CN116752082B

CN116752082B - Method for preparing high-hardness high-wear-resistance nitriding layer on surface of eutectic high-entropy alloy

Info

Publication number: CN116752082B
Application number: CN202310496633.5A
Authority: CN
Inventors: 胡静; 申嘉辉; 安旭龙; 魏伟
Original assignee: Changzhou University
Current assignee: Changzhou University
Priority date: 2023-05-05
Filing date: 2023-05-05
Publication date: 2025-02-18
Anticipated expiration: 2043-05-05
Also published as: CN116752082A

Abstract

The invention discloses a method for preparing a high-hardness high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy, and belongs to the technical field of nitriding treatment of alloy surfaces. In order to widen the engineering application of the high-entropy alloy, the invention adopts a direct current glow ion nitriding furnace to carry out surface nitriding treatment on the eutectic high-entropy alloy, uses Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy as a base material, introduces heat treatment and sand blasting to pretreat the eutectic high-entropy alloy, and then carries out nitriding treatment, so that the nitriding effect can be improved, and the hardness and wear resistance of the surface of the base body can be further improved through heat, thereby widening the application prospect of the material.

Description

Method for preparing high-hardness high-wear-resistance nitriding layer on surface of eutectic high-entropy alloy

Technical Field

The invention belongs to the technical field of alloy surface nitriding treatment, and particularly relates to a method for preparing a high-hardness high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy.

Background

Ion nitriding is a chemical heat treatment mode for forming a nitriding layer on the surface of a base material so as to improve the surface performance of a part, can endow the surface of the part with various special performances such as high hardness, high wear resistance, high corrosion resistance, oxidation resistance, fatigue resistance and the like, and is an important means for strengthening the surface of the part. The method is environment-friendly, saves energy and is widely applied.

The high-entropy alloy is also called as multi-principal element alloy, is used as a novel alloy material, attracts a plurality of researchers to conduct extensive research after birth, finds that the single-phase high-entropy alloy is difficult to balance the strength and the ductility of the alloy, so that the researchers introduce the concept of the eutectic alloy into the preparation of the high-entropy alloy, and newly develops the eutectic high-entropy alloy, and the eutectic high-entropy alloy is the high-entropy alloy material closest to engineering application due to excellent casting performance.

At present, related researches are carried out on preparing a nitriding layer from a single-phase high-entropy alloy, but the single-phase high-entropy alloy has no method for meeting the balance of strength and plasticity because of the structure and the structure, and the eutectic high-entropy alloy has a lamellar eutectic structure formed by a softer face-centered cubic structure phase and a harder body-centered cubic structure phase, so that the plasticity and the strength can be well considered, researchers find that the casting fluidity of the eutectic high-entropy alloy is good, the cost can be saved, and the surface nitriding treatment is carried out on the eutectic high-entropy alloy, so that the surface performance of the eutectic high-entropy alloy can be improved, and the prospect of the high-entropy alloy in engineering application can be increased.

In order to widen the engineering application of the high-entropy alloy, the inventor adopts a direct current glow ion nitriding furnace to carry out surface nitriding treatment on the eutectic high-entropy alloy, and the adopted Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy comprehensively considers the cost and the performance of the base material of the eutectic high-entropy alloy which is comparatively ideal to carry out surface nitriding. The surface nitriding treatment can improve the surface hardness and wear resistance of the material, thereby widening the application prospect of the material.

Disclosure of Invention

This section is intended to outline some aspects of embodiments of the application and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description of the application and in the title of the application, which may not be used to limit the scope of the application.

The present invention has been made in view of the above and/or problems occurring in the prior art.

Therefore, the invention aims to overcome the defects in the prior art and provide a method for preparing a high-hardness high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy.

In order to solve the technical problems, the invention provides the following technical proposal that comprises,

Preparing a eutectic high-entropy alloy substrate, carrying out ion nitriding treatment after pretreatment on the substrate, and preparing a nitriding layer with high hardness and high wear resistance on the surface of the substrate after the treatment is finished;

wherein the pretreatment includes a heat treatment and a sand blasting treatment.

As a preferable scheme of the method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy, the preparation method of the eutectic high-entropy alloy matrix comprises the following steps of,

Taking Al, fe, co, ni elements as principal elements, mixing, placing into a vacuum induction smelting furnace, vacuumizing and heating to melt raw materials uniformly, rapidly pouring into a mold, and cooling along with the furnace to form square cast ingots

Wherein the atomic percentages of the elements are 18-20at% of Al, 20-22at% of Co, 20-22at% of Fe and 40-45at% of Ni respectively.

As a preferable scheme of the method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy, the method comprises the steps of heat treatment, wherein the treatment temperature is 400-600 ℃, and the treatment time is 5-30 min.

The method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy is characterized in that the sand blasting pretreatment comprises the following steps of performing sand blasting under the conditions of air inlet pressure of 0.4-0.6 MPa, sand blasting under the conditions of pressure of 0.4-0.6 MPa, spraying angle of 45-90 degrees and sand blasting time of 5-10 min.

As a preferable scheme of the method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy, the ion nitriding treatment comprises the following steps of,

Placing the pretreated eutectic high-entropy alloy on a cathode disc of a nitriding furnace, sealing the nitriding furnace, and opening a vacuum pump to vacuumize the furnace after electrifying;

when the pressure in the furnace is stable, the working voltage and current are slowly regulated, and hydrogen is introduced to enable glow to be generated in the furnace;

the temperature in the furnace is increased by utilizing the glow discharge phenomenon, the air pressure and the hydrogen flow in the furnace are continuously regulated, and the surface of the alloy is cleaned by sputtering;

And (3) introducing nitrogen after sputtering, keeping the gas ratio of the hydrogen to the nitrogen to be 1-2:3-4, and carrying out heat preservation treatment after the temperature in the furnace is stable, thereby finally obtaining the nitriding layer.

As a preferable scheme of the method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy, the pressure and the hydrogen flow in the furnace are continuously regulated to 280-320 Pa, and the hydrogen flow rate is 480-520 mL/min.

The method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy is characterized by comprising the step of sputtering cleaning, wherein the sputtering time is 25-35 min.

As a preferable scheme of the method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy, the air pressure in the furnace is 380-420 Pa during heat preservation treatment, the heat preservation temperature is 500-550 ℃, and the heat preservation time is 2-6 hours.

As a preferable scheme of the method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy, the thickness of the nitriding layer is 1-10 mu m.

As a preferable scheme of the method for preparing the high-hardness high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy, the hardness of the alloy surface is 584-803 HV, and the wear rate is lower than 10 ^-5N·mm/mm³.

The invention has the beneficial effects that:

(1) The invention uses eutectic high-entropy alloy which is close to engineering application as an object to carry out nitriding treatment, and a nitriding layer with high hardness and high wear resistance is formed on the surface of the eutectic high-entropy alloy, so that the surface hardness and wear resistance of the alloy in an as-cast state are greatly improved;

(2) According to the invention, heat treatment and sand blasting treatment are introduced in the process of preparing the nitriding layer to pretreat the surface of the eutectic high-entropy alloy matrix, the structure is stabilized through the heat treatment, and the prefabricated stress is further subjected to the sand blasting treatment, so that the nitriding rate of the pretreated matrix can be greatly improved during nitriding treatment, the nitriding time is shortened, and the nitriding effect is also improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:

FIG. 1 is a diagram of the original surface texture of an Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy.

Fig. 2 is an XRD pattern of Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy.

FIG. 3 is a cross-sectional microstructure of a nitrided sample according to example 2 of the present invention.

FIG. 4 is a cross-sectional line scanning EDS spectrum of a nitriding treatment sample in example 2 of the present invention.

FIG. 5 is a cross-sectional surface scanning EDS spectrum of a nitriding treatment sample in example 2 of the present invention.

FIG. 6 is an XRD pattern of a sample nitrided according to example 2 of this invention.

FIG. 7 is a gold phase diagram of a cross-sectional microstructure of a nitrided sample according to example 3 of the present invention.

FIG. 8 is a gold phase diagram of a cross-sectional microstructure of a nitrided sample according to example 4 of the present invention.

Detailed Description

In order that the above-recited objects, features and advantages of the present invention will become more apparent, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.

Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

The ion nitriding furnace adopted by the invention is a direct current glow ion nitriding furnace, and the hydrogen and the nitrogen which are introduced into the nitriding furnace are common nitrogen and hydrogen with the purity of 99.9 percent.

Example 1

The embodiment provides a preparation method of a eutectic high-entropy alloy, which comprises the following steps:

The elements such as Al, fe, co, ni are taken as principal elements, and the atomic percentages of the elements are 18-20at% of Al, 20-22at% of Co, 20-22at% of Fe and 40-45at% of Ni;

Mixing and then placing the mixture into a vacuum induction smelting furnace, wherein the temperature of the induction smelting furnace is 1500 ℃, the vacuum degree in the furnace is lower than 1 multiplied by 10- ⁵ Pa, the induction current is 200A-600A, vacuumizing and heating are carried out to ensure that the raw materials are melted uniformly, keeping all metals in a liquid state for 10-15 minutes, then rapidly pouring the mixture into a mould, and cooling the mould along with the furnace to form square ingots, thus obtaining the Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy.

The eutectic high-entropy alloy prepared by the embodiment can have better tensile property after casting without conventional heat treatment and deformation treatment.

Fig. 1 is an original surface texture pattern of the Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy prepared in this example, fig. 2 is an XRD pattern of the Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy, and the hardness of the alloy matrix is measured to be 311HV.

The following examples all target the eutectic high-entropy alloy prepared in this example.

Example 2

The embodiment provides a preparation method for preparing an Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic high-entropy alloy surface ion nitriding layer, which comprises the following specific steps:

Heat treatment, namely, carrying out high-entropy combination on Al ₁₉Fe₂₀Co₂₀Ni₄₁ eutectic at 600 ℃ and preserving heat for 30min;

And (3) sand blasting pretreatment, namely cutting the square cast ingot subjected to heat treatment into a small sample with the thickness of 10 multiplied by 3mm by adopting a linear cutting mode, grinding and polishing the surface, and performing sand blasting pretreatment until the surface of the sample is uniform, wherein the sand blasting condition is that the air inlet pressure is 0.5MPa, the sand blasting pressure is 0.5MPa, the injection angle is 90 degrees, and the sand blasting time is 5min.

The ion nitriding treatment, namely slowly opening an air valve to enable the pressure in the nitriding furnace to be consistent with the pressure in the air, lifting the nitriding furnace wall, polishing a cathode disk in the nitriding furnace cleanly by using sand paper, alcohol and the like, and then placing a sample after the sand blasting treatment on the cathode disk in the nitriding furnace;

Opening a vacuum pump valve and a cooling water valve, vacuumizing, and adjusting voltage and current after the air pressure in the furnace is stable during vacuumizing, so that a glow discharge phenomenon is generated in the furnace by introducing hydrogen;

The temperature in the nitriding furnace is increased by utilizing the glow discharge phenomenon, then the gas flow of hydrogen and the gas pressure in the furnace are continuously regulated, the hydrogen flow is regulated to 300mL/min, and sputtering is carried out for 30min when the pressure in the furnace is regulated to 300 Pa;

After sputtering, introducing nitrogen, keeping the ratio of mixed gas in the furnace to H ₂：N₂ =1:3, and then preserving heat for 6 hours under the conditions of 550 ℃ and 400 Pa;

and after the heat preservation is finished, closing the voltage and the current, closing the gas cylinder and the vacuum pump, opening the nitriding furnace after the nitriding furnace is cooled, and taking out the sample, namely forming a nitriding layer on the surface of the substrate.

Fig. 3 is a cross-sectional microstructure of a seeped layer of the sample prepared in this example, fig. 4 is a cross-sectional line scanning EDS spectrum thereof, fig. 5 is a cross-sectional plane scanning EDS spectrum thereof, and fig. 6 is an XRD spectrum of the sample.

The sample compound obtained in this example shown in FIG. 5 had a nitrided layer thickness of about 10 μm, and had a significantly improved surface hardness compared with the hardness of the base body, from 311HV to 803HV, and had a significantly improved surface property by the formation of nitrides as shown in FIG. 6. And the improvement of the surface hardness can improve the wear resistance of the material, and the wear rate of the sample prepared by the embodiment is lower than 10 ^-5N·mm/mm³.

Example 3

The difference between this example and example 2 is that the heat-preservation time of nitrogen gas introduced after sputtering is 2 hours, and the rest of the preparation process is the same as that of example 2.

The microstructure of the cross section of the seepage layer is shown in figure 7, and the surface hardness of the seepage layer is obviously improved from 311HV to 584HV compared with the hardness of a matrix.

Example 4

The difference between this example and example 2 is that the incubation time for nitrogen gas introduction after the sputtering was completed was 4 hours, and the rest of the preparation process was the same as example 2.

The microstructure of the cross section of the seepage layer is shown in figure 8, and the surface hardness of the seepage layer is obviously improved from 311HV to 716HV compared with the hardness of a matrix.

Example 5

The difference between this example and example 2 is that the blasting angle was adjusted to 45 °, the rest of the production process was the same as in example 2, and the surface hardness of the sample obtained in this example was measured to be 778HV.

Example 6

The difference between this example and example 3 is that the blasting angle was adjusted to 45 °, and the other preparation processes were the same as those of example 3, and the surface hardness of the sample prepared in this example was measured to be 545HV.

Example 7

The difference between this example and example 4 is that the blasting angle was adjusted to 45 °, the rest of the production process was the same as in example 4, and the surface hardness of the sample prepared in this example was measured to be 716HV.

Comparative example 1

This comparative example was different from example 2 in that the surface hardness of the sample prepared in this example was 568HV, as measured, in the same manner as in example 2 except that the sand blasting pretreatment was not performed.

Comparative example 2

This comparative example was different from example 3 in that the surface hardness of the sample prepared in this example was found to be 533HV, as in example 2, without the sand blasting pretreatment.

Comparative example 3

This comparative example was different from example 4 in that the surface hardness of the test piece obtained in this example was found to be 544HV, as in example 2, without the sand blasting pretreatment, and in the rest of the production process.

The surface hardness results of the samples prepared in examples 2 to 7 and comparative examples 1 to 3 are shown in Table 1.

Table 1 surface hardness of samples treated with different blasting and nitriding times at 550C nitriding temperature

	6h	2h	4h
				45 Degree sand blasting	778HV	545HV	603HV
90 Degree sand blasting	803HV	584HV	716HV
				No sand blasting	568HV	533HV	544HV

As can be seen from Table 1, the present invention has a remarkable effect on the hardness of the produced nitrided coating by adjusting the blasting conditions and nitriding time, and in the scheme of the present invention, the nitriding efficiency can be remarkably improved by introducing the blasting pretreatment, and a better effect can be achieved in a shorter treatment time, and the nitriding effect can be further improved by adjusting the blasting angle.

Example 8

This example was used to investigate the effect of producing a coating at a nitriding temperature of 400 ℃.

This example differs from example 2 in that the nitriding temperature was adjusted to 400 ℃, and on this basis, the blasting conditions and nitriding time were further adjusted, and the remaining preparation processes were the same as example 2, with the specific parameters and results shown in table 2.

Table 2 surface hardness of samples treated with different blasting and nitriding times at 400C nitriding temperature

	6h	2h	4h
				45 Degree sand blasting	437HV	411HV	426HV
90 Degree sand blasting	465HV	435HV	452HV
				No sand blasting	410HV	384HV	395HV

As can be seen from table 2, under the same treatment process under other conditions, when the nitriding temperature was adjusted to 400 ℃, the properties of the produced nitrided coating were greatly reduced compared to the nitriding temperature of 550 ℃, and the hardness increase was not significant compared to the substrate that was not nitrided, indicating that the properties of the produced nitrided coating were not significantly advantageous at the nitriding temperature of 400 ℃.

Example 9

This example was used to investigate the effect of producing a coating at a nitriding temperature of 500 ℃.

This example differs from example 2 in that the nitriding temperature was adjusted to 500 ℃ and the blasting conditions and nitriding time were adjusted on this basis, and the other preparation processes were the same as example 2, with the specific parameters and results shown in table 3.

TABLE 3 surface hardness of samples treated with different sand blasting and nitriding times at 500 ℃ nitriding temperature

	6h	2h	4h
				45 Degree sand blasting	505HV	468HV	486HV
90 Degree sand blasting	545HV	501HV	523HV
				No sand blasting	421HV	411HV	418HV

As can be seen from table 3, under the same treatment process under other conditions, when the nitriding temperature is adjusted to 500 ℃, the performance of the prepared nitriding coating is improved to a certain extent compared with the nitriding temperature of 400 ℃, but a certain gap is left compared with the nitriding temperature of 550 ℃, and meanwhile, when the nitriding temperature is improved to 550 ℃ from 500 ℃, the hardness improvement effect of the substrate is remarkable as can be seen from table 1.

In summary, it can be seen that the invention pretreats the surface of the eutectic high-entropy alloy matrix by introducing sand blasting in the process of preparing the nitriding layer, and the matrix subjected to sand blasting pretreatments can greatly improve the nitriding rate, shorten nitriding time and improve nitriding effect at the same time during nitriding treatment.

It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.

Claims

1. A method for preparing a high-hardness high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy is characterized by comprising the following steps of,

Taking Al, fe, co, ni elements as principal elements, mixing, placing into a vacuum induction melting furnace, vacuumizing and heating to enable raw materials to be melted uniformly, rapidly pouring into a mold, cooling along with the furnace to form square casting, and preparing the eutectic high-entropy alloy matrix, wherein the atomic percentages of the elements are 18-20at%, 20-22at% of Co, 20-22at% of Fe and 40-45at% of Ni respectively;

Carrying out ion nitriding treatment after carrying out heat treatment and sand blasting treatment on the substrate, and preparing a nitriding layer with high hardness and high wear resistance on the surface of the substrate after the treatment is finished;

Wherein the treatment temperature of the heat treatment is 400-600 ℃ and the treatment time is 5-30 min;

The sand blasting condition of the sand blasting treatment is that the air inlet pressure is 0.4-0.6 MPa, the sand blasting pressure is 0.4-0.6 MPa, the injection angle is 45-90 degrees, and the sand blasting time is 5-10 min.

2. The method for producing a high hardness and high wear resistance nitrided layer on a eutectic high entropy alloy surface according to claim 1, wherein the ion nitriding treatment includes,

3. The method for preparing a high-hardness and high-wear-resistance nitriding layer on the surface of the eutectic high-entropy alloy according to claim 2, wherein the pressure and the hydrogen flow in the furnace are continuously adjusted to 280-320 Pa, and the hydrogen flow rate is 480-520 mL/min.

4. The method for preparing a high-hardness high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy according to claim 2, wherein the sputtering cleaning is performed for 25-35 min.

5. The method for preparing a high-hardness high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy according to claim 2, wherein the air pressure in the furnace is 380-420 Pa, the heat preservation temperature is 500-550 ℃, and the heat preservation time is 2-6 h.

6. The method for preparing a high-hardness and high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy according to any one of claims 1-5, wherein the thickness of the nitriding layer is 1-10 μm.

7. The method for preparing a high-hardness and high-wear-resistance nitriding layer on the surface of a eutectic high-entropy alloy according to any one of claims 1-5, wherein the hardness of the alloy surface is 584-803 HV, and the wear rate is lower than 10 ^-5N·mm/mm³.