TUNGSTEN CARBIDE T025
A popular hard face seal material available in several grades depending upon hardness and corrosion resistance.
The most popular grades are nickel base and cobalt base tungsten carbide. Nickel has better corrosion resistance, but the cobalt is harder.
- Cobalt and nickel are the common binders used to hold the tungsten particles together. Each is susceptible to selective chemical attack of this metallic binder that will leave a skeletal surface structure of tungsten carbide particles.
- Galvanic corrosion can take place between a passivated stainless steel shaft or seal face holder and the active nickel in the nickel base tungsten carbide seal face. This can be a real problem in caustic and other high pH fluids. The temperature at the seal face is higher than the temperature of the sealing fluid so the attack takes place quicker.
- The metallic binders in tungsten carbide are also subject to galvanic attack near copper, brass or bronze.
There is some evidence that the nickel remains active in the nickel base matrix and can react with the passivated stainless steel found in the metal parts of the mechanical seal to create a galvanic corrosion problem.