High Temperature Materials for Gas Turbines: The Present and Future

Increased operating temperatures and higher efficiency in gas turbines and jet engines can reduce CO2 emission, thus contributing to the prevention of global warming. To achieve this goal, it is essential to improve the properties of high temperature materials. Various Ni-base superalloys are used for high-temperature components, e.g., combustors and high-pressure turbine blades and vanes, that determine the power and efficiency of jet engines and industrial gas turbines. Among them, single crystal (SC) superalloys have the highest temperature capabilities. A third-generation SC alloy has been used practically in Jet engines and fourth-generation SC alloys with platinum group metals additions are being developed for the next generation Jet engines. In land-based gas turbines also SC superalloys have been introduced to increase their inlet gas temperatures, and thus thermal efficiencies. As for new materials, intermetallic alloys, refractory alloys, ceramics, etc., are also being developed as possible alternative materials. Some unique materials have recently been proposed in Japan and being evaluated. INTRODUCTION Advancements in materials for high-temperature structural components, such as high-temperature high-pressure turbine materials, have contributed greatly to improving the temperature capabilities and efficiency of jet engines and industrial gas turbines. This paper summarises the history of advancements in Ni-base superalloys for turbine blades and vanes, outlines the achievements made by various gas-turbine projects, and describes how these materials have been applied. A summary of the status of new materials including refractory alloys, ceramics, etc., and future prospects of these materials are also provided in this paper. Fig.1 Improvement in temperature capability of Ni-base superalloys, with Japanese project targets for new Ni-base SC superalloys. Fig.2 Typical microstructure of the Ni-base SC superalloy with a γ/γ’ coherent structure. Copyright (C) 2003 by GTSJ Manuscript Received on October 14, 2003 Proceedings of the International Gas Turbine Congress 2003 Tokyo November 2-7, 2003