1. Corrosion resistance. Corrosion means that the seal face is damaged because of medium. Sealing is weakened when seal faces being damaged. For that, seal face must have corrosion resistance. Corrosion resistance of materials depends on components and chemical stability of materials.  

 

2. Abradability. Seal face can be damaged for friction caused by relative motion. The damage weakens seal. So the materials of seal face should have good abradabilty, especially for gate valve. Abradability is determined by the characteristics of materials.

 

3. Erosion resistance. The seal face can be damaged when medium passing through at a high speed. The destruction is obvious in throttle valve and safety valve which are applicable for high temperature high pressure steam, having great influence on seal. So, erosion resistance is one of key requirements.

 

4. Hardness. The hardness cannot descend when working temperature falling.

 

5. Linear expansivity of seal face should close to body materials. It can avoid loose and extra stress caused by high temperature 

 

6. Materials must have anti oxidation, thermal fatigue resistance and thermal cycle under high temperature.

 

However, none of materials can meet all of above requirements currently. Materials can only meet several requirements for different categories and usages. For example, seal face should have excellent erosion resistance when using for high speed medium. Seal face should have high hardness for solid impurities included in medium.