HIGH ENTROPY ALLOY POWDER FOR LASER CLADDING AND APPLICATION METHOD THEREOF

Abstract

The present disclosure discloses a high-entropy alloy powder for laser cladding and a use method thereof. The alloy powder is CoCrFeMnNiC.sub.x, and x has a value of 0.1-0.15. The specific method includes: subjecting a 45 steel substrate to surface pretreatment, mixing the weighed CoCrFeMnNi high-entropy alloy powder with different content of a nano-C powder uniformly and pre-placed on the pre-treated substrate surface to form a prefabricated layer, then placing the prefabricated layer at 80-90° C. for constant temperature treatment for 8-12 h, and under a protective atmosphere, subjecting the cladding powder to laser cladding on the surface of the 45 steel. The method of the present disclosure prepares a CoCrFeMnNiC.sub.x high-entropy alloy coating with performance superior to the CoCrFeMnNi high-entropy alloy coating.

Claims

1. A high-entropy alloy powder for laser cladding, wherein the alloy powder is CoCrFeMnNiC.sub.x, and x has a value of 0.1 to 0.15.

2. A method for preparing a laser cladding coating with the high-entropy alloy powder according to claim 1, specifically comprising the following steps: (1) subjecting a 45 steel substrate to surface pretreatment: sanding, cleaning, and drying for use; (2) weighing a CoCrFeMnNi high-entropy alloy powder with an equal atomic ratio and a nano-C powder in proportion, and mixing mechanically after weighing; (3) blending the mixed powders with absolute ethanol to prepare a paste, using a mold to bond the paste to a predetermined position on the steel substrate to obtain a prefabricated coating followed by drying, and subjecting a cladding powder to laser cladding on the surface of the 45 steel in a protective atmosphere.

3. The method according to claim 1, wherein in step (2), the CoCrFeMnNi high-entropy alloy powder has an average particle size of less than 25 μm, and a powder purity of no less than 99.9%; the nano-C powder has an average particle size of 30 nm to 50 nm, and a purity of no less than 99.99%.

4. The method according to claim 1, wherein in step (3), the drying is under the following conditions: the prefabricated coating has a thickness of 0.2 mm to 2 mm, and is treated at a constant temperature of 80 to 90° C. for 8 to 12 h.

5. The method according to claim 1, wherein in step (3), the laser cladding is performed by a CO.sub.2 laser, and specific conditions are as follows: a laser power is 3.7 to 4.2 kW, a scanning speed is 200 to 450 mm/min, a spot diameter is 3.0 to 4.0 mm, the protective atmosphere is nitrogen, argon or a mixture of both, a gas flow is 15 to 35 L/min, and a pressure of the protective atmosphere is 0.80 MPa to 1.20 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 shows a metallographic structure of the cross-section of the laser cladding coating in Example 1 of the present disclosure;

[0020] FIG. 2 shows a metallographic structure of the bonding zone of the laser cladding coating in Example 1 of the present disclosure;

[0021] FIG. 3 shows an XRD spectrum of the laser cladding coating of Example 1 of the present disclosure;

[0022] FIG. 4 shows microhardness of the cladding coating and the substrate in Example 1 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present disclosure will be further illustrated below with reference to the embodiments. However, the protection scope of the present disclosure is not limited to the embodiments.

[0024] The chemical composition of the substrate material 45 steel in Examples 1 to 3 of the present disclosure is shown in Table 1:

TABLE-US-00001 TABLE 1 Chemical composition of 45 steel Element C Si Mn Cr Ni Cu Fe Mass fraction % 0.42~0.50 0.17~0.37 0.50~0.80 ≤0.25 ≤0.30 ≤0.25 Balance

Example 1

[0025] A process for preparing a laser cladding layer with the high-entropy alloy powder was performed, which specifically included the following steps:

[0026] (1) Surface pretreatment of a 45 steel substrate: the surface of the metal substrate was firstly sanded with a 200-800 mesh sandpaper to remove the oxide film and rinsed with water, and then was subjected to ultrasonic cleaning in absolute ethanol to remove residual oil and impurities on the surface; after cleaning, the metal substrate was dried in a vacuum environment at 60° C. for 0.5 h for use; the sanding required complete removal of the oxide film on the surface of the metal substrate without coarse scratches, and sanding marks in a consistent direction and a bright surface.

[0027] (2) a CoCrFeMnNi high-entropy alloy powder and a nano-C powder were weighed according to the atomic ratio of CoCrFeMnNiC.sub.0.1, and were mechanically mixed after weighing, wherein the nano-C powder had an average particle size of 50 nm and a purity of no less than 99.99%.

[0028] (3) The weighed mixed powders were blended with absolute ethanol with a purity of no less than 99.7% to prepare a paste, and a mold was used to bond the paste to a predetermined position on the 45 steel substrate to obtain a prefabricated coating with a thickness of 1 mm, which was then placed at 90° C. for a constant temperature treatment for 10 hours; the cladding powder was subjected to laser cladding on the surface of the 45 steel under a protective atmosphere to obtain a cladding coating composed of cladding points distributed in an array; the laser cladding was performed by a CO.sub.2 laser, wherein the laser power was 4.2 kW, the scanning speed was 450 mm/min, the spot diameter was 3 mm, the protective atmosphere was a mixed gas of Ar and N.sub.2, the gas flow was 25 L/min, and the pressure of the protective atmosphere was 1.20 MPa.

[0029] A D/max-3BX type X-ray diffractometer was used to characterize the CoCrFeMnNiC.sub.0.1 high-entropy alloy coating in this example with an object image; the result shows that the object image is mainly composed of FCC phase.

[0030] The microhardness of the cladding layer was measured by using a HVS-1000A type microhardness tester, the pressure was 0.2 kg, and the hardness of the coating and the metal substrate was measured after 15 s of holding pressure. From calculation, the average microhardness of the 45 steel substrate is 163.4 HV.sub.0.2, and the average hardness of the CoCrFeMnNi high-entropy alloy coating is 211.2 HV.sub.0.2, which is 1.29 times that of the metal substrate.

[0031] The coating was corroded with aqua regia, and the metallographic photos of the cladding layer were obtained with a Leica DFC280 vertical metallurgical microscope, as shown in FIG. 1 and FIG. 2. It may be seen from the figures that the cladding layer is well bonded without obvious cracks or pores and has a dense structure. The D/max-3BX type X-ray diffractometer was used to characterize the CoCrFeMnNiC.sub.0.1 high-entropy alloy material coating with an object image; the result shows, as shown in FIG. 3, that it is mainly composed of FCC phase.

Example 2

[0032] The process for preparing a laser cladding layer with the high-entropy alloy powder in this example specifically included the following steps:

[0033] (1) Pretreatment of a substrate: the surface of the metal substrate was firstly sanded with a 200-800 mesh sandpaper and rinsed with water, and then was ultrasonically cleaned in absolute ethanol and dried in a vacuum environment at 80° C. for 0.5 h for use. The sanding required complete removal of the oxide film on the surface of the metal substrate without large scratches, and sanding marks in a consistent direction and a bright surface.

[0034] (2) A CoCrFeMnNi high-entropy alloy powder and a nano-C powder were weighted according to the atomic ratio of CoCrFeMnNiC.sub.0.15, and mechanically mixed after weighing, wherein the nano-C powder had an average particle size of 30 nm and a purity of no less than 99.99%.

[0035] (3) The mixed powders were blended with anhydrous ethanol with a purity of no less than 99.7% to prepare a paste, and a mold was used to bond the paste to a predetermined position on the 45 steel substrate to obtain a prefabricated coating with a thickness of 1 mm, which was then placed at 85° C. for a constant temperature treatment for 8 hours; under a protective atmosphere, the cladding powder was subjected to laser cladding on the surface of the 45 steel to obtain a cladding coating composed of cladding points distributed in an array; the laser cladding was performed by a CO.sub.2 laser, wherein the laser power was 3.7 kW, the scanning speed was 200 mm/min, the spot diameter was 4 mm, the protective gas was N.sub.2, the gas flow was 20 L/min, and the pressure of the protective atmosphere was 1.10 MPa.

[0036] A D/max-3BX type X-ray diffractometer was used to characterize the CoCrFeMnNiC.sub.0.15 high-entropy alloy coating with an object image; the result shows that the object image is mainly composed of FCC phase.

[0037] The microhardness of the cladding layer was measured by using a HVS-1000A type microhardness tester, the pressure was 0.2 kg, and the hardness of the coating and the metal substrate was measured after 15 s of holding pressure. From calculation, the average microhardness of the 45 steel substrate is 160.8 HV.sub.0.2, and the average hardness of the CoCrFeMnNiC.sub.0.15 high-entropy alloy coating is 203.3 HV.sub.0.2, which is 1.26 times that of the metal substrate.

Comparative Example 1

[0038] A process for preparing a laser cladding coating with the high-entropy alloy powder was performed, which specifically included the following steps:

[0039] (1) Surface pretreatment of a 45 steel substrate: the surface of the metal substrate was firstly sanded with a 200-800 mesh sandpaper to remove the oxide film and rinsed with water, and was then subjected to ultrasonic cleaning in absolute ethanol to remove residual oil and impurities on the surface; after cleaning, the metal substrate was dried for 1 hour in a vacuum environment at 70° C. for use; the sanding required complete removal of the oxide film on the surface of the metal substrate without coarse scratches, and sanding marks in a consistent direction and a bright surface.

[0040] (2) A CoCrFeMnNi high-entropy alloy powder was weighted. The weighed CoCrFeMnNi high-entropy alloy powder was blended with absolute ethanol with a purity of no less than 99.7% to prepare a paste, and a mold was used to bond the paste to a predetermined position of the 45 steel substrate to obtain a prefabricated coating with a thickness of 1 mm, which was then placed at 80° C. for a constant temperature treatment for 8 hours; under a protective atmosphere, the cladding powder was subjected to laser cladding on the surface of the 45 steel to obtain a cladding coating composed of cladding points distributed in an array; the laser cladding was performed by a CO.sub.2 laser, wherein the laser power was 3.7 kW, the scanning speed was 200 mm/min, the spot diameter was 3 mm, the protective gas was Ar, the gas flow was 15 L/min, and the pressure of the protective atmosphere was 1.00 MPa.

[0041] The microhardness of the cladding layer was measured by using a HVS-1000A type microhardness tester, the pressure was 0.2 kg, and the hardness of the coating and the metal substrate was measured after 15 s of holding pressure, with the result shown in FIG. 4. From calculation, the average microhardness of the 45 steel substrate is 158.4 HV.sub.0.2, and the average hardness of the CoCrFeMnNi high-entropy alloy coating is 188.1 HV.sub.0.2, which is 1.19 times that of the metal substrate.

[0042] In summary, a D/max-3BX type X-ray diffractometer was used to characterize the CoCrFeMnNiC.sub.x high-entropy alloy coatings with object images; the results show that the object images of the cladding coatings in Example 1, Example 2 and Comparative Example 1 are all mainly composed of FCC phase. The microhardness of the cladding layers were measured by using a HVS-1000A type microhardness tester, the pressure was 0.2 kg, and the hardness of the coatings and the metal substrates was measured after 15 s of holding pressure. The hardness of the cladding coatings are significantly improved in Example 1, Example 2 and Comparative Example 1 compared with that of the substrates, with the coating hardness of Example 1>Example 2>Comparative Example 1. Thus, it can be seen that with the increase in C atoms, the strength of the alloy is firstly increased and then decreased. Nevertheless, compared with the CoCrFeMnNi high-entropy alloy coating in Comparative Example 1, the strength of the CoCrFeMnNiC.sub.0.1 high-entropy alloy coating in Example 1 and the CoCrFeMnNiC.sub.0.15 high-entropy alloy coating in Example 2 are both significantly improved.