Intercrystalline Segregation
Grain boundary segregation is the enrichment of alloying elements at grain boundaries during solidification. This leads to inhomogeneities and impairs corrosion resistance.
Physical-Chemical Mechanism
During the cooling of metals, certain elements or impurities can become concentrated locally at the boundaries between crystal grains (grain boundaries). This process, known as grain boundary segregation, is driven by diffusion and can be influenced by various factors such as temperature gradients and chemical stresses.
Metallurgical Relevance & Risks in Welding
Grain boundary segregation leads to microstructural inhomogeneities that impair the material's corrosion resistance. Non-uniform segregation can speed up corrosion damage and reduce the service life of components. Additionally, it can promote the formation of cracks or damage in the weld, particularly when the material is under chemical attack.
Workshop Practice & Action Instructions
To minimize grain boundary segregation and enhance corrosion resistance, it is important to ensure controlled cooling and a homogeneous weld pool. This can be achieved through the use of shielding gases, controlling the melting temperature, and performing post-weld heat treatments such as austenitizing. For critical applications, it is advisable to use special welding methods or materials that are less susceptible to grain boundary segregation.