Improving the weldability and service performance of nickel- and iron-based superalloys by grain boundary engineering

Journal Article · Tue Dec 01 04:00:00 EST 1998 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-998-0214-y· OSTI ID:316039

Lehockey, E M; Palumbo, G; Lin, P ^[1]

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1. Ontario Hydro Technologies, Toronto, Ontario (Canada)

The principal limitation of today`s Ni- and Fe-based superalloys continues to be their susceptibility to intergranular degradation arising from creep, hot corrosion, and fatigue. Many precipitation-strengthened superalloys are also difficult to weld, owing to the formation of heat-affected zone (HAZ) cracks during postweld heat treatments (PWHTs). The present work highlights significant improvements in high-temperature intergranular degradation susceptibility and weldability arising from increasing the relative proportion of crystallographically special low-{Sigma} CSL grain boundaries in the microstructure. Susceptibility of intergranular degradation phenomena is reduced by between 30 and 90 pct and is accompanied by decreases in the extent and length of PWHT cracking of up to 50-fold, with virtually no compromise in mechanical (tensile) properties upon which the functionality of these specialty materials depends. Collectively, the data presented suggest that engineering the crystallographic structure of grain boundaries offers the possibility to extend superalloy lifetimes and reliability, while minimizing the need for specialized welding techniques which can negatively impact manufacturing costs and throughput.

• Sponsoring Organization: USDOE
• OSTI ID: 316039
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 12 Vol. 29; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRACKS
GRAIN BOUNDARIES
HEAT AFFECTED ZONE
HEAT RESISTING ALLOYS
HEAT TREATMENTS
RELIABILITY
SERVICE LIFE
WELDABILITY