Ducropur, Ducrolloy - New chromium materials

Abstract
"Ducropur" and "Ducrolloy" - powder metallurgically produced chromium and chromium base alloys represent a unique combination of different properties : high strength at elevated temperatures and good corrosion resistance to a large variety of chemicals as well as to hot gases. The present paper shows that Ducropur is one of the most resistant materials (better than LC-Ni) in hot caustic soda applications. Furthermore, it is shown that Ducrolloy Cr44Fe5AlO.3TiO.5Y₂O₃ is almost inert to boiling concentrated nitric acid. The corrosion rate is lower than that of most HNO₃-resistant alloys cited in the literature. Finally, the hot air oxidation/nitridation behaviour of Ducropur can be improved by small additions of rare earth oxides and alloying with iron and aluminum. Alloys such as Cr1La₂O³ and Cr44Fe5AlO.3TiO.5Y₂O₃ form tight protective layers and are promising materials for various hot gas applications.