摘要
目的研究不同Co含量电沉积Ni-Co纳米镀层的热稳定性能及其扩散连接应用效果。方法在TC4钛合金表面电沉积Ni-Co镀层,改变镀液中Co含量(0、5、20g/L),利用金相显微镜(OA)和透射电镜(TEM)观察分析镀层800℃热处理前后的微观组织。在真空扩散设备中进行TC4钛合金低温扩散连接(800℃、1 h),利用万能拉伸机检测扩散连接接头的剪切性能。结果添加Co元素不仅能够减小镀层晶粒至19.2 nm,还能够提高其热稳定性能。纯镍镀层在800℃热处理5 h后晶粒长大至17.2μm,而Ni-20 g/L Co镀层晶粒在相同条件下仅长大到10.5μm且生长初期并未发现异常长大晶粒。以2.5μm厚的Ni-Co镀层为中间层进行TC4钛合金低温扩散连接,接头剪切强度高达543.4 MPa。结论Co元素的添加降低了晶界能量,提高了Ni-Co镀层的热稳定性能;作为TC4钛合金扩散连接的中间层,提高了原子的扩散系数,实现了TC4钛合金低温扩散连接,对工程应用具有重要意义。
The work aims to study the thermal stability and diffusion bonding effect of electrodeposited Ni-Co nano-coating with different Co contents.The Ni-Co nano-coating on the matrix of TC4 titanium alloy was electrodeposited by adjusting the content of the Co element(0,5,20 g/L)in the plating solution.The microstructure of Ni-Co nano-coating before and after heat treatment at 800℃was observed through metallographic microscope(OM)and transmission electron microscope(TEM).The low-temperature diffusion bonding(800℃,1 h)of TC4 alloy occurred in vacuum diffusion facilities and the shear property was tested with a universal testing machine.The addition of the Co element not only decreased the grain size of Ni-Co coating to 19.2 nm but also improved the thermal stability.The grain size of pure Ni coating treated at 800℃for 5 h reached 17.2μm.However,the grain size of Ni-Co coating with 20 g/L Co can only grow to 10.5μm at the same conditions and there was no abnormal growing grain in the early growth stage.The shear strength of the joint can reach 543.4 MPa in the low-temperature diffusion bonding process of TC4 titanium alloy with 2.5μm thick Ni-Co coating as interlayer.The Co element not only reduces the grain boundary energy of Ni-Co coating but also improves the thermal stability of Ni-Co coating.As an interlayer in the diffusion bonding process of TC4 titanium alloy,the Ni-Co coating improves the diffusing coefficient of the atom,realizes the low-temperature diffusion bonding of TC4 titanium alloy and is of great significance to engineering applications.
作者
王国峰
刘永康
陈玉清
张靖轩
王月林
WANG Guo-feng;LIU Yong-kang;CHEN Yu-qing;ZHANG Jing-xuan;WANG Yue-lin(School of Materials Science and Engineering,Harbin 150001,China;b.National Key Laboratory for Precision Hot Processing of Metals,Harbin Institute of Technology,Harbin 150001,China;Shenyang Aircraft Corporation,Shenyang 110013,China)
出处
《精密成形工程》
北大核心
2022年第4期115-121,共7页
Journal of Netshape Forming Engineering
基金
国家科技重大专项(MJZ-2018-G-59)。
关键词
电沉积
Ni-Co纳米镀层
热稳定性
低温扩散连接
electro-deposition
Ni-Co nano-coating
thermal stability
low-temperature diffusion bonding
