Abstract—Gas turbine engines have been widely used in electricity power generation in industry and aviation. The performance of gas turbine engines is limited by the temperature and strength capabilities of the materials used in the engine. Silicon nitride based ceramics have been expected to be candidates for gas turbine engine components due to their promising mechanical properties at high temperatures. On this basis, over the last 40 years large number of programs in the world has been working to produce ceramic components for gas turbines with the goals of increasing efficiency and lowering emissions. But there are some difficulties that limit the use of structural ceramics based silicon nitride in gas turbine components. Creep performance is one of those problems and creep performance of a material is one of the major factors for determining its high temperature application. In this study creep behavior of SiAlON ceramics, which are solid solutions of silicon nitride ceramics, were investigated at temperatures from 1100 ˚C to 1400 ˚C under stresses from 50 to 150 MPa in air. Index Terms—Advanced ceramics, creep, gas turbine engines, high temperature failures, SiAlON. I. INTRODUCTION Gas turbine engines have been widely used in power generation in industrial sector and aviation. The development of gas turbine engines and the increase in fuel efficiency depends on the development of high temperature materials with the intended performance. Silicon nitride based ceramics have been expected to be candidates for gas turbine engine components due to their promising mechanical properties at high temperatures. On this basis, over the last 40 years large number of programs has been working to produce ceramic components for gas turbines to increase fuel efficiency and to lower emissions. But there are some difficulties that limit the use of structural ceramics based silicon nitride in gas turbine components. Creep performance is one of those problems and creep performance of a material is one of the major factors for determining its high temperature application [1]-[4]. Service deterioration in gas turbine engine components is inevitable. Therefore, gas turbine components have various life-limiting failure types. Life-limiting failure types are determined by conditions of a component operated in service. Most common life-limiting failure types of gas turbine hot section parts are creep, oxidation, low and high cycle fatigue, and corrosion. For the best efficiency, gas turbines must operate to highest possible temperatures. But the performance of gas turbine engines is limited by the temperature and Manuscript received July 8, 2014; revised November 20, 2014. Alper Uludag and Dilek Turan are with Faculty of Aeronautics and Astronautics, Anadolu University, Eskişehir, 26470, Turkey (e-mail: alperuludag@anadolu.edu.tr, dtetik@anadolu.edu.tr). strength capabilities of the materials used in the engine. The endurance of the gas turbine engine components to high temperature conditions mainly depends on the creep resistance of materials. Creep may be defined as a time-dependent deformation at elevated temperature and constant stress, following then, that a failure from such a condition is referred to as a creep failure. The temperature at which creep begins depends on the material composition. The end of useful service life of the high-temperature components are usually failed by a creep [1], [5]. Among components of gas turbine engine turbine blades and sometimes the high pressure stages of compressor blades are subject to creep as a consequence of operating at high temperatures and stresses, and creep is eventually the life-limiting process for all blades so exposed. Blades may elongate and contact the non-rotating components due to creep, and dismantling of the engine for repair and replacement of both blades and non-rotating components would be necessary [6]. Fig. 1 shows a photo of aircraft engine turbine blade on which creep damage observed during routine inspection. Fig. 1. Creep damage on a blade observed during routine inspection [6]. The high temperature mechanical properties, especially creep, of silicon nitride based ceramics depend on the type and amounts of sintering additives used in the processing of these materials [4], [7]. During sintering, additives such as yttrium or rare earth oxides (with alumina) react with surface oxides on the silicon nitride particles and some of the nitride itself to form a M-Si-(Al)-O-N liquid (M=Y or Ln) which on cooling remains as a glass, located both at grain triple points and as intergranular films [3], [8]. The presence of these amorphous grain boundary phases in the grain boundaries and triple junctions results in beneficial effects to the mechanical properties at ambient temperatures. Higher strength and toughness are obtained as a consequence of the acicular grain growth and the reduction of the inherent flaw size. But at Alper Uludag and Dilek Turan SiAlON Ceramics for the High Temperature Applications: High Temperature Creep Behavior International Journal of Materials, Mechanics and Manufacturing, Vol. 3, No. 2, May 2015 105 DOI: 10.7763/IJMMM.2015.V3.176