What is it about?
Trace Boron additions (in parts per million) to high temperature Co and Ni alloys improve properties like strength and ductility. However, how exactly this improvement comes is still not clear. Boron is easy to detect with neutron in metallic alloys. We therefore attempted to understand the boron addition effect in Co-Re-base alloys using diffraction and other measurement techniques using neutron and synchrotron scattering. Advantage of neutron and high energy synchrotron is that bulk samples can me measured as compared to microscopy. Secondly measurements can be done at very high temperatures (above 1000°C) where the alloys are actually used in gas turbine engines.
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Why is it important?
Co-Re based alloys are being developed by us to increase the temperature capability in gas turbines, which increases efficiency and reduces CO2 emission. Presently used Ni-superalloys cannot be used at these high temperature. Alloy development is a long drawn process and needs a complete understanding of the alloy system as well as tuning properties and improving them. It is the purpose of these study to find if and how Boron addition improve the alloy property and try to understand the functioning mechanism of this improvement.
Perspectives
Co-Re alloys shows promise as they melt at temperatures > 200°C than Ni-superalloys. The properties in superalloys are limited at high temperatures by their melting temperature. However, for use of any alloy in a gas turbines, many properties must be satisfactory as gas turbine engines operate not only at very high temperature, the environment is highly oxidizing and corrosive. Co-Re alloy show both good strength as well as satisfactory corrosion and oxidation resistance. However, much work is still needed before these alloys can be actually used in gas turbines.
Dr Debashis Mukherji
Technische Universitaet Braunschweig
Read the Original
This page is a summary of: Neutron and synchrotron probes in the development of Co–Re-based alloys for next generation gas turbines with an emphasis on the influence of boron additives, Journal of Applied Crystallography, August 2014, International Union of Crystallography,
DOI: 10.1107/s1600576714013624.
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