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  • 1
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    Changes in solidified microstructures (1984)
    In:  CASI
    Details
    Publication Date: 2006-06-08
    Description: The properties and casting behavior of metals are significantly affected by their cast structure. This structure is optimized by producing columnar versus equiaxed grains and coarse versus fine grains by controlling solidification conditions. The transition from columnar to equiaxed grains is favored by: constitutional supercooling with effective nucleation of free dendrites; melting off and transport of dendrite tips and arms; mechanical vibration; falling down of free dendrites from a chilled top surface; and induced flow in the solidifying structure by oscillation of rotation.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center Fundamentals of Alloy Solidification Appl. to Industrial Processes; p 91-104
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Effect of reduction of strategic columbium additions in Inconel 718 alloy on the structure and properties (1982)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: The amount of columbium which can be removed from Inconel alloy 718 without degrading its high temperature properties was determined. The elements that are substituted are: vanadium and tungsten together and separately; increasing the molybdenum level from 3.0% to 5.8% and increasing the boron to 0.04%.
    Keywords: METALLIC MATERIALS
    Type: NASA. Lewis Research Center COSAM (Conserv. Of Strategic Aerospace Mater.) Program Overview; p 133-140
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Effect of reduction of strategic Columbium addition in 718 Alloy on the structure and properties (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A series of alloys was developed having a base composition similar to Inconel 718, with reduced Cb levels of 3.00 and 1.10 wt% Cb. Substitutions of 3.0% W, 3.0W + 0.9V or Mo increased from 3.0% to 5.8% were made for the Cb in these alloys. Two additional alloys, one containing 3.49% Cb and 1.10% Ti and another containing 3.89% Cb and 1.29% Ti were also studied. Tensile properties at rooom and elevated temperatures, stress-rupture tests, and an analysis of extracted phases were carried out for each of the alloys. Additions of solid solution elements to a reduced Cb alloy had no significant effect on the properties of the alloys under either process condition. The solution and age alloys with substitutions of 1.27% i at 3.89% Cb had tensile properties similar top hose of the original alloy and stress-rupture properties superior to the original alloy. The improved stress-rupture properties were the result of significant precipitation of Ni3Ti-gamma prime in the alloy, which is more stable than gamma' at the elevated temperatures. At lower temperatures, the new alloy benefits from gamma' strengthening. With more precise control and proper processing, the reduced Cb direct-age alloy could substitute for Alloy 718 in high strength applications.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-174841 , NAS 1.26:174841
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Fastener load tests and retention systems tests for cryogenic wind-tunnel models (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A-286 stainless steel screws were tested to determine the tensile load capability and failure mode of various screw sizes and types at both cryogenic and room temperature. Additionally, five fastener retention systems were tested by using A-286 screws with specimens made from the primary metallic alloys that are currently used for cryogenic models. The locking system effectiveness was examined by simple no-load cycling to cryogenic temperatures (-275 F) as well as by dynamic and static loading at cryogenic temperatures. In general, most systems were found to be effective retention devices. There are some differences between the various devices with respect to ease of application, cleanup, and reuse. Results of tests at -275 F imply that the cold temperatures act to improve screw retention. The improved retention is probably the result of differential thermal contraction and/or increased friction (thread-binding effects). The data provided are useful in selecting screw sizes, types, and locking devices for model systems to be tested in cryogenic wind tunnels.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-85805 , L-15751 , NAS 1.15:85805
    Format: application/pdf
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  • 5
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    Thermal fatigue behavior of H-13 die steel for aluminum die casting with various ion sputtered coatings (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Sputtered coatings of Mo, W, Pt, Ag, Au, Co, Cr, Ni, Ag + Cu, Mo + Pt, Si3N4, A1N, Cr3C2, Ta5Si3, and ZrO2 were applied to a 2-inch-square, 7-inch-long thermal fatigue test specimen which was then internally water cooled and alternately immersed in molten aluminum and cooled in air. After 15,000 cycles the thermal fatigue cracks at the specimen corners were measured. Results indicate that a significant improvement in thermal fatigue resistance was obtained with platinum, molybdenum, and tungsten coatings. Metallographic examination indicates that the improvement in thermal fatigue resistance resulted from protection of the surface of the die steel from oxidation. The high yield strength and ductility of molybdenum and tungsten contributed to the better thermal fatigue resistance.
    Keywords: METALLIC MATERIALS
    Type: NASA-CR-165300
    Format: application/pdf
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  • 6
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    Sputtered protective coatings for die casting dies (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This investigation determined whether selected ion beam sputtered coatings on H-13 die steel would have the potential of improving the thermal fatigue behavior of the steel used as a die in aluminum die casting. The coatings were selected to test candidate insulators and metals capable of providing protection of the die surface. The studies indicate that 1 micrometer thick W and Pt coatings reduced the thermal fatigue more than any other coating tested and are candidates to be used on a die surface to increase die life.
    Keywords: METALLIC MATERIALS
    Type: NASA-TM-81735 , E-803 , 1981 Intern. Conf. on Met. Coatings,; Apr 06, 1981 - Apr 10, 1981; San Francisco, CA; United States
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  • 7
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    Sputtered protective coatings for die casting dies (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Three experimental research designs investigating candidate materials and processes involved in protective die surface coating procedures by sputter deposition, using ion beam technologies, are discussed. Various pre-test results show that none of the coatings remained completely intact for 15,000 test cycles. The longest lifetime was observed for coatings such as tungsten, platinum, and molybdenum which reduced thermal fatigue, but exhibited oxidation and suppressed crack initiation only as long as the coating did not fracture. Final test results confirmed earlier findings and coatings with Pt and W proved to be the candidate materials to be used on a die surface to increase die life. In the W-coated specimens, which remained intact on the surface after thermal fatigue testing, no oxidation was found under the coating, although a few cracks formed on the surface where the coating broke down. Further research is planned.
    Keywords: METALLIC MATERIALS
    Type: International Conference on Metallurgical Coatings; Apr 06, 1981 - Apr 10, 1981; San Francisco, CA
    Format: text
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