Role of Niobium in high temperature alloys

[ben]

What are the different roles of niobium in high temperature alloys?

[octane]

Considering the use in furnace tube materials, Niobium is added to decrease the migration of chrome from the matrix during carbide precipitation, thus avoiding the detriment of mechanical properties due to the lack of chromium.

[mechcolor]

There are three things to consider when adding Nb for high temperature furnace tubes.
1. Its strength to form strong carbides causing partial replacement of Chromium-carbides (lesser the better).
2. Its ability to resist rupture at high temperatures minimizing the creep rate.
3. Eventual improvement in the mechanical properties but limited within 900 - 1100 C.

[ivani1]

Attaching a paper here, "Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy".
This will provide you particular details, however summarized version has already been shared by other friends.