What are the methods for processing zirconia ceramic valve cores

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Zirconia ceramic valve core, with its high hardness, wear resistance, corrosion resistance, and high temperature resistance, has become an ideal substitute for traditional metal valve cores in industrial fields such as energy and power, chemical metallurgy, and water treatment. However, its processing faces challenges such as high material brittleness and high precision requirements.

Core Processing Methods and Technological Processes
The processing of zirconia ceramic valve cores requires a combination of material characteristics and precision manufacturing requirements to form a multi process collaborative process chain, which mainly includes the following key links:

1. Preparation and cutting of raw materials
   Powder preparation: prepare ultrafine zirconia powder with uniform particle size distribution (D50 ≤ 0.5 μ m) and purity ≥ 99.5% by sol-gel method, hydrothermal synthesis method or coprecipitation method to ensure that the density of sintered materials is ≥ 99%.
   Blank forming: By using cold isostatic pressing technology, the powder is compressed into a uniformly dense blank, reducing the difference in sintering shrinkage rate. For complex structure valve cores, injection molding or 3D printing technology can be used to achieve near net size molding.
   Cutting process: Based on the characteristics of brittle materials, hydraulic cutting or laser cutting is preferred to replace traditional mechanical cutting. Hydraulic cutting uses high-pressure water jet (pressure ≥ 300MPa) combined with garnet abrasive to achieve heat free zone cutting, with edge roughness Ra ≤ 3.2 μ m.
2. Precision grinding and polishing
   Flat grinding: Using a double-sided grinding machine, diamond micro powder (particle size W5-W40) is used as the abrasive, and the processing effect of flatness ≤ 1 μ m and surface roughness Ra ≤ 0.1 μ m is achieved through constant pressure control (pressure 0.5-2MPa).
   Spherical polishing: For ball valve cores, magneto rheological polishing technology is used to control the viscosity of the polishing solution through a magnetic field, achieving ultra precision machining with spherical roundness ≤ 0.5 μ m and surface smoothness up to W2 level (equivalent to mirror polishing).
   Edge chamfering: EDM or ultrasonic machining is used to chamfer the edge of the valve core by 0.1-0.3mm, eliminating stress concentration points and reducing the risk of brittle fracture.
3. CNC precision carving and irregular machining
   Tool selection: Diamond coated tools (hardness HV ≥ 8000) or polycrystalline diamond (PCD) tools must be used, with a hardness more than 1.5 times that of zirconia, to avoid rapid tool wear during processing.
   Speed control: The spindle speed must be strictly controlled within the range of 8000-12000rpm. Low rotational speed (<6000rpm) can cause excessive cutting force and lead to cracking; If the speed is too high (>15000rpm), it may cause tool vibration due to centrifugal force, resulting in excessive surface waviness.
   Feed strategy: Adopting layered milling technology, with a single layer cutting depth of ≤ 0.05mm and a feed rate controlled between 50-100mm/min, efficient machining is achieved through a combination of small cutting depth and high feed rate.
4. Sintering and post-processing
   High temperature sintering: sinter the material in a vacuum or inert gas atmosphere at 1600-1700 ℃ for 4-6 hours to achieve a density of over 99% of the theoretical density, with a Rockwell hardness HRA ≥ 88 and a flexural strength ≥ 800MPa.
   Toughening treatment: By adding 3-5 mol% yttrium oxide (Y2O3) as a stabilizer and utilizing the martensitic transformation toughening mechanism, the fracture toughness is increased to 8-10 MPa · m ¹/², significantly improving the impact resistance.
   Surface coating: Deposition of diamond-like carbon (DLC) coating on the sealing surface of the valve core, with a thickness of 2-5 μ m, can reduce the friction coefficient to 0.05-0.1 and improve wear resistance by 3-5 times.

Difficulties in Processing and Technological Innovation Solutions

1. Processing defects caused by material brittleness
   Problem: The fracture toughness of zirconia ceramics is only 1/10 of that of metals, and microcrack propagation is prone to occur during processing, leading to edge fracture or surface cracks.
   Solution:
   Process optimization: Adopting ultrasonic assisted machining technology, cutting force is reduced through high-frequency vibration (20-40kHz) to minimize the probability of crack formation.
   Equipment upgrade: Using a five axis linkage CNC machine tool, the cutting force is evenly distributed through tool path optimization to avoid local stress concentration.
2. Difficulty in controlling shrinkage rate
   Problem: During the sintering process, the volume shrinkage rate can reach 15-20%, and improper control can lead to dimensional deviations.
   Solution:
   Powder modification: Add 0.5-1wt% alumina (Al2O3) as a sintering aid, reduce the sintering temperature by 50-100 ℃, and control the shrinkage fluctuation within ± 0.5%.
   Compensation design: Set a compensation amount of 2-3% in the CAD model, verify the actual shrinkage rate through reverse engineering, and achieve precise size control.
3. Low efficiency in processing irregular structures
   Problem: The processing of complex flow channels or asymmetric structures requires multiple clamping, with a single piece processing time of up to 8-12 hours.
   Solution:
   Rapid prototyping technology: Using photopolymerization 3D printing (SLA) to prepare ceramic bodies, combined with low-temperature degreasing (800 ℃) and rapid sintering (1500 ℃/2h), the processing cycle is shortened to within 24 hours.
   Composite machining center: integrates milling, grinding, and electrical discharge machining (EDM) functions into one, reducing clamping times and improving machining efficiency by more than 40% through process integration.

Typical application scenarios
Energy and electricity: In the steam pipelines of thermal power plant boilers, zirconia valve cores can withstand high temperatures of 650 ℃ and pressures of 10MPa, solving the problem of jamming caused by thermal expansion of metal valve cores. The maintenance cycle has been extended from once a month to once a year.
Chemical metallurgy: In sulfuric acid transportation systems, its corrosion resistance increases the valve life from 6 months to over 5 years, reducing downtime losses caused by leaks by approximately 2 million yuan per year.
Water treatment: In the particle filter valve of seawater desalination systems, its wear resistance increases filtration efficiency by 30% while reducing energy consumption by 15%.

The manufacturing of zirconia ceramic valve core is a systematic engineering that integrates material science and cutting-edge precision machining technology. From dry pressing/injection molding to high-temperature sintering, and finally diamond grinding and ultra precision polishing, every process is crucial. It is through these advanced processing methods that zirconia powder has been transformed into high-performance industrial products, perfectly solving many drawbacks of traditional valve cores in terms of lifespan, sealing, feel, hygiene, and reliability. It has become an undisputed choice in the fields of high-end bathroom and precision fluid control.

Brudeze Ceramics supplies and sells a wide range of high-quality quartz glass, including alumina ceramics, zirconia ceramics, silicon nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics, boron carbide ceramics, bioceramics, machinable ceramics, etc. We can meet the customization requirements of various ceramic products.