Effect of fluidized bed CVD aluminide coatings on the cyclic oxidation of austenitic AISI 304 stainless steel

Austenitic AISI 304 stainless steel finds a vast variety of applications due to its good performance in different environments and its relatively low price. However, its high temperature operation limit is restricted to approximately 950°C due to the formation of volatile CrO3 under oxygen environments. Thus, the application of aluminide coatings may increase the upper temperature LIMIT of this steel. Chemical vapour deposition in fluidised bed reactors (CVD-FBR) has been used to coat AISI 304 steel at temperatures of 525°C for 1.5 h followed by a heat treatment up to 900°C. Cyclic oxidation experiments of both coated and uncoated specimens have been conducted under atmospheric pressure air at 950°C. The results are very promising for the application of the CVD-FBR process as a surface modification technology since the behaviour of the coated specimens is much better than that of the uncoated ones.