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Advances in excimer laser processing of materials

Description: The use of pulsed excimer lasers to surface processing of materials hinges on an understanding of the nature of the interaction between the laser energy and the material. The application of this understanding of the laser materials interaction to surface modification must also recognize the existence of thermodynamic driving forces and kinetic limitations in light of the short duration of a single pulse event. For species that have higher solubility in the liquid than in the solid phase, segregation by ``zone refinement`` from multiple passes by a solidification front to the surface results in surface enrichment of those species. The most obvious applications for surface processing occur where the bulk properties of a component are not commensurate with the needed surface properties. Improvements in surface mechanical properties have been observed in a number of metal and ceramic alloys. In the microelectronics industry, apart from micromachining or material removal applications, for which excimers are indeed well suited, the same features of the laser-materials interaction that are used to modify the mechanical or electrochemical properties of a surface can be used to advantage. Further advances, such as those demonstrated in microelectronics, await application-specific developments. 22 refs., 1 fig.
Date: August 1, 1996
Creator: Jervis, T.R.; Nastasi, M. & Hirvonen, J.-P.
Partner: UNT Libraries Government Documents Department

Simulation of surface roughness during the formation of thermal spray coatings

Description: The formation of a thermal spray coating was analyzed to identify methods to reduce the surface roughness of the coating. A new methodology was developed which uses a string of equally spaced node points to define the shape of the coating surface and to track the shape change as the thermal spray mass is deposited. This allows the calculation of arbitrary shapes for the coating surface which may be very complex. The model simulates the stochastic deposition of a large number of thermal spray droplets, where experimental data is used for the mass flux distribution on the target surface. This data shows that when the thermal spray mass impinges on the target surface, a large fraction of it (over-spray) splashes off the target and is re-deposited with a small spray angle, resulting in a large coating roughness. This analysis was used in a parameter study to identify methods for reducing the coating roughness. Effect of the shape of the profile for the pre-roughened substrate was found to be small. Decreasing the droplet size by a factor of 2 decreased the roughness by 13%. Increasing the spray angle for the over-spray by a factor of 2 decreased the roughness by 50%, and decreasing the amount of over- spray by a factor of 2 decreased the roughness by 51%.
Date: July 1, 1996
Creator: Kanouff, M.P.
Partner: UNT Libraries Government Documents Department

Experimental measurement and numerical simulation of residual stresses in a carburized layer of a 5120 steel

Description: A combined experimental and numerical study of residual stress and microstructure has been performed for a carburized steel 5120 specimen. Specimens were cut from 5120 steel bar stock, in the shape of hockey pucks and were subsequently carburized and quenched. X-ray diffraction was used to record stress profiles through the case for the martensite and retained austenite on the two flat surfaces oriented up and down during the quench. Layer removal was performed by electropolishing. Rietveld analysis was used to determine the lattice parameters of the phases at each depth varying with both carbon content and stress. The experimental measurements are compared with a numerical simulation of the phase transformation and the metallurgical changes following the carburization and quench. Results am discussed in the context of the microstructure and the role played by the retained austenite in interpretation. In addition the carbon profile obtained from the lattice parameters is compared with profiles measured using burnout.
Date: September 1, 1995
Creator: Rangaswamy, P.; Bourke, M.A.M.; Shipley, J.C. & Goldstone, J.A.
Partner: UNT Libraries Government Documents Department

Active plasma source formation in the MAP diode

Description: The Ion Beam Surface Treatment (IBEST) program is exploring using ion beams to treat the surface of a wide variety of materials. These experiments have shown that improved corrosion resistance, surface hardening, grain size modification, polishing and surface cleaning can all be achieved using a pulsed 0.4-0.8 MeV ion beam delivering 1-10 J/cm{sup 2}. The Magnetically-confined Anode Plasma (MAP) diode, developed at Cornell University, produces an active plasma which can be used to treat the surfaces of materials. The diode consists of a fast puff valve as the source of gas to produce the desired ions and two capacitively driven B-fields. A slow magnetic field is used for electron insulation and a fast field is used to both ionize the puffed gas and to position the plasma in the proper spatial location in the anode prior to the accelerator pulse. The relative timing between subsystems is an important factor in the effective production of the active plasma source for the MAP diode system. The MAP diode has been characterized using a Langmuir probe to measure plasma arrival times at the anode annulus for hydrogen gas. This data was then used to determine the optimum operating point for the MAP diode on RHEPP-1 accelerator shots. Operation of the MAP diode system to produce an ion beam of 500 kV, 12 kA with 40% efficiency (measured at the diode) has been demonstrated.
Date: July 1, 1995
Creator: Lamppa, K.P.; Stinnett, R.W. & Renk, T.J.
Partner: UNT Libraries Government Documents Department

Hydroforming of Multi-Cell Niobium and NbCu-Clad Cavities

Description: Technological aspects of seamless tube fabrication and multi-cell cavity production by hydroforming will be discussed. Problems related to the fabrication of seamless cavities from bulk niobium are mainly solved. Several two cell- and three cell- niobium cavities have been produced by hydroforming at DESY. A 9-cell cavity of the TESLA shape has been completed from three sub-sections at company ZANON. The cavity was treated by electropolishing (EP) and successfully RF-tested. Two 3-cell units equipped with niobium beam pipes are being RF-tested after BCP surface treatment. The temperature mapping method with Jlab’s two-cell thermometry system is applied for performance analysis. It is of particular interest to compare the seamless cavity quench locations to those from standard cavities. The cryogenic test results and the T-mapping findings will be discussed. Of special interest is the combination of the seamless technique with NbCu cladding, i.e. the fabrication of cavity from bimetallic clad NbCu tube by hydroforming. Fabrication of single-cell and multi-cell NbCu clad cavities by hydroforming from bimetallic tubes is proven. Some test results will be presented.
Date: May 1, 2009
Creator: X. Singer, I. Jelezov, A. Matheisen, W. Singer, P. Kneisel
Partner: UNT Libraries Government Documents Department

Advance in Vertical Buffered Electropolishing on Niobium for Particle Accelerators*

Description: Niobium (Nb) is the most popular material that has been employed for making superconducting radio frequency (SRF) cavities to be used in various particle accelerators over the last couple of decades. One of the most important steps in fabricating Nb SRF cavities is the final chemical removal of 150 {mu}m of Nb from the inner surfaces of the SRF cavities. This is usually done by either buffered chemical polishing (BCP) or electropolishing (EP). Recently a new Nb surface treatment technique called buffered electropolishing (BEP) has been developed at Jefferson Lab. It has been demonstrated that BEP can produce the smoothest surface finish on Nb ever reported in the literature while realizing a Nb removal rate as high as 10 {mu}m/min that is more than 25 and 5 times quicker than those of EP and BCP(112) respectively. In this contribution, recent advance in optimizing and understanding BEP treatment technique is reviewed. Latest results from RF measurements on BEP treated Nb single cell cavities by our unique vertical polishing system will be reported.
Date: September 1, 2011
Creator: Wu, A. T.; Jin, S.; Mammosser, J. D.; Reece, C. E.; Rimmer, R. A.; Lin, L. et al.
Partner: UNT Libraries Government Documents Department

R&D for the Sponge Cleaning of Superconducting RF Cavity

Description: The Electro-polishing process is the best candidate of final surface treatment for the production of ILC cavities. Nevertheless, the broad distribution of the gradient caused by field emitters in cavities is sitll a serious problem for the EP process. Ethanole- and degreaser-rinse processes after the EP process were found to be effective to decrease the field emmitter in recent studies, however, these are not perfect yet. We tried to test the sponge cleaning as the post EP process to remove the field emitter inside the cavcity. This article describe the results of series tests with a proto-type sponge-cleaning tool for single-cell cavity at KEK.
Date: May 1, 2009
Creator: Saeki, T; Hayano, H; Kato, S; Nishiwaki, M; Sawabe, M; Ueno, K et al.
Partner: UNT Libraries Government Documents Department

DIFFUSION OF H THROUGH PD MEMBRANES EFFECTS OF NON-IDEALITY ON DH AND ED

Description: H diffusion constants, D{sub H}, have been obtained from steady-state fluxes across Pd membranes with the downstream side maintained at p{sub H2} {approx} 0. Good linearity of plots of H flux versus (1/d), where d is the thickness, attests to the H permeation being bulk diffusion controlled in this temperature (423 to 523K) and p{sub H2} range ({le} 0.2 MPa). D{sub H} values have been determined at constant p{sub up} and also at constant (H/Pd)=r conditions. H fluxes through Pd membranes with three different surface treatments have been investigated (polished (un-oxidized), oxidized, and palladized) in order to determine the effects of these pretreatments. The palladized and oxidized membranes give similar D{sub H} values but the polished membranes give values about 12% lower. For diffusion in a concentration gradient D{sub H}*(c{sub H}/RT)(d{mu}{sub H}/dx) is the more proper description, where c{sub H} is the H concentration, rather than D{sub H}(dc{sub H}/dx) where D{sub H} and D{sub H}* are the concentration-dependent and independent diffusion constants. D{sub H}* can be obtained from D{sub H} using the thermodynamic factor, D{sub H}(r) = D{sub H}*({partial_derivative}lnp{sub H2}{sup 1/2}/{partial_derivative}lnr){sub T} = D{sub H}*f(r). In the commonly employed situation where there is a large difference in concentrations between the upstream and downstream sides of a membrane, the thermodynamic factor varies with distance through the membrane and this should be allowed for in obtaining D{sub H}*. Procedures are given and utilized for using D{sub H}(c{sub H}) to determine D{sub H}* values when there is a large concentration gradient through the membrane. Activation energies for diffusion, E{sub D}(c{sub H}), have been determined. E{sub D} is found to increase with c{sub H} which can be attributed to the thermodynamic factor. D{sub H}* values have been found to increase with H content.
Date: March 9, 2007
Creator: Shanahan, K
Partner: UNT Libraries Government Documents Department

Comparison of Cavitation-Erosion Resistance of Carburized and Carburized-Plus-Nitrided 316LN Stainless Steel in Mercury

Description: Annealed type 316LN stainless steel in the (1) carburized and the (2) carburized plus nitrided conditions was evaluated for cavitation-erosion resistance in ambient temperature mercury using a vibratory horn method. The results indicated that, relative to the specimens receiving only the carburizing treatment, the specimens that received both surface treatments exhibited substantially greater weight loss, general thinning, and profile development as a function of sonication time - with all observed degradation limited to the nitrided layer. Further, the nitride layer was observed to be susceptible to extensive cracking (occasionally leading to spallation), but the cracking was never observed to penetrate into the carburized layer. These screening test results suggest there is no improvement in cavitation-erosion resistance associated with augmentation of the carburizing treatment with plasma nitriding.
Date: May 1, 2007
Creator: Pawel, Steven J
Partner: UNT Libraries Government Documents Department

Effect of Surface Treatment on the Performance of CARALL, Carbon Fiber Reinforced Aluminum Joints

Description: Fiber-metal laminates (FML) are the advanced materials that are developed to improve the high performance of lightweight structures that are rapidly becoming a superior substitute for metal structures. The reasons behind their emerging usage are the mechanical properties without a compromise in weight other than the traditional metals. The bond remains a concern. This thesis reviews the effect of pre-treatments, say heat, P2 etch and laser treatments on the substrate which modifies the surface composition/roughness to impact the bond strength. The constituents that make up the FMLs in our present study are the Aluminum 2024 alloy as the substrate and the carbon fiber prepregs are the fibers. These composite samples are manufactured in a compression molding process after each pre-treatment and are then subjected to different tests to investigate its properties in tension, compression, flexural and lap shear strength. The results indicate that heat treatment adversely affects properties of the metal and the joint while laser treatments provide the best bond and joint strength.
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Date: August 2017
Creator: Bandi, Raghava
Partner: UNT Libraries

High-Throughput Laser Peening of Metals Using a High-Average-Power Nd: Glass Laser System

Description: Laser shot peening, a surface treatment for metals, is known to induce residual compressive stresses to depths of over 1 mm providing improved component resistance to various forms of failure. Recent information also suggests that thermal relaxation of the laser induced stress is significantly less than that experienced by other forms of surface stressing that involve significantly higher levels of cold work. We have developed a unique solid state laser technology employing Nd:glass amplifier slabs and SBS phase conjugation that enables this process to move into high throughput production processing.
Date: November 1, 1999
Creator: Dane, C.B.; Hackel, L.A.; Halpin, J.; Daly, J.; Harrisson, J. & Harris, J.
Partner: UNT Libraries Government Documents Department

National Metal Casting Research Institute final report. Volume 2, Die casting research

Description: Four subprojects were completed: development and evaluation of die coatings, accelerated die life characterization of die materials, evaluation of fluid flow and solidification modeling programs, selection and characterization of Al-based die casting alloys, and influence of die materials and coatings on die casting quality.
Date: June 1, 1994
Creator: Jensen, D.
Partner: UNT Libraries Government Documents Department

Cratering behavior in single- and poly-crystalline copper irradiated by an intense pulsed ion beam

Description: When treated with intense pulsed ion beams (IPIB), many materials exhibit increased wear resistance, fatigue life, and hardness. However, this treatment often results in cratering and roughening of the surface. In this work, high purity single crystal and polycrystalline copper samples were irradiated with pulses from an IPIB to gain insight into the causes of this cratering behavior. Samples were treated with 1,2,5, and 10 shots at 2 J/cm{sup 2} and 5 J/cm{sup 2} average energy fluence per shot. Shots were about 400 ns in duration and consisted of a mixture of carbon, hydrogen, and oxygen ions at 300 keV. It was found that the single crystal copper cratered far less than the polycrystalline copper at the lower energy fluence. At the higher energy fluence, cratering was replaced by other forms of surface damage, and the single crystal copper sustained less damage at all but the largest number of shots. Molten debris from the Lucite anode (the ion source) was removed and redeposited on the samples with each shot.
Date: December 31, 1998
Creator: Wood, B.P.; Bitteker, L.J.; Waganaar, W.J. & Perry, A.J.
Partner: UNT Libraries Government Documents Department

The electrochemical behavior of Ti and Ti alloys subjected to pulsed ion beam surface treatment

Description: Pulsed high-energy ion beams have been used to thermally treat Ti and Ti alloy surfaces to alter the electrochemical response. Two regimes have been explored: rapid melt and resolidification, and ion beam mixing. In this report, results from initial studies are presented exploring effect of these two regimes on the electrochemical behavior of Ti and Ti alloys.
Date: October 1, 1996
Creator: Sorensen, N.R.; Buchheit, R.G.; Renk, T.R.; Grabowski, K.S. & Thompson, M.O.
Partner: UNT Libraries Government Documents Department

Method for removing a stripe from the coating of a Fabry-Perot mirror

Description: We describe a method for removing a stripe from the coating of a Fabry-Perot mirror. This is accomplished by scraping off the soft coating with a finely lapped steel blade mounted on a precision mechanism to accurately position the blade and guide it for straight cuts. The width of the stripe is determined by selecting a blade of desired size. Previous methods and attempts are discussed.
Date: October 1, 1997
Creator: Perry, S.J. & Steinmetz, L.L.
Partner: UNT Libraries Government Documents Department

Hydrogen Solubility in Austenitic Stainless Steels

Description: Hydrogen solubility was directly measured in specimens of Types 304L, 21-6-9, and modified A-286 austenitic stainless steels saturated with hydrogen at 69 MPa pressure at 470 K. Nitrogen in Type 21-6-9 stainless steel and precipitate morphology in the modified Type A-286 stainless steel altered the hydrogen solubility. Cold work and surface treatment had only minor effects on hydrogen solubility in the three stainless steels. This reports discusses this study.
Date: May 21, 1981
Creator: Caskey, G.R. Jr.
Partner: UNT Libraries Government Documents Department

Surface Treatment for Improving Sulfidation Resistance of Fossil Power Systems

Description: The purpose of the cooperative research and development agreement (CRADA) between ABB Combustion Engineering, Inc. and the Oak Ridge National Laboratory (ORNL) was to develop improved, longer life, and corrosion resistance surfaces for fossil power system components for use primarily in sulfidizing environments. Four surface protection techniques were to be explored. These included diffusion process, weld overlay, hot-isostatic processing, and various spraying methods. The work was to focus on Fe{sub 3} Al-based iron aluminide to increase the component life. The successful completion of the CRADA would have required the achievement of the following four goals: (1) fabrication development, (2) characterization and possibly modification of the alloy to optimize its manufacturability and environmental resistance, (3) testing and evaluation of the specimens, and (4) fabrication and testing of prototype parts. Because of lack of active participation from the participant, this CRADA did not achieve all of its goals and was terminated prematurely. Work carried out at ORNL on the CRADA is described in this report.
Date: March 9, 2001
Creator: Sikka, V.K.
Partner: UNT Libraries Government Documents Department

Effect of Mercury Velocity on Corrosion of Type 316L Stainless Steel in a Thermal Convection Loop

Description: Two 316L thermal convection loops (TCLs) containing several types of 316L specimens circulated mercury continuously for 2000 h at a maximum temperature of 300 C. Each TCL was fitted with a venturi-shaped reduced section near the top of the hot leg for the purpose of locally increasing the Hg velocity. Results suggest that an increase in velocity from about 1.2 m/min (bulk flow) to about 5 mmin (reduced section) had no significant impact on compatibility of 316L with Hg. In addition, various surface treatments such as gold-plating, chemical etching, polishing, and steam cleaning resulted in little or no influence on compatibility of 316L with Hg when compared to nominal mill-annealed/surface-ground material. A sensitizing heat treatment also had little/no effect on compatibility of 316L with Hg for the bulk specimen, although intergranular attack was observed around the specimen holes in each case. It was determined that carburization of the hole area had occurred as a result of the specimen fabrication process potentially rendering the specimens susceptible to corrosion by Hg at these locations. To avoid sensitization-related compatibility issues for SNS components, selection of low carbon grades of stainless steel and control of the fabrication process is recommended.
Date: March 23, 2001
Creator: Pawel, SJ
Partner: UNT Libraries Government Documents Department

Oxide film microstructure: the link between surface preparation processes and strength/durability of adhesively bonded aluminum. Final report

Description: Strength and durability of adhesive bonding of aluminum alloys structures are intrinsically determined by the surface microstructures and interfacial failure micromechanisms. The current project presents a multidisciplinary approach to addressing critical issues controlling the strength and durability of adhesive bonds of aluminum alloys. Three main thrust areas have been pursued: surface treatment technology development to achieve desirable surface microstructures; relationship between surface structure and properties of adhesive bonds; and failure mechanisms of adhesively bonded components.
Date: November 30, 2000
Creator: Hsia, K. Jimmy; Pearlstein, Arne J.; Scheeline, Alexander & Shang, Jian Ku
Partner: UNT Libraries Government Documents Department

Development of Seamless Niobium Cavities for Accelerator Applications

Description: Superconducting niobium cavities for application in particle accelerators are usually fabricated by standard techniques such as forming of subcomponents by deep drawing and joining by electron beam welding. Even though these techniques are being used successfully in many larger-scale accelerator projects and improvements in accelerating gradients have been achieved over the last several years, there are often still problems with making defect-free electron beam welds. In addition, the manufacturing costs for such devices are significant and a drastic reduction in production costs is a necessary condition for future very large scale applications in, e.g., linear colliders. Seamless cavities made by spinning from a single sheet of material will dramatically reduce the fabrication costs and eliminate any problems associated with electron beam welding. The fabrication technique for seamless niobium cavities has been developed over the last few years at INFN LNL and several proto type single-cells of different material thickness and purity have been manufactured as well as a 5-cell cavity. Results from tests on these cavities after application of surface treatment techniques, such as buffered chemical polishing, ``barrel polishing'' and high temperature heat treatments, are discussed in this contribution. Q-values as high as 10{sup 11} and accelerating gradients up to E{_}acc {approximately} 30 MV/m have been measured.
Date: March 1, 1999
Creator: Kneisel, P. & Palmieri, V.
Partner: UNT Libraries Government Documents Department

Surface modification: advantages, techniques, and applications

Description: Adequate performance of materials at elevated temperatures is a potential problem in many systems within the chemical, petroleum, process, and power-generating industries. Degradation of materials occurs because of interaction between the structural material and the exposure environment. These interactions are generally undesired chemical reactions that can lead to accelerated wastage and alter the functional requirements and/or structural integrity of the materials. Therefore, material selection for high-temperature applications must be based not only on a material strength properties but also on resistance to the complex environments prevalent in the anticipated exposure environment. As plants become larger, the satisfactory performance and reliability of components play a greater role in plant availability and economics. However, system designers are becoming increasingly concerned with finding the least expensive material that will satisfactorily perform the design function for the desired service life. This present paper addresses the benefits of surface modification and identified several criteria for selection and application of modified surfaces in the power sector. A brief review is presented on potential methods for modification of surfaces, with the emphasis on coatings. In the final section of the paper, several examples address the requirements of different energy systems and surface modification avenues that have been applied to resolve the issues.
Date: March 1, 2000
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department