Plunger for boric acid injection pump and manufacturing method

Abstract

The invention discloses a plunger for a boric acid injection pump and a manufacturing method of the plunger, and the manufacturing method comprises the following steps: respectively taking a plunger body and graphite as a base material and a target material, and depositing on the surface of the plunger body through a low-temperature coating process to form a tough integrated carbon-based film; the thin film has various excellent properties such as high hardness, high wear resistance, low friction coefficient, chemical inertness, corrosion resistance and thermal stability, the plunger manufactured by the manufacturing method is used for a boric acid injection pump, the plunger can stably work in a boric acid environment at a higher temperature and resist boric acid corrosion, and the friction energy consumption and the heat productivity can be reduced; therefore, according to the manufacturing method, the plunger is coated with the diamond-like coating, the requirements for friction resistance, abrasion resistance and corrosion resistance of the boric acid injection pump under the dynamic and static conditions can be well met, and the problems that an existing plunger is prone to corrosion and cannot meet the use requirement of the boric acid injection pump easily can be effectively solved. The service life of the boric acid injection pump is guaranteed, and the working stability is improved.

Description

Technical Field

[0001] The invention belongs to the technical field characterized by a plating process in chemistry, and in particular relates to a plunger for a boric acid injection pump and a manufacturing method thereof. Background Art

[0002] The emergency boric acid injection system is an emergency protection system used to inject boric acid solution into the reactor coolant system in the event of an accident transient, so as to achieve core boronization and ensure the subcritical state of the core. The boric acid injection pump used to transport the boric acid solution is one of the core components of the emergency boric acid injection system. Boric acid injection pumps mostly use plunger-type positive displacement pumps. The main structural components of plunger-type positive displacement pumps include a pump cylinder part and a transmission part. The pump cylinder part is mainly composed of a cylinder body, a plunger, a sealing device, a suction valve, and a discharge valve. The plunger-type positive displacement pump relies on the reciprocating motion of the plunger in the cylinder body to change the volume of the sealed working chamber to achieve the suction and discharge of the medium.

[0003] When the plunger type positive displacement pump is working, the plunger is immersed in the pumping medium and impacted by the conveying medium. Compared with other parts, it is more susceptible to erosion by the conveying medium. In order to reduce the erosion rate of the plunger and increase the service life of the plunger type positive displacement pump, it is necessary to set a coating on the surface of the plunger. At present, Ni60 coating with good corrosion resistance and wear resistance is mostly used. However, since the medium conveyed by the boric acid injection pump is a boric acid solution with a volume concentration of 7000-9000ppm, a temperature of 25-60℃, and a pH value of 3-4, the working environment of the plunger of the boric acid injection pump is relatively harsh. After the plunger type positive displacement pump with Ni60 coating conveys the boric acid solution for a short time, the macroscopic and microscopic states of the plunger surface are as follows: Figure 1 and Figure 2 As shown in the figure, the Ni60 coating is corroded with several holes in the boric acid environment. When the holes extend to the plunger base, the boric acid solution will directly corrode the plunger base through the holes, causing the plunger to be quickly corroded and damaged, resulting in the plunger with conventional Ni60 coating being difficult to meet the use requirements of the boric acid injection pump. Therefore, it is necessary to design a new plunger coating and manufacturing method to ensure the service life of the boric acid injection pump and improve its working stability. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a plunger for a boric acid injection pump and a manufacturing method thereof, so as to solve the technical problems that the existing plunger is easily corroded and difficult to meet the use requirements of the boric acid injection pump, thereby achieving the effect of ensuring the service life of the boric acid injection pump and improving its working stability.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for manufacturing a plunger for a boric acid injection pump comprises the following steps: 1) machining and adjusting the roughness of the surface of the plunger body; 2) using the plunger body as a mother material and graphite as a target material, and adopting a low-temperature coating process to deposit a strong and tough integrated carbon-based film on the surface of the plunger body.

[0006] Furthermore, in step 1), the plunger body is made of austenitic stainless steel or duplex stainless steel.

[0007] Furthermore, in step 1), the roughness of the surface of the plunger body is adjusted to be greater than or equal to 3.2 μm.

[0008] Furthermore, in step 2), the deposition thickness of the strong and tough integrated carbon-based film is 2-5 μm, the surface hardness is above 2000 HV, and the friction coefficient is 0.05.

[0009] Furthermore, step 2) includes the following sub-steps: 21) placing the plunger body in a coating chamber and evacuating and heating it, 22) preheating the target material and applying a bias voltage to the base material, 23) etching the surface of the plunger body, 24) using the target material to plate a base layer on the surface of the plunger body, 25) using the target material to plate a transition layer on the base layer, and 26) using the target material to plate a carbon layer on the transition layer.

[0010] Furthermore, in step 21), the heating temperature is 150° C. to 180° C. and the duration is 120 min to 150 min.

[0011] Furthermore, in step 22), the preheating temperature is 120° C. to 150° C., the duration is 100 min to 150 min, and the applied bias voltage is 400 V to 800 V.

[0012] Furthermore, in step 23), the temperature in the coating chamber is maintained at 150° C. to 180° C. and the vacuum degree is maintained at 2E+0 to 5E+0.

[0013] Further, in step 24), the temperature in the coating chamber is maintained at 150°C to 180°C and the vacuum degree is 1.5E+0; in step 25), the temperature in the coating chamber is maintained at 120°C to 150°C and the vacuum degree is 2E+0; in step 26), the temperature in the coating chamber is maintained at 18°C ​​to 25°C and the vacuum degree is 3E-3.

[0014] The present invention also includes a plunger for a boric acid injection pump, which is manufactured by the manufacturing method described above.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The manufacturing method of the plunger for the boric acid injection pump described in the present invention uses the plunger body and graphite as the mother material and the target material respectively, and deposits a strong and tough integrated carbon-based film on the surface of the plunger body through a low-temperature coating process; the strong and tough integrated carbon-based film has multiple excellent properties such as high hardness, high wear resistance, low friction coefficient, chemical inertness, corrosion resistance and thermal stability; the plunger prepared by the manufacturing method is used for the boric acid injection pump, which can not only stably work in a boric acid environment with a high temperature and resist boric acid corrosion, but also reduce friction energy consumption and heat generation; the manufacturing method described in the present invention uses a diamond-like coating to coat the plunger, which can better meet the anti-friction, anti-wear and anti-corrosion requirements of the boric acid injection pump under dynamic and static conditions, and can effectively solve the problem that the existing plunger is easily corroded and difficult to meet the use requirements of the boric acid injection pump, thereby achieving the effect of ensuring the service life of the boric acid injection pump and improving its working stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a macroscopic state diagram of the plunger with Ni60 coating described in the background technology being corroded by boric acid; Figure 2 The microscopic state diagram of the plunger with Ni60 coating described in the background technology being corroded by boric acid; Figure 3 A table diagram of the low-temperature coating process flow in the manufacturing method described in the embodiment; Figure 4 The figure is a macroscopic state diagram of the plunger made by the manufacturing method described in the example after running in boric acid. DETAILED DESCRIPTION

[0017] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] Embodiment: A method for manufacturing a plunger for a boric acid injection pump comprises the following steps: 1) machining and adjusting the roughness of the surface of the plunger body; 2) using the plunger body as a base material and graphite as a target material, and using a low-temperature coating process to deposit a strong and tough integrated carbon-based film on the surface of the plunger body.

[0019] The manufacturing method of the plunger for the boric acid injection pump of the present invention uses the plunger body and graphite as the mother material and the target material respectively, and deposits a strong and tough integrated carbon-based film on the surface of the plunger body through a low-temperature coating process; the strong and tough integrated carbon-based film has multiple excellent properties such as high hardness, high wear resistance, low friction coefficient, chemical inertness, corrosion resistance and thermal stability; when the plunger prepared by the manufacturing method is used in the boric acid injection pump, it can resist boric acid corrosion due to its good chemical inertness and strong corrosion resistance, and can reduce friction energy consumption and reduce the heat generation of the boric acid injection pump due to its low friction coefficient, and can work stably in a boric acid environment with a high temperature due to its good thermal stability; therefore, the manufacturing method of the present invention uses a diamond-like coating to coat the plunger, which can better meet the anti-friction, anti-wear and anti-corrosion requirements of the boric acid injection pump under dynamic and static conditions, and can effectively solve the problem that the existing plunger is easily corroded and difficult to meet the use requirements of the boric acid injection pump, and achieves the effect of ensuring the service life of the boric acid injection pump and improving its working stability.

[0020] Specifically, in step 1), the plunger body is made of austenitic stainless steel or duplex stainless steel; This can reduce the possibility of corrosion of the non-coated surface when it comes into contact with boric acid or nitric acid media, thereby ensuring the functionality of the parts.

[0021] Specifically, in step 1), the roughness of the surface of the plunger body is adjusted to be greater than or equal to 3.2 μm; In this way, better surface roughness can make the surface of the plunger body have better wettability, thereby ensuring the bonding force between the deposited layer and the surface of the plunger body.

[0022] Specifically, in step 2), the deposition thickness of the strong and tough integrated carbon-based film is 2-5 μm. During implementation, the deposition thickness of the strong and tough integrated carbon-based film can be 2 μm, 3 μm, 4 μm and 5 μm. The surface hardness of the strong and tough integrated carbon-based film is above 2000 HV and the friction coefficient is 0.05. In this way, the lower thickness can ensure that part of the tangential force acting on the strong and tough integrated carbon-based film during the operation of the equipment is borne by the relatively soft plunger body, preventing relative sliding between the film layer interface and the plunger body; higher hardness and lower friction coefficient can reduce the occurrence of failure caused by heat, particle wear and other reasons of parts at higher operating speeds.

[0023] See also Figure 3, step 2) includes the following sub-steps: 21) placing the plunger body in a coating chamber and evacuating and heating it, 22) preheating the target material and applying a bias voltage to the base material, 23) etching the surface of the plunger body, 24) using the target material to plate a primer layer on the surface of the plunger body, 25) using the target material to plate a transition layer on the primer layer, 26) using the target material to plate a carbon layer on the transition layer; In this way, a multi-layer diamond-like coating is formed on the surface of the plunger body through the above steps, which is not only conducive to ensuring the overall structural strength of the diamond-like coating and further improving the corrosion resistance of the plunger, but also conducive to improving the firmness of the coating combined with the surface of the plunger body to avoid the coating from falling off.

[0024] Specifically, in step 21), the heating temperature is 150°C to 180°C, and the duration is 120min to 150min; during implementation, the heating temperature can be 150°C, 160°C, 170°C and 180°C, and the heating duration can be 120 min, 130 min, 140 min and 150 min; In this way, since the accuracy of the size of the parts after processing will be affected by temperature, and experiments have found that the deformation of austenitic stainless steel and the duplex plunger body will exceed 0.01mm after exceeding 180°C, making it difficult to assemble, and the critical temperature of the coating is 150°C. Therefore, the final choice of coating within the temperature range can not only ensure the smooth coating process, but also will not affect the assembly.

[0025] Specifically, in step 22), the preheating temperature is 120°C to 150°C, the duration is 100min to 150min, and the applied bias voltage is 400V to 800V; during implementation, the preheating temperature can be 120°C, 130°C, 140°C and 150°C, the preheating duration can be 100 min, 110 min, 120 min, 130 min, 140 min and 150 min, and the applied bias voltage can be 400 V, 500 V, 600 V, 700 V and 800 V; In this way, preheating the target within the temperature range for a longer time can further ensure that the target separates the coating particles faster, and ensures that the particle concentration and uniformity reach the optimal state, so that the density of the coating is better; the use of bias voltage is directly related to the vacuum degree and the structure of the reaction chamber. Generally, the higher the vacuum degree, the smaller the bias voltage is used, and the lower the furnace vacuum degree, the larger the bias voltage is used.

[0026] Specifically, in step 23), the temperature in the coating chamber is maintained at 150° C. to 180° C., the vacuum degree is 2E+0 to 5E+0, and the etching treatment time is 150 min to 220 min. During implementation, the temperature in the coating chamber can be maintained at 110° C., 120° C., and 130° C., and the etching treatment time can be 150 min, 160 min, 170 min, 180 min, 190 min, 200 min, 210 min, and 220 min. In this way, the vacuum degree is mainly to ensure the stability of the oxygen bonds in the strong integrated carbon-based film. The lower the vacuum degree, the better. At present, the vacuum degree of domestic molecular pumps can reach 5E+0, which can make the stability and roughness of the film better.

[0027] Specifically, in step 24), the temperature in the coating chamber is maintained at 150°C to 180°C, the vacuum degree is 1.5E+0, and the time for plating the base layer is 200min to 300min; during implementation, the temperature in the coating chamber can be maintained at 120°C, 130°C, 140°C and 150°C, and the time for plating the base layer can be 200 min, 220 min, 240 min, 260 min, 280 min and 300 min.

[0028] In step 25), the temperature in the coating chamber is maintained at 120°C to 150°C, the vacuum degree is 2E+0, and the time for coating the transition layer is 200min to 300min; during implementation, the temperature in the coating chamber can be maintained at 120°C, 130°C, 140°C and 150°C, and the time for coating the transition layer can be 200 min, 220 min, 240 min, 260 min, 280 min and 300 min.

[0029] In step 26), the temperature in the coating chamber is maintained at 18-25°C, the vacuum degree is 3E-3, and the carbon coating time is 200 min to 300 min. During implementation, the temperature in the coating chamber can be maintained at 18°C, 20°C, 23°C and 25°C, and the carbon coating time can be 200 min, 220 min, 240 min, 260 min, 280 min and 300 min.

[0030] The macroscopic state of the plunger prepared by the manufacturing method described in this embodiment after running in boric acid is as follows: Figure 4 As shown, the diamond-like coating on the plunger is not only complete in morphology but also smooth and flat; it can be seen that the manufacturing method of the present invention uses a diamond-like coating to coat the plunger, so that the plunger can better meet the anti-friction, anti-wear and anti-corrosion requirements of the boric acid injection pump under dynamic and static conditions; using it for the boric acid injection pump is beneficial to improving the service life and working stability of the boric acid injection pump.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for manufacturing a plunger for a boric acid injection pump, characterized in that: The method comprises the following steps: 1) processing and adjusting the roughness of the surface of the plunger body; 2) using the plunger body as a base material and graphite as a target material, and adopting a low-temperature coating process to deposit a strong and tough integrated carbon-based film on the surface of the plunger body.

2. The method for manufacturing a plunger for a boric acid injection pump according to claim 1, characterized in that: In step 1), the plunger body is made of austenitic stainless steel or duplex stainless steel.

3. The method for manufacturing a plunger for a boric acid injection pump according to claim 1, characterized in that: In step 1), the roughness of the surface of the plunger body is adjusted to be greater than or equal to 3.2 μm.

4. The method for manufacturing a plunger for a boric acid injection pump according to claim 1, characterized in that: In step 2), the deposition thickness of the strong and tough integrated carbon-based film is 2-5 μm, the surface hardness is above 2000 HV, and the friction coefficient is 0.

05.

5. The method for manufacturing a plunger for a boric acid injection pump according to claim 1, characterized in that: Step 2) includes the following sub-steps: 21) placing the plunger body in a coating chamber and evacuating and heating it, 22) preheating the target material and applying a bias voltage to the base material, 23) etching the surface of the plunger body, 24) using the target material to plate a base layer on the surface of the plunger body, 25) using the target material to plate a transition layer on the base layer, and 26) using the target material to plate a carbon layer on the transition layer.

6. The method for manufacturing a plunger for a boric acid injection pump according to claim 5, characterized in that: In step 21), the heating temperature is 150° C. to 180° C. and the heating duration is 120 min to 150 min.

7. The method for manufacturing a plunger for a boric acid injection pump according to claim 6, characterized in that: In step 22), the preheating temperature is 120°C to 150°C, the duration is 100min to 150min, and the applied bias voltage is 400V to 800V.

8. The method for manufacturing a plunger for a boric acid injection pump according to claim 7, characterized in that: In step 23), the temperature in the coating chamber is maintained at 150° C. to 180° C. and the vacuum degree is maintained at 2E+0 to 5E+0.

9. The method for manufacturing a plunger for a boric acid injection pump according to claim 8, characterized in that: In step 24), the temperature in the coating chamber is maintained at 150°C to 180°C and the vacuum degree is 1.5E+0; in step 25), the temperature in the coating chamber is maintained at 120°C to 150°C and the vacuum degree is 2E+0; in step 26), the temperature in the coating chamber is maintained at 18 to 25°C and the vacuum degree is 3E-3.

10. A plunger for a boric acid injection pump, characterized in that: The plunger for the boric acid injection pump is manufactured by the manufacturing method according to any one of claims 1 to 9.

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