Method for improving surface performance of nickel-based alloy

Abstract

The invention discloses a method for improving the surface performance of a nickel-based alloy, which comprises the following steps: alloying Pb on the surface of a nickel block, and supersaturating and alloying Pb on the nickel surface to obtain a Pb-rich Ni-Pb alloy layer. Specifically, firstly, Pb powder and a Ni block are mixed through ball milling, so that a layer of Pb powder is attached to the surface of the Ni block; and then a high-current pulse electron beam irradiation technology is utilized to obtain a Pb-rich Ni-Pb alloy layer on the nickel surface. According to the method, the lead is alloyed on the surface of the nickel-based metal, so that the processing performance of the nickel alloy is improved, the lubricity is improved, the corrosion resistance is improved, and the surface hardness of the alloyed nickel-based material is ensured.

Description

Technical Field

[0001] The invention relates to a method for optimizing metal surface properties, and in particular to a method for improving the surface properties of a nickel-based alloy. Background Art

[0002] Nickel is widely used in fields such as stainless steel and alloy steel. Nickel-based alloys have high strength and resistance to oxidation corrosion in high temperature environments and are used in industries such as aviation, shipbuilding, chemicals, electronics and medicine.

[0003] The main processing methods to improve the surface performance of nickel-based alloys and increase their service life include: coating technology, surface treatment, heat treatment, material design, etc. For widely used coating technologies, such as using carbide coatings, ceramic coatings or metal coatings to protect the alloy surface, the corrosion resistance, wear resistance and high temperature performance of nickel-based alloys can be improved. However, the degree of bonding between the coating and the alloy surface needs to consider multiple factors, and there are defects such as insufficient adhesion and easy peeling. At present, the non-equilibrium processing technology - high-current pulsed electron beam (HCPEB) irradiation is used, and a non-equilibrium structure is formed on the alloy surface by combining material design.

[0004] Intense pulsed electron beam equipment is a device that can generate low energy (10-40 keV), high current (10 2 -10 3 A / cm²) and short pulse width (about 10 microseconds). Compared with laser, electron beam has a high absorption coefficient on the metal surface, high efficiency, and is not affected by the optical properties of the material. During HCPEB irradiation, high energy (10 8 ~10 9 W / cm 2 ) is instantly deposited on the surface of the material, causing the surface of the irradiated material to heat, melt and solidify rapidly at the same time, which in turn causes the surface of the material to melt and cool, and then forms a remelting layer on the surface; in addition, phase change, grain refinement and surface composition homogenization are all possible. HCPEB surface treatment technology is an effective way to improve the mechanical properties of materials. Therefore, the development of electron beam surface treatment technology is of great value for the application of nickel-based materials.

[0005] For the surface of HCPEB irradiated materials, the conventional metal surface alloying pretreatment method is to mix the alloy powder with a binder, apply it on the metal surface, and then irradiate it with an electron beam. The pre-irradiated layer prepared in this way has a low degree of bonding with the surface of the metal material, and a large amount of alloy powder is sputtered and lost during the irradiation process, and finally only a small amount of alloy powder forms an alloy layer on the surface. At the same time, considering the solid solubility of the binary alloy, this processing method is not easy to form a supersaturated solid solution, and it is difficult to obtain excellent performance after high solid solubility. Summary of the invention

[0006] Purpose of the invention: In view of the above-mentioned prior art, a method for improving the surface properties of nickel-based alloys is proposed to improve the processing properties of nickel alloys and ensure the surface hardness of nickel-based materials after alloying.

[0007] Technical solution: A method for improving the surface performance of a nickel-based alloy, comprising: alloying Pb on the surface of a nickel block, supersaturating the nickel surface with alloying Pb, and obtaining a Pb-rich Ni-Pb alloy layer.

[0008] Furthermore, firstly, Pb powder and Ni block are mixed by ball milling to make a layer of Pb powder adhere to the surface of Ni block; then, a high-current pulsed electron beam irradiation technology is used to obtain a Pb-rich Ni-Pb alloy layer on the nickel surface.

[0009] Furthermore, during the ball milling process, the ball-to-material mass ratio is 7-10:1, the rotation speed of the ball mill is 200-300 r / min, and the ball milling time is 2-3 hours.

[0010] Furthermore, in the high-current pulse electron beam irradiation technology, the irradiation height is 10-25 cm, and the irradiation energy density is 4-6 J / cm 2 The irradiation times are 10 to 30 times.

[0011] Beneficial effects: 1. This method alloys lead on the surface of nickel-based metal, thereby improving the processing performance of nickel alloy, increasing lubricity and improving corrosion resistance.

[0012] 2. The addition of lead will reduce the hardness of the Ni-Pb alloy layer, which cannot meet the strength requirements in practical applications. The present invention adopts the method of ball milling Ni block and Pb powder, so that the surface of the Ni matrix and the Pb powder are combined by mechanical alloying to increase the degree of alloying. The high-current pulsed electron beam equipment irradiates the surface of the matrix material after the Pb powder is attached. The extremely high-energy energy beam acts on the surface of the material instantly, causing the surface to undergo a process of sudden heating, extreme cooling and directional solidification at the same time, thereby forming a dense, ultra-fine grain and uniformly distributed strengthening layer on the surface, thereby improving the mechanical properties of the material surface. This method can make up for the defect of lead reducing strength, improve the surface performance of nickel-based metals, and extend the service life of devices.

[0013] 3. The method of the present invention has low cost, short cycle, high efficiency and simple operation process, and plays an extremely important role in the practical application of nickel-based alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1Surface scanning images of Ni-Pb alloy samples; (a, b) are after 10 electron beam irradiations, (c) is the backscattering image corresponding to (b), (d, e) are after 20 electron beam irradiations, (f) is the backscattering image corresponding to (e), (g, h) are after 30 electron beam irradiations, (i) is the backscattering image corresponding to (h); Figure 2 Surface microhardness of pure nickel sample and Ni-Pb sample. DETAILED DESCRIPTION

[0015] The present invention will be further explained below in conjunction with the accompanying drawings.

[0016] The method of the present invention alloys Pb on the surface of the nickel block, supersaturates the nickel surface with Pb, and obtains a Pb-rich Ni-Pb alloy layer. The addition of Pb in the Ni-Pb alloy layer can reduce the melting point of the Ni-Pb alloy, making it easier to process and cast, improving lubricity, forming a lubricating film on the friction surface, reducing wear, and improving corrosion resistance.

[0017] The addition of lead will reduce the hardness of the Ni-Pb alloy layer, which cannot meet the strength requirements in practical applications. The strengthening treatment method of the present invention firstly mixes Pb powder and pure Ni block by ball milling to make a layer of Pb powder adhere to the surface of Ni block; then uses high-current pulse electron beam irradiation technology to obtain an alloyed sample containing Pb on the surface of nickel, and the surface has a high-hardness strengthening layer.

[0018] In this method, the Ni block and Pb powder are ball-milled to combine the Ni substrate surface with the Pb powder through mechanical alloying to increase the degree of alloying. The high-current pulsed electron beam device irradiates the surface of the substrate material after the Pb powder is attached. The extremely high-energy energy beam acts on the surface of the material instantly, causing the surface to undergo a process of sudden heating, extreme cooling and directional solidification at the same time, thereby forming a dense, ultra-fine grained and uniformly distributed strengthening layer on the surface, thereby improving the mechanical properties of the material surface.

[0019] The ball-to-material ratio, rotation speed, and ball-milling time during ball milling will affect the alloy layer pre-setting effect of the sample. Selecting appropriate ball milling parameters is very critical for the preparation of the mechanical alloying layer and has an indirect effect on the subsequent irradiation effect. Among them, the ball-to-material mass ratio is maintained at 7~10: 1, the speed of the ball mill is 200-300 r / min, and the ball milling time is 2-3 hours.

[0020] The irradiation intensity, number of irradiations, and height of the electron beam are the key to controlling the formation of a strengthening layer on the sample surface. The irradiation height is 10-25 cm, the irradiation acceleration voltage is 27 keV, the current pulse duration is 1.5 μs, and the energy density is 4-6 J / cm 2, the beam spot diameter is 50-60 mm, the pulse interval is 8-10 s, and the vacuum degree is 5×10 -3 The number of irradiation particularly affects the formation of compounds in the alloy layer, thereby affecting the actual performance. The number of irradiation in the method of the present invention is 10 to 30 times.

[0021] In this embodiment 1, 13 grams of pure lead powder is cut into 1 cm 3 A pure nickel block of about 27 grams and a 300-gram stainless steel grinding ball are evenly mixed in a ball mill. The ball mill is pre-filled with high-purity argon to prevent oxidation during the ball milling process. The ball milling time is 3 hours and the rotation speed is 300 r / min. After ball milling, a nickel block with lead powder attached to the surface is obtained, and a mechanical alloying effect is formed between the powder and the substrate surface. The sample is then irradiated with a high-current pulsed electron beam device. The irradiation acceleration voltage is 27 keV, the current pulse duration is 1.5 μs, and the energy density is 6 J / cm 2 , the beam spot diameter is 60 mm, the irradiation height is 18 cm, the pulse interval is 10 s, and the vacuum degree is 5×10 -3 Pa, and a dense Ni-Pb alloy layer is obtained on the surface.

[0022] In this method, the Pb powder after mechanical ball milling adheres to the nickel surface, and after the impact of the grinding ball, the nickel surface is not smooth enough. After electron beam irradiation, the surface is heated and melted rapidly. Multiple irradiations lead to more energy deposition. The eruption of impurities in the subsurface layer reduces the probability of nucleation of molten pits. The surface molten pits fuse with each other and the number decreases, thereby achieving the effect of surface polishing and even purification. Figure 1 (a) to (c) are the surface morphologies of the ball-milled samples after 10 electron beam irradiation, where (a, b) are the surface morphologies at different magnifications, and (c) is the corresponding backscattering image of (b). It can be seen that after 10 irradiations, the nickel surface has produced molten pits of different sizes, and a large number of aggregated Pb particles are precipitated. Due to the large atomic number of Pb, it presents a high brightness effect. The Pb particles are about 150 nm in size and are densely and evenly distributed on the nickel surface. The surface morphology of the sample after 20 irradiations is shown in (d) to (f). Most of the deeper molten pits tend to be flat after remelting, and the size of the precipitated Pb particles is only about 50 nm. The surface of the alloy layer after 30 irradiations is more dense, with basically no deeper molten pits, and the lead particles are smaller in size, as shown in (g) to (i).

[0023] Generally, the hardness of the alloy will decrease after adding Pb element. The present invention adopts mechanical ball milling to increase the degree of alloying, and uses non-equilibrium processing means to increase the hardness of the surface of the nickel substrate doped with a large amount of Pb element, thus making up for the defect of insufficient strength caused by conventional alloying Pb. Figure 2It can be seen that the hardness of the Ni-Pb alloy layer irradiated 10 times is much lower than that of the pure nickel surface. The surface microhardness is significantly improved after multiple irradiations. The surface hardness after 30 irradiations is slightly higher than that of the pure nickel sample, which makes up for the strength decrease defect after alloying Pb.

[0024] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the surface properties of a nickel-based alloy, characterized in that: include: Pb is alloyed on the surface of the nickel block, and the nickel surface is supersaturated with the alloyed Pb to obtain a Pb-rich Ni-Pb alloy layer.

2. The method for improving the surface properties of nickel-based alloy according to claim 1, characterized in that: First, Pb powder and Ni block are mixed by ball milling to make a layer of Pb powder adhere to the surface of Ni block; then, a Pb-rich Ni-Pb alloy layer on the nickel surface is obtained by high-current pulsed electron beam irradiation technology.

3. The method for improving the surface properties of nickel-based alloy according to claim 2, characterized in that: During the ball milling process, the ball-to-material mass ratio is 7-10:1, the rotation speed of the ball mill is 200-300 r / min, and the ball milling time is 2-3 hours.

4. The method for improving the surface properties of nickel-based alloy according to claim 2 or 3, characterized in that: In the high-current pulse electron beam irradiation technology, the irradiation height is 10-25 cm, and the irradiation energy density is 4-6 J / cm 2 The irradiation times are 10 to 30 times.

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