Wen Zhifeng, Li Qi, Liu Fengmei, Dong Yong, Zhang Yupeng, Hu Wei, Li Likun, Gao Haitao
School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China.
China-Ukraine Institute of Welding, Guangdong Academy of Sciences, Guangdong Provincial Key Laboratory of Advanced Welding Technology, Guangzhou 510650, China.
Materials (Basel). 2023 Mar 23;16(7):2554. doi: 10.3390/ma16072554.
As a technology for micro-deformed solid-phase connection, transient liquid phase (TLP) diffusion bonding plays a key role in the manufacture of heating components of aero engines. However, the harmful brittle phase and high hardness limit the application of TLP diffusion bonding in nickel-based superalloys. In this paper, a new strategy in which a low-boron and high-titanium interlayer can restrain the brittle phase and reduce the hardness of the TLP-diffusion-bonded joint is proposed. With this strategy, the NiAl joint can achieve a high strength of 860.84 ± 26.9 MPa under conditions of 1250 °C, 6 h and 5 MPa. The microhardness results show that the average microhardness of the joint area is 420.33 ± 3.15 HV and is only 4.3% higher than that of the NiAl base material, which proves that this strategy can effectively inhibit the formation of the harmful brittle phase in the joint area. The results of EBSD show that 7.7% of the twin boundaries exist in the isothermal solidification zone, and only small amounts of secondary precipitates are observed at the grain boundaries in the joint, which indicates that twin boundaries may play a dominant role in crack initiation. This study provides a feasible avenue to suppress the brittle phase in TLP-diffusion-bonded joints.
作为一种微变形固相连接技术，瞬间液相（TLP）扩散连接在航空发动机加热部件的制造中起着关键作用。然而，有害的脆性相和高硬度限制了TLP扩散连接在镍基高温合金中的应用。本文提出了一种新策略，即采用低硼高钛中间层来抑制脆性相并降低TLP扩散连接接头的硬度。采用该策略，在1250℃、6h和5MPa条件下，NiAl接头可实现860.84±26.9MPa的高强度。显微硬度结果表明，接头区域的平均显微硬度为420.33±3.15HV，仅比NiAl母材高4.3%，这证明该策略可有效抑制接头区域有害脆性相的形成。电子背散射衍射（EBSD）结果表明，等温凝固区存在7.7%的孪晶界，接头中晶界处仅观察到少量二次析出相，这表明孪晶界可能在裂纹萌生中起主导作用。本研究为抑制TLP扩散连接接头中的脆性相提供了一条可行的途径。
