Low-temperature preparation method of high wear-resistant boride layer on surface of GH4169 alloy

Abstract

The application discloses a low-temperature preparation method of a high-wear-resistance boride layer on a GH4169 alloy surface, and belongs to the technical field of wear-resistant material preparation. By using a solid powder embedding boronizing technology and adjusting a boronizing agent (3%-6% KFB4, 10% ZrO2, and the rest being B4C), a high-hardness and high-wear-resistance boride layer with a thickness of about 8.2 microns is successfully prepared on the surface of a solid solution GH4169 nickel-based high-temperature alloy under low-temperature conditions of 800 DEG C. Compared with a traditional high-temperature boronizing process of the GH4169 alloy, the boronizing method can unify the aging process of the alloy heat treatment and the boronizing process, avoids a secondary heat treatment process after the high-temperature boronizing, and significantly improves the wear resistance of the GH4169 alloy. The preparation process of the boride layer is simple, the cost is low, and the boride layer with good quality and firm combination can be obtained.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a high-wear-resistance boride layer prepared on a surface of GH4169 nickel-based alloy at low temperature, and belongs to the technical field of wear-resistant material preparation. BACKGROUND

[0002] GH4169 nickel-based alloy is widely applied in the field of aerospace due to good high-temperature strength, fatigue strength, corrosion resistance and the like, but has prominent problems of low surface hardness and poor wear resistance, especially under high-temperature service environment, lubricating oil fails, and strong dry friction is caused between materials, which limits the application of the alloy. Surface chemical heat treatment can greatly improve the surface hardness and wear resistance of metal materials. Common surface heat treatment methods mainly include nitriding, carburizing and boronizing, but due to the limited solubility of carbon and nitrogen in nickel, carburizing and nitriding are not ideal for nickel-based alloy, and boron can form a wide range of strong intermetallic compounds with nickel, so boronizing can well form a stable boronizing layer on the nickel-based alloy, and becomes a commonly used surface strengthening method for the nickel-based alloy.

[0003] Boronizing refers to a process that steel or non-ferrous metal materials are placed in a boron-containing medium, heated to a boronizing temperature and kept for a period of time, so that boron atoms are penetrated into the surface layer of the metal to form a boride layer. There are many preparation methods of the boride layer material, which can be divided into solid powder boronizing, liquid boronizing, gas boronizing, paste boronizing and electrolytic boronizing according to the state of the reaction medium. Among them, the solid powder boronizing is widely applied due to the advantages of simple equipment, simple operation, easy cleaning of the workpiece surface and low cost of the boronizing agent.

[0004] For solid boronizing, the boronizing temperature, boronizing time and component of the boronizing agent will all affect the thickness and structure of the boronizing layer. Among them, the boronizing temperature is the most important factor, and if the temperature does not meet the requirement, the boride layer cannot be effectively formed on the surface of the alloy. At present, the traditional boronizing temperature is generally higher than 900 DEG C, and the boronizing layer grows slowly when the temperature is lower than this value. However, since the GH4169 alloy needs to be subjected to solid solution (1020 DEG C-1055 DEG C, 1h) and aging (775 DEG C-800 DEG C, 8h) heat treatment to obtain a reasonable internal structure and then to guarantee the mechanical properties, the traditional solid-phase boronizing will have a negative effect on the aging hardening of the alloy due to the excessively high temperature, and the mechanical properties after aging are reduced. Therefore, how to effectively unify the boronizing process and the aging process of the nickel-based alloy is a problem to be solved at present. SUMMARY

[0005] The application aims to reduce the boronizing temperature and improve the thickness of the boride layer on the surface of the GH4169 nickel-based alloy material at low temperature, so as to improve the surface hardness and wear resistance of the alloy.

[0006] The method of the application utilizes solid-phase powder embedding boronizing technology, on the basis of original boronizing agent, 10% ZrO2 is added as a catalytic agent, a boride layer with a thickness of about 8.2 microns is successfully formed on the solid solution GH4169 substrate, the layer has high hardness and good wear resistance.

[0007] The method does not use special equipment, the process operation is simple, the workpiece surface is clean, the cost of the penetrating agent is low, and the method is suitable for various shapes of work, effectively improves the thickness of the boronizing layer on the surface of GH4169 under low temperature conditions, and has high practical application value.

[0008] In order to realize the above technical purpose, the technical scheme of the application is as follows:

[0009] 1) sandpaper polishing line cutting rolled state GH4169 substrate to 1000#, and then using alcohol ultrasonic cleaning and drying for standby;

[0010] 2) The self-prepared boronizing agent is weighed according to the set mass ratio, mixed and then poured into a container, and put into a ball mill for ball milling to make it uniformly mixed;

[0011] 3) Put the mixed boronizing agent into a high-temperature drying box and dry at 150 DEG C for 2h, and then take out for standby;

[0012] 4) After cleaning, the sample is buried in the boronizing agent and placed in a sealed container, the sealed container is loaded into a tube furnace, and argon is introduced as a protective gas;

[0013] 5) Heat to 800 DEG C at a heating rate of 10 DEG C / min, and keep for 8h, so that the boron element in the boronizing agent diffuses into the surface of the substrate to form a boronizing layer, and then the furnace is cooled to room temperature and the sample is taken out;

[0014] 6) The surface of the sample is slightly polished using 2000# sandpaper to remove the residual boronizing agent; and the sample is ultrasonically washed with alcohol and dried for sealed storage.

[0015] The used substrate is solid solution GH4169 nickel-based superalloy, and the size of the sample is Ф30*2mm.

[0016] The self-prepared boronizing agent has the following mass percentage: 3%-6% KFB4, preferably KFB4, 10% ZrO2, and the balance is B4C.

[0017] The application has the following beneficial effects:

[0018] A high-quality boride layer is successfully prepared on the surface of the solid solution GH4169 nickel-based alloy material by using low-temperature solid-phase boronizing technology of chemical heat treatment, the boronizing temperature is reduced by adjusting the composition of the boronizing agent, and the wear resistance of the nickel-based alloy material is improved.

[0019] The GH4169 alloy is embedded in the self-prepared boronizing agent, and a boride coating with a thickness of about 8.2 μm is grown at a lower temperature of 800 ℃ for 8 h. The friction coefficient of the boride coating is lower than 0.65 and the wear rate is lower than 3.5×10 -5 mm 3 / N·m under different load conditions, proving that the boride coating has good wear resistance under different load conditions. The preparation method is simple, the cost is low, the obtained permeated layer material has the advantages of high hardness and good wear resistance, and has good application prospect in the field of wear resistance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 SEM images of the microstructure of the boride permeated layer prepared in Example 1-Example 4;

[0021] Figure 2 EDS result images of the boride permeated layer prepared in Example 1-Example 4;

[0022] Figure 3 XRD patterns of the boride layer prepared in Example 1-Example 4;

[0023] Figure 4 XRD patterns of the boronizing agent powder used in Example 4 before and after sintering;

[0024] Figure 5 Surface hardness maps of the samples in Example 1-Example 4;

[0025] Figure 6 Friction coefficient curves of the boride permeated layer in Example 4 under conditions of 10N, 30N and 50N;

[0026] Figure 7 Wear rate column charts of the boride permeated layer in Example 4 under conditions of 10N, 30N and 50N;

[0027] Figure 8 SEM images and EDS result images of the local surface morphology of the boride permeated layer in Example 4 after friction under a load of 10N for 30 minutes.

[0028] Figure 9 SEM images and EDS result images of the local surface morphology of the boride permeated layer in Example 4 after friction under a load of 30N for 30 minutes.

[0029] Figure 10 SEM images and EDS result images of the local surface morphology of the boride permeated layer in Example 4 after friction under a load of 50N for 30 minutes. DETAILED DESCRIPTION

[0030] The application will be further described in connection with the following examples, but the application is not limited to the following examples.

[0031] Example 1: In this example, GH4169 substrate is selected.

[0032] Firstly, the GH4169 substrate is pretreated. The treatment process includes polishing the GH4169 substrate with 180-1000# sandpaper until the surface wire cutting marks are completely removed. After washing the surface with deionized water, the substrate is placed in a beaker containing alcohol, ultrasonic cleaned for 10 minutes, dried, and then sealed in a sample bag with dust-free paper for use.

[0033] The self-prepared boronizing agent is weighed according to the weight ratio of 87% B4C, 3% KBF4 and 10% Al2O3, mixed, then poured into a ball mill jar, put into a ball mill for 2h to make it uniformly mixed, and sealed in a sample bag for standby.

[0034] The mixed boronizing agent is placed in a high-temperature drying oven and dried at 150℃ for 2h. After drying, it is taken out for standby;

[0035] The ceramic crucible is washed with deionized water and anhydrous ethanol in turn, and dried for standby. The dried boronizing agent is evenly spread on the bottom of the crucible, with a height of about half the height of the crucible. The GH4169 alloy sample after ultrasonic cleaning and drying is placed above the boronizing agent. After placing the sample, the boronizing agent is evenly spread over the entire crucible, and the boronizing process is ready to start.

[0036] The crucible is placed in the center of the tube furnace, vacuumed and gas washed under argon atmosphere, so that the tube furnace is filled with argon. This process is repeated three times. Finally, argon is introduced to balance the internal pressure of the tube furnace with the external atmospheric pressure, and argon is continuously introduced as a protective gas. The tube furnace program is set to heat at a rate of 10℃ / min to 800℃, and the temperature is kept for 8h. The boron element in the boronizing agent diffuses into the surface of the substrate to form a boronizing layer. Then the furnace is cooled to room temperature and the sample is taken out.

[0037] After boronizing, the sample is taken out of the boronizing agent, and attention should be paid not to scratch the surface of the sample when taking it out. 2000# sandpaper is used to slightly polish the surface of the sample to remove the residual boronizing agent on the surface of the sample. The sample is washed with deionized water and ultrasonic cleaned in anhydrous ethanol for 10 minutes to completely remove the residual boronizing agent and other impurities on the surface of the sample. After drying, the sample is packed in a sample bag with dust-free paper.

[0038] The specific steps of examples 1-4 are as described in example 1, and the specific proportion of boronizing agent (weight ratio) is shown in table 1.

[0039] Table 1: Specific component proportion (weight ratio) and process parameter setting of examples 1-4.

[0040]

[0041] The thickness and structure of the boronized layer from the surface to the inside of the sample were characterized by scanning electron microscopy (SEM), and the SEM morphology of the cross section is shown in Figure 1 .

[0042] SEM results Figure 1 Fig. (a) shows that the boride layer thickness obtained in Example 1 is about 4.1 μm, Figure 1 Fig. (b) shows that the boride layer thickness obtained in Example 2 is about 7.1 μm, and the boronized layer thickness is increased by 73%. Figure 1 Fig. (c) shows that the boride layer thickness obtained in Example 3 is about 6.4 μm, Figure 1 Fig. (d) shows that the boride layer thickness obtained in Example 4 is about 8.2 μm, and the boronized layer thickness is increased by 28%. Under the same KBF4 content conditions, the boronized layer thickness is improved after replacing Al2O3 with ZrO2.

[0043] The micro-area element type and atomic proportion analysis of the boronized coating from the surface to the inside was performed by X-ray energy dispersive spectroscopy (EDS), and the micro-area analysis results are shown in Figure 2 .

[0044] The EDS results show that the boron atomic concentration of the boride layer of Examples 1-4 gradually decreases with the increase of the distance to the surface, and the boron concentration of the boronized layer of Example 2 is higher than that of Example 1, and the boron concentration of the boronized layer of Example 4 is higher than that of Example 3. The addition of ZrO2 improves the thickness of the boronized layer and the boron concentration in the boride layer under low temperature conditions. ZrO2 improves the boronizing efficiency by promoting the generation of active boron atoms.

[0045] The phase analysis of the boride layer obtained in Examples 1-4 was performed by X-ray diffractometer (XRD), and the XRD patterns are shown in Figure 1 . The XRD results show that the phase of the boronized layer of Example 1 and Example 2 is the metastable phase Fe x Ni 23-x B6, and the phase structure does not change basically under the condition of 3% KBF4. The phase of the boronized layer of Example 3 mainly has Cr5B3, Cr2B and Fe x Ni 23-x B6, and the phase of the boronized layer of Example 4 mainly generates Cr5B3 and Cr2B, Ni2B and Fe x Ni 23-x B6. Among them, Cr2B is the stable phase of chromium boride under the condition of low boron concentration, Cr5B3 is the stable phase of chromium boride under the condition of medium boron concentration, Ni2B is the stable phase of nickel boride under the condition of high boron concentration, and Fe x Ni 23-xB6 is a metastable phase of nickel boride. The addition of ZrO2 to the boride layer of Comparative Example 3 and Example 4 causes the boride layer to generate a more stable nickel boride phase.

[0046] The phase of the boronizing agent powder around the substrate before and after the reaction in Example 4 was analyzed by X-ray diffractometer (XRD), and the XRD pattern is shown in Figure 2 The XRD results show that the powder after the reaction generates Zr7O 8.79 F 7.91 .

[0047] KBF4 is a known and widely used catalyst that decomposes to produce KF and BF3 during the reaction. BF3 and B4C react to generate [B] and BF2, and boron atoms and gaseous substances such as BF3 are adsorbed on the surface of the workpiece and produce an interfacial reaction. During the reaction, active boron atoms may be generated in the process of reacting with the substrate, and boron atoms entering the surface layer of the sample diffuse into the interior of the workpiece. In Example 4, ZrO2 was added as a catalyst after the reaction to generate Zr7O 8.79 F 7.91 , ZrO2 reacts with BF3, consumes F atoms, produces more active boron atoms during the reaction, increases the concentration of active boron atoms, promotes the process of boronizing reaction, and increases the thickness of the boronizing layer and the boron concentration of the boronizing layer. The specific reaction equations are shown below.

[0048] KBF4 = BF3 + KF (1)

[0049] 2BF3 + B4C = 3BF2 + 3[B] + C (2)

[0050] 3BF2 = [B] + 2BF3 (3)

[0051] y[B] + xMe → Me x B y (4)

[0052]

[0053] BF3 + ZrO2 → Zr7O 8.79 F 9.71 + BF2 + [B] (6)

[0054] The surface hardness values of the samples of Examples 1-4 were tested using a Vickers hardness tester under the conditions of 100 g, 500 g and 1000 g force, respectively. The hardness of the substrate was about 280 HV, and the hardness value of the surface of the boronized sample was significantly improved. With the same KBF4 content, the surface hardness of the boride layer obtained after adding ZrO2 was greater. The boride layer improves the wear resistance of the material by increasing the hardness of the surface of the substrate. The boronized layer of Example 4 has a higher thickness and a greater surface hardness value, so it is presumed that the wear resistance of the sample of Example 4 is better. The introduction of ZrO2 as a catalyst can obtain a boride layer with better wear resistance.

[0055] In order to verify the wear resistance of the boronized layer obtained under the conditions of Example 4, a friction and wear tester was used to test the friction and wear of the sample surface under different load conditions at room temperature and in the same air humidity environment. The friction and wear tester was preheated for 30 minutes, and the program was set to reciprocating friction with a friction distance of 5 mm, a load of 10 N, 30 N and 50 N, a test time of 30 minutes, a running speed of 33.3 mm / s, and a vice rubbing vice of Si3N4 ball. The friction coefficient results are shown in Figure 6

[0056] The friction coefficient of the sample obtained under the condition of 10 N first increased and then decreased, and finally stabilized at about 0.6, with an average friction coefficient of 0.63. The friction coefficient of the sample obtained under the condition of 30 N first increased and then decreased, and finally stabilized at about 0.6, with an average friction coefficient of 0.60. Under the condition of 50 N, the friction coefficient was relatively stable, with an average friction coefficient of 0.49. The average friction coefficient of the boride layer obtained under the three different load conditions was less than 0.65, indicating that the boride layer had stable wear resistance.

[0057] The wear amount and wear rate of the boronized layer of Example 4 under different load conditions were calculated using a laser confocal microscope, and the results are shown in Figure 7 -5 3 -5 3 -6 3 The wear amount and wear rate of the boronized layer of Example 4 under different load conditions were calculated using a laser confocal microscope, and the results are shown in Figure 7 The wear rate under the condition of 10 N was 3.227 x 10 -5 mm 3 The wear rate under the condition of 30 N was 1.744 x 10 -5 mm 3 The wear rate under the condition of 50 N was 8.546 x 10 -6 mm 3 The wear rate of the boride layer under the three different load conditions was low, indicating that it had good wear resistance.

[0058] The morphology of the surface wear scar of the sample of Example 4 under different load conditions was characterized by scanning electron microscopy (SEM), and the friction and wear mechanism of the boronized layer was analyzed. Figure 8The surface morphology of the sample of Example 4 under a load of 10N is relatively flat, and the surface is a furrow with different depths, and there is a small flaky exfoliation in a local area. The wear mechanism is mainly abrasive wear. According to the EDS spectrum test, the furrow area contains boron and oxygen, and the oxygen content is relatively high in the deep furrow. The flaky exfoliation area contains a large amount of oxygen, so oxidation wear occurs during the wear process. The surface of the wear scar contains boron atoms, which indicates that the boride layer is not completely worn under low load conditions, and has good wear resistance. Figure 9 The surface morphology of the sample of Example 4 under a load of 30N is relatively flat, and the middle part is a furrow with different depths and a small amount of flaky exfoliation. The wear mechanism is mainly abrasive wear. According to the EDS spectrum test, the wear scar area with a relatively flat edge contains boron and a small amount of oxygen. In the flaky exfoliation area, the oxygen content is relatively high. The furrow area with a lighter color in the wear scar contains a small amount of boron and a large amount of oxygen. Oxidation wear occurs during the wear process. The surface of the relatively flat wear scar contains boron atoms, which indicates that the boride layer improves the wear resistance of the material surface under this load condition. Figure 10 The surface morphology of the sample of Example 4 after friction and wear under a high load of 50N is relatively flat, and there is a shallow furrow morphology and a small amount of flaky exfoliation. The edge part of the wear scar has white fine particles, which indicates that the wear of the boronized sample is mainly abrasive wear. EDS test on different morphology areas of the wear scar shows that the white particle area of the edge contains boron and a small amount of oxygen. The relatively flat area in the middle of the wear scar contains boron and oxygen, and the proportion is close to 1:1. The oxygen content of the flaky exfoliation area is relatively high, and the boron content is relatively low. The boronized layer is accompanied by oxidation wear during the friction process. The boronized layer is still relatively flat under a high load, and the friction coefficient and wear rate are also relatively low, so the boronized layer has good wear resistance.

Claims

1. A method for low temperature preparation of a high wear resistant boride case on a GH4169 alloy surface, characterized in that, Comprising the following steps: 1) Sand paper polishing wire cutting rolling state GH4169 matrix to 1000#, and then using alcohol ultrasonic cleaning and drying for standby; 2) The self-prepared boronizing agent is weighed according to the set mass ratio, mixed and then poured into a container, and put into a ball mill for ball milling to make it uniformly mixed, wherein the mass percentage composition of the self-prepared boronizing agent is 6% KFB4, 10% ZrO2 and the balance of B4C; 3) The mixed boronizing agent is put into a high-temperature drying box and dried at 150℃ for 2h, and then taken out for standby; 4) After cleaning, the sample is buried in the boronizing agent and placed in a sealed container, the sealed container is loaded into a tube furnace, and argon is introduced as a protective gas; 5) heating to 800℃ at a heating rate of 10℃ / min, holding for 8h, so that boron element in boronizing agent diffuses into the surface of the substrate to form a boronized layer, and then furnace cooling to room temperature to take out the sample, wherein the phase of the boronized layer is mainly Cr5B3, Cr2B, Ni2B and Fe x Ni 23-x B6; 6) The surface of the sample is slightly polished using 2000# sandpaper to remove the residual boronizing agent; and the sample is ultrasonically washed with alcohol, dried and then sealed and stored.

2. The process for low temperature production of a high wear resistant boride case on GH4169 alloy according to claim 1, characterized in that, The used matrix is a solid solution state GH4169 nickel-based superalloy, wherein the sample size is Ф30x2mm.

Images