Preparation method of AlCoCrFeNi-based wear-resistant high-entropy alloy coating

Abstract

The invention relates to a preparation method of an AlCoCrFeNi-based wear-resistant high-entropy alloy coating, which comprises the following steps of: uniformly mixing AlCoCrFeNi high-entropy alloy powder and Cr 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 is sprayed to the surface of a pretreated base material, so that the AlCoCrFeNi + Cr coating is obtained. The method is simple and easy to implement, and the obtained AlCoCrFeNi + Cr coating has excellent wear resistance, is suitable for the surfaces of mechanical engineering parts, and has good application prospects in the field of wear protection of large-scale devices and in the aspect of friction reduction and wear resistance of machines in severe environments.

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 wear-resistant high-entropy alloy coating. Background Art

[0002] With the development of modern industry, the service requirements of mechanical parts in terms of resistance to wear, corrosion and fracture are becoming more and more stringent. Surface coating technology is the most basic means to protect the surface of mechanical equipment and its important components. Preparing a protective coating with good anti-friction and anti-wear properties on the surface of the workpiece is a feasible method to solve the problem of friction and wear of the workpiece.

[0003] High entropy alloy is a new alloy concept proposed in the early 21st century. Different from the design concept of traditional alloys with one or two alloys as the main elements and supplemented by other alloy elements, high entropy alloy is an alloy composed of 5 or more elements in equimolar or nearly equimolar ratio, with the content of each element between 5% and 35%, and its performance is determined by all the constituent elements. It has high entropy effect, lattice distortion effect, hysteresis diffusion effect and "cocktail effect", can present a simple solid solution structure, and exhibits excellent mechanical properties, corrosion resistance, radiation resistance and wear resistance. It has broad application prospects in aviation, aerospace, nuclear energy, chemical industry and weapon equipment. There are thousands of combinations of high entropy alloys in composition design. With the continuous deepening of composition design research, the system of high entropy alloys is becoming more and more perfect, but the performance of high entropy alloys is limited by composition design, and the high cost of high entropy alloys limits its application in engineering. Since friction, wear and lubrication occur on the surface and interface of materials of relatively moving parts, surface engineering technology can be used to prepare anti-wear and friction-reducing functional protective coatings to further expand the application range of high entropy alloys. High entropy alloy coatings not only have the excellent properties of high entropy alloys, but also because the coatings may contain metastable phases, strengthening phases or special nanostructures, certain mechanical and protective properties can be significantly enhanced.

[0004] Thermal spraying is a technology that heats the spray material to a molten or semi-molten state through a heat source, and accelerates it with a high-temperature and high-speed flame flow, so that it collides and combines with the surface of the substrate to form a layered coating. The metal-based and ceramic-based coatings prepared by thermal spraying have the characteristics of fast deposition speed, high bonding strength, and excellent wear resistance. In addition, the production cost of thermal spraying technology is low, and it is especially suitable for various large-sized components and industrial mass production. It has very significant technical and economic advantages, and is therefore widely used in the preparation of various anti-wear protective functional coatings. Summary of the invention

[0005] 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 wear-resistant high-entropy alloy coating.

[0006] To solve the above problems, the present invention discloses a method for preparing an AlCoCrFeNi-based wear-resistant high-entropy alloy coating, which is characterized in that: the method refers to mixing AlCoCrFeNi high-entropy alloy powder and Cr 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+Cr coating.

[0007] 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.

[0008] The mass percentage of Cr in the composite powder is 0.2-8.0%.

[0009] The conditions of the supersonic flame spraying are that the fuel flow rate is 6.5~7.5 GPH; the carrier gas is argon, 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.

[0010] 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.

[0011] An AlCoCrFeNi-based wear-resistant high-entropy alloy coating prepared by the method as described above.

[0012] Compared with the prior art, the present invention has the following advantages: 1. The present invention prepares a body-centered cubic (BCC) phase AlCoCrFeNi+Cr coating by supersonic flame spraying technology. The prepared coating has a higher hardness value (hardness of about 11.50 GPa), which further enhances the friction reduction and wear resistance of the coating.

[0013] 2. The method of the present invention is simple and easy to implement. The obtained AlCoCrFeNi+Cr coating is suitable for the surface of mechanical engineering parts and has good application prospects in the field of wear protection of large-scale devices and friction reduction and anti-wear of machinery in harsh environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0015] Figure 1 This is a SEM image of the AlCoCrFeNi high entropy alloy powder described in the present invention.

[0016] Figure 2 This is a SEM image of the Cr powder described in the present invention.

[0017] Figure 3 This is the XRD diagram of the AlCoCrFeNi+Cr mechanical mixed powder and coating described in the present invention.

[0018] Figure 4 It is a curve diagram of the change of the friction coefficient of the AlCoCrFeNi+Cr coating of the present invention in the pre-grinding stage and the stable wear stage under paraffin lubrication conditions over time.

[0019] Figure 5 It is a histogram of the wear rate of the AlCoCrFeNi+Cr coating of the present invention in the pre-wear stage and the stable wear stage under paraffin lubrication conditions. DETAILED DESCRIPTION

[0020] A preparation method of an AlCoCrFeNi-based wear-resistant high-entropy alloy coating, comprising the steps of: uniformly mixing AlCoCrFeNi high-entropy alloy powder and Cr by ball milling or mechanical means to obtain a 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+Cr coating with excellent wear resistance.

[0021] 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.

[0022] The mass percentage of Cr in the composite powder is 0.2~8.0%.

[0023] The conditions for supersonic flame spraying are that the fuel flow rate is 6.5~7.5 GPH; the carrier gas is argon, and its flow rate is 8~12L / min; the oxygen flow rate is 1800~1850 SCFH; intermittent or continuous spraying is adopted, the interval between the two sprayings is greater than 2s, and the spraying distance is 300~500 mm.

[0024] 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.

[0025] 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.

[0026] Embodiment A method for preparing an AlCoCrFeNi-based wear-resistant 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.

[0027] 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 Cr powder (as Figure 2 The two powders are mechanically mixed and uniformly mixed. The mixed powder is a body-centered cubic (BCC) phase (as shown in Figure 3 as shown).

[0028] S3. Add the mixed powder obtained in S2 to a supersonic flame spraying gun, melt the powder, and then spray it onto the substrate surface to obtain an AlCoCrFeNi+Cr 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 8 L / min, the fuel flow rate was 6.5 GPH, the oxygen flow rate was 1800 SCFH, and intermittent spraying was adopted. The interval between the two sprayings was 2 s, the number of sprayings was 4, and the spraying distance was 370 mm.

[0029] The tribological properties of the prepared coating were investigated using a micro-motion friction and wear testing machine.

[0030] 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.

[0031] 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.

[0032] Test results: In the later stage of friction, the friction coefficient remains stable at around 0.19 (such as Figure 4 The wear rate in the stable stage is 3.4 × 10 -7 mm 3 ·N -1 ·m -1 (like Figure 5 as shown).

[0033] In summary, the AlCoCrFeNi+Cr coating shows excellent anti-wear properties under paraffin lubrication conditions.

Claims

1. A method for preparing an AlCoCrFeNi-based wear-resistant high-entropy alloy coating, characterized in that: The method comprises the steps of uniformly mixing AlCoCrFeNi high entropy alloy powder and Cr 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+Cr coating.

2. The method for preparing an AlCoCrFeNi-based wear-resistant 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 wear-resistant high-entropy alloy coating according to claim 1, characterized in that: The mass percentage of Cr in the composite powder is 0.2-8.0%.

4. The method for preparing an AlCoCrFeNi-based wear-resistant 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 6.5~7.5 GPH; the carrier gas is argon, 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 wear-resistant high-entropy alloy coating prepared by the method according to any one of claims 1 to 4.

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