Microstructural aspects in Inconel X-750

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5574787

Sinha, A K

The precipitation hardened Inconel X-750 is extensively used in both PWR and BWR as bolts, pins, spring components, etc., mainly because of this alloy's excellent high temperature strength and good oxidation and corrosion resistance. However, this alloy has experienced some intergranular stress corrosion cracking. It has been reported that the SCC resistance of Inconel X-750 can be improved by direct aging in the precipitation regime of 704 to 871/sup 0/C. Therefore, the microstructural changes that occur when Inconel X-750 is thermally treated between 704/sup 0/C and 871/sup 0/C for up to 200 hours following a 2-hour solution anneal at 1075/sup 0/C, or 1149/sup 0/C, or 1204/sup 0/C has been studied. Optical, transmission electron, and scanning and Auger electron microscopy were used in order to establish the most appropriate aging sequence for this alloy which will produce a suitable precipitation morphology and distribution of secondary carbides and intermetallics. The precipitation morphology and analysis of ..gamma..' (L1/sub 2/), secondary M/sub 23/C/sub 6/ and primary MC carbide phases for each heat treatment cycle were studied using TEM techniques. The coarsening kinetics of the ..gamma..' particle growth obeyed the time-law prediction of Lipshitz-Slazor-Wagner theory of diffusion controlled growth at all aging temperatures. The ..gamma..' precipitate lost coherency by the nucleation of dislocation loops within the precipitate, the interaction of dislocation at the interface and attraction of matrix dislocations to the particle/matrix interface.

• Research Organization: Minnesota Univ., Minneapolis (USA)
• OSTI ID: 5574787
• Country of Publication: United States
• Language: English

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