【摘要】 FGH98高温合金和DD5单晶有望在高温环境中服役.在本研究中,我们采用Ni/高熵合金（Ni/HEA）复合中间层实现了FGH98与DD5的高性能扩散连接.FGH98高温合金、DD5单晶和Ni/HEA复合中间层间元素互扩散导致焊缝处形成细小Ni₃Al相（γ’）增强FCC固溶体的复合组织,实现了高强度界面结合.温度是影响界面元素扩散的关键参量.当焊接温度从1075℃提高至1130℃时,界面处元素扩散剧烈,促进了界面空隙闭合和复合扩散区增厚,有利于接头性能提升.然而,过高的扩散温度（1160℃）导致FGH98高温合金和HEA层中形成粗晶组织及化合物相,使接头性能恶化.FGH98-DD5连接体系最优工艺参数为:焊接温度为1130℃、焊接压力为2 MPa、焊接时间为1 h.接头最高抗剪强度为650 MPa,剪切过程中接头表现为韧性断裂.该研究可为界面元素扩散调控提供科学借鉴,也为FGH98高温合金与DD5单晶的可靠连接提供了理论和技术支持.更多还原

【Abstract】 FGH98 superalloys and DD5 single crystals are highly desired to work together in high-temperature service environments.In this study,the FGH98-DD5 robust joining was enabled by diffusion bonding using a hybrid interlayer of Ni and high-entropy alloy（Ni/HEA）.Elemental interdiffusion among the FGH98 superalloy,DD5 single crystal,and Ni/HEA hybrid interlayer triggered the formation of individual tiny Ni₃Al phase（γ’）-reinforced face-centered cubic（FCC） matrix composite structures,resulting in the high-strength interfacial bonding.Temperature plays a key role in regulating the elemental interdiffusion.As the temperature required for diffusion bonding increased from 1075 to 1130℃,the elemental interdiffusion intensified to promote the void closure at interfaces and the thickening of composite diffusion zones（γ’-reinforced FCC matrix composites）,which favors joint strengthening.Nevertheless,the too-high diffusion temperature（1160℃） led to the formation of coarse grains and additional carbides in the FGH98 superalloy and HEA layer,deteriorating the joint performance.Ultimately,the optimal diffusion bonding condition was identified as 1130℃ for 1 h with a low pressure of 2 MPa under vacuum,in which the FGH98-DD5 joint underwent a ductile fracture with a shear strength of up to 650 MPa.This study provides scientific insight for modulating interdiffusion behavior,as well as theoretical and technical support for joining FGH98 superalloys reliably with DD5 single crystals.更多还原