高Cr铸造镍基高温合金K4648凝固行为的研究  

Investigation of the Solidification Behavior of a High Cr Content Cast Ni-Base Superalloy K4648

作　　者：郑亮[1] 肖程波[1] 唐定中[1] 顾国红[1] 汤鑫[1] 

机构地区：[1]北京航空材料研究院先进高温结构材料国防科技重点实验室,北京100095

出　　处：《稀有金属材料与工程》2008年第9期1539-1544,共6页Rare Metal Materials and Engineering

摘　　要：采用等温凝固淬火工艺与差热扫描量热相结合的方法对高Cr铸造镍基高温合金K4648的凝固过程进行研究,得到合金在不同温度下的等温凝固组织、相析出顺序图和凝固特性曲线。结果表明:K4648合金的液相线温度为1340℃,由DSC确定的宏观固相线(3.1%残余液相,体积分数,下同)和等温凝固法确定的微观固相线(0.5%残余液相)温度分别为1248和1180℃。K4648合金固、液相线温度范围内的初生相主要为MC碳化物和α-Cr相,它们的析出温度分别为1310和1190℃。初生α-Cr相固溶30%(原子分数)以上的Ni,显微硬度是基体的3倍,是一种脆性相。凝固过程中Cr的严重枝晶间偏析促进了该相的形成,初生α-Cr相在铸造过程中应加以控制。The solidification process of a high Cr content cast Ni-base superalloy K4648 was comparatively investigated by the method of differential scanning calorimeter （DSC） and isothermal solidification quenching experiment. The solidified microstructure, phase precipitation diagram in sequence and solidification characteristic curve were obtained. The results indicate that K4648 alloy has a liquidus temperature of 1340 ℃. The macro-solidus temperature is 1248 ℃, which is determined by DSC with 3.1% residual liquid phase volume. The end of solidification happens at 1180 ℃ with 0.5 % residual liquid phase vol., which can be designated as micro-solidus temperature. Being primary phases, the α-Cr was formed at 1190 ℃, which was at the late solidification and between the macro- and micro-solidus temperatures range. The onset of MC carbide precipitation took place at 1310 ℃. The solubility of Ni in the primary α-Cr phase can reach over 30 %（ atomic Fraction）. The primary α-Cr is a brittle phase, and its microhardness is 3 times of that of the y matrix. The solidification process should be controlled in order to reduce the size and the quantity of the primary α-Cr phase.

关 键 词：镍基高温合金 K4648 高Cr 凝固 α—Cr相 

分 类 号：TG132.3[一般工业技术—材料科学与工程] TG111.4[金属学及工艺—合金]