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Aero Engine Ceramics—the Vision, the Reality and the Progress

Figure 1 shows ceramic exhaust nozzle petals and their application on a military engine. The ceramic material used is one of the most advanced materials in the world today. It consists of two-dimensional woven and laminated silicon carbide fibres in a chemical vapour infiltrated silicon carbide matrix. In this application this material will eventually be expected to perform at 1200°C, 300°C hotter than today's cooled metal petals and last four times longer. To date the petals have been successfully interchanged with the existing metal petals, which run in a cooled environment on this engine. The Rolls–Royce target is to develop ceramics which operate up to 1400°C, which is 500°C hotter. Before ceramic nozzle petals can enter service there are many difficult issues that must be addressed. One of these is the present long and very costly production route. This application illustrates the reality of applying ceramics to aero engines. It is one of the easier applications! Why is it worth persevering with this difficult technology? The industry is a very competitive one. Ceramic materials offer the potential for significant performance improvements. They may in time create the competitive edge which means the difference between a growing or shrinking market share.