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Development of wear-resistant coatings for cobalt-base alloys

Description: The level of nuclear plant radiation exposure due to activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. Laboratory pin-on-disc and rolling contact wear tests were used to evaluate the wear performance of several coatings. Based on the results of these tests, multilayer Cr-nitride coatings and ion nitriding are the most promising approaches.
Date: October 22, 1999
Creator: Cockeram, B.V.
Partner: UNT Libraries Government Documents Department

Effect of electron irradiation on the 3C-4H transformation in a Co-Fe alloy

Description: Preliminary results are presented of a study of electron irradiation on the martensitic transformation in a relatively dilute terminal solid solution of Co+5.75 wt% Fe. The experiments demonstrate qualitatively the profound effect that the damage structure produced by electron irradiation can have on these simple martensitic transformations. Further study is being pursued to attempt to quantify the transformation retardation effect.
Date: March 1, 1996
Creator: Allen, C.W. & Mori, H.
Partner: UNT Libraries Government Documents Department

Theory of point-defects, non-stoichiometry, and solute additions in SmCo{sub 5+x}-Sm{sub 2}Co{sub 17{minus}y} and related compounds

Description: There is considerable interest in the possibility of producing Sm-Co-based nanocomposite magnets by rapid solidification and other far-from-equilibrium processing methods. Thermodynamic and kinetic models are quite valuable in understanding and optimizing such methods. This paper describes a method of estimation, utilizing tight-binding-based bond-order interatomic interaction potentials, of the thermodynamic properties of point defects such as vacancies, interstitials, antisite defects, and solute additions in the SmCo{sub 5+x} and Sm{sub 2}Co {sub 17}-y phases and related rare-earth-transition metal compounds. Illustrative calculations for point defects in SmCo{sub 5} will be presented. The results suggest a unified model of the thermodynamic properties of the SmCo{sub 5+x} -- Sm{sub 2} Co{sub 17{minus}y} region of the phase diagram, based on the 1-5 structure and the replacement of Sm by interacting dumb-bell interstitials to form the 2-17 structure; the model is similar in nature to theories of the thermodynamics of metal hydrides.
Date: September 3, 1998
Creator: WELCH,D.O.
Partner: UNT Libraries Government Documents Department

X-ray photoemission studies of rare earth hard magnets

Description: From 19th conference on magnetism and magnetic materials; Boston, Massachusetts, USA (13 Nov 1973). An attempt was made to probe the electronic properties of the RCo/sub 5/ compounds by x-ray photoelectron spectroscopy studies of SmCo/sub 5/ and PrCo/sub 5/ and to relate the results to the properties o f the pure metals and to the picture developed to describe the magnetism of the compounds. Results indicate a valence band structure similar to that of Co metal; there is the suggestion that if there is charge flow it is off the rare-earth sites; there appears to be significant change in the 4f spectra from that of the pure rareearth metals; and there is a suggestion of f-- d hybridization. (auth)
Date: January 1, 1973
Creator: Cuthill, J.R.; McAlister, A.J.; Erickson, N.E. & Watson, R.E.
Partner: UNT Libraries Government Documents Department

Materials Performance in a Radioactive Waste/Glass Melter System Environment

Description: Corrosion coupons were exposed in a scale demonstration melter system in order to evaluate the performance of alternate materials for use as top head and off gas components in the Defense Waste Processing Facility (DWPF) melter at the DOE`s Savannah River Site. The demonstration system is a 1/10 scale prototypic version of the DWPF melter. In DWPF, high activity radioactive waste will be vitrified and encapsulated for long-term storage. Fifteen different nickel and cobalt base alloys were exposed for five months to corrosive vapors and molten glass, characteristic of the DWPF melter except for radioactivity. Process conditions included temperatures approaching 900{degree}C and a synthetic acid waste containing formates, halides, sulfates, phosphates, nitrates, and mercury. Severe oxidation of the N06625 in both the splash zone and vapor space was attributed to the formation of MoO{sub 3}. Cobalt containing alloys experienced significant degradation in this environment. Results of the metallurgical examination showed that alloys containing 50 wt % Ni, 25 wt % Cr, and additions of 2 to 3 wt % of either aluminum or silicon performed comparably or better than the N06690 in both the splash zone and in the vapor space near the lid. Corrosion rates for these alloys did not exceed 0.2 mm per year (8 mpy).
Date: December 1, 1995
Creator: Imrich, K.J. & Jenkins, C.F.
Partner: UNT Libraries Government Documents Department

Mechanical properties of aluminized CoCrAlY coatings in advanced gas turbine blades

Description: The microstructure/composition and mechanical properties (22-950 C) in aluminized CoCrAlY coatings of advanced gas turbine blades have been examined using scanning Auger microprobe and a small punch (SP) testing method. Aluminized coatings were made of layered structure divided into four regimes: (1) Al enriched and Cr depleted region, (2) Al and Cr graded region, (3) fine grained microstructure with a mixture of Al and Cr enriched phases and (4) Ni/Co interdiffusion zone adjacent to the interface SP tests demonstrated strong dependence of the deformation and fracture behavior on the various coatings regimes. Coatings 1 and 2 showed higher microhardness and easier formation of brittle cracks in a wide temperature range, compared to coatings 3 and 4. The coating 3 had lower room temperature ductility and conversely higher elevated temperature ductility than the coating 4 due to a precipitous ductility increase above 730 C. The integrity of aluminized coatings while in-service is discussed in light of the variation in the low cycle fatigue life as well as the ductility in the layered structure.
Date: July 1, 1997
Creator: Kameda, J.; Bloomer, T.E.; Sugita, Y.; Ito, A. & Sakurai, S.
Partner: UNT Libraries Government Documents Department

Optical and magneto-optical properties of single crystals of RFe{sub 2} (R = Gd, Tb, Ho, and Lu) and GdCo{sub 2} intermetallic compounds

Description: The author has studied the diagonal and off-diagonal optical conductivity of RFe{sub 2}(R = Gd, Tb, Ho, Lu) and GdCo{sub 2} single crystals grown by the flux method. Using spectroscopic ellipsometry the author has measured the dielectric function from 1.5 to 5.5 eV. The magneto-optical Kerr spectrometer at temperatures between 7 and 295 K and applied magnetic fields between 0.5 to 1.6 T. The apparatus and calibration method are described in detail. Using magneto-optical data and optical constants he derives the experimental value of the off-diagonal conductivity components. Theoretical calculations of optical conductivities and magneto-optical parameters were performed using the tight binding-linear muffin tin orbitals method within the local spin density approximation. He applied this TB-LMTO method to LuFe{sub 2}. The theoretical results obtained agree well with the experimental data. The oxidation effects on the diagonal part of the optical conductivity were considered using a three-phase model. The oxidation effects on the magneto-optical parameters were also considered by treating the oxide layer as a nonmagnetic thin transparent layer. These corrections change not only the magnitude but also the shape of the optical conductivity and the magneto-optical parameters.
Date: February 12, 1999
Creator: Lee, S.J.
Partner: UNT Libraries Government Documents Department

Development of wear-resistant coatings for cobalt-base alloys

Description: The costs and hazards resulting from nuclear plant radiation exposure with activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. However, the hardnesses of many cobalt-base wear alloys are significantly lower than conventional PVD hard coatings, and mechanical support of the hard coating is a concern. Four approaches have been taken to minimize the hardness differences between the substrate and PVD hard coating: (1) use a thin Cr-nitride hard coating with layers that are graded with respect to hardness, (2) use a thicker, multilayered coating (Cr-nitride or Zr-nitride) with graded layers, (3) use nitriding to harden the alloy subsurface followed by application of a multilayered coating of Cr-nitride, and (4) use of nitriding alone. Since little work has been done on application of PVD hard coatings to cobalt-base alloys, some details on process development and characterization of the coatings is presented. Scratch testing was used to evaluate the adhesion of the different coatings. A bench-top rolling contact test was used to evaluate the wear resistance of the coatings. The test results are discussed, and the more desirable coating approaches are identified.
Date: March 1, 1999
Creator: Cockeram, B.V.
Partner: UNT Libraries Government Documents Department

The role of microstructural phenomena in magnetic thin films. Progress report, [August 1990--December 1991]

Description: We have pursued two lines of research during the first year and a half of this work. In the main portion of the project we have performed fundamental investigations of the microstructure and crystallographic texture of Co based alloys deposited on Cr underlayers. This has included atomic resolution electron microscopy of the cross-sections of CoNiCr on Cr thin films, as well as studies of the microstructures and properties of magnetic thin films produced with interlayers of Cr. The other portion of our work has centered on understanding the crystallography and crystal structure of CoSm/Cr thin films. These CoSm films have the potential of being utilized as high density media, but their structure is not yet understood.
Date: December 31, 1991
Creator: Laughlin, D. E. & Lambeth, D. N.
Partner: UNT Libraries Government Documents Department

Micromagnetics and microstructure of epitaxially grown Co and Co-Cr films suitable for perpendicular magnetic recording

Description: Highly c-axis oriented, single crystal films of Co{sub 1-x}Cr{sub x} (0{le} {times} {le} 0.3) have been grown epitaxially on mica substrates by e-beam evaporation. Films grown on Ru underlayers have an average grain size of 50--80nm, negligibe fcc content and very narrow c-axis dispersions. For Co films (x=0), the as-grown magnetization structure are mainly 180{degree} domain walls with a uniform distribution of cross-ties for thinner samples ({le} 300{Angstrom}), whilst thicker (>400{Angstrom}) ones show stripe domains. These images were analysed in detail to measure that wall widths and associated energy densities for as-grown, remanent and ac- magnetised samples. As expected, the magnetic properties of these films are composition dependent. However, for any Cr concentration, these films exhibit the largest saturation magnetisation when compared with either sputtered or evaporated samples. This enhancement can be attributed to a nanometer-scale segregation of Cr, which in these samples, which in these samples, could be particularly aided by the diffusion on the close-packed planes of the films with very narrow c-axis dispersions. Preliminary X-ray microanalysis and NMR data support this interpretation.
Date: July 1, 1994
Creator: Krishnan, K. M.; Takeuchi, T.; Hirayama, Y.; Donnet, D. M.; Honda, Y. & Futamoto, M.
Partner: UNT Libraries Government Documents Department

Positron lifetime measurements as a non-destructive technique to monitor fatigue damage. Progress report

Description: The critical parts (electronics in the base of the photomultipliers) of the electronics have been brought under temperature control of within plus or minus 0.1 deg C thus minimizing drift problems. In data analysis a computer program is functioning in which there are no fixed experimental parameters. This permits much more accurate results. Samples of pure Ni and a Ni-66.5% Co alloy have been fatigued to failure. Positron lifetime and x-ray particle size were measured at various fatigue lives and transmission electron microscopy was performed after failure. Good correlation was found between the three techniques and it appears that positron lifetime can be used as an effective tool to study fatigue mechanisms. It is a more sensitive nondestructive measurement than is x- ray particle size. It has been established that grain boundaries make a distinct contribution to the positron lifetime. Positron lifetime increases with plastic tensile strain in a manner dependent on initial grain size and in a manner consistent with existing work hardening theories. There are indications that the positron lifetime may be sensitive to hydrogen embrittlement or hydrogen assisted cracking (HAC) in steels. Experiments to study lifetime changes during cyclic softening and cyclic hardening of ArSI 4340 steel are beginning. (auth)
Date: September 1, 1973
Creator: Byrne, J.G.
Partner: UNT Libraries Government Documents Department

The role of microstructural phenomena in magnetic thin films

Description: We have pursued two lines of research during the first year and a half of this work. In the main portion of the project we have performed fundamental investigations of the microstructure and crystallographic texture of Co based alloys deposited on Cr underlayers. This has included atomic resolution electron microscopy of the cross-sections of CoNiCr on Cr thin films, as well as studies of the microstructures and properties of magnetic thin films produced with interlayers of Cr. The other portion of our work has centered on understanding the crystallography and crystal structure of CoSm/Cr thin films. These CoSm films have the potential of being utilized as high density media, but their structure is not yet understood.
Date: January 1, 1991
Creator: Laughlin, D.E. & Lambeth, D.N.
Partner: UNT Libraries Government Documents Department

Laboratory galling tests of several commercial cobalt-free weld hardfacing alloys

Description: Since the mechanical properties of most wear materials are generally insufficient for structural applications, hardfacing alloys have been traditionally weld deposited to provide a wear resistance surface for a base material. An important attribute of a hardfacing alloy that is subjected to high load sliding contact is the resistance to adhesive (galling) damage. Although Co-base hardfacing alloys generally possess excellent galling wear resistance, there is interest in developing cobalt-free replacement hardfacings to reduce radiation exposure costs. A laboratory galling test has been developed for weld hardfacing deposits that is a modification of the standardized ASTM G98-91 galling test procedure. The procedure for testing a weld hardfacing deposit on a softer base metal using a button-on-block configuration is described. The contact stresses for the initiation of adhesive galling damage were measured to rank the galling resistance of several commercial Fe-base, Ni-base and Co-base hardfacing alloys. Although the galling resistance of the Fe-base alloys was generally superior to the Ni-base alloys, neither system approached the excellent galling resistance of the Co-base alloys. Microstructure examinations were used to understand the micro-mechanisms for the initiation and propagation of galling damage. A physical model for the initiation and propagation of adhesive wear is used to explain the lower galling resistance for the Ni-base hardfacings and to understand the influence of composition on the galling resistance of Ni-base alloys. The composition of some Ni base hardfacings was modified in a controlled manner to quantify the influence of specific elements on the galling resistance.
Date: April 1, 1997
Creator: Cockeram, B.V.; Buck, R.F. & Wilson, W.L.
Partner: UNT Libraries Government Documents Department

Annealing behavior of high permeability amorphous alloys

Description: Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.
Date: June 1, 1980
Creator: Rabenberg, L.
Partner: UNT Libraries Government Documents Department

Microstructure and properties of step aged rare earth alloy magnets. [Co-Sm-Cu-Fe-Zr]

Description: Alloys with compositions Co-25.5 wt/o Sm-8 w/o Cu-15 w/o Fe-3 w/o Zr and Co-Sm-Cu-Fe-1.5 w/o Zr have been step aged to produce magnets with coercive force (iHc) in the range of 10 to 25k0e. The high coercive force magnets are typically aged at 800 to 850/sup 0/C for 10 to 30 hours following the solution treatment at 1150/sup 0/C. Subsequently, these are step aged to produce materials with high coercivity. The microstructure in all these alloys has a 2 phase cellular morphology with 2:17 phase surrounded by a 1:5 boundary phase. The long aging treatments at 800 to 850/sup 0/C lead to coarsening of the two phase structure. The subsequent step-aging does not change the morphology, but only changes the chemical composition of the two phases. Best properties are obtained in materials with a coherent microstructure of optimum boundary phase thickness and optimum chemical composition. The highest values of iHc obtained so far are approx. 26k0e and approx. 16 k0e for the 3% Zr and 1.5% Zr alloys respectively. The best hard magnetic properties of (BH) max = 33 MG0e and iHc = 13k0e are for a 25% Sm-20% Fe-4 Cu-2% Zr alloy.
Date: November 1, 1980
Creator: Mishra, R.K.; Thomas, G.; Yoneyama, T.; Fukuno, A. & Ojima, T.
Partner: UNT Libraries Government Documents Department

The oxidation behavior of Co-15 wt % Cr alloy containing dispersed oxides formed by internal oxidation

Description: Internal oxidation pretreatments of Co-15wt%Cr and Co-15wt%Cr-1wt%Ti were carried out using a Rhines pack in quartz, in mullite and in alumina. A dispersion of titanium oxide particles formed in the Ti-containing alloy as a result of the internal oxidation. However, silicon also diffused into all treated specimens when the pretreatments were carried out in quartz or in mullite. The effect of various pretreatments on the subsequent oxidation of these alloys was studied at 1000{degree}C, and compared with that of Co-15wt%Cr-1wt%Si alloy. The main purpose of this study was to determine the relative effectiveness of the dispersed oxide particles and the contaminated silicon on the selective oxidation of chromium. It was found that the oxidation behavior of both treated alloys were strongly affected by the degree of silicon contamination. Selective oxidation of chromium to form a nearly continuous protective Cr{sub 2}O{sub 3} scale was achieved with greater than 0.4wt% silicon. The presence of dispersed particles reduced initial oxidation rate, but was ineffective in promoting Cr{sub 2}O{sub 3} scale formation.
Date: December 1, 1991
Creator: Hou, P. Y.; Shui, Z. R. & Stringer, J.
Partner: UNT Libraries Government Documents Department

Weld overlay coatings for erosion control. Task A: Literature review, progress report

Description: A literature review was made. In spite of similarities between abrasive wear and solid particle erosion, weld overlay hardfacing alloys that exhibit high abrasion resistance may not necessarily have good erosion resistance. The performance of weld overlay hardfacing alloys in erosive environments has not been studied in detail. It is believed that primary-solidified hard phases such as carbides and intermetallic compounds have a strong influence on erosion resistance of weld overlay hardfacing alloys. However, relationships between size, shape, and volume fraction of hard phases in a hardfacing alloys and erosion resistance were not established. Almost all hardfacing alloys can be separated into two major groups based upon chemical compositions of the primary solidified hard phases: (a) carbide hardening alloys (Co-base/carbide, WC-Co and some Fe base superalloys); and (b) intermetallic hardening alloys (Ni-base alloys, austenitic steels, iron-aluminides).
Date: March 3, 1993
Creator: Levin, B.; DuPont, J. N. & Marder, A. R.
Partner: UNT Libraries Government Documents Department

Al/sub 2/O/sub 3/ adherence on CoCrAl alloys

Description: Adherence of protective oxides on NiCrAl and CoCrAl superalloys has been promoted by a dispersion of a highly oxygen reactive element or its oxide being produced within the protection system. Two aspects of this subject are investigated here: the use of Al/sub 2/O/sub 3/ as both the dispersion and protective oxide; and the production of an HfO/sub 2/ dispersion while simultaneously aluminizing the alloy. It was found that an Al/sub 2/O/sub 3/ dispersion will act to promote the adherence of an external scale of Al/sub 2/O/sub 3/ to a degree comparable to previously tested dispersions and an HfO/sub 2/ dispersion comparable to that produced by a Rhines pack treatment is produced during aluminization.
Date: April 1, 1980
Creator: Kingsley, L.M.
Partner: UNT Libraries Government Documents Department

FY 1984 and FY 1985 geochemistry and materials studies in support of the Magma Energy Extraction Program

Description: Geochemistry and materials studies are being performed in support of the Magma Energy Extraction Program. The work is largely restricted to: (1) characterizing magmatic environments at sites of interest, (2) testing engineering materials in laboratory simulated magmatic environments, (3) investigating chemical mass transport effects inherent in designs for direct contact heat exchangers, and (4) evaluating degassing hazards associated with drilling into and extracting energy from shallow magma. Magma characterization studies have been completed for shallow magma at Long Valley, Coso volcanic field, and Kilauea volcano. The behavior of 17 commercially available materials has been examined in rhyolite magma at 850/sup 0/C and 200 MPa for periods up to seven days. Analysis of reaction products from materials tests to date indicate that oxidation is the main corrosion problem for most alloys in rhyolitic magma. Considerations of corrosion resistance, high-temperature strength, and cost indicate nickel-base superalloys offer the most promise as candidates for use in rhyolitic magma.
Date: April 1, 1986
Creator: Westrich, H. R.; Weirick, L. J.; Cygan, R. T.; Reece, M.; Hlava, P. F.; Stockman, H. W. et al.
Partner: UNT Libraries Government Documents Department

Vacuum properties of sintered SmCo/sub 5/ magnets

Description: There are many desirable applications of powerful, rare-earth permanent magnets made of sintered SmCo/sub 5/ material within vacuum systems. One application is the use of large numbers of SmCo/sub 5/ magnets to provide the undulating magnetic field in a free-electron-laser wiggler structure. Tests were conducted at Los Alamos to determine the suitability of SmCo/sub 5/ magnets in a vacuum environment of approx. 10/sup -6/ torr. The vacuum performances of the wiggler system, with and without the SmCo/sub 5/ magnets (having approx. 11% of the total surface area) installed, were essentially identical. These tests indicate that SmCo/sub 5/ magnets have good vacuum properties and are suitable for use in many vacuum systems.
Date: December 1, 1981
Creator: Warren, R.W.; DePaula, R.F. & Hansborough, L.D.
Partner: UNT Libraries Government Documents Department

DOE/JPL advanced thermionic technology program. Progress report No. 32, February--March 1978

Description: Optimized performance data for converter No. 183 with a L605 alloy emitter and a nickel collector are presented for emitter temperatures of 1300, 1400, and 1500 K. The L605 work function is plotted versus the ratio of emitter temperature to cesium reservoir temperature. Progress on the combustion-heated thermionic device and hot shell development are reported. The design of the guarded triode converter with a ring electrode is described. A diagram of the variable-spaced hybrid converter is included. (WHK)
Date: January 1, 1978
Partner: UNT Libraries Government Documents Department

Long term materials test program. Quarterly report, October-December 1983

Description: The long-term exposure of gas turbine vane and blade base alloys and a variety of protective coating systems to the effluent from a pressurized fluidized bed coal combustor has reached 4398 hours. After 4053 hours, FeCrAlY overlay coatings and platinum/rhodium-aluminide pack diffusion coatings show excellent resistance to corrosion attack at 1500/sup 0/F. Cobalt-base coatings are somewhat more susceptible to hot corrosion, and the unprotected nickel and cobalt-base alloys are most susceptible to corrosion, although corrosion rates have decreased to less than 1 mil/1000 hours for all materials at 1500/sup 0/F; i.e., corrosion penetration data is evolving parabolically. The three-stage cyclone cleanup system became severely distorted after approximately 5600 hours total service life. Distortion of the cyclones contributed to an increased dust loading to the material test sections, 110 to 250 ppM versus normal loadings of 30 to 90 ppM, for a period of about 75 hours. This increase in dust loading caused severe erosion of the airfoils in the high-velocity test section. Metal recession ranged 4 to 18 mils of leading edge loss on the impulse airfoils, and 11 to 27 mils of leading edge loss on the reaction airfoils. A new three-stage cyclone system was installed and dust loadings now range from 15 to 45 ppM.
Date: January 1, 1984
Partner: UNT Libraries Government Documents Department