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Surface treatment method for nitrided case of steel material

A technology for surface treatment and iron and steel materials, applied in the field of material processing, can solve the problem of brittleness of the nitriding layer, etc., and achieve the effect of improving the brittleness of the nitriding layer, improving hardness and wear resistance, and low cost

Inactive Publication Date: 2012-07-11
NORTHEASTERN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] found in literature retrieval of prior art, W.P.Tong etc. published the title in "Science" ("Science", 2003 volume 299 pages 686-688) "Nitriding Iron at Lower Temperatures" ("Low temperature nitriding of iron") paper found that the use of surface nanotechnology can greatly reduce the traditional nitriding temperature, but this surface nanotechnology low temperature nitriding does not solve the problem of nitriding layer brittle problem

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  • Surface treatment method for nitrided case of steel material
  • Surface treatment method for nitrided case of steel material
  • Surface treatment method for nitrided case of steel material

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Embodiment 1

[0021] Using 20CrMo steel as the raw material, put the sample into the ion nitriding furnace and nitriding at 500°C for 4 hours. Through metallographic microscope and X-ray analysis, it was found that a compound layer with a thickness of 15 μm was obtained on the surface of the sample, and the compound layer contained ε-Fe 3-2 N and γ′-Fe 4 N two kinds of nitrides; the surface hardness of the steel sample after nitriding is 1080HV, and the sample has considerable brittleness through the microhardness tester, which is rated as brittleness level three.

[0022] Ultrasonic cleaning of the 20CrMo steel sample after nitriding treatment was put into the ion nitriding furnace, vacuumed to 0.4Pa, argon gas of 200Pa was introduced, the voltage was applied to 500V, and the sample was heated to 500V by high-voltage glow discharge method. ℃, keep warm for 4 hours, ionize the gas under high pressure, decompose the compound layer by ion bombardment, adjust the voltage and gas flow to zero w...

Embodiment 2

[0025] Using 20CrMo steel as the raw material, put the sample into an ion nitriding furnace and nitriding at 530°C for 5 hours. Through metallographic microscope and X-ray analysis, it was found that a compound layer with a thickness of 19 μm was obtained on the surface layer, and the compound layer contained ε-Fe 3-2 N and γ′-Fe 4 N two-phase; the surface hardness of the sample after nitriding is 1130HV, and the sample is quite brittle by microhardness tester, which is rated as brittle level 3.

[0026] Ultrasonic cleaning of the 20CrMo steel sample after nitriding treatment was put into the ion nitriding furnace, vacuumed to 1Pa, argon gas of 330Pa was introduced, the voltage was applied to 600V, and the sample was heated to 600°C by high-voltage glow discharge, and kept 8h, the gas is ionized by high pressure, and the compound layer is decomposed by ion bombardment. Within 3 minutes after the end of the heat preservation, the voltage and gas flow rate are reduced to zero, a...

Embodiment 3

[0029]Using 20CrMo steel as the raw material, the sample was loaded into an ion nitriding furnace and nitriding at 530°C for 5 hours. Through metallographic microscope and X-ray analysis, it was found that a 19 μm thick compound layer was obtained on the surface of the steel sample, and the compound layer contained ε-Fe 3-2 N and γ′-Fe 4 N two-phase; the surface hardness of the steel sample after nitriding is 1130HV, and the sample has considerable brittleness through the microhardness tester, which is rated as brittleness level 3.

[0030] Put the 20CrMo steel after nitriding treatment into an ion nitriding furnace after ultrasonic cleaning, evacuate to 0.5Pa, introduce hydrogen at 500Pa, apply voltage to 600V, heat the sample to 600°C by high-voltage glow discharge, and keep it warm for 10h , the gas is ionized under high pressure, the compound layer is decomposed by ion bombardment, the voltage and gas flow rate are reduced to zero within 3 minutes after the heat preservati...

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Abstract

The invention belongs to the technical field of material processing, and particularly relates to a surface treatment method for a nitrided case of a steel material. The invention adopts the technical scheme that the method comprises the steps of performing nitriding treatment on nitrided steel which is then loaded into an ion nitriding furnace, starting a vacuum pump in which 200-600Pa hydrogen or argon is charged, starting 500-700V voltage, ionizing gases with high voltage, heating a sample to 500-650 DEG C, performing ion bombardment on a decomposed chemical compound layer on the surface of the steel, carrying out surface nanocrystallization on the steel product sample after the ion bombardment, and then obtaining a pure diffusion layer structure on the surface of the steel product sample; the surface layer of the pure diffusion layer structure is in nano dimension; the hardness of the pure diffusion layer structure is more than or equal to 1240HV; and the nitriding brittleness is Class 1. In the method, the ion bombardment method is used to decompose the chemical compound layer after the nitriding treatment to eliminate the brittleness, then the surface of the steel product is subjected to the surface nanocrystallization to improve the hardness and the abrasive resistance of the sample, and finally the surface layer with high strength and high toughness is obtained; the method has the advantages that the operation is simple, the equipment is mature, the cost is lower, and the production efficiency is higher.

Description

technical field [0001] The invention belongs to the technical field of material processing, and in particular relates to a surface treatment method for a nitriding layer of a steel material. Background technique [0002] In the industrial field, surface nitriding treatment is often used to improve the surface hardness, wear resistance and fatigue strength of steel materials. The nitriding process has obvious advantages in surface strengthening technology, and is widely used in the power machine manufacturing industry, such as steam turbine shaft sleeves and various valves, valve stems, crankshafts in diesel engines, cylinder liners, fuel distribution pump parts, columns, etc. Plug pairs and needle valves, etc. The process is a chemical heat treatment method that infiltrates nitrogen atoms into the surface of the workpiece in a certain medium at a certain temperature. Common nitriding methods include liquid nitriding, gas nitriding and ion nitriding. During the nitriding pr...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23F17/00
Inventor 佟伟平孙建张辉
Owner NORTHEASTERN UNIV