Effects of Pouring Temperature on Microstructure and Properties of K417G Superalloy in Thermally-Controlled Solidification Process

The solidification process of polycrystalline nickel base superalloy can effectively reduce the porosity defects. The microstructure and mechanical properties of K417G alloy were studied at the pouring temperature of 1360, 1380, 1400 and 1420 degrees C. The results show that with the increase in pouring temperature, the porosity decreases significantly, the gamma ' phase size and the (gamma+gamma') eutectic content increase slightly, while the morphology change of M C carbide is not obvious. The overall mechanical properties at 1360 degrees C are significantly lower, the tensile strength and elongation of alloy at 900 degrees C/10-3 s-1 are only 656 MPa and 4.2 %, respectively, and the stress rupture life at 760 degrees C/645 MPa is only 18 h. At 1380-1420 degrees C, the difference of tensile properties at 900 degrees C/10-3 s-1 is relatively small, and the average tensile strength and elongation are 761 MPa and 5.7%, respectively, while the stress rupture property at 760 degrees C/645 MPa tends to decline with the increase in the temperature. The stress rupture life of 1380, 1400 and 1420 degrees C are 88, 80 and 74 h, respectively.