Grain boundary oxidation
Grain boundary oxidation is a selective oxidation reaction at grain boundaries in oxygen-rich environments, which impairs the mechanical strength of the surface.
Physical-Chemical Mechanism of Action
Grain boundary oxidation occurs when metal contacts oxygen in the air or in a furnace. At the boundaries between different grain sizes, the metal reacts faster with oxygen, leading to the formation of an oxide film.
Metallurgical Relevance & Welding Risks
This oxidation can reduce the mechanical load capacity of the surface and cause cracks or corrosion. It particularly affects the toughness and stress-carrying capacity of the metal, leading to an increased risk of hot cracking and weld defects.
Shop Practice & Action Instructions
To avoid grain boundary oxidation, clean the metal thoroughly before welding. Use a clean atmosphere during furnace treatment and ensure proper temperature control. In high-temperature processes like TIG welding, it's important to cool the metal quickly to prevent oxidation.