Niobium carbide precipitation
Niobium carbide precipitation is the release of insoluble niobium carbides from the metal, which prevent creep and intergranular corrosion.
Physical-chemical mechanism of action
Niobium carbide precipitation describes the process where sparingly soluble niobium carbides leave the metal matrix. These particles are stable and remain embedded in the crystal lattice until a certain temperature is reached at which they dissolve and diffuse into the surroundings.
Metallurgical relevance & risks in welding
Niobium carbide precipitation has important metallurgical consequences. It prevents creep of the material at high temperatures, as the free particles stabilize the crystal lattice and limit deformation. Additionally, they block carbon molecules, reducing intergranular corrosion. However, too low a niobium carbide content can make the material more susceptible to creep and corrosion.
Workshop practice & instructions
To make optimal use of niobium carbide precipitation, the welding process should be carried out at temperatures below the niobium carbide precipitation temperature. This ensures that the particles remain in the crystal lattice and exert their stabilizing effect. For high-temperature applications, it is important to use a suitable niobium content in the alloy to increase creep strength and corrosion resistance.