The cyclic flow response and crack growth behavior of Waspaloy at room temperature and 650 C under tensile loading and torsional loading was studied, for two conditions of Waspaloy: fine grain, large gamma prime size; coarse grain, small gamma prime size. The fine grain material showed 5 to 10 percent hardening after about 10 percent of life, with sequent softening to failure at both themperature levels. The coarse grain material showed either stable response or monotonic softening to failure. Early crack initiation was observed on planes of maximum shear, with eventual branching to principle planes under torsional loading; cracks were always normal to load axis under tensile loading. Also, crack paths were intergranular at 650 C, mostly transgranular at room temperature

Mirdamadi, M.

Zahiri, F.

Zamrik, S.

English

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NASA USAAVSCOM
Contractor Report 175052 Technical Report 86-C-14
Axial and Torsional Fatigue
Behavior of Waspaloy
(NASA-CS.-175052) A X I A L AND TOESIONAL % N86-25U54
FATIGUE B E H A V I O E OP W A S P A L O Y Final Report
(Pennsylvania State Ui i iv . ) 27 p
HC A02/HP A01 CSC1 11F Unclas
63/26 .
S. 'Zamrik, M. Mirdamadi, and F. Zahiri
The Pennsylvania State University
University Park, Pennsylvania
April 1986
Prepared for
Lewis Research Center
Under Grant NAG 3-264
NASA
National Aeronautics and
Space Administration
https://ntrs.nasa.gov/search.jsp?R=19860015982 2020-03-20T15:26:48+00:00Z
AXIAL AND TURSIONAL FATIGUE BEHAVIOR OF WASPALOY
S. Zamrlk, H. M1rdamad1, and F. Zahlrl
The Pennsylvania State University
Engineering Science and Mechanics Department
University Park, Pennsylvania 16802
INTRODUCTION
This 1s a brief progress report describing the failure modes observed 1n
completed cyclic and hold-time tests conducted on Waspaloy material at 1200 °F.
The Waspaloy material was made of two grain structures, Identified as fine
grain (16 ym) and coarse grain (124 \an). The material has y1 precipitates
of two sizes, one small (50 A) associated with coarse grain and one large
(1000 A) associated with fine grain.
TESTS CONDUCTED
Axial and torslonal cyclic tests were completed on the two types of
grained structure at room temperature and 1200 °F. Also hold-time tests with
90 sec hold 1n the tension side of the axial loading and 1n the counterclock-
wise side of the torslonal loading. The type of wave shape that was applied
Is shown on the Individual macrograph.
LOW-CYCLE FATIGUE TORSIONAL TESTS (COARSE GRAIN)
Figure 1 shows the failure mode of a coarse grained test specimen that
failed under torslonal shear strain range continuous cycling at 1200 °F.
The failure mode shows a transition from shear observed at room temperature
to tensile stage at 1200 °F. To verify this 45° crack mode, duplicate tests
were conducted at two levels of plastic shear strain ranges, one at
Ay = 0.52 percent to failure and the other at Ay = 92 percent to
failure. In both cases, the failure mode was tensile with cracks at 45° mode
as shown 1n figure 2.
Microscopic examination was conducted using replicas and scanning
electron microscopy techniques. Figure 3 shows the general cracking path at
45° with respect to specimen axis. The zigzagging crack path shown 1n
figure 3(b) was studied with an enlargement shown 1n figure 3(b). The
progress of the crack was hindered by grains that saw little plastic
deformation (slip bands activities) and were 1n elastic condition forcing the
crack to deviate. This 1s shown clearly 1n figure 3(c). Furthermore, at
1200 °F, carbides and precipitates were observed on slip bands and on grain
boundaries as shown 1n figure 3(e). Therefore, the tensile failure mode can
be attributed to the embrlttlement of these carbides, assisted by an oxidation
that enhanced the embrlttlement process. Embrittled regions are sensitive to
normal stresses. Figure 3(e) also shows additional large particles. The
chemical composition of these large particles was found, by x-ray energy
spectrum analysis (fig. 4), to be the same material as that of the matrix.
These large particles have also Initiated crack sites that contributed to
mode I cracking. With respect to the slip mode characteristic, It was found
1n all cases to be planar slip that resulted 1n y' particles shearing.
TORSIONAL HOLD-TIME TEST (COARSE GRAIN)
The test at 1200 °F under 90 sec hold time showed similar failure
characteristics (45°) to that observed under continuous cyclic with little
effect of creep as shown 1n figure 5. Replicas taken on the surface after
failure showed extensive grain boundary cracking, planar slip and some
twinning as shown 1n figure 6. Also observed, an extensive oxidation on slip
bands and grain boundaries. In general, the microscopic behavior of the
hold-time test was similar to that under continuous cyclic except for the
amount of oxidation. The crack growth was also at 45° with respect to
specimen axis.
AXIAL HOLD-TIME TEST (COARSE GRAIN)
The axial hold-time test at 1200 °F, showed the failure to be normal to
the loading axis as shown 1n figure 7. Scanning electron microscopy analysis
2
of the gauge surface, figures 8 and 9, showed mixed ode crack Initiation:
grain boundary cracking and slip band cracking. However, the propagation was
mostly transgranular.
Microscopic comparison between the axial and torslonal hold-time failure
characteristics, revealed extensive multiple slip system activity as well as
twinning to have taken place 1n the axial case. Also the axial case showed a
greater grain boundary cracking. The creep effect was observed to be minimum.
TORSION HOLD-TIME TEST (FINE GRAIN)
The torslonal hold-time test of the fine grained specimen resulted 1n a
shear mode failure (longitudinal crack along specimen axis) as shown 1n
figure 10. The microscopic examination of the gauge surface showed extensive
grain boundary oxidation and some grain boundary cracking that resulted 1n
Inter- and transgranular crack growth. Ill defined oxidized wavy slip bands
(fig. 11), were observed rather than the strict planar slip that was seen 1n
other described tests. Replicas taken on the surface are shown 1n figure 12.
Creep showed an effect when compared to data obtained on coarse grain test.
AXIAL HOLD TIME (FINE GRAIN)
The axial hold-time test of the fine grained specimen showed the failure
to be normal to the loading axis as shown 1n figure 13. The microscopic
examination of the gauge surface showed extensive grain boundary cracking,
wavy slip and considerable oxidation. These features are shown 1n figures 14
and 15. The comparison between the torslonal and the axial hold-time tests of
the fine grained specimen showed distinct features:
(1) The axial hold time produced excessive grain boundary cracking.
(2) The torslonal hold time showed excessive oxidation and less grain
boundary cracking.
(3) Creep effect was greater 1n the axial case.
CYCLIC STRESS-STRAIN RESPONSE
Hysteresis loops for both types of axial and torslonal hold time taken at
half lives are Included 1n figures 16 to 20. The variation 1n the shear
stress range for the case of continuous shear strain cycling at room and
1200 °F shows an Interesting behavior for each type of grained specimen on a
cycle basis. The fine grained material exhibited substantial stress
relaxation during the 90 sec hold time under both axial and torslonal loading,
as may be seen 1n figures 16 and 17. The 90 sec strain hold resulted 1n about
25 percent stress relaxation 1n both cases: for torslonal loading, the cyclic
stress amplitude was about 48 ks1, with 12 ks1 relaxation during the hold.
Similarly, under axial loading the cyclic amplitude was 104 ks1, with 22.4 ks1
relaxation after the 90 sec strain hold.
In comparison, the coarse grained material showed very little stress
relaxation after 90 sec strain hold, as may be seen 1n figures 18 and 19.
This 1s partly due to the softer (lower peak cyclic stresses) condition of the
coarse grain material. Also, 1f time dependent deformation occurs
predominantly at grain boundaries, the coarse grain material would afford a
reduced opportunity for time dependent deformation to occur.
The torslonal cyclic stress-strain behavior of both the fine grain and
coarse grain material 1s summarized 1n figure 20. The fine grain material
shows substantial hardening (about 10 percent Increase over Initial cyclic
stress range) up to 10 to 20 percent of life, followed by softening out to
failure. This behavior was exhibited at both room temperature and 1200 °F.
The coarse grain Waspaloy on the other hand, showed either a flat response at
room temperature, or monotonlc softening at 1200 °F.
CONCLUSIONS
(1) There appears to be reasonable correspondence between axial and
torslonal low-cycle fatigue (LCF) 1n fine grained Waspaloy tested at both 75
and 1200 °F.
(2) There 1s also reasonable correspondence between the damage mechanisms
observed 1n axial and torslonal LCF 1n coarse grained Waspaloy at 75 °F.
However, at 1200 °F a tensile dominated failure mechanism was activated 1n
torslonal loading whereas a plasticity dominated mechanism was activated 1n
axial loading. Also, there was a difference between the fine grained and
coarse grained Waspaloy damage mechanisms at 1200 °F.
(3) During cyclic hold-time experiments, fine grain Waspaloy demonstrated
substantial stress relaxation at 1200 °F, under both axial and torslonal
loading. Very little relaxation was observed in coarse grain Waspaloy. Also,
cyclic hardening was observed 1n fine grain Waspaloy at both room temperature
and 1200 °F; coarse grain Waspaloy exhibited either flat cyclic response or
monotonlc softening.
(4) These experiments demonstrate that LCF damage depends on the material
and heat treatment, the test temperature and the state-of-stress.
ORIGINAL PAGE-13
OF POOR QUALITY
(a)
(b)
Fig. 1 a) Macrophoto of Waspaloy course grain
torsional 1200°F. (Spec.
BF27,ATT=1 .58$,AYP = 0.655& § Nf/2,
Nf=4528) Note primary cracking at
45° to specimen axis on planes of
maximum tensile stress.
b) Applied wave form (10 cpm).
ORIGINAL PAGE IS
OF POOR QUALITY
(a)
(b)
Fig. 2 a) Macrophoto of Waspaloy course grain
torsional 1200°F. (Spec.
BF4,/VYT=1 .34?,AYp=0.52$ to failure,
Nf=5500) Note primary cracking at
**5° to specimen axis on planes
maximum tensile stress.
b) Applied wave form (10 cpm).
SPEC. AXIS
a
0 1 '3 k x 1 0k v 127*
(a)
SPEC. AXIS
(b)
Fig. 3 a) Primary crack at 45° to the specimen
axis (Spec. BF^) on planes of maximum
tensile stress.
b) Enlarged region of (a) showing slip band
formation and crack orientation and
propagation. It also shows undeformed
grain ahead of the crack front forcing
the crack to change direction.
ORIGINAL PAGE IS
OF POOR QUALITY
I
SPEC. AXIS
(c)
SPEC. AXIS
(d)
Fig. 3 c) Enlarged region of (b), showing further
details of the crack arrest and
orientation.
d) Micrograph showing the major crack was
due to large particles (inclusions) in
the grain.
SPEC. AXIS
50k x 1 0k M 131
(e)
Fig. 3) Micrograph showing the crack was initiated
on the maximum tensile stress and
propagated at 45° to the slip bands, Mode
I crack propagation. Note large particle
formation.
10
Fig. 4) X-Ray energy spectrum analysis revealed
the content of the particles (inclusions)
to be Ni, Cr, Mo, Co, Ti.
(a)
1.5 sec
(b)
Fig. 5 a) Macrophoto of Waspaloy course grain:
Torsion with hold time. (Spec.
BF25,AYT=1 .55/&,AYin=0.6435& @ Nf/2,
Nf=2691, T=1200°F, t-90 Sec.)
Note primary crack at 45° to the
specimen axis on plane of maximum
tensile stress.
b) Applied wave form.
ORIGINAL PAGE 13
OF POOR QUALITY
SPEC. AXIS
(a)
(b)
Fig. 6 a,b) Replicas of gage surface along the
major crack at 40X. Mixed mode crack-
ing is shown, grain boundary cracking,
twining deformation, multiple slip
system are observed.
13
(a)
1.5 sec 90 sec
(b)
Fig. 7 a) Macrophoto of Waspaloy course grain:
Axial with hold time. (Spec.
BF8,AeT=0.7$,Aeln=0.295£ @ Nf/2,
Nf=987, T=1200°F, t=90 Sec.)
Note primary crack normal to the
loading axis.
b) Applied wave form.
14
ORIGINAL PAGE 53
OF POOR QUALITY
SPEC. AXIS
030k x 1 0 k v 403
(a)
(b)
Fig. 8 a) Micrograph showing primary crack normal
to the loading axis.
b) Mixed mode crack initiation and trans-
granular crack propagation. Note multiple
slip systems operating, also deformation
twining is observed.
15
SPEC. AXIS
f
0 . 7 8 k x 18kv 404
(a)
(b )
Fig. 9 a,b) Slip bands intersecting oxidized
grain boundaries induced cracking,
also multiple slip systems and
deformation twining is observed.
16
ORIGINAL PAGE 13
OF POOR QUALITY
(a)
1. 5 sec — •90 sec-
(b)
Fig. 10 a) Macrophoto of Waspaloy fine grain:
Torsion with hold time. (Spec.BAlS,
AYT=1.9^,AYin=0.5585£ & Nf/2,Nf=1653,
T=1200°F,t=90 Sec.).
Note primary crack is along the specimen
axis
b) Applied wave form.
17
SPEC. AXIS
\ (a)
.•l**:*»*v *
II
(b)
Fig. 11 a) Primary crack along the specimen axis,
intergranular and transgranular cracking
is observed, extensive oxiedation on the
grain boundaries.
b) Note wavy and oxidized slip bands.
18
ORIGINAL PAGE 13
OF POOR QUALITY
SPEC. AXIS
(a)
I
(b)
19
(a)
1.5 sec- 90 sec
(b)
Fig. 13 a) Macrophoto of waspaloy fine grain:
Axial with hold time. (Spec.
BA30,AeT=1.01$,Aeln=0.32$ g Nf/2,
Nf=587, T=1200°F, t=90 Sec.)
Note primary cracking normal to the
loading axis.
b) Applied wave form.
20
ORIGINAL PACE !
OF POOR QUALITY
SPEC. AXIS
(a)
(b)
Fig. 14 a) Twin boundary cracking, oxidized slip
bands are observed
b) Cracking along the grain boundaries,
also note wavy slip bands
SPEC. AXIS
\
(b)
Fig. 15 a,b) Replicas of the gage surface at
extensive grain boundary cracking
above and below the primary crack
are observed.
.
•
22
700 750
Fig. 16) Torsional hysteresis loops for small grain Waspaloy (Spec. BA13), tested at 1200 °F under 90 sec hold time.
(AyT= 1.94%, Ayin • 0.558% at N f/2. Nf • 1653).
,a=28.02ksi
Fig. 17) Uniaxial hysteresis loops for small grain Waspaloy (Spec. BA30), tested at 1200 °F under 90 sec tension
hold time. (AET • 1.01%, Aein • 0.32% at Nf • 587).
23
|TCCW
1000 1087 1178
Fig. 18) Torsional hysteresis loops for large Waspaloy (Spec. BF25), tested at 1200 °F under 90 sec hold time.
(Ayr - 1.55%, Ayjn - 0.643 at Nf 12, Nf • 2691).
351 400 449 450 451 500
Fig. 19) Uniaxial hysteresis loops for large grain Waspaloy (Spec. BF8), tested at 1200 °F under 90 sec tension hold
time. (AeT • 0.70%, Aein • 0.29% at Nf 12. Nf • 987).
24
10 100
Cycles, N
1000
SG,RT,AyT = 1.98%, Ayl
LG,RT,ArT= 1.53%, Ay
SG,HT,Ay
LG,HT,AyT
LG,HT,AyT
LG,HT,AyT
a 56%
0.52%
l.94%, Ayp-0.56%
1.93%, Ay^=0.92%
1.58%, Ayp-0.65%
1.34%, Ay p*- 0.52%
type of Strain Control Test.
10000
Fig. 20) Shear stress range variation with cycle for small grain (SG) and large grain (LG) Waspaloy, tested under
continuous cycling (10 cpml at room (RT) and 1200 °F (HTI temperatures.
25
1. Report No.
 NA$A CR_! 75(552
USAAVSCOM TR-86-C-14
2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle
Axial and Torslonal Fatigue Behavior of Waspaloy
5. Report Date
April 1986
6. Performing Organization Code
7. Author(s)
S. Zamrlk, M. M1rdamad1, and F. Zah1r1
8. Performing Organization Report No.
None
10. Work Unit No.
9. Performing Organization Name and Address
The Pennsylvania State University
Engineering Science and Mechanics Dept.
University Park, Pennsylvania 16802
11. Contract or Grant No.
NAG 3-264
12. Sponsoring Agency Name and Address
U.S. Army Aviation Research and Technology Activity -
AVSCOH, Propulsion Directorate, Lewis Research Center,
Cleveland, Ohio 44135 and NASA Lewis Research Center,
Cleveland, Ohio 44135
13. Type of Report and Period Covered
Contractor Report
14. Sponsoring Agency Code
505-63-11
15. Supplementary Notes
Final report. Project Manager, Robert C. Bill, Propulsion Directorate, U.S. Army
Aviation Research and Technology Activity - AVSCOM, Cleveland, Ohio 44135.
16. Abstract
The cyclic flow response and crack growth behavior of Waspaloy at room tempera-
ture and 650 °C under tensile loading and torslonal loading was studied, for two
conditions of Waspaloy: fine grain, large y1 size; coarse grain, small y'
size. The fine grain material showed 5 to 10 percent hardening after about 10
percent of life, with sequent softening to failure at both temperature levels.
The coarse grain material showed either stable response or monotonlc softening to
failure. Early crack Initiation was observed on planes of maximum shear, with
eventual branching to principal planes under torslonal loading; cracks were
always normal to load axis under tensile loading. Also, crack paths were Inter-
granular at 650 °C, mostly transgranular at room temperature.
17. Key Words (Suggested by Authcrfs))
Fatigue; Tension; Torsion; High
temperature; Superalloy; Waspaloy
18. Distribution Statement
Unclassified - unlimited
STAR Category 26
9. Security Classlf. (of this report)
Unclassified
20. Security Classlf. (of this page)
Unclassified
21. No. of pages
22
22. Price*
A02
'For sale by the National Technical Inlormation Service, Sprlnglield, Virginia 22101
National Aeronautics and
Space Administration
Lewis Research Center
Cleveland. Otiio 44135
Official Business
Penally for Private Use $300
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Axial and torsional fatigue behavior of Waspaloy

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