Niobium in tool steels and cemented carbides

Niobium is an element of high affinity towards carbon and forms a very stable carbide. Therefore it is well suited as a carbide-forming alloying element in the production of tool steels and hard metal alloys. This paper first deals with the metallurgical fundamentals, such as the influence of niobium on the solidification behavior of high speed steels, segregation of the MC-carbides during solidification, effect of the solidification rate on the precipitation of monocarbides, solubility of niobium in austenite, effect on secondary hardness, M2C decomposition and methods for the achievement of higher niobium-contents in high-speed steels. In a second part selected examples of use are referred to in the categories of high speed steels, hot working tool steels, cold working tool steels and steels for plastic moulds. A short summary of niobium in cemented carbide completes the paper. (AU)