Metal material surface strengthening method based on mixed surface nanocrystallization technology

Abstract

The invention discloses a metal material surface strengthening method based on a mixed surface nanocrystallization technology, which comprises the following steps: step 1, metal material surface treatment: grinding and polishing the metal material surface; step 2, preparing particles with nanoscale; step 3, forming a coating layer on the surface of the metal body by using the nanoparticles; 4, forming a compound with different components from the metal matrix on the metal surface layer through chemical treatment; compared with the prior art, the method has the advantages that the pitting corrosion resistance of the treated metal is improved; the low-temperature nitriding process is optimized due to nanocrystallization of crystal grains on the metal surface layer, remarkable increase of crystal boundaries, generation of residual compressive stress and improvement of surface roughness, and the hardness, wear resistance and corrosion resistance of the metal surface are improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal material surface strengthening, in particular to a metal material surface strengthening method based on hybrid surface nano-crystallization technology. Background Art

[0002] During their service life, metal materials may come into long-term contact with corrosive oxidants and reducing agents in high-humidity environments. Since corrosion generally starts from the surface of the material, improving the corrosion resistance of the material through surface treatment has more cost and time advantages than developing completely new materials. Surface nanomaterialization technology, as a means of surface strengthening, can form a nanolayer on the surface of the material. Its advantages mainly lie in that it does not change the external dimensions of the material, the process is simple and easy, the cost is low, and there is no environmental pollution problem with the currently used anodizing process. Currently, the most commonly used method for surface nanomaterialization research is surface mechanical grinding. The processing process involves placing a large number of spherical projectiles in a "U"-shaped vacuum container. The upper part of the container fixes the sample, and the lower part is connected to a vibration generator. The product surface is very rough, which further limits its further application in industry.

[0003] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above technical defects and provide a metal material surface strengthening method based on hybrid surface nano-crystallization technology.

[0005] In order to solve the above problems, the technical solution of the present invention is a metal material surface strengthening method based on hybrid surface nano-crystallization technology, which includes the following steps:

[0006] Step 1: Surface treatment of metal materials: grinding and polishing the surface of the metal materials;

[0007] Step 2: preparing nano-sized particles;

[0008] Step 3: Forming a coating layer of nanoparticles on the surface of the metal body;

[0009] Step 4: Form a compound with a composition different from that of the metal matrix on the metal surface through chemical treatment.

[0010] Furthermore, in step one, the metal material is initially in an annealed state, and is first quenched at a quenching temperature of 500°C for 60 minutes, then cooled with 40-60°C water for 20 minutes, and artificially aged for 10 hours within 5 hours after quenching, and then the sample surface is ground and polished.

[0011] Furthermore, in step three, a CNC shot peening machine is used to perform supersonic particle bombardment surface treatment on the aluminum alloy. The shot material is stainless steel S110, the shot diameter is 0.3 mm, the spray angle is 90°, the working pressure is 0.53 MPa, the air flow rate is 1200 m / s, the spray distance is 130 mm, and the spray time is 10 min.

[0012] Furthermore, in step four, the chemical treatment method is to perform low-temperature nitriding treatment on the surface of the metal material. The nitriding furnace adopts a tubular resistance furnace, and the nitriding atmosphere adopts pure ammonia. During nitriding, the metal material is placed in a quartz tube, and the pure ammonia is first decomposed in a pre-decomposition furnace to obtain the required nitrogen potential before being passed into the nitriding furnace.

[0013] The advantages of the present invention compared with the existing technology are:

[0014] 1. The pitting corrosion resistance of the metal treated by the present invention is improved; the metal surface grains are nanometerized, the grain boundaries are significantly increased, the residual compressive stress is generated and the surface roughness is improved, which optimizes the low-temperature nitriding process and improves the hardness, wear resistance and corrosion resistance of the metal surface. DETAILED DESCRIPTION

[0015] In order to make the contents of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention.

[0016] A metal material surface strengthening method based on hybrid surface nano-crystallization technology is characterized by comprising the following steps:

[0017] Step 1: Surface treatment of metal materials: grinding and polishing the surface of the metal materials; the metal materials are initially in an annealed state, and are first quenched at a quenching temperature of 500°C for 60 minutes, then cooled with 40-60°C water for 20 minutes, artificially aged for 10 hours within 5 hours after quenching, and then the sample surface is ground and polished.

[0018] Step 2: preparing nano-sized particles;

[0019] Step 3: Form a coating layer of nanoparticles on the surface of the metal body; use a CNC shot peening machine to perform supersonic particle bombardment on the aluminum alloy surface treatment, the projectile material is stainless steel S110, the projectile diameter is 0.3mm, the spray angle is 90°, the working air pressure is 0.53MPa, the air flow rate is 1200m / s, the spray distance is 130mm, and the spray time is 10min.

[0020] Step 4: Chemical treatment forms a compound on the metal surface that has a different composition from the metal matrix. This chemical treatment involves low-temperature nitriding of the metal surface. The nitriding furnace uses a tubular resistance furnace and a pure ammonia atmosphere. During nitriding, the metal is placed in a quartz tube. The pure ammonia is first decomposed in a pre-decomposition furnace to achieve the desired nitrogen potential before being passed into the nitriding furnace.

[0021] The purpose of using a pre-decomposition furnace is to make the nitriding gas reach the nitrogen potential required for the experiment before it enters the nitriding furnace, and to make the nitrogen potential in the nitriding furnace relatively stable. When the nitriding temperature does not change, the nitrogen potential is controlled by adjusting the flow rate of ammonia and the temperature of the pre-decomposition furnace. The ammonia decomposition rate is obtained by measuring the partial pressure of ammonia in the tail gas with an ammonia decomposition meter.

[0022] Example 1

[0023] A metal material surface strengthening method based on hybrid surface nano-crystallization technology is characterized by comprising the following steps:

[0024] Step 1, surface treatment of the metal material, grinding and polishing the surface of the metal material; the initial state of the metal material is annealed, first quenching, the quenching temperature is 500 ° C, holding for 60 minutes, and then cooling with 40-60 ° C water for 20 minutes, artificial aging for 10 hours within 5 hours after quenching, and then grinding and polishing the sample surface. The metal is a 100mm*40mm*5mm 214 aluminum alloy plate. 2A14 is an Al-Mg-Si-Cu alloy, and the mass fraction of the chemical formula is: Cu 4.2%, Mg 0.6%, Si 0.8%, Mn 0.8%, Fe 0.7%, Zn0.3%, Ni 0.1%, Ti 0.15%, Al 91.4%, and other components account for 0.15%.

[0025] Step 2: preparing nano-sized particles;

[0026] Step 3: Form a coating layer of nanoparticles on the surface of the metal body; use a CNC shot peening machine to perform supersonic particle bombardment on the aluminum alloy surface treatment, the projectile material is stainless steel S110, the projectile diameter is 0.3mm, the spray angle is 90°, the working air pressure is 0.53MPa, the air flow rate is 1200m / s, the spray distance is 130mm, and the spray time is 10min.

[0027] Step 4: Chemical treatment forms a compound on the metal surface that has a different composition from the metal matrix. This chemical treatment involves low-temperature nitriding of the metal surface. The nitriding furnace uses a tubular resistance furnace and a pure ammonia atmosphere. During nitriding, the metal is placed in a quartz tube. The pure ammonia is first decomposed in a pre-decomposition furnace to achieve the desired nitrogen potential before being passed into the nitriding furnace.

[0028] The purpose of using a pre-decomposition furnace is to make the nitriding gas reach the nitrogen potential required for the experiment before it enters the nitriding furnace, and to make the nitrogen potential in the nitriding furnace relatively stable. When the nitriding temperature does not change, the nitrogen potential is controlled by adjusting the flow rate of ammonia and the temperature of the pre-decomposition furnace. The ammonia decomposition rate is obtained by measuring the partial pressure of ammonia in the tail gas with an ammonia decomposition meter.

[0029] The low-temperature gas nitriding equipment uses pure ammonia as the experimental atmosphere. Nitriding is performed at four temperatures: 300°C, 400°C, and 450°C, with nitriding times of 3, 6, 9, and 12 hours, respectively. The sample, after surface nano-treatment, is placed in the quartz tube of a resistance furnace and placed in the isothermal zone of the furnace. The inlet and outlet pipes are connected, and the flow valves are opened to remove air from the pipes and quartz tube. After the air is completely exhausted, the pre-decomposition furnace and nitriding furnace are heated. The gas flow rate and pre-decomposition furnace temperature are adjusted so that the pure ammonia is decomposed in the pre-decomposition furnace before being passed into the nitriding furnace, with the exhaust gas discharged into a water tank. The ammonia decomposition rate is determined by measuring the ammonia partial pressure in the exhaust gas using an ammonia decomposition meter. After the experiment, the nitriding furnace is turned off, but ammonia is continued to be introduced. Once the furnace temperature drops to 150°C, the ammonia introduction is stopped, and the sample is allowed to air cool.

[0030] Example 2

[0031] Friction and wear performance test

[0032] The test sample was fabricated into a standard-sized disk, paired with a GCr15 ball. The load was 10N, and the test duration was 30 minutes. Wear tests were performed on the original surface, the nano-treated surface, and the nano-treated surface infiltrated with ammonia at 450°C. The sample was then cleaned in acetone and ethanol solutions, dried, and weighed using an electro-optical analytical balance. The friction coefficient was calculated and recorded using the testing machine's built-in software. Friction and wear characteristics were evaluated by comparing the sample's wear mass before and after wear and by comparing the change in the friction coefficient during wear.

[0033] Corrosion resistance test

[0034] The potentiodynamic anodic polarization curves were measured in a 3.5% neutral NaCl solution using a standard saturated calomel electrode (SCE) as the reference electrode. The 6% FeCl2 aqueous solution was maintained at 50°C in a water bath. After immersion in the solution for 72 hours, the samples were removed and immediately cleaned with an ultrasonic cleaner and dried. The morphology of the corroded surface was then observed using an AMRAY-1000B scanning electron microscope (SEM) to characterize the corrosion resistance.

[0035] Microhardness measurement

[0036] Prepare a cross-sectional metallographic sample (without metallographic corrosion), and measure gradually from the surface to the center of the sample, with a point spacing of 15μm to 30μm, until the hardness value is close to that of the metal matrix. Measure 3 points at each depth and take the average value, and then use the average value to make a curve of microhardness change.

[0037] Metallographic microscopic analysis

[0038] The cross-sectional structural characteristics of a 0Cr18Ni9 stainless steel sample were observed using a metallographic microscope. To prepare the cross-sectional metallographic specimen, a 10mm x 10mm sample was cut from the sample using electrospark cutting technology. The sample was first coarsely ground to 1000 grit with water-grinded sandpaper and then polished with diamond paste. After observing under an optical microscope for obvious scratches, the sample was etched with an FeCl solution to reveal distinct grain boundaries. Metallographic analysis was performed before and after shot peening for comparison purposes.

[0039] X-ray diffraction

[0040] A Cu target (1.54060°) was used, with a tube voltage of 40 kV, a current of 40 mA, and an experimental temperature of 293 ± 1 K. A full-spectrum continuous scan (40-140°) was performed to determine the sample's phase composition, followed by a step scan of specific diffraction peaks with a step size of 0.02°. The nanocrystallization of the material after supersonic particle bombardment was characterized, and the average grain size and microstrain of the treated surface layer were calculated using the Scherrer equation.

[0041] The above description of the present invention and its embodiments is non-limiting. In short, if a person skilled in the art is inspired by the above description and designs a similar structure and embodiment to the technical solution without departing from the purpose of the present invention, they should fall within the scope of protection of the present invention.

Claims

1. A method for strengthening the surface of a metal material based on hybrid surface nano-crystallization technology, characterized in that: The following steps are involved: Step 1: Surface treatment of metal materials: grinding and polishing the surface of the metal materials; Step 2: preparing nano-sized particles; Step 3: Forming a coating layer of nanoparticles on the surface of the metal body; Step 4: Form a compound with a composition different from that of the metal matrix on the metal surface through chemical treatment.

2. The method for surface strengthening of metal materials based on hybrid surface nano-crystallization technology according to claim 1, characterized in that: In step 1, the metal material is initially in an annealed state, and is first quenched at a quenching temperature of 500°C for 60 minutes, then cooled with 40-60°C water for 20 minutes, artificially aged for 10 hours within 5 hours after quenching, and then the sample surface is ground and polished.

3. The method for surface strengthening of metal materials based on hybrid surface nano-crystallization technology according to claim 1, characterized in that: In step three, a CNC shot peening machine is used to perform supersonic particle bombardment surface treatment on the aluminum alloy. The shot material is stainless steel S110, the shot diameter is 0.3 mm, the spray angle is 90°, the working pressure is 0.53 MPa, the air flow rate is 1200 m / s, the spray distance is 130 mm, and the spray time is 10 min.

4. The method for surface strengthening of metal materials based on hybrid surface nano-crystallization technology according to claim 1, characterized in that: In step 4, the chemical treatment method is to perform low-temperature nitriding treatment on the surface of the metal material. The nitriding furnace adopts a tubular resistance furnace, and the nitriding atmosphere adopts pure ammonia. During nitriding, the metal material is placed in a quartz tube. The pure ammonia is first decomposed in a pre-decomposition furnace to obtain the required nitrogen potential before being passed into the nitriding furnace.