INFLUENCE OF , TANTALUM, AND ON THE HICROSTRUCTURE AND WECHANlCAL PROPERTIES OF SINGLE CRYSTALS . ./ Michael V, Nathal National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio and L. 3. Ebert Case Western Reserve University Cleveland, Ohio

The purpose of this study was to investigate the influence of Co, Ta, and W on the microstructure and mechanical properties of nickel-base super- single crystals. A matrix of alloys was based on Mar-M 247 stripped of C, 8, Zr, and Hf. The microstructures of the alloys were exaislrnedusing optical and electron microscopy, extraction, X-ray diffraction, and differential thermal analysis, Tensile and creep-rupture tests were per- formed at 1000" C. An increase in tensile and creep strength resulted when Co was removed from alloys containing high refractory contents, but Co effects vJere negligible for alloys with lower refractory metal levels. In the composition range stuaied, W was more effective than Ta in increasing the creep resistance. The mechanical properties will be discussed in rela- tion to the microstructures of the alloys.

107 ORIG\NAL PAGE Is OF POOR QUALtn

- COSAM - TENSILE AND CREEP-RUPTURE TESTS AT loooOC - MICROSTRUCTURAL FEATURES : y' VOLUME FRACTION y' COARSEMNG RATE y, y' COMPOSITION yyMISMATCY TCP FORMATION

SI NGLE CRYSTAL ALLOY MATRIX

ALLOY C OMPOSlTlON TC P NOTES Co Ta W FORMATION' A 0 0 10 NONE B 0 3 10 1TO 2% NASAIR 103 2 CASTINGS C 0 0 13

1oe ORIGINAL PAGE IS OF POOR QUALlrV TRANSFORMATION TEMPERATURES AS A FUNCTION OF COMPOSITION 0 3Ta-lOW 0 OTa-1OW 14% A OTa-13W ~iniiiniic

24% TEMPER - TEMPER - ATURE, ATURE oc '300

1250

----I - ___ 1-

2150 L lmr 11% ; 0 5 10 wt % COBALT

wt. % GAMMA PRIME AS A FUNCTION OF COMPOSITION

0 3Ta-1OW 0 OTa-1OW A OTa-13W

40

wt SCOBALl

109 loo00 C ULTIMATE TENSILE STREMGTH OF [lo01 ORIENTED SINGLE CRYSTALS AS A FUNCTION OF COMPOSITION

700 r 0 3Ta-lOW 0 OTa-l0:V Ls OTa-13W

90 L

ULTIMATE uLnrvm TENSILE 80 - TENSILE STRENGTH, STRENGTH, kri MPa

0 5 10 wt %COPALT

10000 C TENSILE OF [loo] ORIENTED SINGLE CRYSTALS AS A FUNCTION OF COMPOSITION

0 3Ta-lOW 0 OTa-lOW A OTa-13W 40 'F 0 ElONGATl ON, _n 70 30 0 0

20 0

I 0 5 10 wt. %COBALT

111 d CASTING 6-2 -

STRESS, 20 ksi

'O49Lu 50 51 52 53 54

P 0 (T + 4601 (20 + LOG t1~10-3

RUPTURE LIFE OF [ 1001 ORIENTED SINGLE CRYSTALS AS A FUNCTION OF COMPOSITION l@C, 148 MPa (21.5 ksi)

1200 3Ta-lOW 0 OTa-1OW A 0'3-13W

lo00

800

R UP:!IRE LIFE, 600 hr

400

I1 0 5 10 wt. SbCOBALl

112 ORlGlNAL PAGE 19 OF POOR QUALlrV

10000 c

R2 t 81.5 5.14

STRESS. ksi

0 0 20 'oI)-.;3 'oI)-.;3 .65 .67 .69 wt % GAMMA PRIME

11J

SUMMARY

MCROSTRUCTURE OF ALLOYS

L MCREASE CO: IAICR€ASE IN y' SOLVUS : INCREASE IN wt%f (3 Ta-1CW) : INCREASE IN TCP PHASF FORMATl3N

2 SUBSllTUTE Ni FOR la: STRONG MCREASE IN y' SOLVUS : STRONG DECREASE fN wt % y' 3. Sli8STITUlE W FOR la: SMAU DECREASE IN y' SOLVUS : SMALL DECREASE IN V& 4bf'

MCHANICAL PROPERTIES a SINGLE CRYSTAL ALLOYS 1. DECREASE Co: lNCREA5E IN CREEP RESISTANCE AND TENSILE STRENGTH FOR ME HIGH ITa + WI LEVELS : VERY SMALL EFFECT FOR THE LW (Ta + W) LEVELS 2. ALL AUOYS HAD TENSILE ELONGATiONS GREATER THAN 18% LOWER STRENGTH ALLOYS HAD HIGHER DUCTILITY ?. TUNGSTEN IS MORE EFFECTIVE THAN Ta FOR CREEP RESISTANCE 4. l@C STRCSS CAPABILITY IS STRORGLY CORRELATED WITH wt%y' 5. CASTING POROSIN APPEARS TO BE A MORE SERIOUS DEFECT THAN THE PRESENCE a TCP PHASES

116