What causes intergranular oxidation?

Intergranular oxidation is caused by the diffusion of oxygen along the grain boundaries of a material, leading to localized oxidation. Here are the primary causes:

  1. High Temperatures: Elevated temperatures accelerate the diffusion of oxygen into the grain boundaries, promoting oxidation.
  2. Alloy Composition: Certain alloying elements, such as chromium and aluminum, can form oxides more readily, contributing to intergranular oxidation.
  3. Oxidizing Environment: Exposure to environments rich in oxygen, such as air or combustion gases, increases the likelihood of oxidation.
  4. Stress Concentrations: Mechanical stresses can enhance the diffusion of oxygen along grain boundaries, exacerbating oxidation.

Prevention:

  • Temperature Control: Minimize exposure to high temperatures or employ protective atmospheres during high-temperature processes.
  • Material Selection: Use alloys with elements that form protective oxide layers, such as chromium in stainless steels.
  • Protective Coatings: Apply coatings or surface treatments to prevent oxygen penetration.

By understanding the causes and implementing preventive measures, intergranular oxidation can be mitigated to protect material integrity and performance.