Improvement of environmental degradation resistance of Fe–Al-based alloys by surface modification treatments

The influence of surface modifications on the resistance of environmental degradation of an Fe–18Al–0.1Nb–2Si alloy was investigated. A variety of surface modification techniques including electroplating, electroless plating, magnetron sputtering, fluidized bed and pack cementation were applied to the alloy to produce various protective coatings. The result of electrochemical hydrogen permeation tests showed that the specimens with a Ni-coating by a magnetron sputtering deposition technique exhibited the lowest hydrogen permeation rate and that the Cr-coating layer by various coating techniques had little influence on reducing the hydrogen permeation rate in the alloy. The room temperature tensile tests showed that a significant improvement in the tensile ductility of the alloy can be achieved by forming an aluminum oxide layer on the specimen surface using a pack cementation in alumina powder.