A wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating structure for an alloy steel base body, and a preparation method and application thereof

Abstract

The present application relates to a wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating structure for alloy steel base body and a preparation method and application thereof, and belongs to the technical field of superhard coating development. x The FeCoCrNi(Al,Ti) high-entropy coating (x=0.5-1) is attached to the iron base body, the high-entropy coating is obtained by 3D printing to obtain a high-entropy coating before modification, and then nitrogen is infiltrated to obtain a product; the high-entropy coating before modification is composed of Fe, Co, Cr, Ni, Al or Ti in an atomic ratio of 1:1:1:1:x; the nitrogen-infiltrated layer obtained after nitrogen infiltration is mainly AlN or TiN, CrN and an FCC phase, the FeCoCrNi(Al,Ti) x high-entropy coating with a hardness greater than 1000 HV and excellent impact resistance and corrosion resistance is obtained for the first time, which widens the application range of alloy quenched and tempered steel.

Description

Technical Field

[0001] The present invention relates to a wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating structure for an alloy steel substrate, a preparation method and an application thereof, and belongs to the technical field of superhard coating development. Background Art

[0002] Alloy quenched and tempered steel is widely used in precision parts in aerospace, aviation, military and other industries, but its main disadvantages are low hardness and easy wear. Common surface modification methods are surface alloying, mechanical strengthening, and coating deposition. Although these processes can improve the hardness and wear resistance of steel, the modified quenched and tempered steel has a large cross-sectional hardness gradient and high brittleness, and is prone to peeling, crushing, cracking, and other problems, resulting in the problem that the service life of the quenched and tempered steel is low and cannot be well solved. Therefore, it is of vital importance to improve the service life, safety factor, and maintenance and replacement cycle of quenched and tempered steel. The present invention prepares a high entropy alloy nitriding layer on the surface of quenched and tempered steel through laser melt deposition-ion nitriding composite surface modification technology, which solves the failure problems of nitrided quenched and tempered steel when in service due to low bonding strength, insufficient toughness, brittle fracture / cracks under high load and high sliding speed conditions. The high entropy alloy nitriding layer obtained by this method has high hardness, excellent wear resistance and corrosion resistance.

[0003] Alloy quenched and tempered steel has good hot workability, hardenability, strength and toughness, and good comprehensive mechanical properties. It is widely used in precision parts in aerospace, aviation, military and other industries. However, its main disadvantages are low hardness and easy wear, which leads to a short service life. Plasma nitriding is a method that uses glow discharge technology to introduce nitrogen into the metal surface, and then the nitrogen diffuses into the material for surface modification. It is the most economical and effective way to improve the hardness, wear resistance and fatigue resistance of steel. After nitriding, the quenched and tempered steel can obtain a nitrided layer with higher hardness and higher wear resistance. However, the cross-sectional hardness gradient of the nitrided layer is large, the brittleness is high, and the corrosion resistance is relatively low. The nitrided layer is prone to peeling under heavy load, impact, thermal vibration and fatigue wear, resulting in the problem of low service life of quenched and tempered steel that cannot be well solved.

[0004] High entropy alloy (HEA) is an alloy composed of 5 or more elements with atomic fractions between 5% and 35%. HEA manifests itself as a delayed diffusion effect in kinetics, a lattice distortion effect in structure, a "cocktail" effect in performance, and a high entropy effect in thermodynamics. Therefore, HEA has the characteristics of structural stability, high strength, high plasticity and toughness, good wear resistance and corrosion resistance. Current studies have shown that nitriding will increase the hardness of the cast high entropy alloy AlCoCrFeNi. For example, Wang Yongxiang found in his master's thesis "Research on the Microstructure and Tribological Properties of the Nitrided Layer of High Entropy Alloys" that after nitriding of the cast high entropy alloy AlCoCrFeNi, a large amount of hard phase is formed on the surface of the alloy. The hardness values ​​before and after nitriding are 522HV and 720HV respectively; the cast high entropy alloy Al 1.3 After nitriding of CoCrFeNi2, a large amount of hard phase is formed on the surface of the alloy. The hardness values ​​before and after nitriding are 340HV and 587HV respectively. The process used is: the cast product is obtained by melting and casting, and then nitriding is performed. The nitriding process uses ammonia as the nitrogen source, and the flow rate of the nitrogen source is 0.4m 3 / h, and nitriding at 550℃ for 9h. This technology did not produce AlCoCrFeNi high entropy alloy with a hardness greater than 1000HV and excellent impact resistance and corrosion resistance. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention optimizes the HEA components and combines laser melt deposition and plasma nitriding processes to obtain FeCoCrNi (Al, Ti) with a hardness greater than or equal to 1000HV and excellent impact resistance and corrosion resistance. x (x=0.5-1) high entropy alloy coating. The coating is used to protect alloy quenched and tempered steel.

[0006] The present invention discloses a wear-resistant, corrosion-resistant and impact-resistant multi-element composite coating structure for an alloy steel substrate. The multi-element composite coating is attached to an iron substrate. The multi-element composite coating is a nitrogen-containing FeCoCrNi (Al, Ti) x High entropy coating;

[0007] The FeCoCrNi(Al,Ti) x The high entropy coating is first obtained by 3D printing before modification, and then nitrided to obtain the product; the high entropy coating before modification is composed of Fe, Co, Cr, Ni, Al or Ti in an atomic ratio of 1:1:1:1:x; its chemical formula is: FeCoCrNi(Al,Ti) x ;

[0008] FeCoCrNiAl obtained after nitriding xThe nitriding layer contains AlN, CrN and FCC phases. The FeCoCrNiTi obtained after nitriding x The nitriding layer contains TiN, CrN and FCC phases.

[0009] The value range of x is 0.5-1.

[0010] The FeCoCrNiAl obtained after nitriding of the present invention x The nitriding layer is mainly composed of AlN, CrN and FCC phases, FeCoCrNiTi x The nitriding layer is mainly composed of TiN, CrN, and FCC phases. This is because the formation enthalpy of Al, Cr, Ti, and N during the nitriding process is relatively negative, making it easier to form AlN, CrN, and TiN. The AlN, CrN, and TiN hard phases can significantly increase the hardness of the HEA nitriding layer. At the same time, the FCC solid solution phase can reduce the hardness gradient of the HEA nitriding layer to enhance the strength support of the HEA on the nitriding layer. In addition, nano-scale nitrides greatly improve the impact resistance and corrosion resistance of the HEA coating.

[0011] As a preferred embodiment, the multi-element composite coating is FeCoCrNiAl containing nitrogen. x High entropy coating. In the present invention, a nitrogen-containing AlCoCrFeNi high entropy alloy coating with a hardness greater than or equal to 1000 HV is obtained for the first time.

[0012] The present invention provides a method for preparing a wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating structure for an alloy steel substrate, comprising the following steps:

[0013] Step 1

[0014] With dry FeCoCrNi(Al,Ti) x A high-entropy alloy powder is used as a raw material, and a 3D printing process is used to prepare a high-entropy coating before modification on a substrate with a clean and dry surface. During 3D printing, the laser power is controlled to be 2000-2750W, the scanning speed is 10-25mm / s, the gas supply volume is 3-10L / min, preferably 4.8-5.2L / min, the powder supply volume is 10-20g / min, preferably 15-16g / min, the overlap rate is 40%-60%, preferably 43%-47%, and the preset coating thickness is 0.5-2.5mm, preferably 1.5-2mm.

[0015] Step 2

[0016] The high entropy coating obtained in step 1 before modification is polished, cleaned with alcohol, and dried. It is then sent to an ion nitriding treatment device for nitriding to obtain FeCoCrNi(Al,Ti) with a hardness greater than 1000HV and excellent impact resistance and corrosion resistance. x High entropy coating;

[0017] During nitriding, the furnace pressure is controlled at 200-230Pa, the workpiece pole power is turned on, the workpiece pole voltage is adjusted to 200-300V, and maintained for 5-20 minutes in order to clean the surface of the HEA coating. Subsequently, the workpiece pole voltage is adjusted to 600-650V, the source voltage is adjusted to 900-950V, and the nitrogen flow rate is 0.3-0.6m 3 / h, plasma nitriding is carried out to raise the surface temperature of the HEA coating to 450-550℃, and the plasma nitriding time is 50-60h.

[0018] The present invention provides a method for preparing a wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate, wherein the dried FeCoCrNi(Al,Ti) x High entropy alloy powder is prepared by the following steps:

[0019] Step A

[0020] Prepare Fe, Co, Cr, Ni, Al or Ti in an atomic ratio of 1:1:1:1:x; mix uniformly to obtain a mixture; Step B

[0021] The mixed material is melted in a non-consumable vacuum melting furnace in an argon atmosphere at atmospheric pressure, with a melting current of 200-300A and 5-8 treatments to obtain an alloy ingot;

[0022] Step C

[0023] The alloy ingot is processed into FeCoCrNi(Al,Ti) in a gas atomization device x Alloy powder; then screen out spherical powder with a particle size of 45-105μm and a purity of ≥99.5% and set aside. The standby powder is placed in a vacuum drying oven for constant temperature drying at 70-100°C for 6-12 hours before printing to obtain dry FeCoCrNi(Al,Ti) x High entropy alloy powder.

[0024] The substrate used in the present invention comprises alloy quenched and tempered steel. As a further preference, the alloy quenched and tempered steel is selected from at least one of 38CrMoAl, 35CrMo, and 40Cr alloy quenched and tempered steels.

[0025] When the alloy quenched and tempered steel is 38CrMoAl alloy steel, the quenching and tempering process is: quenching in oil at 850°C, heating again to 550°C for tempering, and air cooling to room temperature.

[0026] The present invention discloses a preparation method of a wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate. Before starting a laser melt deposition experiment, a substrate is placed on a workbench of a laser melt deposition device. The laser melt deposition system comprises a laser, a coaxial protective gas delivery system, an automatic powder feeding system and a computer control system, and adopts coaxial dual-channel powder feeding. The laser wavelength is 1064 nm, the maximum power of the laser beam is 6000 W, and the laser beam diameter is 4 mm. The specific process parameters of the laser melt deposition are as follows: controlling the laser power to 2000-2750 W, the scanning speed to 10-25 mm / s, the gas feeding volume to 3-10 L / min, preferably to 4.8-5.2 L / min, the powder feeding volume to 10-20 g / min, preferably to 15-16 g / min, the overlap rate to 40%-60%, preferably to 43%-47%, and the preset coating thickness to 0.5-2.5 mm, preferably to 1.5-2 mm.

[0027] Preferably, the present invention provides a method for preparing a wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate. In step one, the process parameters of laser melting deposition are: laser power 2000-2500W, scanning speed 15mm / s, gas supply volume 5L / min, powder supply volume 15.85g / min, and overlap rate 45%.

[0028] Open the powder feeder, open the argon valve, adjust the gas supply pressure to 600 MPa, start the laser melting deposition equipment, and deposit the high entropy alloy coating to be infiltrated.

[0029] The substrate used in the present invention is polished to a mirror surface with sandpaper, and then polished with a polishing machine to a surface roughness R a =1.0-2.0 μm, and then immersed in anhydrous ethanol for ultrasonic cleaning for 10-30 minutes.

[0030] The invention discloses a preparation method of a wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating structure for an alloy steel substrate. The ion nitriding treatment equipment used comprises a pulse plasma multi-element co-penetration furnace.

[0031] In industrial application, the present invention places the cleaned HEA coating sample to be nitrided on the cathode disk of the ion nitriding equipment, evacuates to below 4 Pa, fills the furnace with nitrogen again to make the pressure in the furnace reach 200-400 Pa, evacuates again, repeats twice, and then controls the pressure in the furnace to 200-230 Pa, turns on the workpiece pole power supply, adjusts the workpiece pole voltage to 200-300 V, and maintains it for 5-20 minutes, in order to clean the surface of the HEA to be nitrided, and then adjusts the workpiece pole voltage to 600-650 V, the source voltage to 900-950 V, and the nitrogen flow rate to 0.3-0.6 m 3 / h, plasma nitriding is carried out to raise the surface temperature of the HEA coating to 450-550°C, preferably 550°C, and the plasma nitriding time is 50-60h, preferably 60h.

[0032] As a preference, the polished HEA coating is placed in a plasma multi-element co-penetration furnace for ion nitriding treatment, the furnace pressure is controlled at 220Pa, the workpiece pole power supply is turned on, the workpiece pole voltage is adjusted to 250V, and maintained for 10 minutes, then the workpiece pole voltage is adjusted to 630V, the source voltage is adjusted to 920V, and the nitrogen flow rate is 0.4m 3 / h, plasma nitriding was carried out to raise the surface temperature of the HEA coating to 550℃, and the plasma nitriding time was 60h.

[0033] The present invention provides a preparation method of a wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating structure for an alloy steel substrate. After nitriding is completed, the furnace body is slowly cooled to room temperature and taken out, and the plasma nitriding is completed.

[0034] The present invention combines laser melt deposition and plasma nitriding processes. First, high-purity (greater than 99.9%) raw materials such as Fe, Co, Cr, Ni, Al or Ti are selected and mixed in an atomic ratio of 1:1:1:1:x. HEA ingots are prepared by smelting and casting. Then, the alloy ingots are prepared into FeCoCrNi(Al,Ti) by gas atomization. x High entropy alloy powder. FeCoCrNi(Al,Ti) was deposited by laser melting on a quenched and tempered steel substrate. x High entropy alloy coating, and then plasma nitriding of FeCoCrNi(Al,Ti) x The high entropy alloy coating is nitrided to obtain a HEA nitrided layer.

[0035] Before nitriding, the porosity of the HEA coating before modification is less than 3.0%. The present invention achieves a porosity of the printed coating of less than 3.0% by optimizing the composition and printing process.

[0036] The present invention provides an application of a wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating for an alloy steel substrate is attached to the surface of the alloy quenched and tempered steel, and is used to protect the alloy quenched and tempered steel and improve the comprehensive performance of the alloy quenched and tempered steel, solving the failure problems of the quenched and tempered steel after nitriding due to low bonding strength, insufficient toughness, brittle fracture / cracks, etc. under high load and high sliding speed conditions.

[0037] Principles and advantages

[0038] The balance between Al and Ti content in FeCoCrNi HEA is crucial for both laser melt deposition and plasma nitriding. For laser melt deposition, higher Al or Ti content results in poorer HEA coating formability; whereas for plasma nitriding, higher Al or Ti content increases the hardness of the HEA nitrided layer. Therefore, while ensuring the formability of the HEA coating for laser melt deposition, the present invention selects appropriate Al and Ti contents to achieve a HEA nitrided layer with both high hardness and excellent formability.

[0039] Since the FeCoCrNiAl x The high entropy alloy coating contains Cr and Al elements. The formation enthalpy of Cr, Al and nitrogen is relatively negative. The negative formation enthalpy means that the compound has higher bond energy and better stability. Therefore, FeCoCrNiAl x The nitrides in the nitriding layer are mainly AlN, CrN and FCC. With the appropriate increase of nitriding time, the nitrides formed by Al, Cr and nitrogen will increase to a reasonable range. The solid solution strengthening caused by the diffusion of nitrogen atoms in the nitriding layer and the dispersion strengthening of nitrides lead to the x The hardness of the high entropy alloy nitriding layer has been significantly improved. x The formation enthalpy of Cr, Ti and nitrogen in the high entropy alloy coating is relatively negative, so the solid solution strengthening caused by the diffusion of nitrogen atoms in the nitriding layer and the dispersion strengthening of TiN and CrN lead to the FeCoCrNiTi x The hardness of the high entropy alloy nitriding layer has been significantly improved. In addition, the nano-scale nitride greatly improves the FeCoCrNi(Al,Ti) x Impact and corrosion resistance of high entropy alloy coatings.

[0040] The wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating facing the alloy steel substrate is attached to the alloy quenched and tempered steel to protect the alloy quenched and tempered steel and improve the comprehensive performance of the alloy quenched and tempered steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the morphology of the nitrided layer obtained in Example 1. DETAILED DESCRIPTION

[0042] Example 1:

[0043] (1) The base material is 38CrMoAl and has been tempered. The tempering treatment is as follows: quenching in oil at 850℃, heating again to 550℃ for tempering, and air cooling to room temperature. The base material is also machined and shaped, and the size margin for laser melting deposition is reserved. The powder is FeCoCrNiAl prepared by gas atomization method. 0.5High-entropy alloy powder is produced by atomization: the mixed alloy raw materials are melted in a non-consumable vacuum melting furnace under atmospheric pressure and argon gas at a current of 250A for eight cycles to produce an alloy ingot. The high-entropy alloy powder is then screened for particle size, resulting in a spherical powder with a purity of ≥99.5% and a particle size range of 45-105μm. The powder is then dried at a constant temperature.

[0044] (2) After degreasing and cleaning, the substrate was fixed on the workbench, the deposition distance was adjusted, and the powder feeder and laser were turned on for laser melt deposition. The process parameters for laser melt deposition were: laser power 2000W, scanning speed 15mm / s, gas flow 5L / min, powder feed 15.85g / min, overlap rate 45%, and the thickness of the laser melt deposited HEA coating was 1.8mm.

[0045] (3) After the deposition is completed, the sample is cooled and then subjected to wire cutting, grinding and polishing, so that the thickness of the laser melt deposited HEA coating is 1 mm and the roughness is 1.2 μm.

[0046] (4) The polished HEA coating was placed in a plasma multi-element co-penetration furnace for ion nitriding treatment. The pressure in the furnace was controlled at 220 Pa, the workpiece pole power supply was turned on, and the workpiece pole voltage was adjusted to 250 V. The voltage was maintained for 10 minutes, and then the workpiece pole voltage was adjusted to 630 V, the source voltage was adjusted to 920 V, and the nitrogen flow rate was 0.4 m 3 / h, plasma nitriding was performed to raise the surface temperature of the HEA coating to 550℃, and the plasma nitriding time was 60h. The morphology of the HEA nitrided layer was as follows: Figure 1 As shown, the hardness of the nitrided layer is 1165HV 0.1 , the thickness of the nitriding layer is about 35μm, and the hardness of the HEA layer is 320HV 0.1 , the porosity is about 1.9%.

[0047] Example 2:

[0048] (1) The base material is 38CrMoAl and has been tempered. The tempering treatment is as follows: quenching in oil at 850℃, heating again to 550℃ for tempering, and air cooling to room temperature. The base material is also machined and shaped, and the size margin for laser melting deposition is reserved. The powder is FeCoCrNiAl prepared by gas atomization method. 0.5 High-entropy alloy powder is produced by atomization: the mixed alloy raw materials are melted in a non-consumable vacuum melting furnace under atmospheric pressure and argon gas at a current of 250A for eight cycles to produce an alloy ingot. The high-entropy alloy powder is then screened for particle size, resulting in a spherical powder with a purity of ≥99.5% and a particle size range of 45-105μm. The powder is then dried at a constant temperature.

[0049] (2) After degreasing and cleaning, the substrate was fixed on the workbench, the deposition distance was adjusted, and the powder feeder and laser were turned on for laser melt deposition. The process parameters for laser melt deposition were: laser power 2250 W, scanning speed 15 mm / s, gas flow 5 L / min, powder feed 15.85 g / min, overlap rate 45%, and the thickness of the laser melt deposited HEA coating was 2 mm.

[0050] (3) After the deposition is completed, the sample is cooled and then subjected to wire cutting, grinding and polishing, so that the thickness of the laser melt deposited HEA coating is 1 mm and the roughness is 1.2 μm.

[0051] (4) The polished HEA coating was placed in a plasma multi-element co-penetration furnace for ion nitriding treatment. The pressure in the furnace was controlled at 220 Pa, the workpiece pole power supply was turned on, and the workpiece pole voltage was adjusted to 250 V. The voltage was maintained for 10 minutes, and then the workpiece pole voltage was adjusted to 630 V, the source voltage was adjusted to 920 V, and the nitrogen flow rate was 0.4 m 3 / h, plasma nitriding was carried out to raise the surface temperature of the HEA coating to 550℃, and the plasma nitriding time was 60h. The hardness of the HEA nitrided layer was 1128HV 0.1 , the thickness of the nitriding layer is about 32μm, and the hardness of the HEA layer is 314HV 0.1 , the porosity is about 2.3%.

[0052] Example 3:

[0053] (1) The base material is 38CrMoAl and has been tempered. The tempering treatment is as follows: quenching in oil at 850℃, heating again to 550℃ for tempering, and air cooling to room temperature. The base material is also machined and shaped, and the size margin for laser melting deposition is reserved. The powder is FeCoCrNiAl prepared by gas atomization method. 0.5 High-entropy alloy powder is produced by atomization: the mixed alloy raw materials are melted in a non-consumable vacuum melting furnace under atmospheric pressure and argon gas at a current of 250A for eight cycles to produce an alloy ingot. The high-entropy alloy powder is then screened for particle size, resulting in a spherical powder with a purity of ≥99.5% and a particle size range of 45-105μm. The powder is then dried at a constant temperature.

[0054] (2) After degreasing and cleaning, the substrate was fixed on the workbench, the deposition distance was adjusted, and the powder feeder and laser were turned on for laser melt deposition. The process parameters for laser melt deposition were: laser power 2000W, scanning speed 15mm / s, gas flow 5L / min, powder feed 15.85g / min, overlap rate 45%, and the thickness of the laser melt deposited HEA coating was 1.8mm.

[0055] (3) After the deposition is completed, the sample is cooled and then subjected to wire cutting, grinding and polishing, so that the thickness of the laser melt deposited HEA coating is 1 mm and the roughness is 1.2 μm.

[0056] (4) The polished HEA coating was placed in a plasma multi-element co-penetration furnace for ion nitriding treatment. The pressure in the furnace was controlled at 220 Pa, the workpiece pole power supply was turned on, and the workpiece pole voltage was adjusted to 250 V. The voltage was maintained for 10 minutes, and then the workpiece pole voltage was adjusted to 630 V, the source voltage was adjusted to 920 V, and the nitrogen flow rate was 0.4 m 3 / h, plasma nitriding was carried out to raise the surface temperature of the HEA coating to 450℃, and the plasma nitriding time was 60h. The hardness of the HEA nitrided layer was 1038HV 0.1 , the thickness of the nitriding layer is about 27μm, and the hardness of the HEA layer is 320HV 0.1 , the porosity is about 1.9%.

[0057] Example 4:

[0058] (1) The base material is 38CrMoAl and has been tempered. The tempering treatment is as follows: quenching in oil at 850℃, heating again to 550℃ for tempering, and air cooling to room temperature. The base material is also machined and shaped, and the size margin for laser melting deposition is reserved. The powder is FeCoCrNiAl prepared by gas atomization method. 0.5 High-entropy alloy powder is produced by atomization: the mixed alloy raw materials are melted in a non-consumable vacuum melting furnace under atmospheric pressure and argon gas at a current of 250A for eight cycles to produce an alloy ingot. The high-entropy alloy powder is then screened for particle size, resulting in a spherical powder with a purity of ≥99.5% and a particle size range of 45-105μm. The powder is then dried at a constant temperature.

[0059] (2) After degreasing and cleaning, the substrate was fixed on the workbench, the deposition distance was adjusted, and the powder feeder and laser were turned on for laser melt deposition. The process parameters for laser melt deposition were: laser power 2000W, scanning speed 15mm / s, gas flow 5L / min, powder feed 15.85g / min, overlap rate 45%, and the thickness of the laser melt deposited HEA coating was 1.8mm.

[0060] (3) After the deposition is completed, the sample is cooled and then subjected to wire cutting, grinding and polishing, so that the thickness of the laser melt deposited HEA coating is 1 mm and the roughness is 1.2 μm.

[0061] (4) The polished HEA coating was placed in a plasma multi-element co-penetration furnace for ion nitriding treatment. The pressure in the furnace was controlled at 220 Pa, the workpiece pole power supply was turned on, and the workpiece pole voltage was adjusted to 250 V. The voltage was maintained for 10 minutes, and then the workpiece pole voltage was adjusted to 630 V, the source voltage was adjusted to 920 V, and the nitrogen flow rate was 0.4 m 3 / h, plasma nitriding was carried out to raise the surface temperature of the HEA coating to 550℃, and the plasma nitriding time was 50h. The hardness of the HEA nitrided layer was 1029HV 0.1 , the thickness of the nitriding layer is about 23μm, and the hardness of the HEA layer is 320HV 0.1 , the porosity is about 1.9%.

[0062] Comparative Example 1:

[0063] (1) The base material is 38CrMoAl and has been tempered. The tempering treatment is as follows: quenching in oil at 850℃, heating again to 550℃ for tempering, and air cooling to room temperature. The base material is also machined and shaped, and the size margin for laser melting deposition is reserved. The powder is FeCoCrNiAl prepared by gas atomization method. 0.5 High-entropy alloy powder is produced by atomization: the mixed alloy raw materials are melted in a non-consumable vacuum melting furnace under atmospheric pressure and argon gas at a current of 250A for eight cycles to produce an alloy ingot. The high-entropy alloy powder is then screened for particle size, resulting in a spherical powder with a purity of ≥99.5% and a particle size range of 45-105μm. The powder is then dried at a constant temperature.

[0064] (2) After degreasing and cleaning, the substrate was fixed on the workbench, the deposition distance was adjusted, and the powder feeder and laser were turned on for laser melt deposition. The process parameters of laser melt deposition were: laser power 2000W, scanning speed 15mm / s, gas flow 5L / min, powder feed 15.85g / min, overlap rate 45%, and the thickness of the laser melt deposited HEA coating was 1.7mm.

[0065] (3) After the deposition is completed, the sample is cooled and then subjected to wire cutting, grinding and polishing, so that the thickness of the laser melt deposited HEA coating is 1 mm and the roughness is 1.2 μm.

[0066] (4) The polished HEA coating was placed in a plasma multi-element co-penetration furnace for ion nitriding treatment. The pressure in the furnace was controlled at 220 Pa, the workpiece pole power supply was turned on, and the workpiece pole voltage was adjusted to 250 V. The voltage was maintained for 10 minutes, and then the workpiece pole voltage was adjusted to 630 V, the source voltage was adjusted to 920 V, and the nitrogen flow rate was 0.2 m 3 / h, plasma nitriding was carried out to raise the surface temperature of the HEA coating to 550℃, and the plasma nitriding time was 60h. The hardness of the HEA nitrided layer was 701HV 0.1 , the thickness of the nitriding layer is about 17μm, and the hardness of the HEA layer is 320HV 0.1 , the porosity is about 1.9%.

[0067] Comparative Example 2:

[0068] (1) The base material is 38CrMoAl and has been tempered. The tempering treatment is as follows: quenching in oil at 850℃, heating again to 550℃ for tempering, and air cooling to room temperature. The base material is also machined and shaped, and the size margin for laser melting deposition is reserved. The powder is FeCoCrNiAl prepared by gas atomization method. 0.5 High-entropy alloy powder is produced by atomization: the mixed alloy raw materials are melted in a non-consumable vacuum melting furnace under atmospheric pressure and argon gas at a current of 250A for eight cycles to produce an alloy ingot. The high-entropy alloy powder is then screened for particle size, resulting in a spherical powder with a purity of ≥99.5% and a particle size range of 45-105μm. The powder is then dried at a constant temperature.

[0069] (2) After degreasing and cleaning, the substrate was fixed on the workbench, the deposition distance was adjusted, and the powder feeder and laser were turned on for laser melt deposition. The process parameters for laser melt deposition were: laser power 2000W, scanning speed 15mm / s, gas flow 5L / min, powder feed 15.85g / min, overlap rate 45%, and the thickness of the laser melt deposited HEA coating was 1.8mm.

[0070] (3) After the deposition is completed, the sample is cooled and then subjected to wire cutting, grinding and polishing, so that the thickness of the laser melt deposited HEA coating is 1 mm and the roughness is 1.2 μm.

[0071] (4) The polished HEA coating was placed in a plasma multi-element co-penetration furnace for ion nitriding treatment. The pressure in the furnace was controlled at 220 Pa, the workpiece pole power supply was turned on, and the workpiece pole voltage was adjusted to 250 V. The voltage was maintained for 10 minutes, and then the workpiece pole voltage was adjusted to 630 V, the source voltage was adjusted to 920 V, and the nitrogen flow rate was 0.4 m 3 / h, plasma nitriding was carried out to raise the surface temperature of the HEA coating to 550℃, and the plasma nitriding time was 20h. The hardness of the HEA nitrided layer was 558HV 0.1 , the thickness of the nitriding layer is about 12μm, and the hardness of the HEA layer is 320HV 0.1 , the porosity is about 1.9%.

Claims

1. A wear-resistant, corrosion-resistant, and impact-resistant multi-principal component composite coating structure for an alloy steel substrate, characterized by: The multi-element composite coating is attached to the iron substrate, and the multi-element composite coating is nitrogen-containing FeCoCrNi (Al, Ti) x High entropy coating; The FeCoCrNi(Al,Ti) x The high entropy coating is first obtained by 3D printing before modification, and then the product is obtained by nitriding; The high entropy coating before modification is composed of Fe, Co, Cr, Ni, Al or Ti in an atomic ratio of 1:1:1:1:x; its chemical formula is: FeCoCrNi(Al,Ti) x ; FeCoCrNiAl obtained after nitriding x The nitriding layer contains AlN, CrN and FCC phases. The FeCoCrNiTi obtained after nitriding x The nitriding layer contains TiN, CrN and FCC phases. The value range of x is 0.5-1; The wear-resistant, corrosion-resistant and impact-resistant multi-principal-element composite coating structure facing the alloy steel substrate is prepared by the following steps: Step 1 With dry FeCoCrNi(Al,Ti) x High-entropy alloy powder was used as raw material, and a 3D printing process was used to prepare a high-entropy coating before modification on a clean and dry substrate. During 3D printing, the laser power was controlled at 2000-2750 W, the scanning speed was 10-25 mm / s, the gas flow rate was 3-10 L / min, the powder feed rate was 10-20 g / min, the overlap rate was 40%-60%, and the preset coating thickness was 0.5-2.5 mm. Step 2 The high entropy coating obtained in step 1 before modification is polished, cleaned with alcohol, and dried. It is then sent to an ion nitriding treatment device for nitriding to obtain FeCoCrNi(Al,Ti) with a hardness greater than 1000HV and excellent impact resistance and corrosion resistance. x High entropy coating; During nitriding, the furnace pressure was controlled at 200-230 Pa, the workpiece electrode power was turned on, the workpiece electrode voltage was adjusted to 200-300 V, and maintained for 5-20 minutes, then the workpiece electrode voltage was adjusted to 600-650 V, the source electrode voltage was adjusted to 900-950 V, and the nitrogen flow rate was 0.3-0.6 m 3 / h, plasma nitriding is carried out to raise the surface temperature of the HEA coating to 450-550℃, and the plasma nitriding time is 50-60 h.

2. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate according to claim 1, characterized in that: In step one, During 3D printing, the air supply volume is controlled at 4.8-5.2L / min, the powder supply volume is 15-16g / min, the overlap rate is 43-47%, and the preset coating thickness is 1.5-2mm.

3. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate according to claim 1, characterized in that: In step 2, Plasma nitriding was performed to raise the surface temperature of the HEA coating to 550°C, and the plasma nitriding time was 60 h.

4. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate according to claim 1, characterized in that: The dried FeCoCrNi(Al,Ti) x High entropy alloy powder is prepared by the following steps: Step A Fe, Co, Cr, Ni, Al or Ti are prepared in an atomic ratio of 1:1:1:1:x; and mixed uniformly to obtain a mixture; Step B The mixed material is melted in a non-consumable vacuum melting furnace in an argon atmosphere at atmospheric pressure, with a melting current of 200-300 A and 5-8 treatments to obtain an alloy ingot; Step C The alloy ingot is processed into FeCoCrNi(Al,Ti) in a gas atomization device x Alloy powder; then screen out spherical powder with a particle size of 45-105 μm and a purity of ≥99.5% and set aside. The standby powder is placed in a vacuum drying oven for constant temperature drying at 70-100 ° C for 6-12 h before printing; obtain dry FeCoCrNi(Al,Ti) x High entropy alloy powder.

5. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate according to claim 1, characterized in that: The alloy quenched and tempered steel is selected from at least one of 38CrMoAl, 35CrMo, and 40Cr alloy quenched and tempered steels.

6. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate according to claim 1, characterized in that: During printing, turn on the powder feeder, open the argon valve, adjust the gas supply pressure to 600 MPa, start the laser melting deposition equipment, and deposit the high entropy alloy coating to be infiltrated.

7. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate according to claim 1, characterized in that: After grinding, polish with a polishing machine to a surface roughness of R a =1.0-2.0μm, and then immersed in anhydrous ethanol for ultrasonic cleaning for 10-30 minutes.

8. The wear-resistant, corrosion-resistant and impact-resistant multi-principal component composite coating structure for an alloy steel substrate according to claim 1, characterized in that: Before nitriding, the porosity of the obtained unmodified high entropy coating was less than 3.0%.

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