Carbide Sheath Accumulation
Carbide precipitation clusters are continuous accumulations of carbides at the grain boundaries of high-alloy steels, which can lead to intergranular corrosion or brittleness.
Physical-chemical mechanism of action
Carbide precipitation clusters form by continuous diffusion of carbon into the steel structure. This leads to an accumulation of carbides at grain boundaries, especially when the carbon content exceeds 0.7%.
Metallurgical relevance & risks when welding
These clusters can cause intergranular corrosion that eats away the steel at grain boundaries. Additionally, brittleness can increase, leading to cracks and fractures in the weld structure. This impairs the mechanical properties and service life of the steel.
Workshop practice & instructions
To avoid carbide precipitation clusters, keep the carbon content in the steel below 0.7%. When welding high-alloy steels, careful control of temperature and cooling process is required. Too rapid cooling can promote formation of these clusters. It is advisable to use a controlled cooling process with a time of at least 10 seconds per millimeter of steel thickness.