Ceramic reinforced metal spray powder for valve repair and method of making same

Abstract

The application provides a ceramic reinforced metal spray powder for valve repair and a preparation method thereof, and the method comprises the following steps: ball milling rare earth oxide powder and ceramic powder and ceramic fiber respectively; adding the rare earth oxide powder, the ceramic powder and the ceramic fiber into a dispersant according to a proportion for primary mixing, and obtaining primary mixed powder after ball milling; performing surface treatment on the primary mixed powder and ultrasonic dispersion to obtain the ceramic reinforced metal spray powder; and performing heat treatment on the ceramic reinforced metal spray powder after spraying to obtain a ceramic reinforced valve wear-resistant layer. The ceramic powder with low cost and high hardness, the ceramic fiber with high toughness and the rare earth oxide are combined, the ceramic reinforced metal spray powder is prepared by using an ultrasonic stirring method or a protective gas ball milling method, the wear resistance, the toughness and the corrosion resistance of the valve are improved, the ceramic reinforced metal spray powder is prepared, the process is simple, the powder preparation cost can be effectively reduced, the yield rate and the production efficiency are improved, and the yield rate is more than 98%.

Description

[0001] This invention relates to a ceramic-reinforced metal spray welding powder for valve repair and its preparation method, belonging to the field of metal materials technology. Background Technology

[0002] Slurry valves play a crucial role in modern metallurgical ore washing processes. These valves operate in harsh environments, exposed to high acid and alkali concentrations, and are susceptible to leaks and spills in pipelines, allowing oxygen from the air to easily enter the slurry. Furthermore, the frequent opening and closing of valves during slurry transportation causes abrasive wear on the valve core and body, further promoting oxidative corrosion. The combined effects of abrasive wear and oxidative corrosion accelerate valve core failure, significantly impacting industrial production rates.

[0003] In recent years, plasma spraying technology has become a research hotspot. This technology melts metal powder with an ion beam and sprays it onto the material surface under the action of a protective gas to form a reinforcing layer. It is convenient to process and has excellent results. However, in valve repair, the alloy powder currently used still has many shortcomings in terms of hardness, acid and alkali corrosion resistance, and toughness.

[0004] In view of this, it is indeed necessary to propose a ceramic-reinforced metal spray welding powder for valve repair and its preparation method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a ceramic-reinforced metal spray welding powder for valve repair and its preparation method, which improves the wear resistance, toughness and corrosion resistance of valves while reducing costs.

[0006] To achieve the above objectives, the present invention provides a method for preparing ceramic-reinforced metal spray welding powder for valve repair, mainly comprising the following steps:

[0007] Step 1: Ball mill the rare earth oxide powder, ceramic powder, and ceramic fiber separately;

[0008] Step 2: Add rare earth oxide powder, ceramic powder, and ceramic fiber to a dispersant in proportion and mix them once. After ball milling, a mixed powder is obtained.

[0009] Step 3: Surface-treat and ultrasonically disperse the primary mixed powder;

[0010] Step 4: Mix the primary mixed powder with the alloy powder a second time to obtain ceramic-reinforced metal spray welding powder;

[0011] Step 5: After spraying the ceramic-reinforced metal spray welding powder, heat treatment is performed to obtain the ceramic-reinforced valve wear-resistant layer.

[0012] As a further improvement of the present invention, in step 2, the dispersant is sodium hexametaphosphate with a concentration of 8‰.

[0013] As a further improvement of the present invention, the rare earth oxide powder is 0.04g of CeO2 powder, the ceramic powder is 3g of NbC, the ceramic fiber is 0.8g of Al2O3, and the alloy powder is 97g of Ni60 powder.

[0014] As a further improvement of the present invention, the surface treatment in step 3 includes: calcining the mixed powder at 1200-1500°C to further coat the ceramic powder with rare earth oxides, or preparing a rare earth oxide coating on the surface of the ceramic powder by vacuum evaporation, thereby preparing reinforced particles with a rare earth oxide coating on the surface, and the frequency of ultrasonic oscillation is 20-60KHz.

[0015] As a further improvement of the present invention, the temperature of the vacuum evaporation method is 1500-1700℃.

[0016] As a further improvement of the present invention, the vacuum evaporation temperature is 1700°C.

[0017] As a further improvement of the present invention, in step 4, the primary mixed powder and the alloy powder are mixed a second time by ultrasonic stirring or protective balloon milling.

[0018] As a further improvement of the present invention, the ultrasonic stirring method includes simultaneous ultrasonic oscillation and stirring with a stirring paddle, wherein the frequency of ultrasonic oscillation is 20-60KHz, the speed of stirring paddle is 2500-4500r / min, and the ultrasonic stirring time is 1.5h.

[0019] As a further improvement of the present invention, the movement mode of the milling balls in the protective ball milling method is cascading, and the nitrogen gas flow rate is 1-5 L / m³. 3 ·min.

[0020] The beneficial effects of this invention are as follows: This invention combines low-cost, high-hardness ceramic powder with rare earth oxides, and uses ultrasonic stirring or protective balloon milling to prepare ceramic-reinforced metal spray welding powder. The addition of ceramic powder improves the wear resistance of the valve, while the addition of ceramic fibers improves the toughness and corrosion resistance. The process for preparing ceramic-reinforced metal spray welding powder is simple and can effectively reduce the cost of powder preparation, while improving the yield and production efficiency, with a yield rate of over 98%. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments.

[0022] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0023] Example 1

[0024] NbC, Al2O3 fiber, and CeO2 powder were prepared and ground and dispersed in proportions of 3g, 0.8g, and 0.04g, respectively.

[0025] CeO2 and NbC powder were added to a vacuum evaporation machine and heated to 1700℃. The heat and pressure holding time was 1h. After the heat holding was completed, ultrasonic dispersion was performed for 10min at a frequency of 30kHz.

[0026] For some mineral slurries with high acidity or alkalinity, Ni60 powder with stronger corrosion resistance is selected as the base material. The first-mixed powder and 97g of Ni60 powder are loaded into an ultrasonic stirring device with an ultrasonic frequency of 35KHz and a stirring speed of 3000r / min. The powder preparation is completed after ultrasonic stirring.

[0027] When the prepared powder is used for valve core repair, the valve core is preheated at 500℃. After preheating, it is repaired by spray welding with a spray welding current of 130A. After spray welding, it is sent to a heating furnace for heat preservation and slow cooling to room temperature at 900℃. After slow cooling, stress relief annealing is performed at 400℃ for 4 hours. After annealing, it can be further processed and put into use.

[0028] This invention uses rare earth oxides as additives to increase the viscosity of the molten metal, making it difficult for the ceramic reinforcing phase to rise in the molten metal. This effectively allows the ceramic reinforcing phase to be dispersed and distributed in the molten metal. At the same time, the rare earth oxides also act as nucleation agents in the molten metal, effectively inhibiting grain growth. This results in an effective improvement in the hardness and toughness of the sprayed weld layer, as well as enhanced uniformity of the sprayed weld layer structure. Consequently, the wear of the valve sprayed weld layer becomes more uniform, and it can still effectively perform line sealing even after wear.

[0029] The final spray-welded layer prepared by this invention has a hardness of 58-65 HRc and an impact toughness of 6.5-7.5 J / cm. 2 It is sufficient to meet the requirements of the valve seat material to produce elastic deformation during the valve line sealing process. At the same time, it has good hardness uniformity, which can reduce the wear of the valve seal while ensuring the uniformity of the wear amount. This greatly reduces the number of valve maintenance times and cycles, and effectively enhances its overall life and service life.

[0030] After repairing the slurry valve core and seat, the repair effect was compared with that of the existing stainless steel welding rod repair. The valve repaired with ceramic-reinforced spray welding powder in the alumina slurry valve had a service life of two production cycles, and the re-welding and treatment time after failure was 2 days. In contrast, the valve repaired with stainless steel welding rods had a service life of one production cycle, and the re-welding and treatment time after failure was 5 days. From the perspective of service life, the repair effect of ceramic-reinforced metal spray welding powder is much better than the process used in existing industrial production, and the quality is more stable, which can meet the requirements of stable and continuous industrial production.

[0031] This invention can meet the existing processing procedures in the factory production process. After grinding by a grinding machine, the factory production needs can be met. However, if welding rods are used as a repair method, subsequent repairs still require steps such as lathe processing to make the weld surface flat. The surface of the sprayed weld layer is relatively flat, which greatly reduces the workload and overall processing time even with high hardness, and effectively improves production efficiency.

[0032] This invention combines the high hardness of ceramic powder, the high toughness of ceramic fiber, and the characteristics of rare earth oxides, effectively suppressing the rise of ceramic powder and fiber in molten steel and inhibiting grain growth, thus playing a role in fine grain strengthening. It effectively improves the toughness and hardness of the sprayed welding layer and provides different powder ratios to allow the hardness between the valve core and valve seat to be matched accordingly. On the one hand, this effectively improves the service life of the workpiece, and on the other hand, it reduces the production cost.

[0033] In summary, this invention combines low-cost, high-hardness ceramic powder, high-toughness ceramic fiber, and rare earth oxides, and uses ultrasonic stirring or protective balloon milling to prepare ceramic-reinforced metal spray welding powder. This improves the wear resistance, toughness, and corrosion resistance of valves. The process for preparing ceramic-reinforced metal spray welding powder is simple and can effectively reduce powder preparation costs, while improving yield and production efficiency, with a yield rate of over 98%.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a ceramic-reinforced wear-resistant layer for a valve, characterized in that, Includes the following steps: Step 1: Ball mill the rare earth oxide powder, ceramic powder, and ceramic fiber respectively; Step 2: Add rare earth oxide powder, ceramic powder, and ceramic fiber to a dispersant in proportion and mix them once. After ball milling, a mixed powder is obtained. Step 3: Surface-treat and ultrasonically disperse the primary mixed powder; Step 4: Mix the primary mixed powder with the alloy powder a second time to obtain ceramic-reinforced metal spray welding powder; Step 5: After spraying the ceramic-reinforced metal spray welding powder, heat treatment is performed to obtain a ceramic-reinforced valve wear-resistant layer; the rare earth oxide powder is 0.04g of CeO2 powder, the ceramic powder is 3g of NbC, the ceramic fiber is 0.8g of Al2O3, and the alloy powder is 97g of Ni60 powder. The surface treatment in step 3 includes: calcining the mixed powder at 1200-1500℃ to further coat the ceramic powder with rare earth oxides, or preparing a rare earth oxide coating on the surface of the ceramic powder by vacuum evaporation, thereby preparing reinforced particles with a rare earth oxide coating on the surface, and the frequency of ultrasonic oscillation is 20-60kHz.

2. The preparation method according to claim 1, characterized in that: In step 2, the dispersant is a sodium hexametaphosphate solution with a concentration of 8‰.

3. The preparation method according to claim 1, characterized in that: The temperature for vacuum evaporation is 1700℃.

4. The preparation method according to claim 1, characterized in that: In step 4, the primary mixed powder and the alloy powder are mixed a second time using ultrasonic stirring or protective balloon milling.

5. The preparation method according to claim 4, characterized in that: The ultrasonic stirring method includes simultaneous ultrasonic oscillation and stirring with a stirring paddle. The frequency of ultrasonic oscillation is 20-60kHz, the speed of stirring paddle is 2500-4500r / min, and the ultrasonic stirring time is 1.5h.

6. The preparation method according to claim 4, characterized in that: The movement of the grinding balls in the protective ball milling method is cascading, and the nitrogen gas flow rate is 1-5 L / (m²). 3 ·min).