Effect of grain structure on phase transformation events in Inconel 718

Journal Article · Tue Jun 01 00:00:00 EDT 1993 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(93)90482-8· OSTI ID:6402181

Dahotre, N B; McCay, M H; McCay, T D ^[1]; Hubbard, C R; Porter, W D; Cavin, O B ^[2]

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1. The Univ. of Tennessee Space Inst., Tullahoma (United States)
2. Oak Ridge National Lab., TN (United States)

Nickel base superalloys generally obtain their maximum strength from [gamma][prime][Ni[sub 3](Al,Ti)] and [gamma][double prime][Ni[sub 3](Al,Ti,Nb)] age hardening precipitates. During welding the [gamma][prime] precipitation is very rapid and can lead to strain age cracking, which limits weldability. Thus, the weldable superalloys are limited in their Al and Ti content and hence in their ultimate strength. One method of increasing the ultimate strength of a superalloy, while avoiding strain age cracking, is the addition of Nb. This produces Ni[sub 3]Nb([delta]), and when used in conjunction with a limited amount of [gamma][prime], results in an increase in strength without strain age cracking problems. The [gamma][double prime] does not lead to strain age cracking because its transformation kinetics are too slow for formation during ordinary welding practice. This combination of [gamma][prime] and [gamma][double prime] strengthening is incorporated into the Inconel 718 alloys. The research reported herein was undertaken to determine the time-temperature response of Inconel 718 in the as-cast, wrought and wrought-grain-grown states, using differential thermal analysis (DTA). It is essential to locate the temperature regime of each phase transformation event and to study the transformation sequence in order to tailor sound laser welding techniques for Inconel 718. In the present research, a DTA technique was employed to study both the phase transformation events and the phase transformation sequence as a function of the pre-existing condition of the alloy.

• OSTI ID: 6402181
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 28:11; ISSN SCRMEX; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOY-NI53CR19FE19NB5MO3
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
CRYSTAL STRUCTURE
DATA
DIFFERENTIAL THERMAL ANALYSIS
ELEMENTS
EXPERIMENTAL DATA
FABRICATION
GRAIN SIZE
HEAT AFFECTED ZONE
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INCONEL 718
INCONEL ALLOYS
INFORMATION
IRON ALLOYS
JOINING
LASER WELDING
MATERIALS
METALLURGICAL EFFECTS
METALS
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM
NIOBIUM A
NUMERICAL DATA
PHASE TRANSFORMATIONS
SIZE
THERMAL ANALYSIS
TRANSITION ELEMENTS
WELDING
ZONES