热控凝固工艺中浇注温度对K417G合金组织及性能的影响

Effect of Pouring Temperature on Microstructure and Properties of K417G Superalloy in Thermally-controlled Solidification Process

摘要:

采用热控凝固工艺来制备等轴晶镍基高温合金能有效降低疏松冶金缺陷。本文针对1360℃、1380℃、1400℃和1420℃四种不同浇注温度对K417G合金的组织结构和力学性能进行研究。结果表明，随着浇注温度的升高，疏松含量显著降低，γ′相尺寸及面积分数略微的上升，其次(γ+γ′)共晶含量有稍许增加，而MC碳化物没有明显变化。浇注温度为1360℃的整体力学性能明显偏低，900℃，10-3s-1的抗拉强度和延伸率分别仅为656MPa和4.2%，760℃/645MPa持久寿命仅有18h。在1380℃-1420℃时，900℃，10-3s-1拉伸性能的差异相对较小，平均的抗拉强度及延伸率分别为761MPa和5.7%，而760℃/645MPa的持久性能随温度升高有下降的趋势，1380℃、1400℃和1420℃的持久寿命分别为88h、80h和74h。

Abstract:

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 four different pouring temperatures of 1360 ℃, 1380 ℃, 1400 ℃ and 1420 ℃. The results show that with the increase of pouring temperature, the porosity decreased significantly, the γ" phase size and the (γ+γ") eutectic content increased slightly, while the MC carbide is not obvious. The overall mechanical properties at 1360 ℃ are significantly lower, the tensile strength and elongation of at 900℃, 10-3s-1 are only 656 MPa and 4.2 %, respectively, and the stress rupture life at 760 ℃ / 645 MPa is only 18 h. At 1380 ℃ to 1420 ℃, the difference of tensile properties at 900 ℃, 10-3s-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 ℃ / 645 MPa tends to decline with increasing temperature. The stress rupture life of 1380 ℃, 1400 ℃ and 1420 ℃ are 88 h, 80 h and 74 h, respectively.