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A high-strength and tough nitrided layer on the surface of an iron-based alloy and its preparation method

A technology of iron-based alloys and nitriding layers, applied in metal material coating process, coating, solid-state diffusion coating, etc., can solve problems such as differences in technical means and implementation, optimize initiation and expansion behavior, and expand application range, the effect of improving service life

Active Publication Date: 2019-07-12
SHANGHAI JIAOTONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Compared with the above-mentioned patents, the purpose of the present invention is to comprehensively improve the strength and toughness of the nitrided layer, but there are obvious differences in technical means and implementation

Method used

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  • A high-strength and tough nitrided layer on the surface of an iron-based alloy and its preparation method
  • A high-strength and tough nitrided layer on the surface of an iron-based alloy and its preparation method
  • A high-strength and tough nitrided layer on the surface of an iron-based alloy and its preparation method

Examples

Experimental program
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Effect test

Embodiment 1

[0031] H 13 steel was processed into 80 × 30 × 10 mm thin plate samples after quenching and tempering treatment. After grinding, polishing and cleaning, they were hung in a self-made gas nitriding furnace, heated to 550 ° C, and heated in NH 3 As the medium, nitrogen potential is 0.20 level, gas nitriding treatment for 10h, and then in the furnace N 2 Rapid cooling under protected conditions. Then select projectiles with a diameter of 0.8mm, and carry out surface shot peening on the samples after nitriding treatment under the parameters of 0.15Amm strength and 200% coverage.

[0032] The obtained surface deformation nitriding layer structure of the inventive process is smooth, and no obvious crack occurs (see figure 1 ).

Embodiment 2

[0034] The 38CrMoAl steel was processed into a 70×30×12mm plate sample and placed in a self-made gas nitriding furnace. 3 As the medium, gas nitriding treatment at 530°C, 0.22 and 2.0 nitrogen potential levels for 20h, and then in N 2 Rapid cooling under protected conditions. Then select a projectile with a diameter of 3mm, and carry out surface shot peening on the samples after the above two nitriding processes under the parameters of 0.40Amm intensity and 300% coverage, and find that the conventional gas nitriding layer (nitrogen potential 2.0) layer is shot peened Obvious longitudinal cracks appear after treatment, some of which have been cracked along the compound layer (see figure 2 ).

[0035] Using a pin-disk friction and wear testing machine, the two groups of samples were worn for 30 minutes under a load of 300g, and the surface wear morphology was quite different. The surface deformation nitriding layer obtained in this example has a better combination of strengt...

Embodiment 3

[0037] The preparation method of the high-strength and tough nitriding layer on the surface of the iron-based alloy in this embodiment specifically includes the following steps:

[0038] Step (1): After grinding and polishing the surface of the iron-based alloy sample, put it into a gas nitriding furnace, feed a gaseous nitrogen source, and perform gas nitriding treatment, and control the nitrogen potential at the critical value of the nitrogen potential formed by the compound layer Next, after the gas nitriding treatment is completed, furnace cooling or oil cooling is performed to obtain a nitrided layer without a compound layer;

[0039] Step (2): Perform surface shot peening treatment on the compound-free nitrided layer prepared in step (1), that is, to obtain the high-strength and tough nitrided layer on the surface of the iron-based alloy.

[0040] Wherein, the gas nitriding treatment conditions in step (1) are: the control temperature is 500° C., and the nitriding treatm...

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Abstract

The invention relates to a high-strength and high-toughness iron-based alloy surface nitriding layer and a preparation method thereof. The method comprises the following steps: grinding and polishing the surface of an iron-based alloy sample during preparation, putting the iron-based alloy sample into a gas nitriding furnace, filling a gaseous nitrogen source for carrying out gas nitriding treatment, controlling nitrogen potential to be below a nitrogen potential critical value formed by a compound layer, and carrying out furnace cooling or oil cooling after the gas nitriding treatment is ended to prepare a nitriding layer without the compound layer; and carrying out surface shot blasting reinforcement treatment on the prepared nitriding layer without the compound layer to prepare the high-strength and high-toughness iron-based alloy surface nitriding layer. Compared with the prior art, the hardness of the nitriding layer prepared by the method is equivalent to or even higher than the hardness of the conventional gas nitriding compound layer; the toughness of the nitriding layer prepared by the method is obviously superior to that of the compound layer; meanwhile, the defect of brittle spalling of the conventional gas nitriding parts in service under the condition with heavy load and high shearing stress can be effectively overcome; the application range of the gas nitriding process is broadened.

Description

technical field [0001] The invention belongs to the technical field of surface modification of metal materials, and relates to a high-strength and tough nitriding layer on the surface of an iron-based alloy and a preparation method thereof. Background technique [0002] Gas nitriding is one of the most widely used surface modification technologies in industrial production. It can effectively improve the hardness, wear resistance and corrosion resistance of the surface of steel materials. Usually, the gas nitriding process can be used to obtain the outermost compound layer (ε-Fe 2-3 N+γ′-Fe 4 N-type nitride) and the composite nitriding modified layer composed of subsurface nitrogen diffusion zone. However, the compound layer usually has poor toughness due to high internal stress, especially under the conditions of heavy wear, high shear stress and thermal / mechanical shock, it is prone to fracture and peeling, showing a very short service life. For this reason, the surface ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23C8/26
CPCC23C8/26
Inventor 王博顾剑锋李文政徐骏
Owner SHANGHAI JIAOTONG UNIV
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