The mechanical and physical properties and stress corrosion cracking (SCC) behavior in a deaerated water environment at 360°C were determined for a set of alloy 718 (UNS N07718) single-crystal samples in the (100), (110), and (111) orientations. Mechanical and physical properties varied with orientation. Precracked compact-tension SCC samples loaded to 66 MPa√m survived over 700 days of exposure with no SCC growth. Polycrystalline samples of the same heat displayed significant cracking after 70 days of exposure. Results showed single-crystal technology offers a possibility of achieving superior resistance to SCC, along with design flexibility through selection of optimum crystal orientation.

Subject
Costs, Crack growth, Corrosion fatigue, Materials, Intergranular stress corrosion cracking, Microstructure, Moduli, Nickel based alloys, Corrosion testing, Thermal expansion, Alloys, Heat treatment, Stress corrosion cracking
Keywords:
aerospace environments, alloy 718, fatigue, grain morphology, orientation, nickel and nickel alloys, precipitation hardening, single crystals, stress corrosion cracking, turbines
NACE International
1997
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