Silicon nitride is one of the excellent candidates for the high temperature structural component. Then silicon nitride was joined to itself with Cr-N, Fe-V and Al-SiO2 system by HIP (hot-isostatic-pressing) process. The structure of joining interface was analyzed by the SEM and EPMA, and the bond strength of the joint was measured by the three-point bending test. The results obtained are as follows: Silicon nitride encapsulated into the stainless steel pipe after coating Cy-N was bonded by HIP'ing at 1, 473K. The obvious boundary in the joining interfacial layer was not observed. In case of the capsule-free HIP'ing with N2 gas, these silicon nitride specimens were bonded at 2, 123K. Using Fe-V, the high bending strength of joint was also obtained by the capsule-free HIP'ing with N2 gas like the case of Cr-N joining. The joint with Al-SiO2 system by the capsule-free HIP'ing with N2 gas had the same strength at the elevated temperature such as 873K comparing to the room temperature, because the compound concerned with Si-Al-O-N was produced at the joining interface.
