Tertiary carbide precipitation
Tertiary carbide precipitation is the process where fine special carbides form from supersaturated solid solutions when martensitic steels are tempered. This can lead to increased hardness and improved toughness.
Physicochemical mechanism of action
Tertiary carbide precipitation occurs when the supersaturated solution cools slowly during tempering of martensitic steels. The fine special carbides condense out of the solution and form a homogeneous coarsening in the microstructure.
Metallurgical relevance & risks in welding
These processes can lead to increased hardness and improved toughness of the steel, which improves the mechanical properties. However, uncontrolled tertiary carbide precipitation can also lead to increased stress buildup and possible cracks in the microstructure.
Workshop practice & instructions
To control tertiary carbide precipitation, the steel should cool slowly after tempering. Recommended times are 10 to 20 seconds per millimeter of weld thickness. This prevents uncontrolled coarsening and improves the mechanical properties of the steel.