CN116377376A - A method for low-temperature ion carbonitriding of nickel-based alloys - Google Patents

Abstract

The invention belongs to the technical field of metal surface hardening treatment. In order to solve the problem that the thickness of the permeated layer is low and the corrosion resistance is reduced after the surface treatment of the nickel-based alloy is carried out by the conventional ion carbonitriding method, the invention discloses a nickel-based alloy A method of low temperature ion carbonitriding. In this method, the nickel-based alloy workpiece is first placed in the ion diffusion furnace, and the air pressure in the ion diffusion furnace is evacuated, then argon gas is introduced for glow bombardment, and acetylene, nitrogen and hydrogen are respectively introduced for high-pressure ionization. Carburizing and nitriding, and finally using a formula cleaner to wash off the metal nitrides on the surface. By adopting the method for low-temperature ion carbonitriding of nickel-based alloys of the present invention, a hardened layer with a certain thickness and uniform thickness can be formed on the surface of nickel-based alloys, so that the nickel-based alloys have good corrosion resistance while maintaining the original corrosion resistance. hardness and wear resistance.

Description

A method for low-temperature ion carbonitriding of nickel-based alloys

technical field

The invention relates to the technical field of metal surface hardening treatment, and more specifically relates to a method for low-temperature ion carbonitriding of nickel-based alloys.

Background technique

Nickel-based alloy is an important strategic metal material. It has good corrosion resistance and oxidation resistance, and also has special functional properties such as electromagnetics and memory. It is one of the hot research metals at home and abroad. . However, the wear resistance and other mechanical properties of nickel-based alloys are not ideal, which greatly limits the industrial application of nickel-based alloys. Therefore, ion carbonitriding can be used to improve their mechanical properties.

Carbonitriding is a chemical surface heat treatment process that infiltrates carbon and nitrogen atoms into the surface of a workpiece at a certain temperature and in a certain medium. This process can produce a hardened layer on the nickel-based alloy. It combines the advantages of large hardening depth of carburizing treatment and high hardness of nitriding treatment to a certain extent, so that the workpiece has high hardness, thermal stability and dispersion. At the same time, the depth of the hardened infiltration layer is also large, so the mechanical properties of the material are greatly improved.

Although nickel-based alloys can obtain a hardened layer with better performance through ion nitriding, most of the Cr ions in the nitriding layer of nickel-based alloys are often in the form of chromium-containing nitrides during ion nitriding of nickel-based alloys. Precipitation reduces the corrosion resistance of nickel-based alloys. Moreover, after the traditional nickel-based alloy ion nitriding, a passivation film mainly composed of CrN and Cr2N3 will be formed on the surface to hinder the progress of carbonitriding, resulting in a thin nitride layer formed by nickel-based alloy ion nitriding, and Uneven thickness. Therefore, a low-temperature ion carbonitriding method for nickel-based alloys is proposed, which can improve hardness and wear resistance while maintaining its corrosion resistance.

Contents of the invention

In order to solve the problems of reduced corrosion resistance, thin and uneven thickness of the nitrided layer after the surface treatment of the nickel-based alloy by the carbonitriding treatment method, the present invention proposes a brand new carbonitrided nickel-based alloy. method of infiltration. By adopting the nickel-based alloy carbonitriding treatment process of the present invention, and using an acidic cleaning agent for pickling, the surface nitrides can be removed, so that the nickel-based alloy has good hardness and corrosion resistance while maintaining the original corrosion resistance. Abrasive.

To achieve the above object, the present invention provides the following technical solutions:

A method for low-temperature ion carbonitriding of nickel-based alloys, comprising the steps of:

The first step: put the nickel base alloy workpiece that has been cleaned and dried on the surface into the ion diffusion furnace, and evacuate the air pressure in the ion diffusion furnace to below 10Pa;

Step 2: Introduce argon gas, set the voltage to 750-850V, adjust the gas pressure to less than 80Pa, turn on the glow and bombard for 0.5-2h, and the specific time of bombardment can be 0.5h;

Step 3: Turn off the argon gas, feed acetylene and hydrogen into the ion nitriding furnace for ion bombardment, adjust the gas ratio and increase the air pressure to 100-300Pa, make the temperature in the ion permeation furnace reach 500-550°C, and keep warm 2~10h, then turn off the acetylene gas, wait for the temperature in the furnace to cool down to below 450°C, feed nitrogen gas, turn on the ion permeation furnace, set the temperature at 400~450°C and carry out ion nitriding for 1~5h;

Step 4: Pickling the nickel-based alloy that has completed low-temperature ion carbonitriding with an acidic cleaning agent.

By adopting the above technical scheme, ion carbonitriding is a chemical heat treatment process that utilizes the principle of glow discharge to infiltrate active nitrogen and carbon atoms generated by gas ionization, absorb on the surface of the workpiece and diffuse to the inside to form a hardened layer. Put the workpiece as a cathode into a negative pressure container with a nitrogen-containing medium, and the furnace wall is used as an anode to pass a direct current, and the nitrogen and hydrogen atoms in the medium are ionized. Under the action of a strong electric field, the metal surface is bombarded, and the kinetic energy of the ions is converted When heated to the required temperature as thermal energy, nitrogen and carbon atoms are absorbed by the surface of the workpiece, and diffuse to the inside to form nitrogen and carbide. The present invention improves conventional carbonitriding of nickel-based alloys into two-stage ion carbonitriding, that is, before ion carbonitriding, firstly, high-pressure argon ions are used to sputter the surface of nickel-based alloys to remove the passivation film The purpose of fully activating the surface is to ensure the thickness of the hardened layer; then carry out ion carbonitriding, so that the surface of the nickel-based alloy can achieve a dynamic balance between the sputtering and deposition processes, and promote the rapid infiltration of carbon and nitrogen atoms to ensure the thickness of the hardened layer uniformity, and the present invention adjusts and optimizes the time and temperature, under the premise of ensuring the processing efficiency and processing cost and not reducing the corrosion resistance of the nickel-based alloy, the surface of the nickel-based alloy forms a high-quality hardened surface with a certain thickness and uniform thickness layer, so that nickel-based alloys can obtain good hardness and wear resistance.

Preferably, in the second step, argon high-pressure bombardment is carried out. During the bombardment, the gas pressure must be less than 80Pa and the voltage higher than 750V, so as to ensure a strong enough sputtering effect to eliminate the passivation film on the nickel-based surface.

Preferably, in the third step, the temperature in the ion nitriding furnace is 500°C when performing high-pressure ion carburizing, and further, the ion carburizing time is 8 hours, and the ion nitriding time is 4 hours. The nitrided layer obtained in this way The thickness can reach 13.06μm.

Preferably, in the fourth step, the proportioning of the acid cleaning agent used during pickling is 300ml/L of nitric acid, 40ml/L of hydrofluoric acid, 25g/L of potassium dichromate, 0.5g/L of acid corrosion inhibitor, and the surface The active agent is 2ml/L, and the balance is water; among them, the ratio of nitric acid 300ml/L, hydrofluoric acid 40ml/L, potassium dichromate 25g/L, acid corrosion inhibitor 0.5g/L, surfactant 2ml/L, the balance is water.

Preferably, the fifth step is also included: polishing the nickel-based alloy workpiece completed in the fourth step to achieve a surface roughness Ra<0.8, cleaning the surface of the nickel-based alloy workpiece after pickling and polishing, and drying .

Beneficial effects of the present invention: before ion carbonitriding, first use high-pressure argon ion sputtering on the surface of the nickel-based alloy to achieve the purpose of removing the passivation film and fully activating the surface, and ensure the thickness of the hardened layer; by adjusting the time and temperature On the premise of ensuring the processing efficiency and processing cost without reducing the corrosion resistance of the nickel-based alloy, a high-quality hardened layer with a certain thickness and uniform thickness is formed on the surface of the nickel-based alloy, so that the nickel-based alloy can obtain good hardness and wear resistance; surface nitrides can be removed after pickling with an acidic cleaning agent, so that the nickel-based alloy has good hardness and wear resistance while maintaining the original corrosion resistance.

Description of drawings

Fig. 1 is the schematic diagram one that reflects the thickness of the hardened layer of the nickel-based alloy workpiece in a specific embodiment of the present invention;

Fig. 2 is the schematic diagram two reflecting the thickness of the hardened layer of the nickel-based alloy workpiece in a specific embodiment of the present invention;

Fig. 3 is the schematic diagram three reflecting the thickness of the hardened layer of the nickel-based alloy workpiece in a specific embodiment of the present invention;

Fig. 4 is the schematic diagram four reflecting the thickness of the hardened layer of the nickel-based alloy workpiece in a specific embodiment of the present invention;

Fig. 5 is the schematic diagram five reflecting the thickness of the hardened layer of the nickel-based alloy workpiece according to a specific embodiment of the present invention;

Fig. 6 is a schematic diagram six reflecting the thickness of the hardened layer of a nickel-based alloy workpiece according to a specific embodiment of the present invention;

Figure 7 is a schematic diagram of the surface morphology before and after the test of a specific embodiment of the invention reflecting a nickel-based alloy workpiece;

Figure 8 is a schematic diagram of the surface morphology before and after the test of a specific embodiment of the invention reflecting a nickel-based alloy workpiece II;

Fig. 9 is a third schematic diagram showing the surface morphology of a nickel-based alloy workpiece before and after a test according to a specific embodiment of the present invention.

Implementation

In the present invention, through the improvement of the nickel-based alloy process, a hardened layer with a certain thickness and uniform thickness is formed on the surface of the nickel-based alloy after carbonitriding, so that the nickel-based alloy can obtain good hardness, wear resistance and corrosion resistance .

Comprise the following steps when the present invention is concretely implemented:

The first step is to clean and dry the surface of the nickel-based alloy workpiece to be treated by an ultrasonic cleaning machine to avoid the influence of oil and impurities on the subsequent carbonitriding; then the nickel-based alloy workpiece that has been cleaned and dried The alloy workpiece is placed in the ion infiltration furnace, and the air pressure in the ion infiltration furnace is evacuated to below 10Pa, so as to facilitate the breakdown gas to generate glow discharge. In addition, other surface cleaning and drying processes can also be used to achieve the purpose of derusting, degreasing and drying nickel-based alloy workpieces.

The second step is to feed argon gas into the ion diffusion furnace, set the voltage at 750-850V, adjust the gas pressure below 80Pa, and turn on the ion diffusion furnace to bombard for 0.5h, which can ensure a strong enough sputtering effect to eliminate The oxide film on the surface of the nickel-based alloy and the purpose of fully activating the surface can also improve the cleaning effect of the nickel-based alloy and the heating rate in the ion diffusion furnace, thereby saving time and improving work efficiency.

The third step is to carry out carbonitriding on the nickel-based alloy workpiece. When the temperature in the ion infiltrating furnace reaches 500-550°C, adjust the pressure so that the pressure in the ion infiltrating furnace is 300 Pa for ion carburizing for 8 hours, that is, acetylene and hydrogen are introduced into the ion nitriding furnace for ion bombardment. Through the ion carburizing treatment of this step, strong ion sputtering occurs on the surface of the workpiece, which promotes the change of the surface state of the nickel-based alloy, and achieves the purpose of removing the passivation film and fully activating the surface; stop the introduction of acetylene gas, and start to pass Nitrogen gas (there is hydrogen in the two stages of feeding acetylene and nitrogen gas), so that the pressure in the ion permeation furnace is 300Pa, and the temperature in the ion nitriding furnace is maintained below 450°C for ion nitriding 4h. At this time, by performing low-temperature and high-pressure ion nitriding treatment on the nickel-based alloy workpiece, the surface of the workpiece can achieve a dynamic balance between ion sputtering and ion deposition, and promote the rapid infiltration of nitrogen atoms at low temperature, thereby obtaining a high-quality uniform hardened layer.

The fourth step is to pickle the nickel-based alloy workpiece that has completed the third step of hardening treatment with pickling solution. The proportion of the acidic cleaning agent used is 300ml/L of nitric acid, 40ml/L of hydrofluoric acid, and 25g of potassium dichromate. /L, acid corrosion inhibitor 0.5g/L, surfactant 2ml/L, the balance is water. Then, polish the pickled sample to achieve a surface roughness of Ra<0.8 and improve its surface finish. Finally, the electropolished nickel-based alloy workpiece is cleaned.

The working principle of the present invention is: using the principle of glow discharge, the active nitrogen and carbon atoms generated by the ionization of the nitriding atmosphere are adsorbed on the surface of the workpiece and then diffused to the inside to form a chemical heat treatment process of a hardened layer. Compared with the conventional carbonitriding of nickel-based alloys, the present invention is improved into two-stage ion carbonitriding, that is, before ion carbonitriding, argon ions are firstly used to sputter the surface of nickel-based alloys to remove the passivation film and make the The purpose of fully activating the surface is to ensure the thickness of the hardened layer; then carry out ion carbonitriding, so that the surface of the nickel-based alloy can achieve a dynamic balance between the sputtering and deposition processes, promote the rapid infiltration of carbon and nitrogen atoms, and ensure the uniform thickness of the hardened layer After the carbonitriding treatment, the sample is cleaned with a special acid cleaning agent, and the time and temperature are adjusted and optimized to ensure the processing efficiency and cost without reducing the corrosion resistance of the nickel-based alloy. , to form a high-quality hardened layer with a certain thickness and uniform thickness on the surface of the nickel-based alloy, so that the nickel-based alloy can obtain good hardness, wear resistance and corrosion resistance.

Combined with Table 1, Example 1, when the carburizing temperature in the ion permeation furnace is 500°C, and the nitriding temperature is 360°C, under the condition of feeding argon, the pressure is 300Pa, the time is 12h, and the finally obtained hardened The thickness of the layer is 13.06 μm, as shown in Figure 1; for Comparative Example 3, under other conditions, the experimental condition is changed so that no argon gas is introduced, and the thickness of the finally obtained hardened layer is 9.39 μm, as shown in Figure 3;

Combined with Table 1 and Example 2, when the carburizing temperature in the ion permeation furnace is 550°C and the nitriding temperature is 360°C, under the condition of feeding argon, the air pressure is 300Pa, the time is 12h, and the finally obtained hardened Layer thickness is 17.49 μm, as shown in Figure 2; Comparative Example 4, under satisfying other conditions, change experimental condition to not pass into argon gas, the hardened layer thickness that obtains at last is 12.41 μm, as shown in Figure 4; Under the condition that other external conditions remain unchanged, the thickness of the hardened layer can be increased by injecting argon gas before the experiment. By adopting the low-temperature ion nitriding method of the nickel-based alloy of the present invention, a hardened layer of more than 17 μm can be obtained, thereby satisfying the use of the nickel-based alloy in actual production requirements.

In addition, the thickness of the hardened layer was detected in three different areas where the carbonitriding treatment was completed in Example 1, and the results are shown in Table 2.

Combined with Table 2, the difference in the thickness of the hardened layer detected by the nickel-based alloy in three different regions obtained through Example 1 is less than 1.3 μm, wherein the thickness of the first region is 13.06 μm, as shown in Figure 1; the thickness of the second region is 11.87 μm μm, as shown in Figure 5; the thickness of the third region is 11.77 μm, as shown in Figure 6. By adopting the carbonitriding method of the nickel base alloy of the present invention, a sufficiently thick and uniform hardened layer can be obtained.

For the corrosion resistance experiment of samples after carbonitriding and carbonitriding and pickling, simulate complex working conditions, prepare nickel-based alloy samples in containers, nickel-based alloy samples after carbonitriding treatment, and Samples after carbonitriding treatment and pickling Three kinds of samples after different treatments were subjected to hydrochloric acid full immersion corrosion test. During the test, the sample was placed in a water bath at a temperature of 60°C. The reagent used in the test was a solution of hydrochloric acid (chemical formula: HCl) with a concentration of 9.1%, and the test time was 72 hours. The corrosion rate obtained at the end of the test is shown in Table 3.

In combination with Table 3, the degree of corrosion resistance detected by three different processing conditions of nickel-based alloys, wherein, Example 5 is a sample without any treatment, and its corrosion rate after carrying out the hydrochloric acid full immersion corrosion test is 0.09mm/ a, surface morphology as shown in Figure 7; embodiment 6, for the sample after carbonitriding, after hydrochloric acid full immersion test, there is more weight loss, the corrosion rate is 7.46mm/a, after the test The surface of the sample has serious discoloration and many corrosion products, as shown in Figure 8; in Example 7, after the carbonitriding treatment and pickling of the sample, the corrosion rate was 0.08 mm/a after the hydrochloric acid full immersion test. There was no discoloration on the surface of the sample, as shown in Figure 9;

By adopting the nickel-based alloy carbonitriding method of the present invention, the original corrosion resistance of the nickel-based alloy can be maintained under the premise of obtaining good hardness and wear resistance, and the corrosion resistance of the nickel-based alloy can even be slightly strengthened. Corrosion, so as to meet the requirements of nickel-based alloys for hardness, wear resistance, corrosion resistance and service life in actual use.

Claims (6)

1. a method for low temperature ion carbonitriding of nickel base alloy, is characterized in that, comprises the steps: The first step: put the nickel base alloy workpiece that has been cleaned and dried on the surface into the ion diffusion furnace, and evacuate the air pressure in the ion diffusion furnace to below 10Pa; Step 2: Introduce argon gas, set the voltage to 750-850V, adjust the gas pressure to less than 80Pa, turn on the glow and bombard for 0.5-2h; Step 3: Turn off the argon gas, feed acetylene and hydrogen into the ion nitriding furnace for ion bombardment, adjust the gas ratio and increase the air pressure to 100-300Pa, make the temperature in the ion permeation furnace reach 500-550°C, and keep warm 2~10h, then turn off the acetylene gas, wait for the temperature in the furnace to cool down to below 450°C, feed nitrogen gas, turn on the ion permeation furnace, set the temperature at 400~450°C and carry out ion nitriding for 1~5h; Step 4: Pickling the nickel-based alloy that has completed low-temperature ion carbonitriding with an acidic cleaning agent. 2. the method for nickel base alloy low temperature ion carbonitriding according to claim 1, is characterized in that, in the 4th step, the acid cleaning agent proportioning that uses during pickling is nitric acid 200～500ml/L, hydrogen Fluoric acid 20-50ml/L, potassium dichromate 10-50g/L, acid corrosion inhibitor 0.5-5g/L, surfactant 2-5ml/L, and the balance is water. 3. the method for nickel-based alloy low-temperature ion carbonitriding according to claim 2, is characterized in that, the acid cleaning agent proportioning that uses during pickling is nitric acid 300ml/L, hydrofluoric acid 40ml/L, heavy chromium Potassium acid 25g/L, acidic corrosion inhibitor 0.5g/L, surfactant 2ml/L, the balance is water. 4. The method for low-temperature ion carbonitriding of nickel-based alloys according to claim 1, 2 or 3, characterized in that, in the second step, the bombardment time is 0.5h. 5. according to the method for claim 1 or 2 or 3 described nickel base alloy low-temperature ion carbonitriding, it is characterized in that, in the 3rd step, the time of feeding acetylene is 4～8h, and the time of feeding nitrogen is 2 ~4h. 6. according to the method for claim 1 or 2 or 3 described nickel base alloy low temperature ion carbonitriding, it is characterized in that, also comprises the 5th step: the nickel base alloy workpiece that finishes the 4th step is carried out polishing treatment, reaches Surface roughness Ra<0.8.

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