A 16-blade silicon nitride turbine wheel for use in small turbogenerators. With the recent development of high-performance structural ceramic materials, this ATP project with AlliedSignal asked whether it was possible to develop a process for fabricating ceramic parts inexpensively enough to allow them to be substituted for metal parts, thereby significantly improving equipment performance and reliability. Ceramic substitutes for metal have performed well in certain critical situations. Space flight is one. Ceramic tile coverings on spacecraft form heat shields that protect astronauts re-entering earth atmosphere.
Atmospheric friction heats the tiles to a fiery glow.
But the tiles stay in place and dissipate enough heat for safe re-entry. Metal surfaces would melt under these circumstances, with disastrous results. Cost and Safety Issues Hinder Use Despite such performance advantages, the application of advanced ceramics has been held back by the high cost of fabrication. Whereas metal can be melt-processed or plastically deformed using molding, extruding, stamping or other standard metalworking techniques, many ceramics cannot be processed by these methods. This process is much more limited in the shapes it can achieve than melt-processing or plastic deformation approaches.