Engineering topics

Miner, R. V.

Publications and source records attributed to Miner, R. V..

42 records · Page 3

NASA NTRS1982

Fatigue and creep-fatigue deformation of several nickel-base superalloys at 650 C

Transmission electron microscopy has been used to study the bulk deformation characteristics of seven nickel-base superalloys tested in fatigue and creep-fatigue at 650 C. The alloys were Waspalloy, HIP Astroloy, H plus F Astroloy, H plus F Rene 95, IN 100, MERL 76, and NASA IIB-7. The amount of bulk deformation observed in all the alloys was low. In tests with inelastic strain amplitudes less than about 0.003, only some grains exhibited yielding and the majority of those had the 110 line near the tensile axis. Deformation occurred on octahedral systems for all of the alloys except MERL 76 which also showed abundant primary cube slip. Creep-fatigue cycling occasionally produced extended faults between partial dislocations, but otherwise deformation was much the same as for fatigue cycling.

Miner, R. V.↗

NASA NTRS1981

The fracture morphology of nickel-base superalloys tested in fatigue and creep-fatigue at 650 C

The fracture surfaces of compact tension specimens from seven nickel-base superalloys fatigue tested at 650 C were studied by scanning electron microscopy and optical metallography to determine the nature and morphology of the crack surface in the region of stable growth. Crack propagation testing was performed as part of an earlier study at 650 C in air using a 0.33 Hz fatigue cycle and a creep-fatigue cycle incorporating a 900 second dwell at maximum load. In fatigue, alloys with a grain size greater than 20 micrometers, HIP Astroloy, Waspaloy, and MERL 76, exhibited transgranular fracture. MERL 76 also displayed numerous fracture sites which were associated with boundaries of prior powder particles. The two high strength, fine grain alloys, IN 100 and NASA IIB-7, exhibited intergranular fracture. Rene 95 and HIP plus forged Astroloy displayed a mixed failure mode that was transgranular in the coarse grains and intergranular in the fine grains. Under creep-fatigue conditions, fracture was found to be predominantly intergranular in all seven alloys.

Gayda, J.↗

NASA NTRS1980

Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

Hot-isostatically-pressed powder-metallurgy Astroloy was obtained which contained 1.4 percent porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep-fatigue, tension, and stress-rupture and the results compared with data on sound Astroloy. They influenced fatigue crack initiation and produced a more intergranular mode of propagation but fatigue life was not drastically reduced. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range-life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was changed little.

Miner, R. V.↗

NASA NTRS1978

Wrought nickel-base superalloy

Superalloy for advanced temperature use is suited to cost-saving powder-metallurgy manufacturing methods and has improved phase stability during longtime heating. Wide variety of applications exists where stainless steels are used for oxidation and/or corrosion resistance.

Miner, R. V.↗

NASA NTRS1977

An experimental P/M wrought superalloy for advanced temperature service

A study was undertaken in order to adapt IIB-11 (an experimental wrought superalloy with high temperature strength) to manufacture via powder metallurgy techniques, and to improve its microstructural stability. Three compositional modifications were produced and evaluated. Among the conclusions reached it was found that: (1) IIB-11 having a low C and low Hf alloy content is suitable for advanced temperature turbine disks, and is applicable to fabrication by powder metallurgy techniques, (2) IIB-11, when compared to modifications with higher C and/or higher Hf, is somewhat weaker in tension at intermediate temperatures but superior in tensile ductility, rupture strength and ductility, and stability during long-time heating, (3) increases in the cross-rolling temperature increase the grain size of alloys after solution treatment, and (4) both the lower C modifications develop larger grain sizes than the higher C modification.

Miner, R. V.↗

NASA NTRS1973

Improvement in cyclic oxidation of the nickel-base superalloy B-1900 by addition of one percent silicon

Cast B-1900 with and without 1 weight percent Si was subjected to cyclic oxidation at 1000 and 1100 C in air for 700 and 200 hours, respectively. The results were judged by specific weight change, metallography and X-ray diffraction. Si was found to be of significant value in reducing oxidation attack, probably by increasing scale adherence.

Lowell, C. E.↗