Cathodic arc deposited FeAl coatings: properties and oxidation characteristics

FeAl coatings were deposited on various steel substrates in a cathodic arc deposition system using FeAl alloy cathodes containing 40 and 45 at.% Al. The effects of total gas pressure (argon) and bias voltage on the morphology of the coatings were studied. Coatings were porous at low bias voltages and the porosity decreased with an increase of bias voltage. The thickness of the coatings was varied from 2 to 18 μm by varying the total charge Q (also called bias Ah) on the substrate during the deposition. The average hardness and elastic modulus of 10 μm thick coatings were measured to be 250 HV and 230 GPa, respectively. Isothermal oxidation behavior of FeAl coated on 304SS and 440C steel were studied in the temperature range of 800–1000 °C. The application of FeAl coating (10 μm) on 440C steel reduced the mass gain due to oxidation by four times at 800 °C. FeAl coated 304SS showed a much lower oxidation rate than uncoated 304SS in the temperature range of 800–1000 °C. Both the coating and the oxide scale exhibited a higher resistance to spallation than uncoated steel coupons throughout the oxidation period of 600 h. We show that the excellent high temperature resistance of cathodic arc deposited FeAl coatings can be used to protect conventional steels.