Mechanical properties of M7 high speed cast steel modified with niobium

Some parts of W and V in a high speed M7 steel were replaced by Nb to improve the mechanical properties. Microstructure and mechanical properties of as-cast and heat treated samples of this modified steel were investigated by both light microscope and electron microscope coupled with an EDX analyser. Various heat cycles were applied in order to optimize the mechanical properties of this cast steel. The properties were compared with those of a standard cast and a wrought M7 and a wrought M2 high speed steels for better understanding of the effects of alloy modification. It was shown that high temperature hardness and cutting performance of the modified cast steel in a properly heat treated condition are about 95 and 70% of those of a standard wrought M7 and a wrought M2 steel, respectively.