Development of super alloys for use in challenging industries

Superalloys have the properties that make them special among other materials. Often comprising of various elements they act as a complex entity as compared to traditional materials here often a single element dominates.

Considering the power production, the industrialization that mark the transformation of agrarian society to industrial society has brought social and economic development. It introduces technological innovation that is basically focused on large scale metal extraction and energy production. The power production sector faces new challenges with increasing demand of energy generation.

High temperature materials are developed to sustain their properties at high temperature even also retain their integrity with nominal environmental impacts. Gas turbines such as land based or aero based demanded the development of high temperature materials. These materials should possess the following properties:

a.       Potential to withstand stress at a service temperature near their melting temperature

b.      A significant resistance to mechanical degradation over increased period of time

c.       Withstand extreme service conditions

These high temperature materials are designed to meet the demands of energy efficiency and also reduce the emission of greenhouse gases. Superalloys are widely used in the gas turbine sector thus, it is crucial to understand the function of the different components in a gas turbine. Applications of Inconel bars in different components of gas turbines are volume flow machines. Gas turbines are mainly of the following types: land based and aero/jet engine. Major components of gas turbines are:

Compressor: It includes alternating set of rotating airfoils- rotors and stationary airfoils. It sucks air from outside and compresses it into the combustion chamber to increase in pressure ratio as well as enthalpy.

Combustion chamber: Compressed air enters into combustion chamber to get mixed with fuel and ignition occurs.

Turbine: Hot gas enters the turbine and enlarges resulting into extraction of mechanical work needed to drive the compressor that is performed by a shaft that connects the turbine to compressor.

Exhaust: Gases after combustion find their way through the exhaust. Usually gas turbine emissions are carbon dioxide, carbon monoxide and NOx.

There are different types of gas turbines following their use. The design of a turbine is based on its type like land based gas turbine or jet engine. The basic difference is the variation in thermodynamic cycles and turbine entry temperature that is often stable for land based gas turbine due to fewer start-up or shut down cycles as compared to jet engines where the TET can vary during the full flight cycle.

The hot components in the combustor and turbine are critical considering the thermal and mechanical loads and material used. While designing a gas turbine, main focus is on the TET because of steep increase in TET due to direct association of efficiency of gas turbines and TET and pressure ratio that increases the demands of high temperature functional alloys.

There are different super alloys used for applications in the aircraft industry, chemical plants, power production and nuclear power plants. They are fabricated in cast and wrought forms.