Ni-Co纳米镀层为中间层的TC4钛合金低温扩散连接

Low temperature diffusion bonding on TC4 titanium alloy with Ni-Co nano-coating as intermediate layer

针对钛合金在高温扩散连接时易变形、扩散设备及模具需求苛刻等问题,在TC4钛合金表面电沉积Ni-Co纳米镀层并将其作为中间层,以达到降低扩散连接温度的目的。研究了Co含量对Ni-Co纳米镀层微观组织及性能的影响规律,当Co含量为20 g·L^(-1)时,镀层表面平滑且硬度最高,为537.6 HV,晶粒尺寸最小,为19.2 nm。当镀层厚度为2.5μm、扩散连接温度为800℃时,焊接接头的剪切强度达到543.4 MPa,与不加中间层的焊接试样相比,剪切强度提高了61.4%。Ni-Co纳米镀层作为中间层提高了原子的扩散系数,实现了TC4钛合金在低温、低真空环境中的高质量扩散连接,对工程应用具有重要意义。

For the problems that titanium alloys are easily deformed during high-temperature diffusion bonding, and the requirements of diffusion equipment and molds are strict, the Ni-Co nano-coating was electrodeposited on the surface of TC4 titanium alloy as an intermediate layer to reduce the temperature of diffusion bonding. Therefore, the influence laws of Co content on the microstructure and properties of Ni-Co nano-coating were studied. When Co content was 20 g·L^(-1), the surface of coating was smooth, the hardness was the highest which was 537.6 HV, and the grain size was the smallest which was 19.2 nm. When the thickness of coating was 2.5 μm and the diffusion bonding temperature was 800 ℃, the shear strength of welded joint reached 543.4 MPa, which was 61.4% higher than that of the welded sample without intermediate layer. As an intermediate layer, the Ni-Co nano-coating improves the diffusion coefficient of atoms and realizes the high-quality diffusion bonding of TC4 titanium alloy at low temperature and in low vacuum environment, which is of great significance for engineering application.