Preparation method of AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating

Abstract

The invention relates to a preparation method of an AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating, which comprises the following steps: uniformly mixing AlCoCrFeNi high-entropy alloy powder and Ni / C in a ball milling or mechanical manner to obtain composite powder; and the composite powder is fully melted by using a high velocity oxy-fuel spraying technology and then sprayed to the surface of a pretreated base material, so that the AlCoCrFeNi + Ni / C coating is obtained. The preparation method is simple and easy to implement, and the obtained AlCoCrFeNi + Ni / C coating has good antifriction and wear-resisting performance, has potential application prospects in the environment where a mechanical motion system needs antifriction and wear-resisting, and can be suitable for surfaces of various matrixes and different metal parts.

Description

Technical Field

[0001] The invention relates to the technical field of surface engineering, and in particular to a method for preparing an AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating. Background Art

[0002] The design concept of traditional alloys is to use one or two elements as the main elements, with a content greater than 50%, and to improve the overall performance of the alloy by adding a small amount of other elements. However, adding too many other elements will lead to the appearance of intermetallic compounds, causing the alloy performance to deteriorate. With the development of industrial fields such as aerospace and machinery, traditional alloys are difficult to meet the demanding service requirements of the industry. In 1995, Ye Junwei broke the design concept of traditional alloys and proposed the concept of high entropy alloys on this basis. High entropy alloys are alloys composed of 5 or more elements in equimolar or nearly equimolar ratios. The content of each element is between 5% and 35%, and the performance of high entropy alloys is determined by all elements in the alloy system. High entropy effect, lattice distortion effect, hysteresis diffusion effect and "cocktail effect" coexist, so high entropy alloys have simple solid solution phases, excellent mechanical properties, good corrosion resistance and wear resistance, and can be used in industrial fields such as aerospace, machinery, and chemical industry.

[0003] The AlCoCrFeNi high entropy alloy system has low preparation cost and excellent comprehensive performance, so it has great application prospects. However, the high preparation cost of the overall high entropy alloy material and the complex preparation process limit its application. The use of surface engineering technology to prepare high entropy alloy coatings is the key to promoting the application of high entropy alloys. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a simple and easy-to-implement method for preparing an AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating.

[0005] To solve the above problems, the present invention discloses a method for preparing an AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating, which is characterized in that: the method refers to mixing AlCoCrFeNi high-entropy alloy powder and Ni / C uniformly by ball milling or mechanical means to obtain a composite powder; the composite powder is fully melted by supersonic flame spraying technology and then sprayed onto the surface of a pretreated substrate to obtain an AlCoCrFeNi+Ni / C coating.

[0006] The AlCoCrFeNi high entropy alloy powder is prepared by the following method: firstly, AlxCoCrFeNi, x=0.5-3.0 is mixed, and then Al, Fe, Co, Cr, and Ni raw materials with a purity higher than 99.9% are smelted, spray-cooled, and sieved to obtain a powder with a particle size of ≤45 μm.

[0007] The mass percentage of Ni / C in the composite powder is 0.2-10.0%.

[0008] The conditions of the supersonic flame spraying are that the fuel flow rate is 6.0~7.5 GPH; the carrier gas is argon or nitrogen, and its flow rate is 8~12 L / min; the oxygen flow rate is 1800~1850 SCFH; an intermittent or continuous spraying method is adopted, the interval between the two sprayings is greater than 2 s, and the spraying distance is 300~500 mm.

[0009] The pretreated substrate refers to a substrate that is first degreased by anhydrous ethanol, then ultrasonically cleaned by deionized water, then polished to remove rust, ultrasonically cleaned by acetone, dried, and then sandblasted with corundum.

[0010] An AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating prepared by the method described above.

[0011] Compared with the prior art, the present invention has the following advantages: 1. The present invention prepares AlCoCrFeNi+Ni / C coating by supersonic flame spraying technology. The prepared coating has fine grains inside, which enhances the hardness of the coating. The hardness of the coating (Vickers hardness of about HV660) is about 3.3 times higher than that of the substrate. At the same time, the self-lubricating phase Ni / C is successfully compounded to enhance the friction reduction and wear resistance of the coating.

[0012] 2. The preparation method of the present invention is simple and easy to implement. The obtained AlCoCrFeNi+Ni / C coating has potential application prospects in environments where mechanical motion systems require anti-wear and friction reduction, and can be applied to various substrates and different metal parts surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0014] Figure 1 This is a SEM image of the AlCoCrFeNi high entropy alloy powder described in the present invention.

[0015] Figure 2 This is a SEM image of the Ni / C powder described in the present invention.

[0016] Figure 3 This is the XRD diagram of the AlCoCrFeNi+Ni / C mechanical mixed powder and coating described in the present invention.

[0017] Figure 4 It is a curve diagram of the change of the friction coefficient of the AlCoCrFeNi+Ni / C coating described in the present invention with time in the pre-grinding stage and the stable wear stage under paraffin lubrication conditions.

[0018] Figure 5 It is a histogram of the wear rate of the AlCoCrFeNi+Ni / C coating of the present invention in the pre-wear stage and the stable wear stage under paraffin lubrication conditions. DETAILED DESCRIPTION

[0019] A preparation method of an AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating, comprising the steps of: uniformly mixing AlCoCrFeNi high-entropy alloy powder and Ni / C by ball milling or mechanical means to obtain composite powder; fully melting the composite powder by supersonic flame spraying technology and then spraying the melt onto a pretreated substrate surface to obtain an AlCoCrFeNi+Ni / C coating with good friction reduction performance.

[0020] Wherein: AlCoCrFeNi high entropy alloy powder is prepared according to the following method: firstly, AlxCoCrFeNi, x=0.5~3.0 is mixed, and then Al, Fe, Co, Cr, and Ni raw materials with a purity higher than 99.9% are smelted, spray-cooled, and sieved to obtain a powder with a particle size of ≤45 μm.

[0021] The mass percentage of Ni / C in the composite powder is 0.2~10.0%.

[0022] The conditions for supersonic flame spraying are as follows: the fuel flow rate is 6.0~7.5 GPH; the carrier gas is argon or nitrogen, and its flow rate is 8~12 L / min; the oxygen flow rate is 1800~1850 SCFH; intermittent or continuous spraying is adopted, the interval between the two sprayings is greater than 2 s, and the spraying distance is 300~500 mm.

[0023] The pretreated substrate refers to a substrate that is first degreased by anhydrous ethanol, then ultrasonically cleaned by deionized water, then rusted by polishing, ultrasonically cleaned by acetone, dried, and then sandblasted with corundum.

[0024] The raw materials of the following examples are all commercially available, and the purity of each raw material is ≥99.9%. The spraying experiment uses HV-8000 supersonic flame spraying equipment. The friction experiment uses SRV-IV friction and wear tester.

[0025] Embodiment A method for preparing an AlCoCrFeNi-based self-lubricating composite high entropy alloy coating: S1. Process 45# steel or other steel substrates into Φ24mm×8mm round block specimens, and then pre-treat the steel substrate. First, use anhydrous ethanol to perform ultrasonic cleaning to remove surface oil stains, then use deionized water to wash it, polish it to remove rust, and use acetone to perform ultrasonic cleaning. After the substrate is dry, use corundum to sandblast it.

[0026] S2. Weigh 142.5 g of AlCoCrFeNi high entropy alloy powder with an atomic ratio of 1:1 (such as Figure 1 As shown) and 7.5 g of Ni / C powder (as Figure 2 The two powders are mechanically mixed evenly. The main phase of the mixed powder is body-centered cubic (BCC) phase, and the face-centered cubic (FCC) phase is mainly Ni / C composite phase (as shown in Figure 3 as shown).

[0027] S3. Add the mixed powder obtained in S2 to the supersonic flame spraying gun, fully melt the powder, and then spray it onto the substrate surface to obtain the AlCoCrFeNi+Ni / C coating. The coating has a BCC phase as the main phase structure (such as Figure 3 As shown). During the spraying process, argon was used as the carrier gas with a flow rate of 12 L / min, the fuel flow rate was 7.5 GPH, the oxygen flow rate was 1850 SCFH, and intermittent spraying was adopted. The interval between the two sprayings was 3 s, the number of sprayings was 6, and the spraying distance was 360 mm.

[0028] The tribological properties of the prepared coating were investigated using a micro-motion friction and wear testing machine.

[0029] The friction adopts the ball-disk reciprocating mode. The coating and the commercially available Al2O3 ball with a diameter of 10 mm are used as a dual ball to form a friction pair. The friction test environment is the atmosphere, the test conditions are paraffin lubrication (load: 20 N, reciprocating frequency: 30 Hz, amplitude: 2 mm), and the friction test duration is generally set according to the pre-grinding stage and the stabilization stage.

[0030] First, a 2-minute pre-friction test is conducted at a certain location of the coating, and then a new location is selected for the friction test. This time, the friction time is 2+8 minutes (set in two sections). A 2-minute pre-friction test is conducted first. After the pre-friction is completed, an 8-minute friction test is conducted at the same location (i.e., the roughly stable stage). At this time, the friction coefficient recorded by the experimental instrument will be used as the friction coefficient of the friction stable stage (i.e., the stage mainly investigated by the institute). The wear volume of the above 2-minute and 2+8-minute friction tests is measured respectively, and the wear volume of the stable friction stage is obtained by subtracting the former from the latter.

[0031] Test results: The coating has entered the stable wear stage in the initial 2-minute pre-grinding stage (such as Figure 4 As shown in Figure 2), during the later 8-minute friction process, the friction coefficient remained stable at around 0.14 (as shown in Figure 2). Figure 4 The wear rate in the stable stage is 3.45 × 10 -6 mm 3 ·N -1 ·m -1 (like Figure 5 ), which is higher than the wear rate in the pre-grinding stage (5.74 × 10 -6 mm 3 ·N -1 ·m -1 )Low.

[0032] In summary, the AlCoCrFeNi+Ni / C coating shows excellent friction reduction and anti-wear properties under paraffin lubrication conditions.

Claims

1. A method for preparing an AlCoCrFeNi-based self-lubricating composite high entropy alloy coating, characterized in that: The method comprises the steps of uniformly mixing AlCoCrFeNi high entropy alloy powder and Ni / C by ball milling or mechanical means to obtain a composite powder; the composite powder is fully melted by supersonic flame spraying technology and then sprayed onto a pretreated substrate surface to obtain an AlCoCrFeNi+Ni / C coating.

2. The method for preparing an AlCoCrFeNi-based self-lubricating composite high entropy alloy coating according to claim 1, characterized in that: The AlCoCrFeNi high entropy alloy powder is prepared by the following method: firstly, AlxCoCrFeNi, x=0.5-3.0 is mixed, and then Al, Fe, Co, Cr, and Ni raw materials with a purity higher than 99.9% are smelted, spray-cooled, and sieved to obtain a powder with a particle size of ≤45 μm.

3. The method for preparing an AlCoCrFeNi-based self-lubricating composite high entropy alloy coating according to claim 1, characterized in that: The mass percentage of Ni / C in the composite powder is 0.2-10.0%.

4. The method for preparing an AlCoCrFeNi-based self-lubricating composite high entropy alloy coating according to claim 1, characterized in that: The conditions of the supersonic flame spraying are that the fuel flow rate is 6.0~7.5 GPH; the carrier gas is argon or nitrogen, and its flow rate is 8~12 L / min; the oxygen flow rate is 1800~1850 SCFH; an intermittent or continuous spraying method is adopted, the interval between the two sprayings is greater than 2 s, and the spraying distance is 300~500 mm.

5. An AlCoCrFeNi-based self-lubricating composite high-entropy alloy coating prepared by the method according to any one of claims 1 to 4.

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