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Lowell, C. E.

Publications and source records attributed to Lowell, C. E..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Effects of composition and testing conditions on oxidation behavior of four cast commercial nickel-base superalloys

Four cast nickel-base superalloys were oxidized at 1000 and 1100 C for times up to 100 hr in static air and a Mach 1 gas stream. The oxidation resistance was judged by weight change, metal thickness loss, depletion-zone formation, and oxide formation and morphology. The alloys which formed mostly nickel aluminate (NiAl2O4) and aluminum oxide (Al2O3) (B-1900, VIA, and to a lesser extent 713C) were more oxidation resistant. Poorer oxidation resistance was associated with the appearance of chromium sesquioxide (Cr2O3) and chromite spinel (738X). Refractory metal content had little effect on oxidation resistance. Refractory metals appeared in the scale as tapiolite (NiM2O6, where M represents the refractory metal). Thermal cycling in static air appeared to supply sufficient data for the evaluation of oxidation resistance, especially for alloys which form oxides of low volatility. For alloys of higher chromium levels with high propensities toward forming a chromium-bearing scale of higher volatility, testing under conditions of high gas velocity is necessary to assess fully the behavior of the alloy.

Lowell, C. E.↗
NASA NTRS1974

Effects of diffusion on aluminum depletion and degradation of NiAl coatings

Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 5 mtorr vacuum at 1100 C for 300 hr. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hr cycles on prediffused and as-coated specimens. The prediffusion treatment decreased the oxidation and as-coated specimens. The prediffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.

Smialek, J. L.↗
NASA NTRS1974

Comparison of isothermal and cyclic oxidation behavior of twenty-five commercial sheet alloys at 1150 C

The cyclic and isothermal oxidation resistance of 25 high-temperature Ni-, Co-, and Fe-base sheet alloys after 100 hours in air at 1150 C was compared. The alloys were evaluated in terms of their oxidation, scaling, and vaporization rates and their tendency for scale spallation. These values were used to develop an oxidation rating parameter based on effective thickness change, as calculated from a mass balance. The calculated thicknesses generally agreed with the measured values, including grain boundary oxidation, to within a factor of 3. Oxidation behavior was related to composition, particularly Cr and Al content.

Barrett, C. A.↗
NASA NTRS1974

Addition of silicon improves oxidation resistance of nickel based superalloys

Specific weight changes of nickel-base superalloy B-1900 and B-1900 + 1% Si specimens were tested at 1273 K. B-1900 was losing weight at an increasing rate due to spalling of oxide scale while B-1900 + 1% Si was still gaining weight at low, nearly constant rate. Similar comparison in weight change was observed for specimens tested at 1373 K.

Lowell, C. E.↗
NASA NTRS1973

Isothermal and cyclic oxidation at 1000 and 1100 deg C of four nickel-base alloys: NASA-TRW VIA, B-1900, 713C, and 738X

The isothermal and cyclic oxidation resistance of four cast Ni-base gamma + gamma prime alloys, NASA-TRW Via, B-1900, 713C, and 738X, was determined in still air at 1000 and 1100 C. The oxidation process was evaluated by specific sample weight change with time, sample thickness change, X-ray diffraction of the scales, and sample metallography. The behavior is discussed in terms of the Cr, Al, and refractory metal contents of the alloys.

Barrett, C. A.↗
NASA NTRS1973

Effects of diffusion on aluminum depletion and degradation of NiAl coatings

Experimental demonstration of the effects of diffusion on aluminum depletion and degradation in NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were vacuum annealed at 1100 C to allow diffusion to proceed independently of oxidation. As-coated and as-diffused coatings were compared before and after cyclic furnace oxidation at 1100 C. The extent of degradation was judged by specific weight change, metallography, and electron microprobe analyses.

Smialek, J. L.↗
NASA NTRS1973

Cyclic and isothermal oxidation behavior on some Ni-Cr alloys

It is shown experimentally that 3 wt.% Si and 3 wt.% Mn additions can substantially improve the oxidation resistance of Ni-20Cr under both isothermal and cyclic conditions at 1100 and 1200 C. This is especially true in cyclic oxidation. In all cases, Si offers a greater improvement than Mn; however, the advantage of Si is substantial only during cyclic oxidation at 1200 C. The Si additions which lead to alloys of improved oxidation resistance suppress the formation of NiO and NiCr2O4 even under the most severe test conditions. The mechanism of improvement afforded by Mn appears to be the formation of MnCr2O4 at the expense of NiO and NiCr2O4.

Lowell, C. E.↗
NASA NTRS1973

Cyclic and isothermal oxidation behavior at 1100 and 1200 C of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr alloys

Alloys of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr were cyclically oxidized at 1100 and 1200 C for up to 100 hours. Oxidation behavior was judged by sample thickness and weight change, metallography, diffraction, and microprobe analysis. The least attacked were Ni-40Cr and Ni-20Cr-3Si. The alloy Ni-20Cr-3Mn was much less attacked than Ni-20Cr, but more than the other alloys. The formation of Cr2O3 accounted for the increased resistance of Ni-Cr and Ni-20Cr-3Si, and the formation of MnCr2O4 accounts for the improvement in Ni-20Cr-3mn over Ni-20Cr.

Lowell, C. E.↗
NASA NTRS1973

Formation and breakdown of a protective layer of chromium sesquioxide on L-605 alloy at 1100 C

The formation and breakdown of a protective layer of Cr2O3 on the cobalt-base alloy L-605 during oxidation at 1100 C was evaluated. Deformed surface layers, pressure, and moisture were variables. Increasing surface deformation, decreasing pressure, and decreasing moisture increased time to breakdown. A model was deduced. The breakdown of the Cr2O3 layer was caused by a combination of growth stresses and volatilization. Breakdown exposed a chromium-depleted alloy to air, resulting in very rapid oxidation, which continued until consumption of the depletion zone was complete.

Lowell, C. E.↗
NASA NTRS1973

Effects of diffusion on aluminum depletion and degradation of NiAl coatings

Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 0.0005 torr vacuum at 1100 C for 300 hours. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hour cycles on pre-diffused and as-coated specimens. The pre-diffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.

Smialek, J. L.↗
NASA NTRS1972

Mach 1 oxidation of thoriated nickel chromium at 1204 C /2200 F/.

Electropolished and ground samples of TD-NiCr were exposed to a 1-atm, Mach 1 gas stream at 1204 C for times up to 50 hr. The samples were subjected to both cyclic and isothermal exposure. Weight change, metal loss, X-ray diffraction, metallographic, and electron microprobe analyses were performed. Neither surface preparation nor cyclic-against-isothermal-exposure conditions had a strong effect on the oxidation behavior of the alloy. Initially, a Cr2O3 layer was formed whose volatilization resulted in a very rapid loss of metal - more than 40 microns in the first hour. At about 1 hr, the Cr2O3 layer broke down and NiO began to cover the surface. By 5 hr, the NiO had covered the surface and the rate of loss slowed. The rate-controlling step was diffusion of Cr through NiO.

Lowell, C. E.↗
NASA NTRS1972

The 1200 C cyclic oxidation behavior of two nickel-aluminum alloys (Ni3AL and NiAl) with additions of chromium, silicon, and titanium

The alloys Ni3Al and NiAl with and without 1 and 3 atomic percent chromium, silicon, and titanium replacing the aluminum were cyclically oxidized at 1200 C for times to 200 hours, and the results were compared with those obtained with the alloy B-1900 subjected to the same oxidation process. The evaluation was based on metal recession, specific weight change, metallography, electron microprobe analysis, and X-ray diffraction. The oxidation resistance of Ni3Al was improved by Si, unaffected by Ti, and degraded by Cr. The oxidation resistance of NiAl was slightly improved by Ti, unaffected by Si, and degraded by Cr. The oxidation resistance of Ni3Al with 1 atomic percent Si was nearly equal to that of NiAl. Alloy B-1900 exhibited oxidation resistance comparable to that of Ni3Al + Cr compositions.

Lowell, C. E.↗
NASA NTRS1972

Oxidation of TD nickel at 1050 C and 1200 C as compared with three grades of nickel of different purity

The isothermal oxidation of three nickels of different purity, Ni-200, Ni-270, and JM-Ni, was compared with that of TD-Ni in air at 1050 and 1200 C. The samples were oxidized as ground, as polished, or as annealed and polished. Weight change, metal loss, scale thickness, oxide morphology, and scale texture were determined. In degree of oxidation, TD-Ni was nearly the same as the higher purity materials, Ni-270 and JM-Ni; and less pure Ni-200 oxidized more than the others. However, in microstructure and scale texture the TD-Ni more closely resembled Ni-200. Grinding only charged the texture of the oxides of Ni_200 and TD-Ni.

Lowell, C. E.↗
NASA NTRS1971

Mach 1 oxidation of thoriated nickel chromium at 1204 C (2200 F)

TD NiCr was exposed to a Mach 1, 1-atmosphere gas stream at 1204 C for times up to 50 hours. Weight change, metal thickness loss, X-ray diffraction, metallographic, and electron microprobe analyses were made. Neither surface preparation nor thermal cycling had an appreciable effect on the results. Initially, Cr2O3 formed and volatilized, allowing a rapid metal loss rate of 40 microns per hour. After about 1 hour the Cr2O3 broke down, resulting in an NiO overgrowth. The metal loss rate then slowed to 2.5 microns per hour and remained constant to 50 hours.

Lowell, C. E.↗