Abstract: To explore the optimal composition content of IN617 alloy for stable service under more severe conditions， different composition systems of the alloy were designed by changing the content of carbon and molybdenum， which are the main forming elements of carbides in the precipitation strengthening of the alloy. The effects of element content on the microstructure evolution and mechanical properties of IN617 alloy were systematically analyzed by scanning electron microscopy （SEM）， transmission electron microscopy （TEM）， electron probe microanalysis （EPMA）， differential thermal analysis （DSC）， thermodynamic calculation， tensile and impact tests.The results show that the secondary dendrite spacing can be significantly refined by appropriately increasing the content of C and Mo. When the content of C increases from 0.054% to 0.066%， the secondary dendrite spacing decreases from 13.6 μm to 8.3 μm. When the content of Mo increases from 8.53% to 9.51%， the secondary dendrite spacing decreases from 10.2 μm to 8.3 μm. At the same time， with the increase of element content， the volume fraction of primary precipitates in the as-cast alloy increases significantly. For every 0.01% increase in C， the volume fraction of carbides increases by about 1.0 %. Mo increases by 1.0%， and the volume fraction of carbides increases by about 0.45%.The precipitation mechanism is mainly Ti（C，N）-M₆C-M₂₃C₆ three-phase symbiosis and M₆C-M₂₃C₆ two-phase symbiosis， and the effect of element change on the mechanism is limited. Due to the decrease of dendritic segregation and the increase of carbides， the alloys with high C and Mo contents exhibit better mechanical properties. The tensile strength and yield strength of the low C high Mo alloy at room temperature are 762.5 MPa and 337.0 MPa， respectively. The impact absorbed energy is 463.5 J， and the tensile strength and yield strength at 800 ℃ are 419.5 MPa and 192.0 MPa， respectively. The tensile strength and yield strength of the alloy with high C and low Mo are 770.5 MPa and 323.5 MPa at room temperature， and 409.5 MPa and 192.5 MPa at 800 ℃. The tensile strength of the alloy with high C and high Mo at room temperature is 792.0 MPa， and the yield strength is 340.0 MPa. At 800 ℃， the tensile strength and yield strength of the alloy are 422.0 MPa and 210.0 MPa， respectively， which are higher than those of the other two alloys. However， the toughness of the alloy decreases slightly， and the impact absorbed energy is about 100.0 J lower than that of the alloy with low C content.

Key words: IN617 Alloy, Dendritic Segregation, Microstructure, Mechanical Properties

摘要： 为探讨IN617合金在更严苛条件下稳定服役的最佳成分含量，本研究通过改变合金析出强化中碳化物主要形成元素碳和钼的含量，设计了合金不同成分体系，并采用扫描电镜（SEM）、透射电镜（TEM）、电子探针（EPMA）、差热分析（DSC）、热力学计算、拉伸及冲击试验，系统分析了元素含量变化对IN617合金显微组织演变与力学性能的影响。结果表明，适当提高C和Mo含量可显著细化二次枝晶间距：当w［C］由0.054%提升至0.066%时，二次枝晶间距由13.6 μm缩小至8.3 μm，当w［Mo］由8.53%增至9.51%时，二次枝晶间距由10.2 μm减小至8.3 μm。同时，随元素含量升高，铸态合金中一次析出相体积分数明显增加，其中，w［C］每升高0.01%，碳化物体积分数约增1.0%；w［Mo］升高1.0%，碳化物体积分数增约0.45%。析出机制主要为Ti（C，N）-M₆C-M₂₃C₆三相共生及M₆C-M₂₃C₆两相共生，元素变化对机制影响有限。得益于枝晶偏析的减弱和碳化物的增加，高C和Mo含量的合金表现出更优的力学性能。低C高Mo合金的室温抗拉强度和屈服强度分别为762.5、337.0 MPa，冲击吸收能量为463.5 J，在800 ℃下抗拉强度和屈服强度为419.5、192.0 MPa；高C低Mo的合金在室温下抗拉强度和屈服强度为770.5、323.5 MPa，在800 ℃下抗拉强度和屈服强度为409.5、192.5 MPa；而高C高Mo的合金在室温抗拉强度达792.0 MPa，屈服强度为340.0 MPa；在800 ℃下抗拉强度为422.0 MPa，屈服强度210.0 MPa，较另外两组合金的强度均有升高趋势，但其韧性略有下降，冲击吸收能量较低C含量合金减少约100.0 J。

关键词: IN617合金, 枝晶偏析, 显微组织, 力学性能