Influence of cobalt, tantalum, and tungsten on the high temperature mechanical properties of single crystal nickel base superalloys

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:6176997

Nathal, M V

Cobalt, tantalum, and tungsten concentrations were varied according to a matrix of compositions based on the single crystal version of MAR-M247. Tensile and creep rupture tests on <001> oriented single crystals were performed at 1000/sup 0/C. The microstructures were examined using optical and electron microscopy, differential thermal analysis, x-ray diffraction, and phase extraction. For alloys with the baseline refractory metal level of 3% Ta and 10% W, decreases in Co level from 10 to 0% resulted in increased tensile strength and creep life at high stresses but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta plus W totals, strength was independent of Co level. The increases in tensile strength with increases in refractory metal content were related to the increases in ..gamma..' volume fraction and solid solution hardening. Increases in strength as Co level decreased were considered to be the result of coherency strain hardening from the increased lattice mismatch.

• OSTI ID: 6176997
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101 -- Metals &amp; Alloys-- Preparation &amp; Fabrication
360103* -- Metals &amp; Alloys-- Mechanical Properties
ALLOYS
COBALT ALLOYS
CRYSTALS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
MATERIALS
MECHANICAL PROPERTIES
MONOCRYSTALS
NICKEL ALLOYS
NICKEL BASE ALLOYS
TANTALUM ALLOYS
TUNGSTEN ALLOYS