Metal coating for pressure-bearing equipment under salt and sulfur containing conditions and preparation process thereof

Abstract

The application discloses a metal coating for pressure-bearing equipment under salt and sulfur containing conditions and a preparation process thereof. The metal powder used in the metal coating comprises 86-90% of Ni, 3.0-4.5% of Cr, 1-2.5% of Cu, 0.8-1.0% of Mo, 1.0-2.0% of B and Si. Compared with the prior art, the coating material can meet the requirement of induction heating on material self-fluxing, the pressure-bearing equipment metal coating is prepared by a new coating process method of coating preparation + electromagnetic induction cladding, the corrosion requirement of the salt and sulfur containing hydrogen medium environment is met, the bonding strength between the coating and the base body is greatly improved, the porosity of the coating is eliminated, the mechanical properties of the pressure-bearing equipment base body material are not affected, and the metal coating is an economic new long-acting corrosion resistant metal coating which can be resistant to strong corrosion conditions and can be popularized and used on pressure-bearing equipment.

Description

Technical Field

[0001] This invention relates to a metal anti-corrosion coating for pressure equipment in the fields of oil and gas processing and petrochemicals under salt and hydrogen sulfide conditions, and its preparation process. Background Technology

[0002] Existing metal spraying technology is widely used as a corrosion-resistant and wear-resistant metal coating on structural components such as steel structures and impellers. However, its widespread use in the oil and gas processing and petrochemical industries is limited by drawbacks such as high porosity (generally above 1.0%) and low bonding strength with the base metal (generally below 80 MPa). Especially under harsh corrosive conditions such as high salt and hydrogen sulfide content, pressure equipment often uses high-quality, expensive corrosion-resistant alloys or metal composites, but these are also limited by the fact that existing heat treatment processes can reduce their corrosion resistance. Therefore, there is an urgent need to find an economical new corrosion-resistant coating material and preparation process that can withstand highly corrosive conditions and be widely used in oil and gas processing equipment and pressure equipment in the petrochemical field. Summary of the Invention

[0003] To overcome the aforementioned shortcomings of existing technologies, this invention proposes a metal coating for pressure equipment under salt and sulfur-containing conditions and its preparation process, applicable to H2S+CO2+Cl... - +H2O or CO2 + Cl - The operating temperature in a +H2O medium environment is below 100℃, Cl - The content is 0.5×10 4 -20×0 4 This invention relates to a pressure-bearing metal coating material with H2S content of 0.5%–15.0% (volume fraction) and CO2 content of 1.0%–10.0% (volume fraction); and employs a novel coating preparation process combining pre-coating and post-treatment. This invention effectively overcomes the shortcomings of existing anti-corrosion coatings, such as low bonding strength between the coating and the substrate material and high porosity.

[0004] The technical solution adopted by the present invention to solve its technical problem is: a metal coating for pressure equipment under salt and sulfur conditions, wherein the metal powder used includes: 86% to 90% Ni, 3.0% to 4.5% Cr, 1% to 2.5% Cu, 0.8% to 1.0% Mo, and 1.0% to 2.0% B and Si.

[0005] This invention also discloses a process for preparing a metal coating for pressure equipment under salt and sulfur conditions, comprising the following steps:

[0006] Step 1: Prepare alloy powder PB-Ni90CrCu:

[0007] Metal mixtures are prepared by screening alloys or pure materials according to the proportions, and then fully mixed by vacuum melting. Finally, alloy powder PB-Ni90CrCu with spherical or near-spherical shape and a particle size of 100-300 mesh or finer is produced by gas atomization.

[0008] Step 2: Pre-treat the parts of the inner wall of the pressure equipment that require protection;

[0009] Step 3: Pre-form a corrosion-resistant metal coating, PVB-Ni90CrCu, on the surfaces inside the pressure equipment that come into contact with the corrosive medium.

[0010] (1) Thermal spraying prefabrication: After drying the alloy powder PB-Ni90CrCu in an oven at 105~115℃ for 6~10h, it is loaded into the powder feeding system. Then, the air compressor, water cooling system and flame spraying equipment are started. On the pre-treated qualified metal substrate, the metal base layer is first sprayed with oxyacetylene flame; then the metal intermediate layer or top layer is sprayed with supersonic flame. After multiple sprayings, the prefabrication thickness reaches the specified thickness or above.

[0011] (2) Pre-coating: On the pre-treated substrate, first apply the metal paste evenly from top to bottom and from left to right using a spray gun or brush to ensure uniform coating thickness. The thickness of a single coating should not exceed 0.15 mm. After the coating surface is completely dry, apply the intermediate layer or top layer in the same way until the pre-coated thickness reaches the specified thickness.

[0012] Step 4: Apply electromagnetic induction heating to the pre-formed coating using a continuous scanning heating method;

[0013] Step 5: Surface quality inspection.

[0014] Compared with the prior art, the positive effects of the present invention are:

[0015] The coating material of this invention can meet the requirements of induction heating for material self-fluxing. It prepares metal coatings for pressure equipment through a novel spraying process of coating prefabrication + electromagnetic induction cladding. It not only meets the corrosion requirements of salt-containing and hydrogen sulfide-containing media environments, but also greatly improves the bonding strength between the coating and the substrate (not less than 300MPa) and eliminates the porosity of the coating (generally 0). It is an economical new type of corrosion-resistant material that can withstand strong corrosion conditions and can be widely used in pressure equipment. Detailed Implementation

[0016] A metal anti-corrosion coating for pressure equipment operating in salt and hydrogen sulfide conditions, comprising the following metal powder: 86%–90% Ni, 3.0%–4.5% Cr, 1%–2.5% Cu, 0.8%–1.0% Mo, and 1.0%–2.0% B and Si. The metal powder is produced by gas atomization, and has a spherical or near-spherical shape with a particle size of 100–300 mesh, suitable for metal coating production.

[0017] A method for preparing a metal coating for pressure equipment operating under salt and hydrogen sulfide conditions includes the following steps:

[0018] Step 1: Prepare alloy powder PB-Ni90CrCu or metal paste

[0019] (1) Select alloys or pure materials and prepare metal mixtures according to the following proportions: 86% to 90% Ni, 3.0% to 4.5% Cr, 1% to 2.5% Cu, 0.8% to 1.0% Mo, 1.0% to 2.0% B and Si; achieve full mixing through vacuum melting, and produce alloy powder PB-Ni90CrCu with spherical or near-spherical shape and particle size of 100 to 300 mesh suitable for flame spraying by gas atomization.

[0020] (2) Metal coating preparation: The adhesive is a composite adhesive such as PVA+HPMC, with a ratio of 5%-12%, and the alloy powder PB-Ni90CrCu accounts for 88%-95%. It is mixed at high speed for 20-40 minutes.

[0021] Step 2: Pre-treat and remove rust from the inner walls of the pressure equipment that require protection.

[0022] (1) Pre-treatment of the inner surface of the equipment: smooth the unevenness and non-circular transition of the substrate surface; clean the burrs, welding slag, dust and loose material on the substrate surface; clean any original surface treatment layer (such as nitriding layer, electroplating layer, etc.) on the substrate surface.

[0023] (2) Load the abrasive into the sandblasting equipment, place the sandblasting gun into the pressure vessel through the operating port, start the air compressor, and manually or automatically operate the sandblasting gun to remove rust from the inner wall of the pressure vessel where protection is required, ensuring that the surface rust removal grade is not lower than Sa3.0. Based on the relationship between the coating thickness and the abrasive grain diameter, select 14-mesh or 16-mesh brown corundum as the abrasive according to the designed coating thickness to ensure good adhesion between the coating and the pressure-bearing equipment.

[0024] Step 3: Pre-form a corrosion-resistant metal coating, PVB-Ni90CrCu, on the surfaces inside the pressure equipment that come into contact with the corrosive medium.

[0025] (1) Thermal spraying pre-treatment: After drying the alloy powder in an oven at 105-115℃ for 6-10 hours, it is loaded into the powder feeding system. The air compressor, water cooling system, and flame spraying equipment are started. On the pre-treated substrate, the metal underlayer is first sprayed with an oxy-acetylene flame: the flow rate of the negative pressure gravity powder feeder is adjusted to 78-80 g / min, the spraying distance is ensured to be 80-100 mm, the oxygen pressure is controlled to be 0.8-0.9 MPa and the oxygen flow rate is 16-20 L / min, and the acetylene pressure is controlled to be 0.1-0.12 MPa and the acetylene flow rate is 11-13 L / min to form an oxidizing flame. The 100-300 mesh alloy powder PB-Ni90CrCu is melted and sprayed into a metal underlayer with performance parameters that meet the requirements by manual or automatic operation of the spray gun; then the metal intermediate layer or top layer is sprayed with supersonic spraying: the nitrogen powder feeder pressure is adjusted to 0. At a pressure of 7–0.80 MPa and a nitrogen flow rate of 0.3–0.4 L / min, ensure a spraying distance of 100–120 mm, control the oxygen pressure at 0.8–0.9 MPa and the oxygen flow rate at 30–32 L / min, and control the propane pressure at 0.6–0.7 MPa and the propane flow rate at 16–20 L / min to form an oxidizing flame. Control the flame blowing air pressure at 0.6–0.7 MPa and the air flow rate at 70–80 L / min, and use a spray gun operated manually or robotically to melt and spray 100–300 mesh alloy powder PB-Ni90CrCu into a metal intermediate or surface layer with performance parameters that meet the requirements until the pre-formed thickness reaches or exceeds the specified thickness.

[0026] (2) Pre-coating: On the pre-treated substrate, use metal powder with a mesh size of not less than 300 mesh or finer; first, use a spray gun or brush to evenly coat the metal paste prepared in step one in the order from top to bottom and from left to right to ensure uniform coating thickness, with a single coating thickness not exceeding 0.15 mm; after the coating surface is completely dry (moisture content less than 10%), brush the intermediate layer and top layer in the same way until the pre-coated thickness reaches the specified thickness.

[0027] During the coating prefabrication process, a thickness gauge is used to check the thickness of the metal coating to ensure that the thickness of the corrosion-resistant coating meets the design requirements (generally 0.3mm to 0.8mm); if the thickness is greater than or equal to the specified thickness of 0.1mm or more, the excess coating can be removed by grinding machinery.

[0028] Step 4: Post-coating treatment using electromagnetic induction heating with continuous scanning heating to improve the bonding strength of the coating and eliminate porosity.

[0029] Place the induction heater trajectory control system inside the container, ensuring that the induction heater can move in a circular motion along the inner wall of the pressure vessel (50–120 mm / min), move axially (0–4.0 m), and adjust radially (1–3 mm from the coating surface). Activate the tooling trajectory control system and the high-frequency induction heating control system (set frequency 80–300 kHz, power 50–200 kW) to ensure the coating consistently reaches the induction remelting temperature (960–1050 °C) and the heat-affected zone thickness is less than or equal to 2 mm, guaranteeing no incomplete melting or over-melting defects in the metal coating. After each cladding pass, adjust the tooling so that the induction gun moves approximately 3 / 4 of the induction coil width, ensuring seamless overlap between coating passes. Repeat the above steps manually or robotically until all areas requiring coating are completed.

[0030] Step 5: Surface quality inspection

[0031] The coating surface should be subjected to ultrasonic and dye penetrant testing to ensure that it is free of defects such as cracks, pores, and inclusions. Otherwise, the defective area should be manually ground down to the substrate for local repair until the coating passes the inspection.

[0032] Working principle of the invention

[0033] The alloy contains over 85% nickel, ensuring excellent resistance to stress corrosion cracking (SCC). The addition of over 3% chromium ensures good resistance to pitting corrosion. Boron and silicon guarantee good wettability between the metal coating and the base metal, as well as self-fluxing properties, resulting in a matching hardness and smooth surface, and eliminating porosity within the coating. The addition of small amounts of Mo and Cu ensures good resistance to pitting and crevice corrosion. The absence of carbides in the alloy ensures the coating's plasticity. Combined with flame spraying followed by induction heating or metal paste coating followed by induction heating, the PVB-Ni90CrCu pressure equipment metal coating is guaranteed to withstand corrosion in salty and wet hydrogen sulfide conditions. It also ensures good bonding strength (not less than 300 MPa) between the coating and the substrate, and between the coating components themselves, preventing coating detachment during pressure testing and use.

Claims

1. A metal coating for pressure equipment under salt and sulfur conditions, characterized in that: The metal powder used includes: 86%–90% Ni, 3.0%–4.5% Cr, 1%–2.5% Cu, 0.8%–1.0% Mo, and 1.0%–2.0% B and Si; The preparation process of the metal coating includes: Step 1: Prepare alloy powder PB-Ni90CrCu using the aforementioned metal powder; Step 2: Pre-treat the parts of the inner wall of the pressure equipment that require protection; Step 3: Pre-form a corrosion-resistant metal coating, PVB-Ni90CrCu, on the surface inside the pressure equipment that comes into contact with the corrosive medium; Step 4: The pre-coated coating is clad using electromagnetic induction heating with continuous scanning heating; the induction remelting temperature of the electromagnetic induction heating is 960-1050°C and the heat-affected layer thickness is less than or equal to 2 mm. Step 5: Surface quality inspection.

2. The metal coating for pressure equipment under salt and sulfur conditions according to claim 1, characterized in that: The first step is as follows: Weigh the metal powder according to the ratio, achieve full mixing through vacuum melting, and produce alloy powder PB-Ni90CrCu with spherical or near-spherical shape and particle size of 100-300 mesh by gas atomization method; The third step is as follows: (1) Thermal spraying prefabrication: After drying the alloy powder PB-Ni90CrCu in an oven at 105-115°C for 6-10 hours, it is loaded into the powder feeding system. Then, the air compressor, water cooling system and flame spraying equipment are started. On the pre-treated qualified metal substrate, the metal underlayer is first sprayed with oxyacetylene flame; then the metal intermediate layer or top layer is sprayed with supersonic spraying. After multiple sprayings, the prefabrication thickness reaches the specified thickness or above. (2) Pre-coating: On the pre-treated metal substrate, first apply the metal paste evenly from top to bottom and from left to right using a spray gun or brush to ensure uniform coating thickness. The thickness of a single coating should not exceed 0.15 mm. After the coating surface is completely dry, apply the intermediate layer or top layer in the same way until the pre-coated thickness reaches the specified thickness.

3. The metal coating for pressure equipment under salt and sulfur conditions according to claim 1, characterized in that: The method for pre-treating the inner wall of the pressure equipment requiring protection, as described in step two, is as follows: (1) Grind the uneven and non-circular transition of the substrate surface to make it smooth; clean the burrs, welding slag, dust and loose material on the substrate surface; clean the original surface treatment layer on the substrate surface. (2) Load the abrasive into the sandblasting equipment, place the sandblasting gun into the pressure vessel through the operating hole, start the air compressor, and operate the sandblasting gun to remove rust from the inner wall of the pressure vessel that needs to be protected, ensuring that the surface rust removal grade is not lower than Sa3.

0.

4. The metal coating for pressure equipment under salt and sulfur conditions according to claim 3, characterized in that: The abrasive is 14-mesh or 16-mesh brown corundum.

5. The metal coating for pressure equipment under salt and sulfur conditions according to claim 1, characterized in that: In step three, during the prefabrication of the metal corrosion-resistant coating, a thickness gauge is used to check the thickness of the metal coating to ensure that the thickness of the corrosion-resistant coating meets the design requirements. If the thickness is greater than or equal to the specified thickness of 0.1 mm, the excess coating can be removed by grinding machinery.

6. The metal coating for pressure equipment under salt and sulfur conditions according to claim 2, characterized in that: In step three, the method of using oxyacetylene flame spraying to coat the metal underlayer is as follows: adjust the flow rate of the negative pressure gravity powder feeder to 78-80 g / min, ensure the spraying distance to 80-100 mm, control the oxygen pressure to 0.8-0.9 MPa and the oxygen flow rate to 16-20 L / min, control the acetylene pressure to 0.1-0.12 MPa and the acetylene flow rate to 11-13 L / min, and after forming an oxidizing flame, operate the spray gun to melt and spray 100-300 mesh alloy powder PB-Ni90CrCu into a metal underlayer with performance parameters that meet the requirements.

7. The metal coating for pressure equipment under salt and sulfur conditions according to claim 2, characterized in that: In step three, the method of supersonic spraying of the metal intermediate layer or top layer is as follows: adjust the nitrogen powder feeder pressure to 0.7-0.80 MPa and the nitrogen flow rate to 0.3-0.4 L / min, ensuring a spraying distance of 100-120 mm; control the oxygen pressure to 0.8-0.9 MPa and the oxygen flow rate to 30-32 L / min; control the propane pressure to 0.6-0.7 MPa and the propane flow rate to 16-20 L / min to form an oxidizing flame; control the flame blowing air pressure to 0.6-0.7 MPa and the air flow rate to 70-80 L / min; and use a spray gun operated manually or by a robot to melt and spray 100-300 mesh alloy powder PB-Ni90CrCu into a metal intermediate layer or top layer with performance parameters meeting the requirements.

8. The metal coating for pressure equipment under salt and sulfur conditions according to claim 2, characterized in that: In step three, the method for preparing the metal paste is as follows: use composite adhesive PVA+HPMC as a binder at a ratio of 5%-12%, and mix it with alloy powder PB-Ni90CrCu at a ratio of 88%-95% for 20-40 minutes by high-speed stirring.

9. The metal coating for pressure equipment under salt and sulfur conditions according to claim 1, characterized in that: Step four describes the method of cladding the pre-formed coating using electromagnetic induction heating with continuous scanning heating: The first step is to place the induction heater trajectory control system inside the container to ensure that the induction heater can move in a circular motion of 50-120 mm / min along the inner wall of the pressure vessel, move 0-4.0 m axially, and be adjusted radially within 1-3 mm from the coating surface. The second step is to start the tooling trajectory control system and the high-frequency induction heating control system, with a frequency of 80-300 KHz and a power of 50-200 Kw, to ensure that there are no defects in the metal coating that are not fully melted or over-melted. Third step: After each cladding is completed, adjust the tooling so that the induction gun moves 3 / 4 of the width of the induction coil to ensure that there is no gap between each coating layer. Then repeat the above steps until all areas that need to be sprayed are completed.

10. The metal coating for pressure equipment under salt and sulfur conditions according to claim 1, characterized in that: The surface quality inspection method described in step five is as follows: ultrasonic and colorimetric tests are performed on the coating surface. If the coating has defects such as cracks, pores, or slag inclusions, the defective area is manually ground down to the substrate and local repair is carried out until the inspection is qualified.