Micrograph 729 and full record

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 800Â°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

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