Which materials should be used for gas turbine engine components
With vast increase in the use of energy resources in the modern era, the demand of energy in the modern time, the demand of energy extraction from different resources has specified in recent years. So, wide efforts are made in the technological development of turbo machines that means extraction of energy is energized fluids. This led to power boost by better performing engines in aviation industry. The structural conformability needs relative to the functional needs have also increased with the introduction of nickel based super alloys. Thus there is a need to study the material behaviour and its applications while choosing the best feasible material for an application.
The objective of turbine in an air breathing engine is to extract energy from energized fluid like hot air. A turbine is designed on the basis of principles of aerodynamics and propulsion and also the physical availability and function of turbine is highly based on the material chosen for its production. Often gas turbines are made with high temperature resistant materials for instance, Inconel alloys. These nickel based alloys are precipitation hardened due to which these materials keep their strength even at high temperatures. Additionally many nickel alloys are resistant to creep and corrosion at high thermal conditions.
Usually the turbine blades for high performance gas turbines are made to prevent failure of material during large high temperature operation. The permitted stress level will strongly base on the service temperature and may be referred as a failure limit. It is not uncommon to observe materials compared on the results of measurement of stress to fine failure or cracking.
Wide studies are made to find materials for turbines maintaining strength to weight ratio in due consideration. The main advantage of using nickel alloys in turbines is their higher strength at high temperatures that go up to 1200oC that is what found in modern high performance turbines where the gas temperature is in hundreds of oC.
Nickel based super alloys like Inconel 718 attain high strength and good mechanical properties and creep resistance at high temperature. They offer good surface stability and corrosion and oxidation resistance. Usually they have an austenitic face-centered cubic crystal structure. The use of nickel alloys is majorly in aerospace industry. Nickel based super alloys have outstanding high temperature strength and good corrosion resistance in addition to oxidation resistance at service temperatures up to 1200oF for critical rotating applications and up to 1600oF or 870oC for other less demanding applications.
Nickel base super alloys Inconel bars possess high temperature strength from their solid solution strengthening element like molybdenum, cobalt and chromium and age hardening element like aluminium and titanium. Their strength and stability are higher than stainless steels. They are used in gas turbine engine components that need significant strength and corrosion resistance at high service temperature. Current and potential applications of nickel based super alloys in gas turbines include compressor, rotor discs, spaces, casting and other engine components.