Improvement of the corrosion resistance of steels and MCrAlY coatings by application of a pulsed electron beam

The pulsed electron beam facility GESA I which provides a beam of up to 10 cm diameter, was used to improve the oxidation and corrosion resistance of martensitic steels and of high temperature protective MCrAlY coatings by melt restructuring of the surface. It is shown that corrosion of OPTIFER IVc steel by liquid lead containing 8·10⁻⁶ at% oxygen is avoided by alloying of Al into the surface. The tests so far run 3000 h at 550 °C under control of the oxygen concentration by the H2/H2O ratio in an Ar gas atmosphere above the lead. Treatment of the MCrAlY coating on turbine blade specimens leads to higher oxidation resistance at 950 °C and to excellent adherence of Yttria-stabilized zirconia thermal barrier coatings even after 5000 h of exposure to air.