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Full Record for Micrograph 726

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Micrograph no
726
Brief description
Ni-Superalloy, heat treated above gamma-prime solvus
Keywords
heat treatment Link to MATTER Glossary entry for heat treatment, nickel
Categories
Metal or alloy
System
Ni-X
Composition
Ni, Cr 14.4-15.2, Co 13-18, Mo 3.5-4.5, Al 3.0-3.3, Ti 4.2-4.8, Ta 2.5, Zr 0.05-0.07, C 0.05, B 0.01-0.03 (wt%) (Ni-Superalloy)
Standard codes
Reaction
Processing
Heat treated at 1200ºC for one hour, forced air cool.
Applications
Discs are used for high pressure and intermediate pressure turbine discs in Trent 800/900 series gas turbine engines.
Sample preparation
Ground to 4000 Grade SiC paper and then polished at 6 mm 3 minutes, 1 mm 5 minutes, Colloidal silica 10 minutes. Etched using a ‘Nimonic’ etch which preferentially attacks g'.
Technique
Scanning electron microscopy (SEM) in backscattered electron imaging (BEI) mode
Length bar
10 μm
Further information
Micrograph shows a microstructure now devoid of g' as at this temperature it has become fully dissolved into the matrix. This results in grain growth, partly due to the solution of g' into the g matrix and also because the main mechanism for preventing grain growth, namely the primary g' is no longer present. Carbide phases still exist and act in places to inhibit grain boundary motion and therefore grain growth.

View schematic diagram of g' microstructure
Contributor
R J Mitchell
Organisation
Rolls-Royce University Technology Centre, Department of Materials Science and Metallurgy, University of Cambridge
Date
05/03/03
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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