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Ultrahigh nitrogen austenite phase diffusion hardening covering layer for pump shafts of nuclear grade pumps

A diffusion hardening and coating technology, applied in solid diffusion coating, coating, metal material coating technology and other directions, can solve the problems of human body harm, low hardness of electroplated chromium layer, non-dense structure, etc., to achieve wear resistance and corrosion resistance. The effect of improved performance, simple preparation process and low cost

Inactive Publication Date: 2013-02-13
DALIAN UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The purpose of the present invention is to overcome the following deficiencies in the chrome-plated covering layer of the existing nuclear pump shaft: (1) The three wastes discharged in the chrome-plated process will pollute the environment and cause harm to the human body; (2) The chrome-plated layer The thickness distribution is uneven, the surface roughness precision is low, and subsequent machining is required; (3) The hardness of the electroplated chromium layer is still low, the structure is not dense, and the bonding performance between the coating and the substrate is limited

Method used

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  • Ultrahigh nitrogen austenite phase diffusion hardening covering layer for pump shafts of nuclear grade pumps
  • Ultrahigh nitrogen austenite phase diffusion hardening covering layer for pump shafts of nuclear grade pumps
  • Ultrahigh nitrogen austenite phase diffusion hardening covering layer for pump shafts of nuclear grade pumps

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Effect test

Embodiment 1

[0028] Using plasma source nitriding technology to treat AISI 304 austenitic stainless steel nuclear main pump shaft, the specific process parameters and steps are as follows:

[0029] Clean the surface of the pump shaft of the nuclear main pump, and use an anti-seepage layer to protect the non-hardened surface. After exposing the surface that needs diffusion hardening, place the pump shaft on the workpiece table of the plasma source nitriding device, close the vacuum chamber, and evacuate to Background vacuum 1.5×10 -1 Pa. The working gas ammonia was introduced, the working pressure was maintained at 300 Pa, and a pulsed negative bias of 800 V was applied on the metal screen with a frequency of 1 kHz to generate DC pulsed plasma. The nitriding temperature is 450 °C, and the temperature is kept for 6 hours. After the treatment, the system is closed, cooled to room temperature with the furnace, the vacuum chamber is opened, and the pump shaft of the nuclear main pump is taken...

Embodiment 2

[0031] The main feed pump shaft of 1Cr18Ni9Ti austenitic stainless steel is treated by plasma-based low-energy nitrogen ion implantation technology. The specific process parameters and steps are as follows:

[0032] Clean the surface of the pump shaft of the main feed water pump, place it on the workpiece table after partial anti-seepage protection, close the vacuum chamber, and evacuate to a background vacuum of 1.5×10 -3 Pa, microwave power 1.5 kW, to generate electron cyclotron resonance (ECR) microwave plasma, through the working gas nitrogen, the working pressure is maintained at 5×10 -2 Pa, workpiece pulse bias voltage -2.0 kV, nitriding temperature is 400 °C, nitrogen ion beam current density is 0.6 mA / cm 2 , after 4 hours of treatment, shut down the system, cool down to room temperature with the furnace, open the vacuum chamber, and take out the pump shaft. After testing, the pump shaft of the main feed pump treated by plasma-based low-energy nitrogen ion implantati...

Embodiment 3

[0034] The pump shaft of the waste liquid delivery pump of AISI 304 austenitic stainless steel is treated by DC pulsed plasma-based low-energy ion implantation. The specific process parameters and steps are as follows:

[0035] Clean the surface of the pump shaft of the waste liquid delivery pump, place it on the workpiece table after partial anti-seepage protection, close the vacuum chamber, and evacuate to 5×10 -3 Pa, 700 V pulsed negative bias voltage is applied on the metal screen, the frequency is 1 kHz, the duty ratio is 1:5, DC pulsed plasma is generated, the workpiece bias voltage is -2.0 kV, the duty ratio is 1:5, and 25% of the working gas is passed through N 2 +75%H 2 , the working air pressure is maintained at 5×10 -2 Pa, nitriding temperature is 420 ° C, heat preservation for 8 hours, close the system, cool to room temperature with the furnace, open the vacuum chamber, and take out the pump shaft. After testing, the ultra-high nitrogen austenite phase diffusi...

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Abstract

An ultrahigh nitrogen austenite phase diffusion hardening covering layer for pump shafts of nuclear grade pumps belongs to the field of material surface engineering, and comprises pump shafts of a nuclear first-grade pump, a nuclear second-grade pump and a nuclear third-grade pump, which are made of Fe-Cr-Ni austenite stainless steel, as well as a hardening covering layer and a transition layer, wherein the hardening covering layer and the transition layer have the advantages of wear resistance, corrosion resistance, fatigue resistance and irradiation resistance and are arranged on the surfaces of the pump shafts. The covering layer is characterized in that the ultrahigh nitrogen austenite phase diffusion hardening covering layer, which is 15 to 25 micro in thickness, and has the surface roughness Ra lower than 0.5 micro, is prepared through using a plasma base nitriding method at 250 to 450 DEG C, the preparation of the covering layer is the last procedure in pump shaft manufacture, the hardening covering layer comprises a single ultrahigh nitrogen austenite phase, the peak value of the nitrogen concentrations in gradient distribution is 20 to 35 at.%, the hardness is 15 to 22 GPa, no hole and no microcrack are generated, and the residual compressive stress is higher than 2 GPa. The covering layer has the advantages that the preparation process is simple, follow-up processing is not required, no pollution is caused, and the performance is superior to the electrochromism covering layer used for the current pump shafts of the nuclear grade pumps.

Description

technical field [0001] The invention relates to an ultra-high nitrogen austenite phase diffusion hardening covering layer for a pump shaft of a nuclear pump, which belongs to the field of material surface engineering. Background technique [0002] In the primary, secondary, and tertiary circuits of nuclear power plants and other nuclear and non-nuclear auxiliary systems, nuclear pumps including nuclear primary, secondary, and tertiary pumps are the core cycle power systems. For example, the reactor coolant pump of the first circuit, that is, the nuclear main pump, high and low pressure safety pumps, and top charging pumps; the main feed water pump and condensate water pump of the secondary circuit condensate water system; the circulating cooling pump of the three-circuit circulating cooling water system, nuclear and non-nuclear Containment spray pumps, auxiliary water feed pumps, equipment cooling water pumps, waste liquid delivery pumps for auxiliary systems, important wate...

Claims

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Application Information

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IPC IPC(8): C23C8/38
Inventor 雷明凯朱小鹏李昱鹏李广宇王克胜
Owner DALIAN UNIV OF TECH
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