Alumina ceramics have high strength, high hardness, excellent corrosion resistance and wear resistance, but high brittleness and poor processing performance. Kovar alloy has the advantages of low temperature constant expansion, good thermal matching performance and easy processing. Therefore, the combination of alumina ceramic and kovar alloy can obtain ceramic metal welding parts with excellent properties of both ceramic and metal.
The Advantages and Disadvantages of Alumina Ceramic Welding are As Follows:
Advantages:
1. High wear resistance: Alumina ceramics have excellent wear resistance, far superior to other materials, such as manganese steel and high chromium cast iron, which helps to extend the service life of the equipment.
2. Low density: Its density is only half that of steel, which means that at the same volume, alumina ceramics can carry more weight, thereby reducing equipment load and improving efficiency.
3. High temperature resistance: Alumina ceramics can be used for a long time at temperatures up to 1600°C, suitable for extreme thermal environments.
4. Corrosion resistance: It can resist acid, alkali and other chemical substances, suitable for various chemical treatment occasions.
5. Good electrical insulation: especially in high temperature environments, alumina ceramics can withstand high voltages and are not susceptible to electromagnetic interference.
6. Self-lubricity: The low coefficient of friction of alumina ceramics makes it an ideal material for sliding or rotating parts, reducing maintenance requirements.
7. High pressure resistance: Alumina ceramics can withstand high pressure and remain stable even in high temperature and high pressure environments.
Disadvantages:
1. Poor toughness: the toughness and thermal shock resistance of alumina ceramics are not good, and they cannot withstand sharp changes in temperature, so special attention is needed in processing and use.
2. Processing difficulties: Due to its high hardness and brittleness, alumina ceramics are easy to lead to tool wear and fracture during machining, increasing the processing cost.
The Advantages and Disadvantages of Kovar Alloy Welding are As Follows:
Advantages:
1. Good weldability: Kovar alloy has good weldability and can maintain good air tightness even after nickel plating
2. Pre-welding treatment is important: stress relief annealing should be carried out on the Kovar alloy parts before welding to avoid thermal cracks caused by stress
3. Large thermal resistance: Replaceable alloys have a large thermal resistance (i.e., a small thermal conductivity) and therefore conduct heat more slowly, making them suitable for applications where slow heat dissipation is required.
However, Ceramic and Kovar Welding Also Has Some Potential Disadvantages to be Aware of:
1. Low thermal conductivity: Due to the small thermal conductivity of Kovar alloy, heat is not easily transmitted during the welding process, which may affect the welding efficiency and effect
2. Weld position limitation: In order to prevent ceramic or glass seals from cracking due to overheating welding areas, welding should ensure that the weld is at least 5 to 6 mm away from the ceramic or glass sealing surface.
3. Material compatibility issues: Silver and its alloys should not be present near the weld, as they may cause cracking of the kovar alloy.
In summary, although Kovar alloy can be used as a welding material for ceramics in some cases, some of the above considerations and technical challenges need to be taken into account.