Transient Liquid Phase Bonding of Ultra High Temperature Ceramics

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An effective joining strategy suitable for ultra high temperature ceramics will have to be developed for their wider application. In the present study, the wetting behavior of molten Ni-Nb alloys that will form during the PTLP bonding using Ni/Nb/Ni interlayer on a HfB2 composite processed with MoSi2 addition was systematically investigated. Additionally, a trial on PTLP bond of HfB2 composite with a Ni/Nb/Ni interlayer was also performed at 1500°C. The contact angles of all Ni-Nb alloys rapidly decreased with time and showed good wetting against HfB2 composite. Among them, the pure Ni droplet totally disappeared around 1400°C during heating. SEM-WDS microstructural analysis on the cross section of the wetting sample revealed that the reaction layer contained multiple intermetallic compounds involving Si, suggesting the reaction with the sintering aid MoSi2. With the 40at% Nb addition, the interfacial reaction at the Ni-Nb alloy/HfB2 composite interface was suppressed. Consequently, it was revealed that a well-bonding interface was achieved when HfB2 composite was bonded using the Ni/Nb/Ni interlayer.