Columbium is an alternative name for Niobium. In steels niobium is a common microalloying element, that is added in small which then have a large influence on the resulting mechanical properties.
Strong carbide formers can be used for microalloying to form small precipitates, that is vanadium, niobium, titanium, often used in combination. These elements combine with carbon and nitrogen to make carbides. nitrides and carbonitrides. Vanadium and niobium carbides and nitrides can easily combine together, this may be bacause they have the same crystal structure and similar lattice paramaters.
Looking through some literature recently I was surprised to find a paper on microalloying which had used both niobium and columbium, in different amounts. The paper has 5 authors and is published in Scripta Materialia Influence of short austenitising times on the fracture behaviour or a microalloyed automotive spring steel by Wise, Spice, Davidson, Heitmann and Krauss. Scripta Materialia, 44, 2001, 299-304.