rod.

[0028] The transition layer 21 is made of a Ni-Cr alloy (such as Ni20Cr or Ni80Cr20). It is applied using thermal or cold spraying to form a bonding layer. Arc spraying is used for the transition layer 21, using Ni-Cr alloy wire as the raw material at a temperature of 2800-3000°C. Arc spraying offers advantages such as simple processing, high adhesion strength, and low cost. The transition layer 21 strengthens the bond between the ceramic coating and the metal substrate, mitigates differences in thermal expansion coefficients, and prevents flaking and cracking.

[0029] The ceramic coating 22 is made of zirconium oxide (ZrO2) or silicon nitride (Si3N4) and is applied using vacuum ion spraying. Vacuum ion spraying offers advantages such as high density, low oxidation resistance, and superiority over APS. The ceramic coating 22 provides high hardness, wear resistance, corrosion resistance, and high-temperature protection, and is the core functional layer on the surface of this hydraulic rod.

[0030] The thickness of the ceramic coating 22 is 50-150 μm, and the coating process of the ceramic coating 22 is as follows: 1. The outer rod 2 to which the transition layer 21 has been added is subjected to surface roughening, with the surface roughness Ra=1.6-3.2 μm; 2. The surface is sandblasted, the sandblasting material is Al2O3 particles (particle size 50-100 μm), the sandblasting pressure is 0.5-0.6 MPa; the target roughness is Ra≈3-5 μm, and the ceramic coating 22 is sprayed within 2 hours after borax; 3. Ceramic powder is prepared, and Al2O3+Y2O3-ZrO2 composite powder is selected; the powder needs to have high sphericity, be dry, and flowable Good properties; powder can be obtained by spray drying and stored in moisture-proof sealed containers; 4. Use a layered multi-pass spraying method: the thickness of each pass is controlled at 15-25μm; spray 3 to 6 times to form the target thickness (such as 100μm); the workpiece can use a rotary clamping device to make the spraying more uniform; the coating overlap rate is controlled at 30%-50% to avoid cracking of thick layers; the same coating area is not sprayed continuously for more than 2 minutes to prevent thermal accumulation cracking; 5. After cooling, inspection and necessary polishing or fine grinding are carried out: the surface roughness is polished to Ra≤0.2μm; ensure that the roundness and concentricity are controlled within the range of ±0.01mm. The sandblasting process can remove the surface oxide layer, oil stains, and improve the adhesion strength of the coating. Spraying must be completed within 2 hours after sandblasting to prevent oxidation recurrence;

[0031] The lubricating protective film 23 is made of either boron nitride (h-BN) or polytetrafluoroethylene (PTFE). This layer is applied using a solution coating and drying / curing process. Specifically, the lubricating protective film material is sprayed or dip-coated as a dispersion and then cured by drying at 180°C to 220°C. Boron nitride has the advantages of high thermal conductivity and electrical insulation, while polytetrafluoroethylene has the advantages of strong chemical resistance and a very low coefficient of friction.

[0032] After adopting the above technical solution, the beneficial effects of the present invention are:

[0033] Significantly improved high-temperature resistance: The present invention sprays an alumina-zirconia composite ceramic coating on the surface of the hydraulic rod, enabling it to work stably in an environment as high as 500°C or above, significantly expanding the application range of the hydraulic rod in high-temperature environments.

[0034] Excellent corrosion resistance: The ceramic coating is dense and continuous, which can effectively block the erosion of corrosive media such as acids, alkalis, and salts. It is suitable for highly corrosive scenes such as marine, chemical, and metallurgical industries, extending the product service life.

[0035] High hardness and strong wear resistance: The surface hardness of the coating can reach above Hv1200, with excellent impact and scratch resistance. It can effectively resist the wear caused by reciprocating motion and ensure the long-term stable operation of the hydraulic system.

[0036] The coating is firmly and reliably bonded: a transition metal layer is applied before the ceramic layer is sprayed, effectively enhancing the bonding between the coating and the metal substrate. The adhesion strength is ≥70MPa, avoiding problems such as easy shedding and cracking of traditional coatings.

[0037] Good lubricity and reduced friction resistance: Setting a lubricating protective film on the surface of the ceramic coating can effectively reduce the friction resistance between the hydraulic rod and the seal, reduce seal wear, and at the same time reduce operating temperature rise and energy consumption.

[0038] Strong structural maintainability: The present invention adopts a double-layer structure design of a central rod and an outer rod. The outer rod is a coating-bearing substrate. The outer rod can be replaced separately after wear and tear, which facilitates maintenance, reduces replacement costs, and extends the service life of core components.

[0039] Mature technology, suitable for mass production: Using industrially mature processes such as plasma spraying, the process parameters are controllable, the coating consistency is good, suitable for industrial mass production, and has good economic benefits and application prospects.

[0040] In summary, the present invention has significant improvements in high temperature resistance, corrosion resistance, wear resistance and structural reliability, can meet the high requirements of the hydraulic system on the performance of the hydraulic rod under harsh working conditions, and has wide promotion and application value.

[0041] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A high temperature and corrosion resistant hydraulic rod, characterized by: The invention comprises an inner core rod (1) and an outer layer rod (2). The outer layer rod (2) is sleeve-shaped. The inner core rod (1) is fixedly inserted into the inner core of the outer layer rod (2). The outer layer of the outer layer rod (2) is sequentially provided with a transition layer (21), a ceramic coating (22), and a lubricating protective film layer (23).

2. A high temperature and corrosion resistant hydraulic rod, characterized by: The inner core rod (1) is made of AISI 4140 alloy steel or 42CrMo steel; the outer layer rod (2) is made of Ni-based alloy, high chromium martensitic stainless steel or Ni-Cr-Mo super alloy.

3. A method for preparing a high-temperature resistant and corrosion-resistant hydraulic rod, characterized in that: The inner core rod (1) and the outer layer rod (2) are assembled by a thermal process, specifically, the outer layer rod (2) is heated by hot oil so that the inner diameter of the outer layer rod (2) is increased, and the inner core rod (1) is cooled by liquid nitrogen at the same time. After cooling, the inner core rod (1) is inserted into the outer layer rod (2), and after natural cooling, the outer layer rod (2) and the inner core rod (1) are tightly matched to form a single hydraulic rod.

4. The high temperature and corrosion resistant hydraulic rod according to claim 1, characterized in that: The transition layer (21) is made of Ni-Cr alloy, and the transition layer (21) is formed into a bonding layer by a thermal spraying method or a cold spraying method. The transition layer (21) is formed by arc spraying, the spraying raw material is Ni-Cr alloy wire, and the spraying process temperature is 2800-3000°C.

5. The high temperature and corrosion resistant hydraulic rod according to claim 1, characterized in that: The ceramic coating (22) is made of zirconium oxide or silicon nitride, and the ceramic coating (22) is sprayed by vacuum ion spraying.

6. The high temperature and corrosion resistant hydraulic rod according to claim 4, characterized in that: The thickness of the ceramic coating (22) is 50-150 μm, and the coating process of the ceramic coating (22) is as follows: 1) The outer rod (2) to which the transition layer (21) has been added is subjected to surface roughening, with the surface roughness Ra = 1.6–3.2 μm; 2) The surface was sandblasted, the sandblasting material was Al2O3 particles, the particle size was 50–100 μm, the sandblasting pressure was 0.5–0.6 MPa; the target roughness was Ra≈3–5 μm, and the ceramic coating (22) was sprayed within 2 hours after borax treatment; 3) For ceramic powder preparation, select Al2O3+Y2O3-ZrO2 composite powder; the powder must have high sphericity, be dry, and have good fluidity. The powder can be prepared by spray drying and stored in a moisture-proof sealed container; 4) Use a layered, multi-pass spraying method: control the thickness of each pass to 15–25 μm; spray 3–6 times to achieve the target thickness (e.g., 100 μm); a rotary clamping device can be used on the workpiece to ensure more uniform spraying; control the coating overlap rate to 30%–50% to avoid cracking in thick layers; do not spray the same coating area continuously for more than 2 minutes to prevent thermal cracking. 5). After cooling, carry out inspection and necessary polishing or fine grinding: polish the surface roughness to Ra≤0.2μm; ensure that the roundness and concentricity are controlled within the range of ±0.01mm.

7. The high temperature and corrosion resistant hydraulic rod according to claim 1, characterized in that: The lubricating protective film layer (23) is made of boron nitride or polytetrafluoroethylene, and the lubricating protective film layer (23) is made by a solution coating method + drying and curing process, specifically, the lubricating protective film material is sprayed or dipped in the form of a dispersion, and then dried and cured at 180°C to 220°C.

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