Surface enrichment and grain boundary segregation of niobium in Inconel 718 single- and poly-crystals

Journal Article · Mon Aug 01 00:00:00 EDT 1994 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(94)90294-1· OSTI ID:7277922

Pang, X J; Dwyer, D J ^[1]; Gao, M; Valerio, P; Wei, R P ^[2]

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1. Univ. of Maine, Orono, ME (United States). Lab. for Surface Science and Technology
2. Lehigh Univ., Bethlehem, PA (United States). Dept. of Mechanical Engineering and Mechanics

As a part of a program to study the environmental enhancement of creep crack growth in nickel base alloys, an Inconel 718 (IN718) alloy (100) single crystal was prepared for a planned investigation of the kinetics and mechanisms of reactions with oxygen. During the initial surface characterizations, a strong enrichment of niobium (Nb) within the surface region was observed after heating the surface in ultrahigh vacuum (UHV). The extent of enrichment was wholly unexpected on the basis of existing models and experimental observations. The surface compositions of multiphase systems are also known to be strongly temperature dependent. This temperature dependence will certainly affect chemisorption, dissociation and subsequent reaction of gaseous molecules on freshly exposed (crack) surfaces. In this study, therefore, surface composition of IN718 single-crystal samples as a function of temperature was determined in ultra-high vacuum (UHV). This enrichment suggested that Nb may segregate at grain boundaries of polycrystals during heat treatment, and may play an important role in the subsequent environmental enhancement of crack growth. The segregation of niobium at grain boundaries, therefore, was included as a part of the study.

• OSTI ID: 7277922
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 31:3; ISSN 0956-716X; ISSN SCRMEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOY-NI53CR19FE19NB5MO3
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
CRACK PROPAGATION
CREEP
DATA
ELEMENTS
EXPERIMENTAL DATA
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INCONEL 718
INCONEL ALLOYS
INFORMATION
IRON ALLOYS
MATERIALS
MECHANICAL PROPERTIES
METALS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM
NIOBIUM A
NUMERICAL DATA
SEGREGATION
TRANSITION ELEMENTS