Development of nickel-iron aluminides
The objective of this program is to design and characterize new, improved high-temperature materials based on boron-doped Ni/sub 3/Al + Fe for structural use in advanced coal conversion systems. Chromium is a key alloying element that improves resistance to oxidation, corrosion, and environmental embrittlement in nickel-iron aluminides by promoting the rapid formation of protective oxide scales. Alloying with 3 to 7 at.% Cr dramatically reduces dynamic embrittlement in oxidizing environments at 400 to 800/sup 0/C. Chromium and iron additions increase the stability of the ordered body-centered cubic phase that is brittle at room temperature and weak at elevated temperatures. The formation of the B2 phase in the aluminides leads to lowering the tensile ductility at lower temperatures and the strength at higher temperatures. This study of alloying effects has led to the development of an aluminide with the composition: Ni-18.5 +- 0.5% Al-10.5 +- 0.5% Fe-7 +- 0.5% Cr-0.2% Zr-0.7% Mo-0.1% B( at.%). Corrosion studies have demonstrated that chromium additions of 7 at.% or greater were very effective in minimizing the sulfur attack on nickel-iron aluminides. Sulfidation protection can also be afforded by oxide films produced in air; however, the oxidation temperature should be 1000 to 1050/sup 0/C, and the alloys must contain 3 at.% or greater chromium. The nickel-iron aluminides developed were weldable using both the electron beam and gas tungsten arc processes. 19 refs., 24 figs., 9 tabs.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6091428
- Report Number(s):
- ORNL-6412; ON: DE88001491
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360100* -- Metals & Alloys
ALLOYS
ALUMINIUM COMPOUNDS
ARC WELDING
BORON
CHEMICAL COMPOSITION
CHROMIUM
CHROMIUM ALLOYS
COBALT ALLOYS
CORROSION RESISTANCE
CORROSION RESISTANT ALLOYS
CREEP
DUCTILITY
ELECTRON BEAM WELDING
ELEMENTS
ELONGATION
EMBRITTLEMENT
FABRICATION
GAS TUNGSTEN-ARC WELDING
HAFNIUM
HASTELLOY X
HASTELLOYS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INTERMETALLIC COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
IRON COMPOUNDS
JOINING
MATERIALS
MECHANICAL PROPERTIES
METALS
MOLYBDENUM
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL COMPOUNDS
SEMIMETALS
STAINLESS STEELS
STEELS
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TUNGSTEN ALLOYS
WELDING
YIELD STRENGTH
ZIRCONIUM