CN115679230B - Surface treatment process for improving hydrogen embrittlement resistance of nickel-based corrosion-resistant alloy - Google Patents

Abstract

The invention discloses a surface treatment process for improving hydrogen embrittlement resistance of a nickel-based corrosion-resistant alloy, which comprises the following steps of: (1) laser fusing treatment: carrying out laser treatment on the nickel-based corrosion-resistant alloy sample, wherein the laser power is 100-200W, and the laser processing speed is 5-10 mm/s; (2) solution treatment: carrying out solid solution on the sample subjected to laser treatment at 1000-1040 ℃ for 0.25-0.5 h, and then carrying out air cooling; (3) aging treatment: and (3) aging the air-cooled sample at 600-800 ℃ for 10-22 hours, and then air-cooling to finish the surface treatment. The invention can improve the hydrogen embrittlement resistance of the material by simple methods such as solid solution aging and the like on the premise of not changing the alloy components, has the characteristics of simple production process, high production speed, lower equipment requirement, high production efficiency, small heat influence, reliable quality and the like, and can also be used for processing parts with a certain degree of complexity.

Description

A surface treatment process to improve the hydrogen embrittlement resistance of nickel-based corrosion-resistant alloys

Technical field

The invention relates to the technical field of alloy surface treatment, and specifically relates to a surface treatment process for improving the hydrogen embrittlement resistance of nickel-based corrosion-resistant alloys.

Background technique

Hydrogen embrittlement refers to the phenomenon that the mechanical properties of metal materials are seriously degraded due to hydrogen absorption or hydrogen penetration, and brittle fracture occurs during the processes of smelting, processing, heat treatment, pickling, electroplating, etc., or when used in hydrogen-containing media for a long time. . Hydrogen embrittlement is not only found in ordinary steel, but also in stainless steel, aluminum alloys, titanium alloys, nickel-based corrosion-resistant alloys and zirconium alloys. From the perspective of mechanical properties, hydrogen embrittlement has the following manifestations: hydrogen has little effect on the yield strength and ultimate strength of metal materials, but it seriously reduces the elongation and area reduction, significantly shortens the fatigue life, and significantly reduces the impact toughness value. Under the continuous action of tensile stress below the breaking strength, the material will suddenly break brittlely after a period of time.

Nickel-based corrosion-resistant alloys not only have unique corrosion resistance and even high-temperature corrosion resistance in many industrial corrosive environments, but also have high strength and good plasticity and toughness. They can be smelted, cast, hot and cold deformed, processed, formed and welded, and are widely used. In the nuclear industry, oil and gas extraction, storage and transportation equipment, hydropower, chemical industry and high-temperature pulp production equipment and other industries. Nickel-based corrosion-resistant alloys have excellent hydrogen embrittlement resistance and are widely used in the manufacturing of oil pipeline valves, bolts and other parts in the petroleum industry. With the wide application of nickel-based corrosion-resistant alloys in various industries, the performance requirements for nickel-based corrosion-resistant alloys in industry are getting higher and higher, and the market demand for nickel-based corrosion-resistant alloys with better hydrogen embrittlement resistance is growing.

In terms of improving the hydrogen embrittlement resistance of nickel-based corrosion-resistant alloys, some use special heat treatment methods to improve the hydrogen embrittlement resistance of nickel-based corrosion-resistant alloys. For example, Chinese patent application CN 110564948 A proposes a method of converting some straight grain boundaries in an alloy into zigzag grain boundaries by controlling the cooling rate heat treatment. This method can convert high-energy straight grain boundaries into low-energy zigzag shapes. Grain boundaries, to a certain extent, improve the hydrogen embrittlement resistance of iron-nickel-based corrosion-resistant alloys. This process is an overall heat treatment of the material. When improving the hydrogen embrittlement resistance, there is often the possibility of deterioration in the mechanical properties of the base material. On the other hand, this air-cooling heat treatment method is only for J100 alloy, so this method has certain limitations.

There are also reports on laser cladding of nickel-based corrosion-resistant alloy coatings to enhance the properties of alloys. For example, Chinese patent application CN 108130528 A proposes a method of cladding nickel-based corrosion-resistant alloy coatings on the surface of Monel 400 alloy. The main method is to laser clad a layer of self-prepared nickel-based corrosion-resistant alloy powder on the Monel 400 substrate to improve the properties of the substrate material. Although this method significantly improves the hardness and wear resistance of the material, it does not involve hydrogen resistance. Moreover, this method requires the preparation of suitable nickel-based corrosion-resistant alloy powder in advance, which undoubtedly adds multiple processes and brings uncertainty to the experimental results.

At present, there are no reports on the use of laser melting and solid solution aging to improve the hydrogen embrittlement resistance of alloys. Laser melting treatment uses high-power density laser to interact with metal in a very short time, so that local areas of the metal surface are instantly heated to a very high temperature to melt it. Subsequently, with the help of the heat absorption and conduction of the liquid metal matrix, the melted surface metal quickly solidifies. Solid solution treatment is to heat the alloy to an appropriate temperature and maintain it for a sufficient time to dissolve certain components in the alloy into the matrix to form a uniform solid solution. Then the alloy is rapidly cooled so that the components dissolved into the matrix remain in the matrix. It becomes a supersaturated solid solution in the body, which can improve the ductility and toughness of the alloy and create conditions for further precipitation hardening treatment. Solution treatment is mostly used for non-ferrous alloys. Aging treatment means that metal or alloy workpieces (such as low carbon steel, etc.) have been solid solution treated, quenched from high temperature or deformed by a certain degree of cold working, and then placed at a higher temperature or room temperature to maintain their shape and size, and their properties will improve with time. Varying heat treatment processes. Generally speaking, after aging, the hardness, strength, plastic toughness and internal stress of the material will change.

Contents of the invention

The purpose of the present invention is to provide a surface treatment process for nickel-based corrosion-resistant alloys in response to the above problems, which can reduce the hydrogen embrittlement sensitivity of nickel-based corrosion-resistant alloys by increasing the hydrogen-resistant grain boundary ratio of the surface layer and improve the resistance of existing nickel-based corrosion-resistant alloys. Hydrogen damage capability.

In order to achieve its purpose, the technical solution adopted by the present invention is:

A surface treatment process for improving the hydrogen embrittlement resistance of nickel-based corrosion-resistant alloys, which is characterized by including the following steps:

(1) Laser melting treatment: perform laser treatment on nickel-based corrosion-resistant alloy samples, the laser power is 100~200W, and the laser processing speed is 5~10mm/s;

(2) Solid solution treatment: The laser-treated sample is dissolved in solution at 1000-1040°C for 0.25-0.5 hours, and then air-cooled;

(3) Aging treatment: The air-cooled samples are aged at 600-800°C for 10-22 hours, and then air-cooled to complete the surface treatment.

Preferably, before laser processing in step (1), the alloy sample is ground to remove iron oxide scale and ensure surface flatness to facilitate laser processing.

Preferably, in step (1), the laser treatment is performed by laser scanning along the plate rolling direction, and the laser spot diameter is 1 to 2 mm.

Preferably, the nickel-based corrosion-resistant alloy is an iron-nickel-based corrosion-resistant alloy.

Preferably, the chemical composition of the nickel-based corrosion-resistant alloy is as follows in weight percentage, nickel: 45.0-55.0%, chromium: 19.5-23.0%, titanium: 0.5-2.5%, aluminum: 0.01-0.7%, silicon: ≤ 0.5%, carbon: 0.005-0.04%, molybdenum: 3.0-4.0%, niobium: 2.5-4.5%, copper: 1.5-3.0%, manganese: ≤1.0%, iron: balance.

Preferably, the laser power for laser melting treatment is 100-180W or 100-150W or 150-200W, and the laser processing speed is 5-7mm/s or 7-10mm/s.

Preferably, the solution treatment is performed at 1000-1040°C for 0.3-0.5h or 0.4-0.5h or 0.5h.

Preferably, the aging treatment is performed at 600-750°C for 12-20 hours.

Further preferably, the aging treatment is performed at 600-730°C or 615-730°C or 620-725°C for 14-18h or 15-17h or 16h.

In the above technical solution, the thickness of the nickel-based corrosion-resistant alloy sample plate is 2 to 4 mm or 2 to 3 mm, and the plate is straight without obvious bending.

The beneficial effects of the present invention are:

1. Without changing the alloy composition, the present invention can improve the hydrogen embrittlement resistance of the material only through relatively simple methods such as solid solution aging after laser treatment. It has the characteristics of simple production process, fast production speed, and low equipment requirements. .

2. The present invention adopts laser melting process, which not only has the characteristics of high production efficiency, small thermal influence, reliable quality, etc., but also can be used to process parts with a certain degree of complexity.

Description of drawings

Figure 1 is an SEM image of the nickel-based corrosion-resistant alloy of the experimental group in Example 1 that was laser melted.

Figure 2 is an EBSD diagram of the nickel-based corrosion-resistant alloy of the experimental group in Example 1 after laser melting.

Figure 3 is an EBSD diagram of the nickel-based corrosion-resistant alloy of the experimental group in Example 1 after the solid solution process.

Figure 4 is an EBSD diagram of the aging process of the nickel-based corrosion-resistant alloy of the experimental group in Example 1.

Figure 5 is an SEM image of the nickel-based corrosion-resistant alloy in Example 2 after laser and solid solution processing.

Detailed ways

The present invention will be further described below with reference to the examples, but the present invention is not limited thereby.

The nickel-based corrosion-resistant alloy in each embodiment of the present invention is Incoloy alloy945, the thickness of the sample plate is 2mm, and its chemical composition is: nickel: 45.0-55.0%, chromium: 19.5-23.0%, titanium: 0.5-2.5%, aluminum :0.01-0.7%, silicon: ≤0.5%, carbon: 0.005-0.04%, molybdenum: 3.0-4.0%, niobium: 2.5-4.5%, copper: 1.5-3.0%, manganese: ≤1.0%, iron: balance .

Example 1

1. Alloy surface treatment

To prepare three parallel experimental group samples of the present invention, follow the following steps:

1. Take a sample of 945 nickel-based corrosion-resistant alloy and grind it to remove iron oxide scale and ensure surface flatness to facilitate laser processing and ensure the uniformity of surface quality after laser processing.

2. Laser melting treatment: Perform laser treatment on the polished sample, scan the laser along the plate rolling direction, the laser power is 100W, the laser processing speed is 5mm/s, the spot diameter is 1mm, the overlap rate is 50%, and the separation rate is 50%. The focal length is 2mm. After laser treatment, SEM analysis was performed. As shown in Figure 1, the grain size of the molten pool area after laser was much smaller than that of the matrix area. The upper part of the molten pool showed columnar crystals and the bottom showed equiaxed crystals.

3. Solid solution treatment: The laser-treated sample was solid solutioned at 1000°C for 0.5h, and then air-cooled.

4. Aging treatment: The air-cooled samples are aged at 621°C for 16 hours, and then air-cooled to complete the surface treatment.

Prepare three parallel control samples at the same time, and the control group samples are processed according to the above steps 1, 3, and 4 (that is, only solid solution aging treatment is performed, and no laser melting treatment is performed).

2. Performance testing

The surface-treated samples were hydrogenated and stretched. The hydrogen charging liquid is a mixture of phosphoric acid and poisoning agent. The hydrogen charging temperature is 75°C, normal pressure, and the hydrogen charging time is 5 hours. Tensile testing was carried out in accordance with GB/T 228.1-2010 "Tensile Testing of Metal Materials Part 1 Room Temperature Test Methods", and the mechanical properties of three parallel samples were averaged. The mechanical properties of the experimental group samples and the control group samples are shown in Table 1 below:

Table 1

It can be seen from the results in Table 1 that the average tensile strength of the nickel-based corrosion-resistant alloy surface treated by the method of the present invention is 1135MPa, the yield strength is 833MPa, and the elongation is 13.4%. The control group only has no laser treatment, and other processing steps are exactly the same as the experimental group. The mechanical properties of the samples in the control group after hydrogenation: tensile strength is 1028MPa, yield strength is 758MPa, and elongation is 9.2%. Comparing the two, it can be found that the tensile strength, yield strength, and elongation of the material after laser treatment are significantly improved, and the hydrogen embrittlement resistance of the material is significantly improved.

The present invention uses laser solid solution aging to perform surface treatment on nickel-based corrosion-resistant alloys. The mechanism is mainly to improve the hydrogen embrittlement resistance of the material by increasing the proportion of Σ3 grain boundaries. The increase of Σ3 grain boundaries can not only improve the corrosion resistance of the alloy, but also improve the corrosion resistance of the alloy. It can also improve the hydrogen embrittlement resistance of the material. First of all, the rapid heating and rapid cooling of laser melting refines the grains, which has the effect of strengthening the fine grains. The average grain size in the molten pool area is only about one-third of the matrix grains (Figure 2). The bottom of the molten pool The grain size is about one-fiftieth of the matrix grain, but the proportion of Σ3 hydrogen-resistant grain boundaries at this time is only 2%. Secondly, the solid solution process increases the proportion of Σ3 hydrogen-resistant grain boundaries, and the Σ3 grain boundaries in the surface melting zone increase from 2% to 43.3% (Figure 3). Finally, the aging process increased the Σ3 grain boundaries to 54.2% (Figure 4). This process also further improved the hardness and plasticity of the material.

Example 2

1. Alloy surface treatment

To prepare three parallel experimental group samples of the present invention, follow the following steps:

1. Take a sample of 945 nickel-based corrosion-resistant alloy and grind it to remove iron oxide scale and ensure surface flatness to facilitate laser processing and ensure the uniformity of surface quality after laser processing.

2. Laser melting treatment: Perform laser treatment on the polished sample, scan the laser along the plate rolling direction, the laser power is 200W, the laser processing speed is 10mm/s, the spot diameter is 1mm, the overlap rate is 50%, and the separation rate is 50%. The focal length is 2mm.

3. Solid solution treatment: The laser-treated sample was solid solutioned at 1040°C for 0.5h, and finally air-cooled. Subsequently, SEM analysis was performed. As shown in Figure 5, the grain size of the laser area after solid solution is still smaller than that of the matrix area. At this time, small grains growing up at the bottom of the molten pool can still be observed.

4. Aging treatment: The air-cooled samples are aged at 721°C for 16 hours, and then air-cooled to complete the surface treatment.

Prepare three parallel control samples at the same time, and the control group samples are processed according to the above steps 1, 3, and 4 (that is, only solid solution aging treatment is performed, and no laser melting treatment is performed).

2. Performance testing

The surface-treated samples were hydrogenated and stretched. The hydrogen charging liquid is a mixture of phosphoric acid and poisoning agent. The hydrogen charging temperature is 75°C, normal pressure, and the hydrogen charging time is 5 hours. Tensile testing was carried out in accordance with GB/T 228.1-2010 "Tensile Testing of Metal Materials Part 1 Room Temperature Test Methods", and the mechanical properties of three parallel samples were averaged. The mechanical properties of the experimental group samples and the control group samples are shown in Table 2 below:

Table 2

It can be seen from the results in Table 2 that the average tensile strength of the nickel-based corrosion-resistant alloy surface treated by the method of the present invention is 1097MPa, the yield strength is 784MPa, and the elongation is 17.7%. The control group only has no laser treatment, and other processing steps are exactly the same as the experimental group. The mechanical properties of the samples in the control group after hydrogenation: tensile strength is 1012MPa, yield strength is 773MPa, and elongation is 11.5%. Comparing the two, it can be found that the tensile strength and elongation of the material after laser treatment are significantly improved, and the hydrogen embrittlement resistance of the material is significantly improved.

Example 3

1. Alloy surface treatment

To prepare three parallel experimental group samples of the present invention, follow the following steps:

1. Take a sample of 945 nickel-based corrosion-resistant alloy and grind it to remove iron oxide scale and ensure surface flatness to facilitate laser processing and ensure the uniformity of surface quality after laser processing.

2. Laser melting treatment: Perform laser treatment on the polished sample, scan the laser along the plate rolling direction, the laser power is 150W, the laser processing speed is 7mm/s, the spot diameter is 1mm, the overlap rate is 50%, and the separation rate is 50%. The focal length is 2mm.

3. Solid solution treatment: The laser-treated sample was solid solutioned at 1020°C for 0.5h, and then air-cooled.

4. Aging treatment: The air-cooled samples are aged at 721°C for 16 hours, and then air-cooled to complete the surface treatment.

Prepare three parallel control samples at the same time, and the control group samples are processed according to the above steps 1, 3, and 4 (that is, only solid solution aging treatment is performed, and no laser melting treatment is performed).

2. Performance testing

The surface-treated samples were hydrogenated and stretched. The hydrogen charging liquid is a mixture of phosphoric acid and poisoning agent. The hydrogen charging temperature is 75°C, normal pressure, and the hydrogen charging time is 5 hours. Tensile testing was carried out in accordance with GB/T 228.1-2010 "Tensile Testing of Metal Materials Part 1 Room Temperature Test Methods", and the mechanical properties of three parallel samples were averaged. The mechanical properties of the experimental group samples and the control group samples are shown in Table 3 below:

table 3

It can be seen from the results in Table 3 that the average tensile strength of the nickel-based corrosion-resistant alloy surface treated by the method of the present invention is 1197MPa, the yield strength is 875MPa, and the elongation is 15.6%. The control group only has no laser treatment, and other processing steps are exactly the same as the experimental group. The mechanical properties of the samples in the control group after hydrogenation: tensile strength is 1075MPa, yield strength is 768MPa, and elongation is 10.8%. Comparing the two, it can be found that the tensile strength, yield strength, and elongation of the material after laser treatment are significantly improved, and the hydrogen embrittlement resistance of the material is significantly improved.

Claims (6)

1. A surface treatment process for improving hydrogen embrittlement resistance of nickel-based corrosion-resistant alloy is characterized by comprising the following steps:

and (3) laser fusion treatment: carrying out laser treatment on the nickel-based corrosion-resistant alloy sample, wherein the laser treatment is scanned along the rolling direction of the plate, the laser power is 100-200W, and the laser processing speed is 5-10 mm/s; the nickel-based corrosion-resistant alloy comprises the following chemical components in percentage by weight: 45.0-55.0%, chromium: 19.5-23.0%, titanium: 0.5-2.5%, aluminum: 0.01-0.7%, silicon: less than or equal to 0.5 percent, carbon: 0.005-0.04%, molybdenum: 3.0-4.0%, niobium: 2.5-4.5%, copper: 1.5-3.0%, manganese: less than or equal to 1.0 percent, iron: the balance;

solution treatment: carrying out solid solution on the sample subjected to laser treatment at 1000-1040 ℃ for 0.4-0.5 h, and then carrying out air cooling;

aging treatment: and (3) aging the air-cooled sample at 600-750 ℃ for 10-20 hours, and then air-cooling to finish the surface treatment.

2. The surface treatment process according to claim 1, wherein: polishing the alloy sample to remove iron oxide scale and ensure surface flatness for laser processing before laser processing in step (1).

3. The surface treatment process according to claim 1, wherein: in the step (1), the diameter of a laser spot is 1-2 mm.

4. The surface treatment process according to claim 1, wherein: and carrying out solution treatment at 1000-1040 ℃ for 0.5h.

5. The surface treatment process according to claim 1, wherein: aging treatment is carried out at 600-730 ℃ for 14-18 h.

6. The surface treatment process according to claim 1, wherein: the thickness of the nickel-based corrosion-resistant alloy sample plate is 2-4 mm, and the plate is straight and has no obvious bending.