Chiang Mai Journal of Science

As an economic alternative to NiAl, Fe-based alloys have potential application as materials for the intermediate coating in the fabrication of plasma-sprayed ceramic coatings, usually Al2O3 or Cr₂O₃, on metallic substrates. These ceramic coating are applied to various industrial components to improve wear resistance. The purpose of the intermediate coating is to improve the adhesion between the ceramic coating and the metallic substrate both during the plasma spraying process and during subsequent service. The intermediate coating becomes indispensable when the application requires the ceramic coating to withstand high temperatures. At which, both thermal stress and high temperature corrosion can push the intermediate coating to its limit. Ni-based alloys have proven to be one of the most reliable intermediate coatings in such circumstances where high temperatures is involved. However, the rising price of Ni limits its usage in many applications. This paper thus compares the effect of exposure at 400°C on the adhesion of the Fe-base and Ni-base intermediate coatings. The materials studied are FeAl, FeCrAl and NiAl and NiAl arc sprayed coatings on stainless steel 304 substrates. All three coating were top-coated with a plasma-sprayed Al₂O₃ – 40% TiO₂ coating which is a standard coating used in tribological applications. The works focuses on oxidation testing of the coatings at 400°C. The oxidation behavior of the three coatings is compared and discussed.