Powder metallurgy is the main method for preparing tungsten alloy rings. It achieves near-net-shape forming through powder mixing, molding, and sintering, making it suitable for mass production of ring-shaped structural components.
1. Raw Material Preparation and Powder Mixing
High-purity tungsten powder (purity ≥99.95%) is selected, with a particle size typically ranging from a few micrometers to tens of micrometers, and prepared using methods such as hydrogen reduction. The oxygen content must be strictly controlled to avoid affecting the final performance. Low-melting-point binder metal powders such as Ni, Fe, Cu, and Co (total content 2%-15%) are added, precisely weighed according to the designed ratio. Uniform mixing is achieved using methods such as ball milling and mechanical stirring. If necessary, forming agents (such as paraffin wax) are added to improve flowability, followed by granulation, vacuum drying, and sieving. For special applications, second-phase particles such as titanium carbide (TiC) and yttrium oxide (Y?O?) can be added to achieve dispersion strengthening.
2. Compression Molding
The mixed powder is loaded into a special mold (ring-shaped cavity) and compressed under high pressure to form a ring-shaped billet (green billet). Compression molding is suitable for small to medium-sized ring parts and offers high production efficiency. Cold isostatic pressing (CIP) is suitable for large or high-precision ring billets, producing billets with uniform density. After molding, the billet has a certain strength and can undergo minimal finishing (pre-sintering) to approximate the final shape, reducing subsequent machining.
3. Debinding and Pre-sintering
The forming agent is removed by low-temperature heating. Pre-sintering (approximately 1200℃ for 1 hour in a hydrogen atmosphere) initially shapes the billet, improves its strength and conductivity, and prepares it for high-temperature sintering.
4. High-Temperature Sintering
Liquid-phase sintering is performed in a vacuum, hydrogen, or inert atmosphere furnace. The temperature is typically 1400-1650℃ (depending on the alloy composition; higher temperatures may be required for high tungsten content), and held for a certain time. The binder phase melts to form a liquid phase, filling the gaps between tungsten particles and promoting densification. After sintering, shrinkage is approximately 15%, and density can reach over 98%, even approaching full density. Process parameters (temperature, time, atmosphere) need precise control to avoid excessively large tungsten grains or the volatilization of low-melting-point components. A ring-shaped sintered blank is obtained after sintering, exhibiting high density and good strength.
5. Post-processing and Precision Machining
Tungsten alloys have high hardness and require machining with diamond tools or superhard tools. (1) Shaping and Machining: Grinding both end faces, turning the outer diameter, boring the inner hole, etc., to ensure dimensional accuracy and concentricity. (2) Surface Treatment: Polishing, plating with Cu, Ag, or PVD coatings as needed to improve corrosion resistance or surface quality.
CTIA GROUP and its parent company, Chinatungsten Online, leverage 30 years of professional flexible customization experience to customize high-performance tungsten alloy products according to customer needs, covering a wide range of applications including radiation shielding, industrial sealing, precision instruments, aerospace, medical devices, defense, oil drilling, automotive manufacturing, electronic packaging, high-temperature furnaces, and nuclear protection. CTIA GROUP's tungsten alloy product website is www.tungsten-alloy.com, email is sales@chinatungsten.com, and phone is +86 592 5129595.
