Historical Review of Addressing the Challenges of Use of Ceramic Components in Gas Turbine Engines

Since the invention of the gas turbine engine, engineers have continuously strived to achieve higher operating temperature and improved thermal efficiency. Ceramic-based materials were considered in the 1940s and 1950s, but did not have adequate properties to survive the thermal shock and high temperature conditions. By the end of the 1960s, new materials were developed in the silicon nitride and silicon carbide families that appeared to have potential. Substantial efforts have subsequently been conducted worldwide. These efforts have identified and sought solutions for key challenges: improvement in properties of candidate materials, establishing a design and life prediction methodology, generating a material database, developing cost-effective fabrication of turbine components, dimensional and non-destructive inspection, and validation of the materials and designs in rig and engine testing. Enormous technical progress has been made, but ceramic-based turbine components still have not reached bill-of-materials status. There are still problems that must be solved. In addition, metals-based technology has not stood still. Implementation of sophisticated cast-in internal cooling passages, development of directionally solidified and later single crystal superalloy hot section components, improved alloys, and use of ceramic thermal barrier coatings have combined to allow thermal efficiency increases that exceed the 1970s goals that engineers thought could only be achieved with ceramics. As a result of these metal and design advances, the urgency for use of ceramics has decreased. Emphasis of this paper is on review of the key challenges of implementing ceramic components in gas turbine engines, progress towards solving these challenges, some challenges that still need to be resolved, and a brief review of how technology from the turbine developments has been successfully spun off to important products.