熔体超温处理温度对新型镍基单晶高温合金溶质分配行为的影响

INFLUENCE OF MELT SUPERHEATING TREATMENT TEMPERATURE ON SOLUTE DISTRIBUTION BEHAVIOR OF A NEW Ni-BASED SINGLE CRYSTAL SUPERALLOYS

采用熔体超温处理技术对新型含Re和Ru的镍基单晶高温合金熔体进行不同温度的超温处理,利用EPMA研究了定向凝固过程中合金元素的溶质分布状态及溶质分配系数随熔体超温处理温度变化的演化规律.结果表明,在平界面定向凝固条件下,随熔体超温处理温度的升高,Al,Ta元素在固液界面前沿液相一侧的分布呈现先增大后减小的趋势,而Re,W,Ru,Co元素则呈现与之相反的规律,Mo,Cr元素无明显变化;而熔体超温处理温度对Ru,Co,Mo,Cr元素的溶质分配系数影响较小.熔体超温处理使合金熔体结构发生变化,进而影响元素分布,是导致溶质分配系数发生变化的主要原因.

Solute partition coefficient plays an important role in determining the microstructure and mechanical properties of Ni-based superalloys. Melt superheating treatment can greatly affect the melt structure and redistribution of solute atom in the melt. However, up to date, there are few investigations of the influence of melt superheating treatment on the solute partition coefficient, especially for the new-generation Ni-based single crystal superalloy with additions of Re and Ru. Therefore, in this work, the influence of melt superheating treatment temperature on the solute partition coefficient of a new Ni-based single crystal superalloy with Re and Ru elements under planar solid/liquid（S/L） interface under directional solidification conditions was systematically investigated by using EPMA. It was found that the distribution of solute elements, such as Al, Ta, Ru, Re, W, Co, showed remarkable change in both sides of the S/L interface with increasing melt superheating treatment temperature, but there was little change for the solute elements of Mo and Cr. With increasing the melt superheating treatment temperature, the concentration of solute elements for Al and Ta increased firstly and then decreased, but it showed an opposite trend for Re, W, Ru and Co. Additionally, the change of the solute partition coefficients for Ru, Co, Mo and Cr were small with increasing the melt superheating treatment temperature. The main reasons related to the above changes can be ascribed to that the variation of melt superheating treatment temperature affects the size of the atom clusters in melt, which gives rise to the variation of atomic distribution, and thus leads to the change of solute partition coefficients.