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C-103 MECHANICAL PROPERTIES

Extensive mechanical property testing of C-103 has been performed on raw stock, weldments, coated weldments, and on expended hardware which was formed, welded, and coated. The following mechanical property data has been repeatedly used as design criteria and has been proven to provide a good margin of safety.

Tables 6 and 7 show in graphical form guaranteed mechanical properties for C-103 and typical mechanical properties for C-103. Any values other than those shown on the guaranteed table should be checked with the Sales Department before final specification is written.

Tensiles

Creep Properties

Creep properties of C-103 are shown in Tables 10 and 11 . Tabular data for coated and uncoated C-103 follows. The Larson-Miller formula is expressed with T being Temperature °F.

Figure 12 shows a C-103 metal spinning. The part was shear spun from sheet metal product in a two-step operation then fully machined and finally bulged formed to insure dimensional tolerances. Although the part was used only for technique establishment, aerospace hardware was developed following these guidelines.

Creep Properties

Thermal Stress Cycling

    Note
    1. Coating severely cracked, therefore low elongation.
    2. Broke inside 1” G.L. ductile type fracture.
    3. Broke outside 1” but inside 2” G.L. brittle type fracture.
    4. 1” gage mark came off with coating.
    5. Ductile type fracture.
    6. Broke outside 1” G.L. ductile type fracture.
 Thermal stress cycling tests for C-103 were obtained in laboratory tests using the following parameters:
  1. Radiant heat from quartz lamps in air
  2. 2.Heat coated specimen to 2400°F and hold at temp. for 120 sec.
  3. Cool specimen with CO2 (approximately –100F)
  4. Examine specimen for coating condition
  5. Reheat specimen to 2400°F for 45 sec.
  6. Cool with CO2 for 30 sec.
  7. Repeat (4) and (5) for 20 cycles
  8. Bend test (3T) at room temperature
  9. Examine metallographically

The results of these tests are shown in Table 19 , which follows Tensile properties of coated C-103 after thermal stress cycling are shown in Table 18 .

Modulus of Elasticity

Elastic modulus, thermal conducivity, and total hemispherical emissivity are listed in Tables 20-22 . The emissivity data are for smooth and non-oxidized surfaces which exhibit much lower emissivity values than oxidized material. Also shown in Table 22 is an emissivity value of 0.7-0.82 for silicide coated C-103. This value is for a common Si-20%Fe-20%Cr coating applied by the slurry coat and fusion method. Thermal expansion data are shown in Table 23.

Impact Data

Charpy notched impact data for uncoated C-103

Room Temperature

Specimen No. 1 – 148 ft. – lbs. to fracture
Specimen No. 2 – 159 ft. – lbs. to fracture

-100 °F Temperature

Specimen No. 1 – 79 ft. – lbs. to fracture
Specimen No. 2 – 70 ft. – lbs. to fracture

The height of coated liquid rocket nozzle extension was reduced 28” in 1/4 th of a second using 2,250 lbs. of free-falling weight at room temperature. Although the unit had a total of 600” of longitudinal and girth welds, there were no failures in either weldments or parent metal.

Fatigue Test

A fatigue testing program was devised to test the material, coating and weldments under severe vibration conditions. The material combinations used for this evaluations were:

.020 C-103 to .030 C-103; and .030 C-103 to .025 C-129Y

An outline of this test presents the resume results of fatigue tests performed on welded coupons at temperatures of –320F, ambient, and 1800°F. The following discussion covers this program.

Sheet Coupon Fatigue Unit
The sheet coupon fatigue unit applied to a pure bending moment to the specimen through two 3/8” diameter shafts 16” long. These shafts were supported through Teflon guides. Loading or deflection was held at the desired level with a hydraulically operated servo-feedback system. Signal for load feedback was obtained from the strain gages mounted on the torque rods. The feedback signal for the deflection control was obtained from a resolver mounted on one of the torque rods. Cooling was accomplished by refrigeration techniques, and heating by passing current through the coupon. The current was fed into the coupon through mercury cups. Temperatures were measured with thermocouples and with an optical pyrometer.

Temperature Gradient
Temperature measurements were made to determine the temperature gradient of the specimens at –320F, and 1800°F.
Dynamic Loading of Coupon
Tests were made on the coupons to determine if dynamic loading was a problem. This was done by placing several strain gages on a coupon and comparing the output of these gages to the gages on the torque shafts.

Ambient Fatigue Tests
Coupons were mounted in the fatigue unit and vibrated at the desired bending moment and frequency.

-320 °F Fatigue Tests
The coupons were mounted in the fatigue unit and a bath of liquid nitrogen was raised to immerse the coupon. Each coupon was allowed to reach liquid nitrogen temperature (-320°F). The bath was then lowered until the coupon was just above the fluid, then the coupon was tested. The bath was periodically raised to keep the fluid level the same. This was necessary due to the evaporation of liquid nitrogen.

Temperature Fatigue Tests
1.Fatigue:Coupons were resistance heated to temperature in one minute, and then tested.
2.Thermal Cycle Fatigue:Coupon was tested according to the following test cycle:
    Zero time - vibration started
    15 seconds - heating started
    60 seconds - coupon at temperature
    75 seconds - vibration, heating stopped

Note the coupon was allowed to cool for 3 to 5 minutes and the test cycle repeated for 50 cycles or until failure.

 

Test results
Temperature Gradient
There was no measurable gradient across the coupons at –320F and temperature of the coupon remained at –320F when it was held just above the fluid level. Temperature gradient across the butt weld coupons at 1800°F was 10 to 70°F lower at the weld than at the parent metal, depending on the type and size of the weld.
Dynamic Loading of Coupon
The dynamic loading effect on the coupons depends on frequency and amplitude of displacement. It was found that if the frequency was held below 20 cps for small displacements, and 10 cps for large displacements, dynamic loading was negligible.
DISCUSSION

Most failures occurred in the weld area at –320F and ambient temperatures, while the failures occurred in the parent material for most of the high temperature tests.

Loss of coating was the cause of most failures at high temperatures. A crack would develop in the coating or flake off and cause the base metal to oxidize or develop a hot spot and fail.

This data is presented as a function of bending moment and not stress. The stress can be calculated by this formula:

The actual metal thickness (H) was .030”. (Results of these tests are significant, considering that the temperature gradient across the 7.75” specimen placed a severe strain on the coating.) M is the applied bending moment in inch/lb. B is the metal width which was 1.00” for these tests.

Creep Test