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open access

An investigation of particle trajectories and melting in an air plasma sprayed zirconia

Description: The partially stabilized zirconia powders used to plasma spray thermal barrier coatings typically exhibit broad particle-size distributions. There are conflicting reports in the literature about the extent of injection-induced particle-sizing effects in air plasma-sprayed materials. If significant spatial separation of finer and coarser particles in the jet occurs, then one would expect it to play an important role in determining the microstructure and properties of deposits made from powders c… more
Date: December 31, 1996
Creator: Neiser, R.A. & Roemer, T.J.
Partner: UNT Libraries Government Documents Department
open access

The ORNL beamline at the National Synchrotron Light Source

Description: The Oak Ridge National Laboratory's (ORNL) beamline at the National Synchrotron Light Source (NSLS) incorporates several novel features including x-ray optics based on sagittal focusing with crystals and a cantilevered mirror whose center becomes the pivot for all downstream optical elements. Crystal focusing accepts a much larger horizontal divergence of radiation than a mirror while maintaining excellent momentum transfer and energy resolution. This sagittally bent crystal serves as the secon… more
Date: June 16, 1987
Creator: Habenschuss, A.; Ice, G. E.; Sparks, C. J. & Neiser, R. A.
Partner: UNT Libraries Government Documents Department
open access

Wire melting and droplet atomization in a high velocity oxy-fuel jet

Description: Coatings produced by feeding a steel wire into a high-velocity oxy-fuel (HVOF) torch are being intensively studied by the automotive industry as a cost-effective alternative to the more expensive cast iron sleeves currently used in aluminum engine blocks. The microstructure and properties of the sprayed coatings and the overall economics of the process depend critically on the melting and atomization occurring at the wire tip. This paper presents results characterizing several aspects of wire m… more
Date: July 1, 1995
Creator: Neiser, R.A.; Brockmann, J.E. & O`Hern, T.J.
Partner: UNT Libraries Government Documents Department
open access

Computational fluid dynamic analysis of a High-Velocity Oxygen-Fuel (HVOF) thermal spray torch

Description: The gas dynamics of a High-Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamics (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder feed. The injection nozzle is assumed to be axisymmetric with premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. The aircap, a cronically converging nozzle, achieves choked flow conditions at the exit and a supersonic, under… more
Date: September 1, 1995
Creator: Hassan, B.; Oberkampf, W. L.; Neiser, R. A. & Roemer, T. J.
Partner: UNT Libraries Government Documents Department
open access

Oxidation in HVOF-sprayed steel

Description: It is widely held that most of the oxidation in thermally sprayed coatings occurs on the surface of the droplet after it has flattened. The evidence in this paper suggests that, for the conditions studied here, oxidation of the top surface of flattened droplets is not the dominant oxidation mechanism. In this study, a mild steel wire (AISI 1025) was sprayed using a high-velocity oxy-fuel (HVOF) torch onto copper and aluminum substrates. Ion milling and Auger spectroscopy were used to examine th… more
Date: August 1997
Creator: Smith, M. F.; Neiser, R. A. & Dykhuizen, R. C.
Partner: UNT Libraries Government Documents Department
open access

Computational fluid dynamics analysis of a wire-feed, high-velocity oxygen-fuel (HVOF) thermal spray torch

Description: The fluid and particle dynamics of a High-Velocity Oxygen-Fuel Thermal Spray torch are analyzed using computational and experimental techniques. Three-dimensional Computational Fluid Dynamics (CFD) results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire (DJRW) torch. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Premixed propylene and oxy… more
Date: September 1, 1996
Creator: Lopez, A. R.; Hassan, B.; Oberkampf, W. L.; Neiser, R. A. & Roemer, T. J.
Partner: UNT Libraries Government Documents Department
open access

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 alum… more
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
open access

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. Experimen… more
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
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