Advances in the development of corrosion and creep resistant nano-yttria dispersed ferritic/martensitic alloys using the rapid solidification processing technique

Abstract High-temperature creep and corrosion resistant nano-dispersed ferritic/martensitic (F/M) alloys (such as a T91 steel), or other ‘the oxide dispersion strengthened (ODS) steels’, are under consideration for nuclear applications because of their high-temperature mechanical properties. They consist typically of a high-chromium steel structure dispersed and reinforced by a dispersion of nano-sized rare-earth metal oxides, typically yttrium oxide (Y 2 O 3 ). In this study, the production of ODS based on T91 is examined by adding a 0.3 wt% colloidal Y 2 O 3 dispersion to a T91 steel melt in combination with metallic yttrium (Y M ). The production of the following systems is evaluated: T91–Y 2 O 3 , T91–Y M and T91–Y M –Y 2 O 3 . At first, it was found that when Y M is added to a steel melt, internal oxidation occurs. Furthermore, it was shown that the T91 system with addition of Y 2 O 3 in combination with rare-earth metal Y M, creates a homogeneously dispersed ODS T91 material. Moreover, the role of Y M as a possible surface active element lowering the surface tension at the contact interface is studied. High-temperature contact angle wetting tests between Y 2 O 3 ceramic substrates in contact with an T91 and a [T91+Y M ] melt, combined with auger-electron spectroscopy (AES), indicate the influence of Y M on the surface activity of Y 2 O 3 in contact with T91. After Y M addition, the contact angle between T91 and the Y 2 O 3 substrate lowers down to angles below 90°.