Introducing New Materials into Aero Engines-Risks and Rewards, A User's Perspective

Abstract

Developing and certifying new aircraft engines is expensive. Once introduced, an engine will have a life measured in decades, and manufacturers and users are reluctant to introduce changes for a number of reasons, not least of which are safety, reliability and cost. Thus the opportunities for new material introduction are few and the consequences of an imperfect decision are high. It is therefore imperative that materials engineers utilize any opportunity to introduce material improvements that are presented. This paper will discuss the risks and necessary actions to achieve successful material insertion and will give examples and attributes of successful and unsuccessful alloy development efforts. IntroductionAero engines require specialty materials that can withstand the demanding environments imposed on the various components and sections that ultimately provide energy and thrust. In general, aero engines require materials that are lightweight, high strength, damage tolerant, high temperature capable, oxidation and corrosion resistant with robust, repeatable mechanical properties that can be readily manufactured into components that are inspectable to ensure the required level of quality and mechanical capability. These requirements are also bounded by the absolute need for lowest possible cost and greatest possible availability.

Ceramic Matrix Composites for Aero Engine Applications—A Review

“…Until now, the CMCs used for aero-engine applications are limited to aluminosilicate or alumina/mullite CMCs from the oxide-CMCs and SiC/SiC, C/C, and C/SiC from the non-oxide-CMCs. The barriers associated with such limited use of CMCs include high ceramic matrix development costs, risks with scale-up and material capability uncertainty, and risks of ceramic fillers and reinforcements robustness, which leads to high costs for material qualification and material availability [181]. Furthermore, the aerospace industry has set strict material requirements and specifications that include the material's mechanical, physical, thermal, and chemical properties, which advocate that for a material to be used, it needs to have high strength, stiffness, fatigue durability, damage tolerance, low density, high thermal stability, high corrosion, and oxide resistance [182].…”

Oxidation Resistance of Additively Manufactured Inconel 718 for Gas Turbine Applications

“…an aircraft engine) or driving a generator (e.g. The mechanical properties of materials used in aero engines need be such that they withstand very demanding environments while under stress [10]. These materials need to be lightweight, of high strength, damage and high temperature tolerant, and also oxidation and corrosion resistant.…”

“…Titanium superalloys are the second major constituent, representing a quarter of the total weight in aircraft engines, followed by iron-based superalloys which represent 16% weight. [10] In the gas turbine, the combustion and turbine parts are continuously in contact with hot fluid. The higher the firing temperature in the combustion process, the higher the turbine efficiency and the energy output.…”

“…Sections of a CF6 high bypass turbofan engine used in the Boeing 787 and its material distribution[10] After World War II, the future of jet engines became very promising due to their great thrust, compact size and the simplicity in their overall layout.Dr. Hans von Ohain, a German physicist, and Sir Frank Whittle are recognized as the co-inventors of the jet engine.…”

“…The later stages of the compressors have a temperature range that only allows titanium alloys, with low-density and acceptable strength and other temperature properties. Similar demands in alloys are required for compressor blades and vanes, where traditionally no cooling schemes are usedto mitigate the increasing temperatures on the later stages of the compressor[10].…”