A method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder

Abstract

The present invention relates to a method for preparing a cladding coating using an iron-based metal coating containing nano-iron powder. The method comprises the following steps: 1) preparing the iron-based metal coating by uniformly mixing iron-based pre-alloyed powder, triolein, PVB, anhydrous ethanol, DOP, cyclohexanone, and hydrazine hydrate; 2) soaking a workpiece in the iron-based metal coating two to five times, drying it at 100 to 300°C in a hydrogen atmosphere, then evenly spraying a water glass solution onto the workpiece surface. The workpiece is then held at 200 to 400°C in a hydrogen atmosphere for 0.5 to 4 hours; and 3) subjecting the dried workpiece to carbon arc cladding to form a metallurgical bond. This method has the advantage of forming a uniformly adherent alloy coating on the workpiece surface. After drying the iron-based metal coating containing nano-iron powder, arc cladding is performed to obtain a metallurgically bonded coating, minimizing the thermal impact of the coating densification process on the substrate material and ensuring uniform and tight adhesion of the cladding layer to the component.

Description

Technical Field

[0001] This invention belongs to the field of welding material preparation, and relates to a method for preparing welding coatings using iron-based metal coatings containing nano-iron powder. Background Technology

[0002] In existing technologies, surfacing is a widely used method for material repair and surface strengthening, generally used to prepare wear-resistant, heat-resistant, and impact-resistant coatings. Surfacing processes include arc surfacing, submerged arc surfacing, and electroslag surfacing, using raw materials such as welding electrodes, flux-cored wires, and powder blocks. For small parts and in cases where manufacturing costs are low, arc surfacing has significant advantages. Currently, arc surfacing typically uses powder blocks as raw material, which involves mixing the required alloy components with a binder, pressing them into thin blocks, drying them, and then tightly stacking them on the surface of the workpiece to be repaired. The metallurgically bonded coating is then prepared by melting the powder with an electric arc.

[0003] In the existing technology, the research on high-temperature coating protection cladding technology published by Tian Haoliang et al. in the June 2010 issue of "Welding" involves first coating a nickel-based self-fluxing alloy powder onto a carbon steel surface, followed by coating with a high-temperature protective coating. After drying the coating, the surface is heated in a high-temperature furnace until the melting point of the self-fluxing alloy powder is reached, at which point the alloy spreads on its own. After cooling to room temperature, a cladding layer is obtained. However, for some components with complex shapes and structures, the powder block arc welding process cannot achieve good full coverage and tight spreading, ultimately resulting in insufficient bonding strength between the weld overlay coating and the substrate.

[0004] To address this issue, a process for preparing composite materials using metal coatings has been proposed. This involves preparing alloy powder as a metal coating, uniformly coating it onto the surface of a substrate material, drying it, heating it in a high-temperature furnace to above the powder's melting point or sintering temperature, holding it at that temperature, and then cooling it to obtain the desired coating. However, since the alloy and its melting point have high sintering temperatures, heating the workpiece during coating preparation is equivalent to heat-treating the substrate material, which inevitably affects the material's properties. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder. The method involves forming a uniformly covered weld overlay layer on the surface of a substrate material using the metal coating, followed by drying, and then obtaining a metallurgically bonded coating through arc welding. This reduces the thermal impact of the coating densification process on the substrate material, achieving uniform and tight adhesion between the weld overlay layer and the component. The weld overlay process can be used to prepare a metallurgically bonded coating on the surface of workpieces with complex shapes, avoiding the impact of high-temperature treatment on the substrate material.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder includes the following steps:

[0008] 1) Preparation of iron-based metal coatings

[0009] Iron-based pre-alloyed powder, trioleic acid glyceride, PVB, anhydrous ethanol, DOP, cyclohexanone, and hydrazine hydrate are mixed evenly to obtain an iron-based metal coating.

[0010] 2) Preparation of weld overlay alloy layer

[0011] The workpiece is immersed in iron-based metal coating 2 to 5 times to form a material layer of the required thickness on the workpiece. It is then dried at 100 to 300°C in a hydrogen atmosphere. After that, water glass solution is evenly sprayed onto the surface of the workpiece. Then, the temperature is raised to 200 to 400°C in a hydrogen atmosphere and held for 0.5 to 4 hours.

[0012] 3) Welding treatment

[0013] The dried workpiece is then subjected to carbon arc welding to form a metallurgical bond. The welding current is 230-260A, the voltage is 40-50V, the welding electrode is oscillating in a rectangular manner, DC positive polarity is used, and the arc column height is 4-7mm.

[0014] The iron-based metal coating is composed of the following raw materials in the following parts by weight:

[0015] Iron-based pre-alloyed powder 50%–54%; trioleic acid glyceride 0.15%–0.3%; PVB 4%–6%; anhydrous ethanol 35%–45%; DOP 0.3%–1%; cyclohexanone 2%–4%; hydrazine hydrate 0.15%–0.3%.

[0016] The particle size of the iron-based pre-alloyed powder is ≤10μm.

[0017] The iron-based pre-alloyed powder has a D50 of <5μm and a sphericity of >95.

[0018] The iron-based pre-alloyed powder comprises, by mass percentage:

[0019] Cr 14%–18%, C 2%–6%, balance iron and unavoidable impurities.

[0020] The iron-based pre-alloyed powder comprises, by mass percentage:

[0021] Cr 14%–18%, C 2%–6%, B 0.5%–1.5%, Si 0.8%–1.5%, balance being iron and unavoidable impurities.

[0022] The water glass solution in step 2) has a mass concentration of 70% to 80%.

[0023] The weld overlay layer formed after step 3) has a relative density RD of 100%, a hardness of 66-69 HRC, and a thickness of no more than 5 mm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The method of preparing weld overlay coatings using iron-based metal coatings containing nano-iron powder can form a uniformly adhered alloy coating on the workpiece surface, without being limited by the shape of traditional powder block weld overlays. After drying the iron-based metal coating containing nano-iron powder, a metallurgically bonded coating is obtained by arc welding, reducing the thermal impact of the coating densification process on the substrate material, and achieving uniform and tight adhesion between the weld overlay layer and the component. The weld overlay process can prepare metallurgically bonded coatings on the surface of workpieces with complex shapes, avoiding the impact of high-temperature treatment on the substrate material.

[0026] Iron-based metal coatings containing nano-iron powder use metal powder and solvents such as anhydrous ethanol as raw materials. Baking under a hydrazine hydrate and hydrogen atmosphere prevents oxidation of the alloy powder. The nano-iron powder induces sintering during the drying process, increasing the strength of the weld overlay coating layer after drying.

[0027] Spraying a water glass solution onto the surface of the iron-based metal coating can increase the stability of the metal coating and prevent the weld overlay layer from falling off during the welding process. Detailed Implementation

[0028] The present invention will now be described in detail, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0029] Example 1

[0030] A method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder includes the following steps:

[0031] 1) Preparation of iron-based metal coatings

[0032] The iron-based metal coating is obtained by mixing 52% iron-based pre-alloyed powder, 0.25% trioleic acid glyceride, 4.5% PVB, 40% anhydrous ethanol, 0.25% hydrazine hydrate, 2.5% cyclohexanone, and 0.5% DOP by mass fraction and stirring thoroughly.

[0033] The iron-based pre-alloyed powder is selected with a particle size of <8μm and a D50 of <5μm. The iron-based pre-alloyed powder includes, by mass percentage: 16% Cr, 6% C, and the balance being iron.

[0034] 2) Preparation of weld overlay alloy layer

[0035] The No. 45 steel workpiece was immersed in iron-based metal coating five times (each time after drying before immersion) to prepare a material layer of the required thickness. The workpiece was then kept at 200°C for 2 hours in a hydrogen atmosphere. After that, a 70% water glass solution was uniformly sprayed onto the surface of the workpiece. Finally, the workpiece was heated to 400°C in a hydrogen atmosphere and kept at that temperature for 2 hours.

[0036] 3) Welding treatment

[0037] The dried workpiece was subjected to carbon arc welding to form a metallurgical bond. The welding current was 235A, the voltage was 40V, the welding electrode was used in a rectangular oscillation, DC positive polarity was used, and the arc column height was 5mm. The composite material of the weld overlay layer had a relative density RD of 100% and a hardness of 67HRC.

[0038] Example 2

[0039] A method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder includes the following steps:

[0040] 1) Preparation of iron-based metal coatings

[0041] The iron-based metal coating is obtained by mixing 52% iron-based pre-alloyed powder, 0.25% trioleic acid glyceride, 4.5% PVB, 40% anhydrous ethanol, 0.25% hydrazine hydrate, 2.5% cyclohexanone, and 0.5% DOP by mass fraction and stirring thoroughly.

[0042] The iron-based pre-alloyed powder has a particle size of <10μm and a D50 of <4μm. The iron-based pre-alloyed powder comprises, by mass percentage: 16% Cr, 6% C, 1% B, 0.8% Si, with the balance being iron.

[0043] 2) Preparation of weld overlay alloy layer

[0044] The No. 45 steel was immersed in the metal coating four times (each time after drying before immersion) to prepare a material layer of the required thickness. The layer was then kept at 300°C for 2 hours in a hydrogen atmosphere. After that, a 75% concentration water glass solution was uniformly sprayed onto the surface of the workpiece. Finally, the temperature was raised to 300°C in a hydrogen atmosphere and kept at that temperature for 2 hours.

[0045] 3) Welding treatment

[0046] The dried workpiece is then subjected to carbon arc welding to form a metallurgical bond. The welding current is 240A, the voltage is 40V, the welding electrode is used in a rectangular oscillation, DC positive polarity is applied, and the arc column height is 6mm. The composite material of the weld overlay layer has a relative density of 100% and a hardness of 67.5HRC.

[0047] Example 3

[0048] A method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder includes the following steps:

[0049] 1) Preparation of iron-based metal coatings

[0050] The iron-based metal coating is obtained by mixing 52% iron-based pre-alloyed powder, 0.25% trioleic acid glyceride, 4.5% PVB, 40% anhydrous ethanol, 0.25% hydrazine hydrate, 2.5% cyclohexanone, and 0.5% DOP by mass fraction and stirring thoroughly.

[0051] The iron-based pre-alloyed powder has a particle size of <10μm and a D50 of <1μm. The iron-based pre-alloyed powder comprises, by mass percentage: 16% Cr, 6% C, 1.2% B, 0.8% Si, with the balance being iron.

[0052] 2) Preparation of weld overlay alloy layer

[0053] Q355 steel was immersed in a metal coating 6 times to prepare a material layer of the required thickness. The layer was then kept at 200°C for 1.5 hours in a hydrogen atmosphere. After that, an 80% concentration water glass solution was uniformly sprayed onto the surface of the workpiece. Finally, the temperature was raised to 300°C in a hydrogen atmosphere and kept at that temperature for 2 hours.

[0054] 3) Welding treatment

[0055] The dried workpiece was then subjected to carbon arc welding to form a metallurgical bond. The welding current was 245A, the voltage was 40V, the welding electrode was used in a rectangular oscillation, DC positive polarity was applied, and the arc column height was 7mm. The composite material of the weld overlay layer had a relative density of 100% and a hardness of 66HRC.

Claims

1. A method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder, characterized in that, Includes the following steps: 1) Preparation of iron-based metal coatings Iron-based pre-alloyed powder, triolein, PVB, anhydrous ethanol, DOP, cyclohexanone, and hydrazine hydrate are mixed evenly to obtain an iron-based metal coating; the iron-based metal coating is composed of the following raw materials in the following mass percentages: Iron-based pre-alloyed powder 50%~54%; trioleic acid glyceride 0.15%~0.3%; PVB 4%~6%; anhydrous ethanol 35%~40%; DOP 0.3%~1%; cyclohexanone 2%~4%; hydrazine hydrate 0.15%~0.3%; 2) Preparation of weld overlay alloy layer The workpiece is immersed in iron-based metal coating 2 to 5 times to form a material layer of the required thickness on the workpiece. It is then dried at 100 to 300°C in a hydrogen atmosphere. After that, water glass solution is evenly sprayed onto the surface of the workpiece. Then, the temperature is raised to 200 to 400°C in a hydrogen atmosphere and held for 0.5 to 4 hours. 3) Welding treatment The dried workpiece is then subjected to carbon arc welding to form a metallurgical bond. The welding current is 230~260A, the voltage is 40~50V, the welding electrode is oscillating in a rectangular manner, DC positive polarity is used, and the arc column height is 4~7mm.

2. The method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder according to claim 1, characterized in that, The particle size of the iron-based pre-alloyed powder is ≤10μm.

3. The method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder according to claim 1, characterized in that, The iron-based pre-alloyed powder has a D50 of <5μm and a sphericity of >95.

4. The method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder according to claim 1, characterized in that, The iron-based pre-alloyed powder comprises, by mass percentage: Cr 14%~18%, C 2%~6%, balance iron and unavoidable impurities.

5. The method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder according to claim 1, characterized in that, The iron-based pre-alloyed powder comprises, by mass percentage: Cr 14%~18%, C 2%~6%, B 0.5%~1.5%, Si 0.8%~1.5%, balance iron and unavoidable impurities.

6. The method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder according to claim 1, characterized in that, The water glass solution in step 2) has a mass concentration of 70% to 80%.

7. The method for preparing a weld overlay coating using an iron-based metal coating containing nano-iron powder according to claim 1, characterized in that, The weld overlay layer formed after step 3) has a relative density of 100%, a hardness of 66~69HRC, and a thickness of no more than 5mm.