Effect of Solutionizing Heat Treatment Duration on the ‎Microstructural Defects of CMSX-4 Single Crystal

The purpose of this research is to investigate the possibility of reducing the solutionizing heat treatment duration of CMSX-4 single-crystal superalloy, which normally takes about 18 to 20 hours according to the standard. In this research, three solution heat treatment cycles with reduced time on single crystal samples of CMSX-4 superalloy made by the vertical Bridgman method, has been done and its results have been analyzed. The separation of alloying elements, the percentage of eutectic pools and the amount of porosities have been accurately evaluated based on microstructural measurements with optical microscope (OM), scanning electron microscope (SEM) and energy diffraction spectroscopy (EDS). The results showed that the solutionizing treatment performed with a reduced duration compared to the standard, caused the complete removal of inter-dendritic eutectic pools and the segregation of alloy elements has been reduced by about 30% on average compared to the as-cast sample. But the results have shown that even the longest suggested heat treatment duration was not enough to remove the porosity formed during the solutionizing process and the percentage of porosity has been reached from 0.83% in the as-cast sample to 1.01, 1.75 and 1.41% in heat treated samples for 8.5, 9.5 and 10.5 hours respectively.