High temperature brittle intergranular cracking in high strength nickel alloys undoped and doped with S, Zr, and/or B—II. Solute segregation analysis

In order to clarify the mechanism of high temperature brittle intergranular cracking in high strength nickel alloys, solute segregation at grain boundaries and on high temperature fracture surfaces has been examined by scanning Auger microscopy. Intergranular S segregation producing global embrittli...

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Bibliographic Details
Published in:Acta metallurgica et materialia 1993-02, Vol.41 (2), p.527-537
Main Authors: Kameda, J., Bevolo, A.J.
Format: Article
Language:English
Subjects:
360103 - Metals & Alloys- Mechanical Properties
ALLOYS
Applied sciences
BORON ADDITIONS
BORON ALLOYS
BRITTLENESS
CRACK PROPAGATION
Exact sciences and technology
Fractures
GRAIN BOUNDARIES
MATERIALS SCIENCE
MECHANICAL PROPERTIES
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Metals. Metallurgy
MICROSCOPY
MICROSTRUCTURE
NICKEL ALLOYS
NICKEL BASE ALLOYS
STRESS INTENSITY FACTORS
SULFUR ADDITIONS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TITANIUM ADDITIONS
TITANIUM ALLOYS
ZIRCONIUM ADDITIONS
ZIRCONIUM ALLOYS
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Summary:In order to clarify the mechanism of high temperature brittle intergranular cracking in high strength nickel alloys, solute segregation at grain boundaries and on high temperature fracture surfaces has been examined by scanning Auger microscopy. Intergranular S segregation producing global embrittling effects was found to increase in the following order: alloys with low S or high S and Zr, high S and B, and high S. The grain boundaries extensively contained Ti or Zr rich sulfides in the S-doped alloys and B segregation inducing intergranular toughening in the alloy with high S and B. The alloys with low S, and high S and B showed more strongly S segregation on high temperature fracture surfaces, which was much greater compared with at grain boundaries, than with high S, and high S and Zr. The local stress intensification did not produce a remarkable S enrichment at grain boundaries except near sulfides. It is proposed that S fluxes from crack surfaces and stressed sulfides to the crack tip induce local embrittlement. The composition and temperature effects on the brittle cracking behavior are discussed in terms of the global and local embrittling effects.
ISSN:0956-7151
1873-2879
DOI:10.1016/0956-7151(93)90082-4