Microstructure and mechanical properties of contact-reactive brazed TZM/Nb-Zr joints with Ni interlayer

摘要

Contact-reactive brazing was successfully used to join TZM and Nb-Zr alloys using a Ni interlayer, and sound metallurgical joints were obtained. As the Ni interlayer reacted eutectically with Zr element from the Nb-Zr alloy, a liquid phase appeared at the interface and then solidified, forming Ni10Zr7 and NiZr compounds. Meanwhile, rich-Mo and rich-Nb phases formed adjacent to TZM substrate and a diffusion-induced reaction zone existed in the Nb-Zr alloy as a consequence of the interfacial reactions between substrates and the liquid phase. As the brazing temperature, holding time and interlayer thickness increased, the total width of brazing seam and diffusion-induced reaction zone and the number of Ni-Zr compounds increased continuously. The maximum shear strength of the joint was 345 MPa obtained at 1200 degrees C for 30 min with 120 mu m thick Ni interlayer. The relationship among brazing parameters, microstructure and mechanical properties of the contact-reactive brazed joints were established.