Hydrogen embrittlement
Hydrogen embrittlement is the loss of ductility and toughness due to trapped hydrogen under tensile stress. This can cause sudden failure with no visible deformation.
Physical-Chemical Mechanism of Action
Hydrogen embrittlement occurs when atomic hydrogen is absorbed into the metal and is under mechanical tensile stress. The absorbed hydrogen can move along grain boundaries and damage them. This leads to a loss of ductility and toughness of the material.
Metallurgical Relevance & Risks in Welding
Hydrogen embrittlement can lead to sudden, catastrophic failure of components without visible prior deformation. This is especially dangerous in highly stressed components such as structural frames or machine shafts. Risks increase with hydrogen content density and stress in the material.
Workshop Practice & Instructions
To avoid hydrogen embrittlement, the following measures should be taken:
• Use welding processes with lower hydrogen content such as austenitic steel or MIG welding.
• Keep the weld at low stress and avoid overcritical stresses.
• Perform careful cooling to remove hydrogen from the material.
• Use hydrogen removal techniques such as hydrostatic welding or post-weld heat treatment.