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Sep 1, 1983 - Columbus,Ohio 43201. 13. Type of Report and Period ...... Cowles, B. A., Sims, D. L., and Warren, J. R., "Evaluation of the. Cyclic Behavior of ...
NASA CR-168260

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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_