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Particle Velocity and Deposition Efficiency in the Cold Spray Process

Description: Copper powder was sprayed by the cold-gas dynamic method. In-flight particle velocities were measured with a laser-two-focus system as a function of process parameters such as gas temperature, gas pressure, and powder feed rate. Particle velocities were uniform in a relatively large volume within the plume and agreed with theoretical predictions. The presence of the substrate was found to have no significant effect on particle velocities. Cold-spray deposition efficiencies were measured on aluminum substrates as a function of particle velocity and incident angle of the plume. Deposition efficiencies of up to 95% were achieved. The critical velocity for deposition was determined to be about 640 meters per second. This work investigates both the in-flight characteristics of copper particles in a supersonic cold-spray plume and the build-up of the subsequent coating on aluminum substrates. Velocities were found to be relatively constant within a large volume of the plume. Particle counts dropped off sharply away from the central axis. The presence of a substrate was found to have no effect on the velocity of the particles. A substantial mass-loading effect on the particle velocity was observed; particle velocities begin to drop as the mass ratio of powder to gas flow rates exceeds 3%. The measured variation of velocity with gas pressure and pre-heat temperature was in fairly good agreement with theoretical predictions. Helium may be used as the driving gas instead of air in order to achieve higher particle velocities for a given temperature and pressure. Coating deposition efficiencies were found to increase with particle velocity and decrease with gun- substrate angle. There did not appear to be any dependence of the deposition efficiency on coating thickness. A critical velocity for deposition of about 640 mk appears to fit the data well. The cold-spray technique shows promise as a method for the ...
Date: November 12, 1998
Creator: Dykhuizen, R.C.; Gilmore, D.L.; Neiser, R.A.; Roemer, T.J. & Smith, M.F.
Partner: UNT Libraries Government Documents Department

The effects of the Hartman cavity on the performance of the USGA nozzle used for aluminum spray forming. [Quarterly report, July-- September 1996]

Description: This paper addresses the effects of the Hartman cavity on performance of the USGA (Ultrasonic Gas Atomizer) used for Al spray forming. Numerical simulations of the gas flow field were done in order to establish effects of the cavity on flow development both inside and outside the air nozzles. PDPA measurements were made of gas velocity and turbulence intensity, droplet mean and fluctuating velocity, and droplet size across planes at various distances downstream. High speed imaging is used in the flow region near the orifice exit where recirculation zones are generated and there is concern about metal droplet deposition on atomizer surfaces. Shadowgraphy show presence of shock waves and cells in the emerging gas jets. It was found that the Hartman cavity has little effect on droplet sizes generated; also little effect on spray development. The rectangular slit orifices for the 2 gas jets and the liquid jet generate a spray, after impingement, which is somewhat rectangular in cross section. As the spray develops downstream, it changes shape under influence of entrainment from the gas surrounding the spray. After a distance of 254 mm from nozzle exit, width and breadth of the jet are equal but significant shape change occur further downstream. Gaussian velocity distributions result in liquid flux distributions and metal deposits with Gaussian shapes instead of deposits with uniform thickness.
Date: December 31, 1996
Creator: Mansour, A.; Chigier, N.; Shih, T.I.P. & Kozarek, R.L.
Partner: UNT Libraries Government Documents Department

METAL-MATRIX COMPOSITES AND THERMAL SPRAY COATINGS FOR EARTH MOVING MACHINES

Description: First quarter activities were limited to initial project discussions, laboratory preparation, and some initial coupon preparation. Technical discussion were held with the subcontractors to clearly define their roll in the project. Detailed preparation of the pressure casting lab were started. Initial test coupons were sprayed and provided to Oak Ridge National Lab for infrared lamp fusion trials.
Date: July 1, 2001
Creator: Kiser, Matthew T.
Partner: UNT Libraries Government Documents Department

Impact of Hight Velocity Cold Spray Particles

Description: This paper presents experimental data and an computational model of the cold spray solid particle impact process. Copper particles impacting onto a polished stainless steel substrate are examined. The high velocity impact causes significant plastic deformation of both the particle and the sub- strate, but no melting is observed. The plastic deformation exposes clean surfaces that, under the high impact pressures, result in significant bond strengths between the particle and substrate. Experimental measurements of the splat and crater sizes compare well with the numerical calculations. It is shown that the crater depth is significant and increases with impact velocity. However, the splat diameter is much less sensitive to the impact velocity. It is also shown that the geometric lengths of the splat and crater scale linearly with the diameter of the impacting particle. It is hoped that the results presented will allow better understanding of the bonding process during cold spray.
Date: December 1, 1998
Creator: Dykhuizen, R.C.; Gilmore, D.L.; Jiang, X.; Neiser, R.A.; Sampath, S. & Smith, M.F.
Partner: UNT Libraries Government Documents Department

Non-Destructive Evaluation of Thermal Spray Coating Interface Quality By Eddy Current Method

Description: Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with various surface preparation conditions or spray process parameters. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that different surface preparation conditions and varied process parameters can be successfully differentiated by the impedance value observed from the eddy current probe. The measurement is fairly robust and consistent. This non-contact, nondestructive, easy-to-use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.
Date: August 10, 2006
Creator: Mi, B.; Zhao, G. & Bayles, R.
Partner: UNT Libraries Government Documents Department

A novel technique for the production of cool colored concrete tile and asphalt shingle roofing products

Description: The widespread use of solar-reflective roofing materials can save energy, mitigate urban heat islands and slow global warming by cooling the roughly 20% of the urban surface that is roofed. In this study we created prototype solar-reflective nonwhite concrete tile and asphalt shingle roofing materials using a two-layer spray coating process intended to maximize both solar reflectance and factory-line throughput. Each layer is a thin, quick-drying, pigmented latex paint based on either acrylic or a poly(vinylidene fluoride)/acrylic blend. The first layer is a titanium dioxide rutile white basecoat that increases the solar reflectance of a gray-cement concrete tile from 0.18 to 0.79, and that of a shingle surfaced with bare granules from 0.06 to 0.62. The second layer is a 'cool' color topcoat with weak near-infrared (NIR) absorption and/or strong NIR backscattering. Each layer dries within seconds, potentially allowing a factory line to pass first under the white spray, then under the color spray. We combined a white basecoat with monocolor topcoats in various shades of red, brown, green and blue to prepare 24 cool color prototype tiles and 24 cool color prototypes shingles. The solar reflectances of the tiles ranged from 0.26 (dark brown; CIELAB lightness value L* = 29) to 0.57 (light green; L* = 76); those of the shingles ranged from 0.18 (dark brown; L* = 26) to 0.34 (light green; L* = 68). Over half of the tiles had a solar reflectance of at least 0.40, and over half of the shingles had a solar reflectance of at least 0.25.
Date: November 20, 2009
Creator: Levinson, Ronnen; Akbari, Hashem; Berdahl, Paul; Wood, Kurt; Skilton, Wayne & Petersheim, Jerry
Partner: UNT Libraries Government Documents Department

Research On HVOF Thermal Sprays. Final Technical Report

Description: Independent control of particle velocity and temperature in the HVOF process has been achieved in this research, allowing the variables to change by 170 m/s and 200{degree}C, respectively. The independence was achieved using a specially designed nozzel with multiple axial injection ports, and with an inert diluent added to the oxygen used for combustion. With these changes, notable changes in splat morphology, porosity, and coating oxidation are readily apparent. Increased particle velocity correlates with improved splat deformation, but appears to have little effect on porosity or oxidation. Particle temperature, however, correlates strongly with splat deformation, porosity, and oxidation. In fact, highly dense coatings that have little oxidation can be formed with relatively low velocity particles that have average temperatures in the vicinity of the melting point of the material. This surprising result suggests particle temperature control is the key to creating dense, low-oxide HVOF-sprayed coatings.
Date: April 2, 2003
Creator: Settles, G. S.
Partner: UNT Libraries Government Documents Department

Magnetically controlled deposition of metals using gas plasma. Quarterly progress report, July--September 1996

Description: Objective is to develop a method of spraying materials on a substrate in a controlled manner to eliminate the waste inherent in present plating processes. The process under investigation is magnetically controlled plasma spraying. The field equations have been cast in a format that allows finite element solution. Potential flow and finite element solutions for temperature isolines and velocity vectors are compared for 2-D flow with heat addition.
Date: November 1, 1996
Creator: Woodall, D.M. & Lemmon, E.C.
Partner: UNT Libraries Government Documents Department

Advanced manufacturing by spray forming: Aluminum strip and microelectromechanical systems

Description: Spray forming is an advanced materials processing technology that converts a bulk liquid metal to a near-net-shape solid by depositing atomized droplets onto a suitably shaped substrate. By combining rapid solidification processing with product shape control, spray forming can reduce manufacturing costs while improving product quality. INEL is developing a unique spray-forming method based on de Laval (converging/diverging) nozzle designs to produce near-net-shape solids and coatings of metals, polymers, and composite materials. Properties of the spray-formed material are tailored by controlling the characteristics of the spray plume and substrate. Two examples are described: high-volume production of aluminum alloy strip, and the replication of micron-scale features in micropatterned polymers during the production of microelectromechanical systems.
Date: December 31, 1994
Creator: McHugh, K.M.
Partner: UNT Libraries Government Documents Department

Spray forming metallic support bands on ceramic elements

Description: A study was conducted to assess the feasibility of spray depositing a metal ring on the end of ceramic tubes using a low temperature spray forming process developed at the INEL. 1/16 in.--1.8 in. thick x 1/2 in. wide tin, zinc, and aluminum alloy rings were spray formed using a bench-scale nozzle without damaging the ceramic. Analysis of the deposits indicated that they were suitably dense and exhibited good adherence to the ceramic material.
Date: February 10, 1994
Creator: McHugh, K.D.
Partner: UNT Libraries Government Documents Department

Magnetically controlled deposition of metals using gas plasma. Quarterly progress report, July 1995--September 1995

Description: The objective of this project is to develop a method of spraying materials on a substrate in a controlled manner to eliminate waste inherent in present plating processes. The process will utilize a standard spray gun with the addition of magnetic fields to focus and control the plasma.
Date: December 1, 1995
Partner: UNT Libraries Government Documents Department

Film synthesis on powders by cathodic arc plasma deposition

Description: Cathodic arc plasma deposition was used to coat Al{sub 2}O{sub 3} powder (mesh size 60) with platinum. The power particles were moved during deposition using a mechanical system operating at a resonance frequency of 20 Hz. Scanning electron microscopy and Auger electron microscopy show that all particles are completely coated with a platinum film having a thickness of about 100 nm. The actual deposition time was only 20 s, thus the deposition rate was very high (5 nm/s).
Date: April 1, 1995
Creator: Anders, A.; Anders, S.; Brown, I.G. & Ivanov, I.C.
Partner: UNT Libraries Government Documents Department

Innovative Instrumentation and Analysis of the Temperature Measurement for High Temperature Gasification

Description: The objectives of this project during this semi-annual reporting period are to test the effects of coating layer of the thermal couple on the temperature measurement and to screen out the significant factors affecting the temperature reading under different operational conditions. The systematic tests of the gasifier simulator on the high velocity oxygen fuel (HVOF) spray coated thermal couples were completed in this reporting period. The comparison tests of coated and uncoated thermal couples were conducted under various operational conditions. The temperature changes were recorded and the temperature differences were calculated to describe the thermal spray coating effect on the thermal couples. To record the temperature data accurately, the computerized data acquisition system (DAS) was adopted to the temperature reading. The DAS could record the data with the accuracy of 0.1 C and the recording parameters are configurable. In these experiments, DAS was set as reading one data for every one (1) minute. The operational conditions are the combination of three parameters: air flow rate, water/ammonia flow rate and the amount of fine dust particles. The results from the temperature readings show the temperature of uncoated thermal couple is uniformly higher than that of coated thermal couple for each operational condition. Analysis of Variances (ANOVA) was computed based on the results from systematic tests to screen out the significant factors and/or interactions. The temperature difference was used as dependent variable and three operational parameters (i.e. air flow rate, water/ammonia flow rate and amount of fine dust particle) were used as independent factors. The ANOVA results show that the operational parameters are not the statistically significant factors affecting the temperature readings which indicate that the coated thermal couple could be applied to temperature measurement in gasifier. The actual temperature reading with the coated thermal couple in the gasification could be calibrated ...
Date: October 1, 2005
Creator: Lee, Seong W.
Partner: UNT Libraries Government Documents Department

INNOVATIVE INSTRUMENTATION AND ANALYSIS OF THE TEMPERATURE MEASUREMENT FOR HIGH TEMPERATURE GASIFICATION

Description: During this reporting period, the literature survey including the gasifier temperature measurement literature, the ultrasonic application and its background study in cleaning application, and spray coating process are completed. The gasifier simulator (cold model) testing has been successfully conducted. Four factors (blower voltage, ultrasonic application, injection time intervals, particle weight) were considered as significant factors that affect the temperature measurement. The Analysis of Variance (ANOVA) was applied to analyze the test data. The analysis shows that all four factors are significant to the temperature measurements in the gasifier simulator (cold model). The regression analysis for the case with the normalized room temperature shows that linear model fits the temperature data with 82% accuracy (18% error). The regression analysis for the case without the normalized room temperature shows 72.5% accuracy (27.5% error). The nonlinear regression analysis indicates a better fit than that of the linear regression. The nonlinear regression model's accuracy is 88.7% (11.3% error) for normalized room temperature case, which is better than the linear regression analysis. The hot model thermocouple sleeve design and fabrication are completed. The gasifier simulator (hot model) design and the fabrication are completed. The system tests of the gasifier simulator (hot model) have been conducted and some modifications have been made. Based on the system tests and results analysis, the gasifier simulator (hot model) has met the proposed design requirement and the ready for system test. The ultrasonic cleaning method is under evaluation and will be further studied for the gasifier simulator (hot model) application. The progress of this project has been on schedule.
Date: September 1, 2003
Creator: Lee, Seong W.
Partner: UNT Libraries Government Documents Department

Metal-Matrix Composites and Thermal Spray Coatings for Earth Moving Machines

Description: In the eighth quarter, investigations in both thrusts focused on abrasive wear characterization. For the steel matrix composites, various systems were tested at DOE Albany Research Center using wear tests which produced low stress scratching, high stress gouging, and gouging and impact wear. Based on the wear results, it is uncertain as to whether the composites created have sufficient wear resistance to provide a 2x life increase in a selectively reinforced component in all applications. High stress component abrasive wear tests were conducted at Caterpillar on arc lamp processed, thermal sprayed components. Testing showed that in many cases, arc lamp processing parameters and resulting fusion were insufficient to prevent coating spallation. Of those coatings which experienced only limited spallation, wear life improvements approached 2x and it is expected that project goals can be met with additional process modifications. An overview of the progress during the 8th quarter of this project is given below. Additional research details are provided in the limited rights appendix to this report.
Date: January 1, 2003
Creator: Weaver, D. Trent; Kiser, Matthew T. & Hawk, Jeffrey
Partner: UNT Libraries Government Documents Department

Metal-Matrix Composites and Thermal Spray Coatings for Earth Moving Machines

Description: In the 10th quarter no further work was conducted on the steel matrix composite element of this project. For this element work is effectively complete and all that remains is the composition of the final report. For the thermal spray coating effort, components coated and fused in the previous quarter were subject to high stress abrasive wear testing. Some complications were encountered with the wear testing, but the tests which were completed successfully showed that the coatings provided wear resistance 5x that of the baseline material. Further wear testing is planned for the 11th and final quarter. An overview of the progress during the 10th quarter of this project is given below. Additional research details are provided in the limited rights appendix to this report.
Date: July 1, 2003
Creator: Weaver, D. Trent & Kiser, Matthew T.
Partner: UNT Libraries Government Documents Department

Non-Destructive Evaluation of Thermal Spray Coating Interface Quality by Eddy Current Method

Description: Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with different surface preparation conditions before applying the coating, e.g., grit-blasted surface, wire-brush cleaned surface, and a dirty surface. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that the three surface preparation conditions can be successfully differentiated by looking into the impedance difference observed from the eddy current probe. The measurement is fairly robust and consistent. More specimens are also prepared with variations of process parameters, such as spray angle, stand-off distance, and application of corrosion protective sealant, etc. They are blindly tested to evaluate the reliability of the eddy current system. Quantitative relations between the coating bond strength and the eddy current response are also established with the support of destructive testing. This non-contact, non-destructive, easy to use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.
Date: May 26, 2006
Creator: B.Mi; Zhao, X. & Bayles, R.
Partner: UNT Libraries Government Documents Department

Quantification of corrosion resistance of a new-class of criticality control materials: thermal-spray coatings of high-boron iron-based amorphous metals - Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4

Description: An iron-based amorphous metal, Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} (SAM2X5), with very good corrosion resistance was developed. This material was produced as a melt-spun ribbon, as well as gas atomized powder and a thermal-spray coating. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation. The high boron content of this particular amorphous metal made it an effective neutron absorber, and suitable for criticality control applications. Earlier studies have shown that ingots and melt-spun ribbons of these materials have good passive film stability in these environments. Thermal spray coatings of these materials have now been produced, and have undergone a variety of corrosion testing, including both atmospheric and long-term immersion testing. The modes and rates of corrosion have been determined in the various environments, and are reported here.
Date: March 28, 2007
Creator: Farmer, J C; Choi, J S; Shaw, C K; Rebak, R; Day, S D; Lian, T et al.
Partner: UNT Libraries Government Documents Department

Drying/self-assembly of nanoparticle suspensions.

Description: The most feasible way to disperse particles in a bulk material or control their packing at a substrate is through fluidization in a carrier that can be processed with well-known techniques such as spin, drip and spray coating, fiber drawing, and casting. The next stage in the processing is often solidification involving drying by solvent evaporation. While there has been significant progress in the past few years in developing discrete element numerical methods to model dense nanoparticle dispersion/suspension rheology which properly treat the hydrodynamic interactions of the solvent, these methods cannot at present account for the volume reduction of the suspension due to solvent evaporation. As part of LDRD project FY-101285 we have developed and implemented methods in the current suite of discrete element methods to remove solvent particles and volume, and hence solvent mass from the liquid/vapor interface of a suspension to account for volume reduction (solvent drying) effects. To validate the methods large scale molecular dynamics simulations have been carried out to follow the evaporation process at the microscopic scale.
Date: October 1, 2010
Creator: Cheng, Shengfeng; Plimpton, Steven James; Lechman, Jeremy B. & Grest, Gary Stephen
Partner: UNT Libraries Government Documents Department

Evaluation of Iron Aluminide Weld Overlays for Erosion-Corrosion Resistant Boiler Tube Coatings in Low NOx Boilers

Description: Iron aluminide weld overlays containing ternary additions and thermal spray coatings are being investigated for corrosion protection of boiler tubes in Low NOx burners. The primary objective of the research is to identify overlay and thermal spray compositions that provide corrosion protection of waterwall boiler tubes. In the current phase of work, preliminary corrosion tests were conducted on a binary Fe-Al alloy in multiple complex gases to determine which gases will be used for testing of the ternary alloys. Preliminary solid-state corrosion tests were also conducted to simulate slag-metal interactions seen in Low NOx furnaces. Two powder compositions were chosen for testing of the ternary alloys. A matrix of alloys to be tested in both gaseous and solid-state corrosion experiments was produced based on corrosion literature.
Date: May 16, 2000
Creator: Regina, J.R.
Partner: UNT Libraries Government Documents Department

Automated robot inspection of spray painted surfaces

Description: Applications of paints and coatings can be greatly enhanced by using robotics spraying. Benefits include increased application rates with tighter control over coating finish, quality, and costs. The use of robotics can reduce human exposure to hazardous materials and dangerous spray environments. Successful deployment of a robotics system requires process feedback, automated task and path planning, and teleoperation. This paper describes a measurement system consisting of an inspection sensor and automated path planner for automated robot inspection of painted surfaces. The inspection sensor includes ultrasonic and eddy current components configured in a mechanism providing both compliant force and compliant motion.
Date: December 31, 1995
Creator: Wilkey, A.T. & Schwarz, J.W.
Partner: UNT Libraries Government Documents Department

Spray forming lead strip. Final report

Description: A cooperative research project was conducted between the Idaho National Engineering Laboratory (INEL) and Johnson Controls, Inc. (JCI) to adapt the INEL spray forming process to produce near-net-shape lead alloy strip. The emphasis of the work was to spray form lead strip samples at INEL, using a variety of spray conditions, for characterization at JCI. An existing glove box apparatus was modified at INEL to spray form lead. The main spray forming components were housed inside the glove box. They included a spray nozzle, tundish (crucible), substrate assembly, gas heater and furnaces to heat the nozzle and tundish. To spray form metal strip, liquid metal was pressure-fed at a controlled rate through a series of circular orifices that span the width of the nozzle. There the metal contacted high velocity, high temperature inert gas (nitrogen) which atomized the molten material into fine droplets, entrained the droplets in a directed flow, and deposited them onto glass plates that were swept through the spray plume to form strip samples. In-flight convection cooling of the droplets followed by conduction and convection cooling at the substrate resulted in rapid solidification of the deposit. During operation, the inside of the glove box was purged with an inert gas to limit the effects of in-flight oxidation of the particles and spray-formed strips, as well as to protect personnel from exposure to airborne lead particulate. Remote controls were used to start/stop the spray and control the speed and position of the substrate. In addition, substrate samples were loaded into the substrate translator manually using the gloved side ports of the box. In this way, the glove box remained closed during a series of spray trials, and was opened only when loading the crucible with a lead charge or when removing lead strip samples for shipment to JCI.
Date: April 10, 1996
Creator: McHugh, K.
Partner: UNT Libraries Government Documents Department

U.S. Department of Energy integrated manufacturing predoctoral fellowships: Fellows` annual report 1997--1998

Description: In the uniform droplet spray (UDS) process, a jet of liquid metal is broken up into uniform droplets by applying a periodic perturbation to the jet at a specific frequency and amplitude. The droplets are electrically charged to the same polarity to prevent in-flight merging. As a result of the uniform droplet size distribution, the dynamic and thermal states of the droplets can be precisely controlled in the UDS process. Before the UDS process can be applied to the production of aluminum sheets, the thermal history of the droplets must be understood. The incoming thermal state of the droplets at impact with the substrate significantly affects the degree of droplet consolidation as well as the microstructural grain size, which in turn determine the final material properties of the sprayed part. Therefore, the first step in this research was to simulate and measure the droplet thermal state during flight. The thermal state of a solidifying droplet is defined by its temperature and volume fraction of solid. To predict the temperature and solid fraction of the droplets as functions of flight distance, a thermal model was developed for aluminum binary alloy droplets by assuming Newtonian cooling, no undercooling, and local equilibrium at the solid/liquid interface during solidification. Experiments to validate the droplet thermal model were made with Al-4.5 wt% Cu and Al-4.3 wt% Fe droplets, 275 {micro}m and 250 {micro}m in diameter, respectively. The droplets were quenched at different flight distances and their microstructures were examined metallographically using SEM analysis. By observing the change in microstructure from a fully liquid droplet to a fully solid powder, the solid fraction of the droplet as a function of flight distance can be measured.
Date: May 22, 1998
Partner: UNT Libraries Government Documents Department