阅读说明：本技术 一种Cr-N-C/O多元渗层及其制备方法与应用 (Cr-N-C/O multi-element infiltration layer and preparation method and application thereof ) 是由 洪悦 王磊 黄淑琪 韦春贝 唐春梅 王红莉 许伟 汪唯 郭朝乾 石倩 林松盛 于 2020-12-25 设计创作，主要内容包括：本发明属于多元共渗技术领域,具体涉及一种Cr-N-C/O多元渗层及其制备方法与应用。其制备方法包括如下步骤：(1)在基材表面依次进行渗氮、碳/氧共渗两个阶段的变温处理,在基材表面形成N-C/O渗层；(2)将步骤(1)所得具有N-C/O渗层的基材的表面进行超精磨,消除基材N-C/O渗层表面的缺陷；(3)在700～980℃下,利用渗铬剂在步骤(2)基材的N-C/O渗层的表层进行渗铬处理4～8h,再经表面超精磨处理,制得Cr-N-C/O多元渗层。本发明采用在渗铬前进行渗氮和碳/氧共渗变温处理,利用氮原子对Cr-C渗层的掺杂改性效应和Cr-C-N原子的强相互作用,在保持Cr基渗层的强度、耐磨耐蚀性、抗高温氧化性能的同时,提高Cr基渗层的韧性。(The invention belongs to the technical field of multi-element co-infiltration, and particularly relates to a Cr-N-C/O multi-element infiltration layer, and a preparation method and application thereof. The preparation method comprises the following steps: (1) sequentially carrying out variable temperature treatment of two stages of nitriding and carbon/oxygen co-infiltrating on the surface of the base material to form an N-C/O infiltrated layer on the surface of the base material; (2) performing ultra-precision grinding on the surface of the base material with the N-C/O permeation layer obtained in the step (1) to eliminate the defects of the surface of the N-C/O permeation layer of the base material; (3) and (3) carrying out chromizing treatment on the surface layer of the N-C/O chromizing layer of the base material in the step (2) for 4-8 h by using a chromizing agent at 700-980 ℃, and then carrying out surface ultra-precision grinding treatment to obtain the Cr-N-C/O multi-element chromizing layer. The invention adopts nitriding and carbon/oxygen co-cementation temperature change treatment before chromizing, and utilizes the doping modification effect of nitrogen atoms on the Cr-C cementation layer and the strong interaction of Cr-C-N atoms to improve the toughness of the Cr-based cementation layer while maintaining the strength, wear resistance, corrosion resistance and high-temperature oxidation resistance of the Cr-based cementation layer.)

1. A preparation method of a Cr-N-C/O multi-element infiltration layer is characterized by comprising the following steps:

(1) sequentially carrying out variable temperature treatment of two stages of nitriding and carbon/oxygen co-infiltrating on the surface of the base material to form an N-C/O infiltrated layer on the surface of the base material;

(2) performing ultra-precision grinding on the surface of the base material with the N-C/O permeation layer obtained in the step (1) to eliminate the defects of the surface of the N-C/O permeation layer of the base material;

(3) and (3) carrying out chromizing treatment on the surface layer of the N-C/O chromizing layer of the base material in the step (2) for 4-8 h by using a chromizing agent at 700-980 ℃, and then carrying out surface ultra-precision grinding treatment to obtain the Cr-N-C/O multi-element chromizing layer.

2. The method for preparing a Cr-N-C/O multi-component carburized layer according to claim 1, characterized in that the nitriding in step (1) is carried out at a temperature of 500 to 600 ℃ for 3 to 5 hours; the treatment temperature of the carbon/oxygen co-permeation is 640-750 ℃, and the treatment time is 3-5 h.

3. Method for the production of a Cr-N-C/O multi-component infiltrated layer according to claim 2, characterized in that said nitriding gasIs 20-60% (v/v) N₂N of (A)₂And H₂Forming a mixed gas, wherein the nitriding pressure is 300-800 Pa; the carbon/oxygen CO-permeation gas contains 20-70% (v/v) CO₂CO of₂And H₂The mixed gas of the components alternatively contains 20 to 70 percent (v/v) CH₄CH (A) of₄And H₂A mixed gas of the components; the air pressure of the carbon/oxygen co-permeation is 700-1300 Pa.

4. The method for preparing a Cr-N-C/O multi-element cementation layer as claimed in claim 1, wherein the chromizing agent is composed of 40 wt% to 50 wt% of Cr and 40 wt% to 50 wt% of Al₂O₃3 to 10 weight percent of LaO₃And 3 to 10 wt% of NH₄And Cl.

5. The preparation method of the Cr-N-C/O multi-element infiltrated layer as claimed in claims 1 to 4, wherein the grinding amount of the ultra-precision grinding in the step (2) and the step (3) is less than 1 μm, the roughness of the infiltrated layer surface after the ultra-precision grinding treatment is less than 0.05 μm, and the porosity of the infiltrated layer surface is less than 0.1%.

6. The method of claim 5, wherein the substrate is an iron-based alloy.

7. The method for producing a Cr-N-C/O multi-element infiltrated layer according to claim 6, wherein said iron-based alloy is a tool steel or a bearing steel.

8. The Cr-N-C/O multi-element diffusion layer prepared by the preparation method of any one of claims 1 to 7, wherein the phase composition of the Cr-N-C/O multi-element diffusion layer is Cr₇C₃+Cr₂N + CrN; wherein Cr is₇C₃And Cr₂The proportion of N is 1 (2-4).

9. Use of the Cr-N-C/O multi-pack as defined in claim 8 in an iron-based alloy.

10. A high toughness and high strength material comprising a substrate, wherein said substrate is further provided with a Cr-N-C/O multi-element cementation layer as defined in claim 8; the substrate is tool steel or bearing steel.

Technical Field

The invention belongs to the technical field of multi-element co-infiltration, and particularly relates to a Cr-N-C/O multi-element infiltration layer, and a preparation method and application thereof.

Background

Some key parts in high-end equipment, such as bearings, drill bits, grabbing teeth and the like, are in quite complex working conditions and have high requirements on materials, the required materials meet the performances of wear resistance, corrosion resistance, high-temperature oxidation resistance and the like, and the performances are usually difficult to meet by the traditional tool steel and the bearing steel at the same time. The chromium-based diffusion layer is formed by the method of diffusing chromium on the surfaces of tool steel and bearing steel, so that the wear resistance, corrosion resistance and high-temperature oxidation resistance of the material can be obviously improved.

The treatment of the conventional chromizing method has two disadvantages: 1. the treatment temperature is above 1000 ℃, so that the heat treatment defects such as deformation, segregation, abnormal grain growth and the like can be caused, and the performances of a permeable layer and a matrix can be influenced; 2. the chromizing layer formed by the traditional chromizing method is mainly made of Cr-C compounds, and the Cr-C chromizing layer is easy to peel off and lose efficacy due to brittle cracks under the working condition of large load. In order to solve the defect of high temperature of the traditional chromizing treatment, CN110714182A discloses a composite process of nitriding chromizing, which utilizes nitriding to introduce nitrogen atoms into a matrix and then utilizes strong interaction between Cr and N to accelerate the chromizing process. Although the nitriding and chromizing combined process can shorten the chromizing time or reduce the chromizing temperature, the process forms Cr₂The problem that the toughness of the Cr-based diffusion layer is insufficient under a large-load working condition cannot be solved by the N diffusion layer. Therefore, the service performance of the Cr-based infiltration layer prepared by the prior disclosed process under a large-load working condition is not ideal.

The basic research reported at present mainly focuses on improving the hardness and wear resistance of the Cr-based carburized layer or reducing the chromizing temperature and shortening the treatment time, and no public report is found on the basic research on improving the toughness of the Cr-based carburized layer.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a Cr-N-C/O multi-element seeping layer with high toughness and high strength, a preparation method thereof and application of the Cr-N-C/O multi-element seeping layer with high toughness and high strength. By utilizing the doping modification effect of nitrogen atoms on the Cr-C diffusion layer and the strong interaction of Cr-N-C atoms, the toughness of the Cr-based diffusion layer is improved while the strength, wear resistance, corrosion resistance and high-temperature oxidation resistance of the Cr-based diffusion layer are maintained.

Based on the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a preparation method of a Cr-N-C/O multi-element diffusion layer, which comprises the following steps:

(1) sequentially carrying out variable temperature treatment of two stages of nitriding and carbon/oxygen co-infiltrating on the surface of the base material to form an N-C/O infiltrated layer on the surface of the base material;

(2) performing ultra-precision grinding on the surface of the base material with the N-C/O permeation layer obtained in the step (1) to eliminate the defects of the surface of the N-C/O permeation layer of the base material;

(3) and (3) carrying out chromizing treatment on the surface layer of the N-C/O chromizing layer of the base material in the step (2) for 4-8 h by using a chromizing agent at 700-980 ℃, and then carrying out surface ultra-precision grinding treatment to obtain the Cr-N-C/O multi-element chromizing layer.

According to the invention, nitriding and carbon/oxygen co-cementation are carried out before chromizing, and the toughness of the Cr-based cementation layer is improved while the strength, wear resistance, corrosion resistance and high-temperature oxidation resistance of the Gr-based cementation layer are kept by utilizing the doping modification effect of nitrogen atoms on the Cr-C cementation layer and the strong interaction of Cr-C-N atoms.

Preferably, the nitriding treatment temperature in the step (1) is 500-600 ℃, and the treatment time is 3-5 h; the treatment temperature of the carbon/oxygen co-permeation is 640-750 ℃, and the treatment time is 3-5 h.

According to the invention, the N atom content in the surface layer before chromizing is effectively controlled by strictly controlling the temperature and the treatment time of nitriding treatment and carbon/oxygen co-cementation treatment, on one hand, the chromizing speed is increased by increasing the N atom content in the surface layer before chromizing, so that the chromizing temperature is reduced; on the other hand, the content of N atoms in the surface layer before chromizing treatment is controlled so that Cr7C3 phase and Cr2N phase in the Gr-based carburized layer after chromizing treatment are in a proper proportion range, thereby improving the toughness of the Gr-based carburized layer.

Preferably, the nitriding gas is a gas containing 20-60% (v/v) N₂N of (A)₂And H₂Forming a mixed gas, wherein the nitriding pressure is 300-800 Pa; the carbon/oxygen CO-permeation gas contains 20-70% (v/v) CO₂CO of₂And H₂The mixed gas of the components alternatively contains 20 to 70 percent (v/v) CH₄CH (A) of₄And H₂A mixed gas of the components; the air pressure of the carbon/oxygen co-permeation is 700-1300 Pa.

Preferably, the nitriding and the carbon/oxygen co-nitriding in the step (1) both adopt an ion-nitriding technology, wherein the bias voltage of the ion-nitriding is 500-600V; the basic bias voltage of the ion carbon/oxygen co-diffusion is 500 to 700V.

Preferably, in the ion nitriding and the ion carbon/oxygen co-cementation processes in the step (1), a promoter is addedA penetrant; the penetration enhancer added during ion nitriding is CH₄Or Y₂O₃(ii) a The penetration enhancer added in the process of ion carbon/oxygen co-penetration is Y₂O₃。

Preferably, the thickness of the N-C diffusion layer after nitriding, carbon/oxygen co-diffusion and ultra-precision grinding treatment in the steps (1) and (2) is more than or equal to 20 microns, and the hardness is 400-600 HV.

Preferably, the chromizing agent consists of 40-50 wt% of Cr and 40-50 wt% of Al₂O₃3 to 10 weight percent of LaO₃And 3 to 10 wt% of NH₄And Cl.

Preferably, the grinding amount of the ultra-precision grinding in the step (2) and the step (3) is less than 1 μm, the roughness of the surface of the infiltrated layer after the ultra-precision grinding treatment is less than 0.05 μm, and the porosity of the surface of the infiltrated layer is less than 0.1%.

Preferably, the thickness of the carburized layer after the chromizing treatment and the ultra-precision grinding treatment in the step (3) is more than or equal to 10 microns, and the hardness is more than or equal to 1300 HV.

Preferably, the substrate is an iron-based alloy

Preferably, the iron-based alloy is a tool steel or a bearing steel.

In a second aspect, the invention provides a Cr-N-C/O multi-element infiltration layer prepared by the method, wherein the phase composition of the Cr-N-C/O multi-element infiltration layer is Cr7C3+ Cr2N + CrN; wherein the ratio of Cr7C3 to Cr2N is 1 (2-4).

Experiments show that when the ratio of the Cr7C3 phase to the Cr2N phase in the Cr-based infiltration layer (namely, the Cr-N-C/O multi-element infiltration layer) is 1 (2-4), the Cr-based infiltration layer shows excellent toughness.

In a third aspect, the use of the above Cr-N-C/O multi-element infiltrated layer in an iron-based alloy.

In a fourth aspect, the invention provides a high-toughness and high-strength material, which comprises a base material, wherein the base material is also provided with the Cr-N-C/O multi-element infiltration layer; the substrate is tool steel or bearing steel.

The Cr-N-C/O multi-element infiltration layer is arranged on parts such as tool steel or bearing steel, so that the toughness of the parts can be improved and the service performance of the parts can be improved under the condition of a large load working condition.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, the parts processed by the positive fine fire are sequentially subjected to nitriding multi-component co-infiltration, ultra-precision grinding, chromizing and ultra-precision grinding of carbon/oxygen co-infiltration, and the toughness of the Cr-based infiltration layer is improved while the strength, wear resistance, corrosion resistance and high-temperature oxidation resistance of the Gr-based infiltration layer are maintained by utilizing the doping modification effect of nitrogen atoms on the Cr-C infiltration layer and the strong interaction of Cr-C-N atoms; and the chromizing speed is improved, so that the chromizing temperature is obviously reduced.

(2) The Cr-based diffusion layer, namely the Cr-N-C/O diffusion layer, prepared by the method has the advantages that the proportion of Cr7C3 phase to Cr2N phase in the diffusion layer is 1 (2-4), so that the Cr-based diffusion layer has excellent toughness on the premise of keeping other properties unchanged.

(3) The Cr-N-C/O seeping layer is applied to the surface layers of parts such as tool steel or bearing steel, and the toughness of the parts can be improved and the service performance of the parts can be improved under the condition of a large load working condition.

Drawings

FIG. 1 is an XRD test chart of examples 1 to 2 and comparative examples 1 to 3;

FIG. 2 is a cross-sectional hardness test chart of examples 1 to 2 and comparative examples 1 to 3;

FIG. 3 is a surface indentation method toughness detection chart of examples 1 to 2 and comparative examples 1 to 3.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments. The raw materials used in the following examples are all commercially available general-purpose products unless otherwise specified.

Example 1

A preparation method of a Cr-N-C/O multi-element infiltration layer with high strength and toughness comprises the following steps:

(1) parts which are being subjected to fine finishing treatment, such as tool steel or bearing steel, are prepared according to the machining requirements.

(2) The method is characterized in that the multi-component co-cementation treatment is carried out on the part by adopting an ion cementation technology, and the multi-component co-cementation is a step-by-step variable temperature treatment and comprises an ion nitriding stage and an ion carbon/oxygen co-cementation stage.

Ion nitridingThe gas of the stage is N₂And H₂Mixed gas of composition, N₂And H₂The volume ratio of (A) to (B) is 1: 1; the working pressure in the furnace is 700Pa, and the basic bias voltage is 550V; with CH₄As a penetration enhancer; the ion nitriding treatment temperature is 560 ℃, and the heat preservation time is 3 h.

The gas in the stage of the ionic carbon/oxygen CO-permeation is CO₂And H₂Mixed gas of composition, CO₂And H₂The volume ratio of (A) to (B) is 2: 3; the working pressure in the furnace is 1100Pa, and the basic bias voltage is 600V; with Y₂O₃Is a penetration enhancer; the temperature of the ion carbon/oxygen co-permeation treatment is 640 ℃, and the heat preservation time is 3 hours.

The temperature change mode of linear temperature rise is adopted between the two stages of ion nitriding and ion carbon/oxygen co-infiltrating, the temperature change range is 560-640 ℃, and the temperature rise rate is 10 ℃/min. After the multi-component co-cementation in two stages of ion nitriding and ion carbon/oxygen co-cementation, cooling the mixture in a furnace to 300 ℃, discharging the mixture out of the furnace and air cooling the mixture to room temperature.

(3) And (3) adopting ultra-precision grinding treatment to remove the surface infiltration layer defects of the part subjected to the multi-element co-infiltration treatment in the step (2), such as pores, ablation nodules and the like. The grinding amount of the ultra-precision grinding treatment is less than 1 mu m, the roughness of the surface of the infiltrated layer of the part after the ultra-precision grinding treatment is less than 0.05 mu m, and the porosity of the surface of the infiltrated layer is less than 0.1 percent.

(4) Performing chromizing treatment on the surface of the part chromizing layer superfinished in the step (3) by using a solid chromizing technology, wherein the chromizing treatment temperature is 840 ℃, the chromizing treatment time is 5 hours, and the chromizing agent is prepared from 44 wt% of Cr and 47 wt% of Al₂O₃4 wt% of LaO₃And 5 wt% NH₄And Cl. And continuously placing the chromium-infiltrated product in a furnace for cooling after the chromizing treatment.

(5) And (4) carrying out ultra-precision grinding treatment to remove the surface diffusion layer defect of the part subjected to chromizing treatment in the step (4). The grinding amount of the ultra-precision grinding treatment is less than 1 mu m, the roughness of the surface of the infiltrated layer of the part after the ultra-precision grinding treatment is less than 0.05 mu m, and the surface void ratio is less than 0.1%.

Nitriding, carbon/oxygen co-infiltrating, ultra-grinding, chromizing and ultra-grinding treatment are sequentially carried out on the surface of the part in the steps (1) to (5), and then the infiltrated layer composition on the surface of the part is carried outThe analysis results are shown in FIG. 1, and it can be seen that the Cr-based infiltrated layer produced in this example is composed of Cr₇C₃、Cr₂N, CrN phase composition, found by full spectrum fitting, Cr₇C₃And Cr₂The volume ratio of N is 1: 3.6.

The parts of the embodiment are subjected to the carburized layer hardness detection, and the detection result is shown in fig. 2, so that the carburized layer hardness of the parts prepared by the embodiment is more than or equal to 1300 HV.

The thickness of the infiltrated layer of the parts of this example was measured, and the results are shown in FIG. 2, which shows that the infiltrated layer produced in this example has a thickness of 10 μm or more.

The part of this example was subjected to the test of the surface toughness of the infiltrated layer, and the result is shown in fig. 3, which shows that the toughness of the surface layer of the part sample treated by the method described in this example is significantly improved.

Example 2

A preparation method of a Cr-N-C/O multi-element infiltration layer with high strength and toughness comprises the following steps:

(1) parts which are being subjected to fine finishing treatment, such as tool steel or bearing steel, are prepared according to the machining requirements.

(2) The method is characterized in that the multi-component co-cementation treatment is carried out on the part by adopting an ion cementation technology, and the multi-component co-cementation is a step-by-step variable temperature treatment and comprises an ion nitriding stage and an ion carbon/oxygen co-cementation stage.

The gas in the ion nitriding stage is N₂And H₂Mixed gas of composition, N₂And H₂The volume ratio of (A) to (B) is 1: 1; the working pressure in the furnace is 700Pa, and the basic bias voltage is 570V; with Y₂O₃As a penetration enhancer; the ion nitriding treatment temperature is 600 ℃, and the heat preservation time is 5 hours.

The gas in the stage of the ion carbon/oxygen co-permeation is CH₄And H₂Mixed gas of composition, CH₄And H₂The volume ratio of (A) to (B) is 3: 2; the working pressure in the furnace is 1300Pa, and the basic bias voltage is 700V; Y2O3 is used as a penetration enhancer; the temperature of the ion carbon/oxygen co-cementation treatment is 700 ℃, and the heat preservation time is 3.5 h.

The temperature change mode of linear temperature rise is adopted between the two stages of ion nitriding and ion carbon/oxygen co-infiltrating, the temperature change range is 600-700 ℃, and the temperature rise rate is 10 ℃/min. After the multi-component co-cementation in two stages of ion nitriding and ion carbon/oxygen co-cementation, cooling the mixture in a furnace to 300 ℃, discharging the mixture out of the furnace and air cooling the mixture to room temperature.

(3) And (3) adopting ultra-precision grinding treatment to remove the surface infiltration layer defects of the part subjected to the multi-element co-infiltration treatment in the step (2), such as pores, ablation nodules and the like. The grinding amount of the ultra-precision grinding treatment is less than 1 mu m, the roughness of the surface of the infiltrated layer of the part after the ultra-precision grinding treatment is less than 0.05 mu m, and the porosity of the surface of the infiltrated layer is less than 0.1 percent.

(4) Performing chromizing treatment on the superfinished surface of the part superfinished in the step (3) by using a solid chromizing technology, wherein the chromizing treatment temperature is 800 ℃, the chromizing treatment time is 360min, and the chromizing agent comprises 40 wt% of Cr and 50 wt% of Al₂O₃4 wt% of LaO₃And 6 wt% NH₄And Cl. And continuously placing the chromium-infiltrated product in a furnace for cooling after the chromizing treatment.

(5) And (4) carrying out ultra-precision grinding treatment to remove the surface diffusion layer defect of the part subjected to chromizing treatment in the step (4). The grinding amount of the ultra-precision grinding treatment is less than 1 mu m, the roughness of the surface of the infiltrated layer of the part after the ultra-precision grinding treatment is less than 0.05 mu m, and the surface void ratio is less than 0.1%.

After the surface of the part is subjected to nitriding, co-nitriding with carbon/oxygen, superfinishing, chromizing and superfinishing in sequence in steps (1) to (5), the composition of the carburized layer of the surface of the part is analyzed, and the result is shown in fig. 1, which shows that the Gr-based carburized layer prepared in the present example is formed by Cr₇C₃、Cr₂N, CrN phase composition, found by full spectrum fitting, Cr₇C₃And Cr₂The volume ratio of N is 1: 2.4.

The parts of the embodiment are subjected to the carburized layer hardness detection, and the detection result is shown in fig. 2, so that the carburized layer hardness of the parts prepared by the embodiment is more than or equal to 1300 HV.

The thickness of the infiltrated layer of the parts of this example was measured, and the results are shown in FIG. 2, which shows that the infiltrated layer produced in this example has a thickness of 10 μm or more.

The part of this example was subjected to the test of the surface toughness of the infiltrated layer, and the result is shown in fig. 3, which shows that the toughness of the surface layer of the part sample treated by the method described in this example is significantly improved.

Comparative example 1

The present comparative example, which provides a method for preparing a Cr-N-C/O multi-diffused layer with reference to example 1, differs from example 1 only in that the temperature of the carburizing treatment in step (2) of the present comparative example is different from that in step (2) of the present comparative example, which is 560 ℃.

The composition of the skin layer phase of the Gr-based infiltrated layer obtained in this comparative example was examined, and as shown in fig. 1, it was found that the infiltrated layer phase obtained in this comparative example had a composition of Cr₂N。

The surface layer toughness of the Gr-based infiltrated layer prepared in this comparative example was examined, and the results are shown in fig. 3, and it can be seen that the infiltrated layer prepared in this comparative example has surface layer toughness inferior to the infiltrated layer toughness in examples 1 and 2.

Comparing the detection result of the infiltrated layer of the comparative example with the detection results of the infiltrated layers of the examples 1 and 2, the following conclusion can be drawn: (1) when the N content in the carburized layer after nitriding and carbon/oxygen co-carburization is higher, compared with the published patent CN110714182A and the comparative example 3, the chromizing temperature can be reduced; (2) cr in the chromized layer after chromizing₂When the N phase is more, the toughness of the surface layer of the infiltration layer is difficult to improve.

Comparative example 2

The present comparative example, which provides a method for preparing a Cr-N-C/O multi-diffused layer with reference to example 1, differs from example 1 only in that only ion nitriding treatment is performed in step (2) of the present comparative example, and ion carbo/O co-diffusion treatment is not performed.

This comparative example was used to simulate the nitriding, chromizing treatment processes of the prior art, and the Cr-based diffusion layers produced thereby.

The composition of the skin layer phase of the Gr-based infiltrated layer obtained in this comparative example was examined, and as shown in fig. 1, it was found that the infiltrated layer phase obtained in this comparative example had a composition of Cr₂N。

The surface layer toughness of the Gr-based infiltrated layer prepared in this comparative example was examined, and the results are shown in fig. 3, and it can be seen that the infiltrated layer prepared in this comparative example has surface layer toughness inferior to the infiltrated layer toughness in examples 1 and 2.

Comparing the detection result of the infiltrated layer of the comparative example with the detection results of the infiltrated layers of the examples 1 and 2, the following conclusion can be drawn: (1) when the N content in the carburized layer after nitriding and carbon/oxygen co-carburization is higher, compared with the published patent CN110714182A and the comparative example 3, the chromizing temperature can be reduced; (2) cr in the chromized layer after chromizing₂When the N phase is more, the toughness of the surface layer of the infiltration layer is difficult to improve. This conclusion is the same as that made in comparative example 1.

Comparative example 3

The comparative example provides a method for preparing a Cr-N-C/O multi-element diffusion layer, the specific preparation process refers to the method for preparing the Cr-N-C/O multi-element diffusion layer in example 1, and the comparative example is only different from the example 1 in that the comparative example does not undergo the treatment of the step (2), the step (3) and the step (5), namely the comparative example directly refers to the step (4) to carry out chromizing treatment on the part subjected to the fine fire processing treatment in the step (1), wherein the temperature of the chromizing treatment is 1000 ℃, and the chromizing treatment time is 180 min.

This comparative example was used to simulate a conventional chromizing treatment and the Cr-based chromizing layer produced thereby.

The composition of the skin layer phase of the Gr-based infiltrated layer obtained in this comparative example was examined, and as shown in fig. 1, it was found that the infiltrated layer phase obtained in this comparative example had a composition of Cr₇C₃。

The surface layer toughness of the Gr-based infiltrated layer prepared in this comparative example was examined, and the results are shown in fig. 3, and it can be seen that the infiltrated layer prepared in this comparative example has surface layer toughness inferior to the infiltrated layer toughness in examples 1 and 2.

Comparing the detection result of the infiltrated layer of the comparative example with the detection results of the infiltrated layers of the examples 1 and 2, the following conclusion can be drawn: (1) when the N content in the carburized layer after nitriding and carbon/oxygen co-carburization is higher, the chromizing temperature can be reduced; (2) cr in the chromized layer after chromizing₂When N is more, the toughness of the surface layer of the infiltration layer is difficult to improve; (3) after chromizing treatmentCr in the infiltrated layer₇C₃When the content of phase nitrogen is low, the toughness of the surface layer of the diffusion layer is difficult to improve.

The reason for the poor toughness of the Cr-based carburized layer in comparative examples 1, 2, and 3 is analyzed by combining the results of the carburized layer tests of examples 1 and 2 and comparative examples 1, 2, and 3 as follows:

(1) the N atom concentration of the surface layer is higher before chromizing, and Cr is formed after chromizing₂The N phase is the organization structure of the main composition phase;

(2) the surface layer before chromizing has no N atoms or has low N atom concentration, and forms Cr after chromizing₇C₃And the N doping effect is not obvious.

In addition, the main reasons for the temperature decrease of the Cr-based carburized layer at the chromizing stage are as follows: the surface layer of the sample before chromizing needs a sufficient N atom concentration to increase the chromizing rate, and when the N atom concentration is low or no N atom is present, the temperature of the chromizing treatment needs to be increased.

Therefore, as can be seen from the comparison of the results of comparative examples 1, 2 and 3 with those of examples 1 and 2, in the preparation methods according to examples 1 and 2 of the present invention, the synergy between the ion nitriding and the ion carbo/oxy-nitriding in the multi-component co-cementation step temperature change treatment is particularly important, and only by strictly following the preferred conditions of the present invention with respect to the ion nitriding and the ion carbo/oxy-cementation, a Cr-N-C/O carburized layer in which the preferred ratio of the Cr7C3 phase to the Cr2N phase is maintained can be prepared, and the carburized layer can be provided with good strength and toughness at the same time, and the chromizing temperature can be reduced.

Examples 3 to 10

The preparation methods provided in examples 3 to 10 refer to example 1, the specific parameters are shown in Table 1, and the composition ratios of the main phases in the Cr-N-C/O infiltrated layers finally obtained in examples 3 to 10 are shown in Table 1.

TABLE 1 values of the parameters and the composition of the Cr-based cementite phase obtained in examples 3 to 10

The toughness rating of the infiltrated layer was classified into four categories a-D, etc., as shown in fig. 3. A and the like: the indentation edge had no radial cracks, no arc cracks, as represented by example 1; b and the like: the edge of the indentation has no arc crack, the length of the radial crack is below 50 mu m, and the radial crack can not be observed in low-power metallographic phase, as represented by example 2; c and the like: the edge of the indentation has no arc crack, the length of the radial crack is more than 100 mu m, and the radial crack can be observed in low-power metallographic phase, which is represented by a comparative example 2; d, and the like: radial cracks and arc cracks at the edges of the indentation can be observed in the low-power metallographic phase, and are represented by comparative example 1 and comparative example 3.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.