Development of Brazing Technology for Ceramic Turbocharger Rotors

In addition to the performances of the ceramic materials themselves, development of joining technologies of ceramic wheels with metal shafts is very important for putting ceramic rotors into practical use. Though silicon nitride has excellent strength at high temperature and is best suited as the ceramic wheel material, the corresponding bonding technology for its use in turbo-chargers has not been totally successful to this point in time.

This report presents the brazing technology of the ceramic rotors, which were successfully developed and first introduced into the market in 1985. Currently there are two types of ceramic rotors(Fig. 1) being manufactured using the same brazing technology as described herein. The major points are as follows:

1. 1.
   A chemical bond has been developed as an approach for achieving the rotor's practical use.
2. 2.
   Application of active brazing needed no standard metallizing process for bonding silicon nitride to the metal shaft.
3. 3.
   A laminated Multi Buffer Layer was developed through FEM analysis and the corresponding bonding tests.
4. 4.
   Various evaluations proved that the brazing technology developed met all specifications required for the ceramic rotors.