Effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys

Conference · Sat Mar 01 04:00:00 EST 1986

OSTI ID:7007075

Barrett, C A

Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m(PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. The cobalt levels ranged from 0 wt % to the nominal commercial content in each alloy. The alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200 and 100 hr respectively. An oxidation attack parameter, Ka derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr/sub 2/O/sub 3//chromite spinel or Al/sub 2/O/sub 3//aluminate spinel depending on the CR/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al/sub 2/O/sub 3//aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr alloys while a 5.0 wt % Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides perhaps due to the formation of the omni-present trirutile Ni(Ta,Cb,Mo,W)2O6. Both scales break down as increasing amounts of NiO is formed.

• Research Organization: National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
• OSTI ID: 7007075
• Report Number(s): N-86-31702; NASA-TM-87297; E-2952; NAS-1.15:87297; CONF-860340-13
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOY-IN-738
ALLOYS
ALUMINIUM ALLOYS
BORON ADDITIONS
BORON ALLOYS
CARBON ADDITIONS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHROMIUM ALLOYS
COBALT
COBALT ALLOYS
COHERENT SCATTERING
DIFFRACTION
ELEMENTS
ENGINES
GAS TURBINE ENGINES
HEAT ENGINES
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INTERNAL COMBUSTION ENGINES
MATERIALS
METALS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIMONIC 115
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
SCATTERING
TANTALUM ALLOYS
TITANIUM ALLOYS
TRANSITION ELEMENTS
TUNGSTEN ALLOYS
VARIATIONS
WASPALOY
X-RAY DIFFRACTION
ZIRCONIUM ADDITIONS
ZIRCONIUM ALLOYS