Intergranular Oxidation
Edge oxidation is the selective oxygen attack on alloy-specific elements at the grain boundaries during annealing. This weakens the bond and requires mechanical rework.
Physical-Chemical Mechanism
Surface oxidation occurs when oxygen selectively reacts at the grain boundaries of the surface layer. This can lead to local changes in alloy content and weaken the material.
Metallurgical Relevance & Welding Risks
Surface oxidation can degrade the mechanical properties of the material, such as reducing strength or toughness. It increases susceptibility to cracking and can alter the microstructure.
Workshop Practice & Actions
To avoid surface oxidation, the weld should be cooled as quickly as possible. This can be achieved with an appropriate cooling strategy. For highly oxidizable alloys, it is important to protect the material well before the annealing process and to carry out careful mechanical finishing after welding.