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DoITPoMS Micrograph Library Full Record for Micrograph 729
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Full Record for Micrograph 729

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Micrograph no
729
Brief description
Ni-Superalloy, exposed microstructure
Keywords
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
Exposed at 800°C for 2 500 hours.
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 <span class="symbol">m</span>m 3 minutes, 1 <span class="symbol">m</span>m 5 minutes, Colloidal silica 10 minutes.
Technique
Scanning electron microscopy (SEM) in backscattered electron imaging (BEI) mode
Length bar
10 μm
Further information
Following exposure at temperature typical of that found in the modern gas turbine engine, there exist two white phases, one with intergranular distribution and the other smaller particles, apparently randomly distributed. The larger semi-continuous intergranular phase is likely to be either the M23C6 carbide or the deleterious TCP phase, s. Previous work has concluded that this phase is indeed s, which is detrimental to mechanical strength, in particular creep life by embrittlement of the grain boundaries.

Region 1: g matrix
Region 2: g' particle
Region 3: Topologically close packed phase, s



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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