How To Avoid Hydrogen Embrittlement
By By Daniel HerringIf as a result of plating or other operations you suspect that hydrogen absorption has taken place in a part, it need not be a permanent condition. If cracking does not occur and the environmental conditions are changed so that no hydrogen is generated on the surface of the metal, the hydrogen can re-diffuse out of the steel and part ductility can be restored.
Performing a hydrogen bake-out cycle – the term "bake-out" involves both diffusion within the metal and outgassing or an embrittlement relief – is a powerful method in eliminating hydrogen before damage can occur. Key variables are temperature, time at temperature and concentration gradient (atom movement).
For example, electroplating provides a source of hydrogen during the cleaning and pickling cycles, but by far the most significant source is cathodic inefficiency. A simple hydrogen bake-out cycle can be performed to reduce risk of hydrogen damage (Table 1). The most important caution is that over-tempering or softening of the steel can occur if you are not careful, especially on a carburized or induction-hardened part.
Daniel H. Herring - Tel: (630) 834-3017)
Dan Herring is president of THE HERRING GROUP, which specializes in consulting services (heat treatment and metallurgy) and technical services (industrial education/training and process/equipment assistance. He is also a research associate professor at the Illinois Institute of Technology/Thermal Processing Technology Center.He can be reached at: This e-mail address is being protected from spambots. You need JavaScript enabled to view it.
