Abstract
When the chromium diffusion coating of nickel superalloys was treated in a system containing iron, an extremely corrosive layer was often obtained and the chromium content of the layer was decreased.
This paper describes the chemical reactions on the metal surface and some experiments conducted for explaining the above phenomenon.
The results showed that the behavior of iron had bad effects on the properties of the diffusion layer such as decrease in surface chromium concentration, corrosion resistance, and oxidation resistance, acceleration in peeling of diffused layer and deterioration of diffusion agent.
Therefore, it was concluded that the mixing of iron with the diffusion agent must be prevented and the use of a mild steel vessel must be avoided.
