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NASA CR-168260
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National Aeronautics and Space Administration
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CREEP FATIGUE OF LOW-COBALT SUPERALLOYS: WASPALOY, PM U 700, AND WROUGHT U 700 September
1, 1983
by B. N. Leis, R. Rungta, and A. T. Hopper
BATTELLE-COLUMBUS
LABORATORIES
Prepared for
National Aeronautics and Space Administration
l[l Zll_IIl A.=vIIIV F, P "i q _NGLEYRESEARCH CE_JTER _--
LEWIS RESEARCH CENTER
LIBRARY,NASA
Contract No. NAS3-23289
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1. Report No.
2. Government Accession No.
3. Recipient's Catalog No.
NASACR-168260 4. Title and Subtitle
5. Report Date
Creep Fatigue of Low-Cobalt and Wrought U 700
Superalloys:
Waspalloy,
PM U 700,
7. Author(s)
Brian
September I, 1983 6. Performing Organization Code 8. Performing Organization Report No.
N. Leis,
Ravi Rungta, and Allen
T. Hopper 10. Work Unit No,
G-8030-0001
9. Performing Organization Name and Address
Battelle
ColumbusLaboratories
11. Contract or Grant No.
505 King Avenue Columbus,Ohio 43201 13. Type of Report and Period Covered
12. Sponsoring AgencyNameandAddress NASA Lewis Research Center 21000 BrookparkRd Cleveland, Ohio 44135 15. Supplementary
Final 14.Sponsoring AgencyCode
Notes
16. Abstract
The work was performed in support of the NASA COSAM program. The objective of this study was to evaluate the influenceof cobalt content on the high temperature creep fatigue crack initiation resistance of three primary alloys. These were Waspalloy, Powder U 700, and Cast U 700, with cobalt contents ranging from 0 up to 17 percent. Waspalloy was studied at 538 C whereas the U 700 was studied at 760 C. Constraintsof the program required investigationat a single strain range using diametral strain control. The approachwas phenomenological,using standard low cycle fatigue tests i.nvolving continuous cycling tension hold cycling, compression hold cycling, and symmetric hold cycling. Cycling in the absence of or between holds was done at 0.5 Hz, whereas holds when introduced lasted l minute. The plan was to allocate two specimens to the continuous cycling, and one specimen to each of the hold time conditions. Data was taken to document the nature of the cracking process, the deformation response, and the resistance to cyclic loading to the formationof small cracks and to specimen separation. The influenceof cobalt content on creep fatigue resistancewas not judged to be very significant based on the results generated. However, this situationmay be a consequence of the type of experiments performedmeaning the conclusionsof the study should not be considered as generally valid. Specific conclusionswere that the hold time history dependence of the resistance is as significant as the influenceof cobalt content and increasedcobalt content does not produce increasedcreep-fatigue resistance on a one-to-one basis.
17. Key Words (Sugg_ted
by Author(s))
18. Distribution
Statement
cobalt, high temperaturecreep fatigue crack initiation,Waspalloy, Powder U 700, Cast U 700, deformation response
19. Security Classif. (of this reI:_rt)
20. Security Classif. (of this page)
21. No. of Pages
55 • For sale by the NationalTechnical InformationService,Springfield.Virginia 22161 _--
NASA-C-168(Rev.10-75)
22. Price"
EXECUTIVESUMMARY
The objective cobalt
content
resistance
of this
on the high tempertature
of three
primary
alloys.
of the NASACOSAMprogram. tures
study was to evaluate
investigated
creep fatigue
the influence crack initiation
The work was performed in support
Materials,
cobalt
contents,
and test
tempera-
%
Test Temperature,
were as follows:
Alloy
Cobalt Compositions,
Waspaloy
13.5, 9.0,
Wrought U 700
17.0,
12.8,
8.6,
4.3,
0
760
Powder MET. U 700
17.0,
12.8,
8.6,
4.3,
0
760
Constraints
of the program required
range using diametral using standard
of
strain
low cycle
4.5,
538
investigation
control.
fatigue
0
at a single
strain
The approach was phenomenological,
tests
involving
cycling
tension
hold cycling,
Cycling
in the absence of or between holds was done at 0.5 Hz, whereas
holds when introduced
compression hold cycling,
continuous
lasted
1 minute.
and symmetric hold cycling.
The plan was to allocate
two
specimens to each of the hold time conditions. Data was taken to document the nature of the cracking the deformation were reported
response, for
and the resistance
each of the following
Number of cycles
to first
2.
NO• Number of cycles
to 10 percent stress
loading.
indication
of failure
3.
Number of cycles
to 5 percent
4.
range, N5. Number of cycles
to 50 percent
5.
range, N50. Number of cycles
to failure
i
by cracking,
drop in stabilized
to peak compressive
the specimen, Nf.
Results
parameters:
i.
of peak tensile
to cyclic
process,
stress,
drop in stabilized
ratio Ni. load
drop in stabilized
load
by complete separation
of
C
6.
Total
strain
range at Nf/2.
7.
Elastic
8.
Inelastic
9.
Creep strains
strain
range at Nf/2.
strain
range at Nf/2.
per cycle
10.
Stress range at Nf/2.
11.
Amount of stress
12.
Mean stress
The influence
at Nf/2.
relaxation
per cycle at Nf/2.
at Nf/2.
of cobalt
content
not judged to be very significant summarized in the following
on creep fatigue
based on the results
resistance
generated,
and
figures.
Col:x]It
"I"_!
SymOolC_mnt
Coc_itk)n TH
0 CoOQJt
was
0%
TH-Te .... hold CH - Compression hold
SHCM
TeSlf
SH " Syr*nmetr_
hold
Symbol¢onmmT Co_