Effect of Cu Addition on Solidification Microstructure in High Carbon High Speed Steel Type Cast Alloy

Abstract

Effect of copper addition on solidification microstructure was investigated for high carbon high speed steel type alloys (Fe-2.0%C-5%Cr-5%Mo-5%V-0~4%Cu). The microstructure of all as-cast specimens with different copper content was composed of dendrite of primary γ, MC-γ eutectic and M2C-γ eutectic but it was found X-ray diffraction peaks of α phase by X-ray diffractometry. The volume fraction of each phase in solidification microstructure was approximately constant regardless of copper content. The shapes of dendrite of primary γ changed significantly in response to amount of copper addition: that of specimen with no copper was equiaxed while that of specimen containing copper was columnar which tends to be marked with increasing amount of copper addition. Furthermore, the secondary dendrite arm spacing λ2 decreased with increasing amount of copper addition. As a result, it concluded that the effect of copper addition on solidification microstructure is columnar crystallization and decreasing λ2 of the dendrite with primary γ.