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

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 similar to 4%Cu). The microstructure of all as-cast specimens with different copper content was composed of dendrite of primary gamma, MC-gamma eutectic and M2C-gamma eutectic but it was found X-ray diffraction peaks of alpha 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 gamma 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 lambda(2) 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 lambda(2) of the dendrite with primary gamma.