investigation of advanced processed single-crystal turbine blade alloys

200 Pages·08.07 MB·English

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INVESTIGATION OF ADVANCED PROCESSED
SINGLE-CRYSTAL TURBINE BLADE ALLOYS
Prepared by:
B.J. Peters
C.M. Biondo
D.P. DeLuca
United Technologies Corporation
Pratt & Whitney
Government Engines & Space Propulsion
P.O. Box 109600
West Palm Beach, FL 33410-9600
December 1995
Final
Period of Performance from 16 December 1991 through 31 December 1995
Prepared for:
George C. Marshall Space Flight Center
National Aeronautics and Space Administration
Marshall Space Flight Center, AL 35812
Under Contract: NAS8-39050

INVESTIGATION OF ADVANCED PROCESSED
SINGLE-CRYSTAL TURBINE BLADE ALLOYS
Prepared by:
B.J. Peters
C.M. Biondo
D.P. DeLuca
United Technologies Corporation
Pratt & Whitney
Government Engines & Space Propulsion
P.O. Box 109600
West Palm Beach, FL 33410-9600
December 1995
Final
Period of Performance from 16 December 1991 through 31 December 1995
Prepared for:
George C. Marshall Space Flight Center
National Aeronautics and Space Administration
Marshall Space Flight Center, AL 35812
Under Contract: NAS8-39050

NASA
Report Document Page
NationalAeronauticsand
SpaceAdministration
1. Report No. 2. Government Accession No. 3. Reciplent'e Catalog No.
FR-24007
4. Title end Subtitle 5. Report Date
Investigation ofAdvanced Processed Single-Crystal Turbine Blade Alloys
6. Performing Organization Code
52661
7. Authors 8. Performing OrgenlzaUon Report No.
Program Manager: D.P. DeLuca = FR-24007
Principal Investigators: B.J. Peters and C.M. Biondo
9. Performing Organization Name and Address 10. Work Unit No.
United Technologies
Pratt &Whitney
Government Engines &Space Propulsion
P.O. Box 109600, West Palm Beach, FL 33410-9600 11. Contract or Grant No.
NAS8-39050
12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered
George C. Marshall Space Flight Center CPFF/16 December 1991 -31 December 1995
National Aeronautics and Space Administration
Marshall Space Flight Center, AL 35812 14. Sponeorlng Agency Code
15. Supplementary Notes
16. Abstract
This investigation studied the influence of thermal processing and microstructure on the mechanical properties of the single-crystal, nickel-
based superalloys PWA 1482 and PWA 1484. The objective of the program was to develop an improved single-crystal turbine blade alloy that
isspecifically tailored for use inhydrogen fueled rocket engine turbopumps.
High-gradient casting, hot isostatic pressing (HIP), and alternate heat treatment (HT) processing parameters wer_ _veloped to produce
pore-free, eutectic-free microstructures with different _'precipitate morphologies.
Test materials were cast inhigh thermal gradient solidification (greater than 30°C/cm [137°F/in.l) casting furnaces for reduced dendrite arm
spacing, improved chemical homogeneity, and reduced interdendritic pore size.
The HIP processing was conducted in40-cm (15.7-in.) diameter production furnaces using a set of parameters selected from atrial matrix
study. Metallography was conducted on test samples taken from each respective trial runto characterize the as-HIP microstructure.
Post-HIP alternate HT processes were developed foreach of the two alloys. The goal of the alternate HT processing was to fully solution the
eutectic y/y'phase islands and todevelop a series of modified "y'morphologies forsubsequent characterization testing. This was accomplished
by slow cooling through the _'solvus atcontrolled rates to precipitate volume fractions of large y'. Post-solution alternate HT parameters were
established foreach alloy providing additional volume fractions of finer precipitates.
Screening tests included tensile, high-cycle fatigue (HCF), smooth and notched low-cycle fatigue (LCF), creep, and fatigue crack growth
evaluations performed inair and high pressure (34.5 MPa [5 ksi]) hydrogen at room and elevated temperature. Under the most severe embrit-
tling conditions (HCF and smooth and notched LCF in34.5 MPa [5 ksi]hydrogen at 20°C (680F), screening test results showed increases in
fatigue lifetypically on the order of 10X, when compared to the current Space Shuttle Main Engine (SSME) Alternate Turbopump (AT) blade
alloy (PWA 1480).
17. Key Words (Suggested by Author[s]) 18. Distribution Statement
PWA 1482, PWA 1484, bimodal "y',eutectic-free, fatigue crack, growth, high-pressure
hydrogen, hydrogen embrlttlement, SSME AT
19. Security Cla_fficstion (of 20. Security Classification (of this Page) 21. No. of Pages 22. Price
this Report) Unclassified 195
Unclassified

FOREWORD
The work for this program, Investigation of Advanced Single-Crystal Turbine Blade Alloys, was performed
under National Aeronautics and Space Administration (NASA) Contract NAS8-39050. The sponsoring agency
was the NASA, George C. Marshall Space Flight Center, Marshall Space Flight Center, Alabama. The NASA
Program Monitor was Deborah Diane Schmidt.
The program was conducted at the Materials and Mechanics Engineering Laboratories, Pratt & Whitney
(P&W), West Palm Beach, Florida. The Principal Investigators for this program were B.J. Peters. and C.M.
Biondo. The P&W Program Manager was D,P. DeLuca.
iii

EXECUTIVE SUMMARY
The objective of this program was to develop an advanced turbine blade alloy for use in liquid rocket
turbopumps. The study focused on microstructural modifications to two single-crystal nickel-based superalloys;
PWA 1484 and PWA 1482. These superalloys both exhibited significantly better durability than the blade alloys,
directionally-solidified (DS) columnar-grained Mar-M246+Hf and PWA 1480, which are currently used in the
National Aeronautics and Space Administration (NASA) Space Shuttle Main Engine (SSME).
The program improvements in low-cycle fatigue (LCF), high-cycle fatigue (HCF), and melt margin have
provided the NASA/Pratt & Whitney (P&W) SSME Altemate Turbopump (AT) Program with a turbine blade alloy
possessing an attractive balance of properties with increased durability. At the writing of this report, PWA 1484 is
invarious stages of test and evaluation under the ATD Program leading to its potential implementation as a turbine
vane alloy in the AT ltigli-Pressure Fuel Turbopump (HPFTP). The results of preliminary HPFTP blade and vane
casting trials with the Advanced Processed PWA 1484 are shown in the following figure.
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