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Proceedings Papers
ITSC2024, Thermal Spray 2024: Proceedings from the International Thermal Spray Conference, 130-137, April 29–May 1, 2024,
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Restoring the damaged shaft parts to extend their service life is an economical and environmentally friendly solution. In recent years, the laser metal deposition (LMD) process has received increasing attention in component restoration. However, the residual stress and deformation inevitably occur due to the heat input, leading to the deflection of the repaired shafts. Therefore, this study aims to minimize the deflection of LMD-repaired shaft parts through parameter optimization. The width and height of the LMD deposit as a function of the laser power and traverse speed were achieved by fitting a series of one-pass experimental results. Based on it, the finite element analysis was conducted to clarify the effect of the repairing conditions (e.g., laser power, traverse speed, and initial substrate temperature) on the deflection and residual stress distribution of the shaft parts after LMD repairing. A 304 stainless steel round bar with a diameter of 6 mm was served as the component to be repaired. The deposit was 316L stainless steel, whose deposition process was realized by the element birth and death technique. The results indicated that the free-end of the specimen experienced complicated deformation during the LMD and cooling process. After cooling off, the substrate presents a residual compressive stress along the axial direction. Moreover, the substrate deflection can be reduced by improving the initial substrate temperature. This study provided an important reference for optimizing the process parameters in repairing the shaft parts.
Proceedings Papers
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 241-242, May 11–14, 2015,
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The mist cooling technique was developed and applied to various thermal spraying guns. For example, aluminum-magnesium coatings prepared using a gas flame thermal spraying gun with mist cooling had superior anticorrosion characteristics. Stellite coating thermally sprayed with mist cooling had higher anti-cavitation-erosion characteristics. Next, we endeavored to develop high velocity oxygen fuel guns with mist gas cooling to improve high-temperature toughness.
Proceedings Papers
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 713-717, May 11–14, 2015,
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Different directions characterize the advances being made in thermal spraying today. On the one hand, spray processes are becoming colder, on the other hand, high-performance systems are being designed which enable a higher powder throughput, thus making production faster and more efficient. The current spectrum of substrate materials is much broader and even more versatile, as can be seen with new materials which prevent thermal stresses from arising during the production process. More and more applications require the use of special cooling methods to increase the cooling efficiency and, in turn, optimize the process. An ongoing objective of the gas industry is to offer the user hardware which not only exploits all the advantages of CO 2 , for example, but which is also suited to new applications.
Proceedings Papers
ITSC2014, Thermal Spray 2014: Proceedings from the International Thermal Spray Conference, 113-118, May 21–23, 2014,
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In this study, a suspension containing Mg-Al-spinel nanopowder was deposited on bond-coated IN738 and stainless steel disks by suspension plasma spraying with and without substrate cooling. Coating surfaces and cross-sections were examined by SEM, EDS, and XRD analysis and thermal cycling tests were performed. SEM images of coatings obtained on cooled stainless steel show a unique columnar microstructure with a cauliflower-like surface. XRD spectra of the nanopowder and coatings revealed evidence of phase changes in the material deposited on cooled substrates. In preparing samples for thermal cycling tests, a YSZ layer was deposited on bond-coated IN738 prior to spraying the suspension. Double-layered Mg-Al-spinel/YSZ thermal barrier coatings produced on cooled substrates exhibited a thermal cycling lifetime of 2000 cycles at 1390°C, compared to 101 cycles for the TBCs sprayed without substrate cooling. The superior performance of the TBCs sprayed with substrate cooling is attributed to the densification of the coatings, revealed by SEM images, and possibly the formation of CaO-6Al 2 O 3 needles and Al 2 O 3 precipitates as identified by EDS measurements.
Proceedings Papers
ITSC2014, Thermal Spray 2014: Proceedings from the International Thermal Spray Conference, 414-419, May 21–23, 2014,
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The aim of this study is to better understand the formation of nonbonded splat-to-splat interfaces in thermally sprayed ceramic coatings. To that end, the surfaces between splats in plasma-sprayed La 0.5 Sr 0.5 CoO 3 (LSCO) coatings were examined and compared to free splat surfaces. The results show that free splat surfaces are relatively smooth, while adjacent surfaces at intersplat interfaces are quite rough. The observation implies that nonbonded splat-to-splat interfaces were never bonded, having fractured due to interface shear stress generated during splat cooling.
Proceedings Papers
ITSC 2009, Thermal Spray 2009: Proceedings from the International Thermal Spray Conference, 1067-1071, May 4–7, 2009,
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Advances in thermal spraying are occurring in two general directions. On the one hand, spray processes are becoming colder, facilitating the production of oxide-free coatings in air atmospheres. On the other hand, new systems are being developed that enable higher powder throughput, thus making production faster and more efficient. In order to lock in these time-saving advantages, more and more applications are using CO 2 as a cooling medium to increase cooling efficiency and optimize spraying processes. This paper provides an overview of the use of CO 2 and its suitability for new applications.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 1311-1317, May 2–4, 2005,
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A numerical study has been conducted on yttria stabilized zirconia and molybdenum splat cooling taking into account the effects of various parameters. In particular, the effect of the splat thickness, the splat/substrate interface thermal resistance, the latent heat of solidification and the substrate initial temperature on the solidification occurrence and kinetics have been studied. A two-dimension model of heat transfer taking into account the phase change during rapid solidification with an enthalpy formulation has been used for these calculations.
Proceedings Papers
ITSC 2004, Thermal Spray 2004: Proceedings from the International Thermal Spray Conference, 407-411, May 10–12, 2004,
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Two directions characterize the advances being made in thermal spraying today. On the one hand, the spray processes are becoming colder, as with cold spraying which facilitates the production of oxide-free coatings in the atmosphere. On the other hand, high-performance systems are being developed which enable a higher powder throughput, thus making production faster and more efficient. This development has made it more important than ever to maintain this time-saving advantage and not lose it as a result of cooling intervals. More and more applications require the use of CO 2 as a cooling medium to increase the cooling efficiency and, in turn, optimize the process. An ongoing objective of the gas industry is to offer the user hardware which not only exploits all the advantages of CO 2 , but which is also suited to new applications.
Proceedings Papers
ITSC 2004, Thermal Spray 2004: Proceedings from the International Thermal Spray Conference, 1004-1007, May 10–12, 2004,
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It has been said that plasma-sprayed ceramics particles are often supercooled before the impact on substrate. Some numerical models of the droplet impact actually included the supercooling effects. However, there is no report that has experimentally confirmed the effects on splat morphology. Therefore, in this research, we have mainly investigated the supercooling effects on splat morphology as well as splat microstructure. To achieve this, we developed an in-situ measurement technique utilizing radiation from a melt particle to monitor the impact of single particle successively under plasma spraying. The system was able to identify each single particle, which enabled us to correlate the splat morphology with impact velocity and thermal history of each particle during the impact. Yttria-stabilized zirconia powders were sprayed onto quartz glass substrate by the argon-hydrogen dc-rf hybrid plasma under atmospheric pressure. Waveforms of emissions and thermal history obtained during the impact were precisely analyzed. Especially, we closely examined thermal history during particle spreading to find the recalescence. In addition, splat morphologies were examined statistically in relation to their thermal histories. Based on the measurement, we also evaluated the viscosity of zirconia, cooling rate, and thermal contact resistance experimentally.
Proceedings Papers
ITSC 2001, Thermal Spray 2001: Proceedings from the International Thermal Spray Conference, 865-873, May 28–30, 2001,
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As underlined in 1981 by Mc Pherson, thermo-mechanical properties of plasma-sprayed coatings depend not only on the way particles flatten and resulting splats solidify and cool down, but also on the thermal history of particle layering at the same location. To illustrate what is our present knowledge in that field, plasma-sprayed alumina coatings will be considered through modelings and measurements. The first part of this paper discusses the phenomena linked with particle impact and splat formation: splashing, spreading, solidification and grain growth, angle of impact in conjunction with particle parameters at impact and substrate surface parameters (chemistry, phase structure and roughness, temperature). The second part examines splats layering. It addresses the influence of plasma jet heat flux, relative velocity torch-substrate, powder flow rate and deposition efficiency on splat time-temperature evolution and resulting quenching stress, coating adhesion/cohesion and microstructure. The shadow effect when spraying off normal angle is also discussed. The last part deals with the effect of the successive cooling and reheating of passes on coating properties, and condensation of the vapor issued from evaporating particles.
Proceedings Papers
ITSC1998, Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 693-697, May 25–29, 1998,
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This paper examines the stress state of plasma-sprayed amorphous coatings of Fe-B with additions of Ni, Cr, and Mo. Internal stresses depend on the type of plasma gas used, the thickness and composition of the coating, and the material and temperature of the substrate. In this study, additional cooling of the substrate was found to be the most efficient way to reduce internal stresses. Amorphous coatings were also found to improve fatigue strength by as much as 25-30%, which is attributed to the formation of compressive stresses in the coating layers adjoining the substrate.
Proceedings Papers
ITSC1998, Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 1025-1032, May 25–29, 1998,
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Experimental apparatus simulating a horizontal belt caster has been constructed for the study of thin strip casting of steels and light metal alloys. In this apparatus, the solidifying metal is deposited onto a moving substrate. The substrate was flame sprayed with various commercial coatings while its speed and the thicknesses of strip produced matched industrial values. The main objective of the present work was to determine the influence of various operational variables on local cooling rates and final microstructures. To this end, experiments were carried out to study the effects of various types of coating, roughness of the substrate, initial superheat, and strip thickness on heat fluxes. An interesting feature of this equipment is that the strip is subjected to different rates of cooling at the lower and upper surfaces, allowing two different rates of solidification to be studied simultaneously.
Proceedings Papers
ITSC1998, Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 1293-1297, May 25–29, 1998,
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Thermal spraying involves high temperatures which can be a serious problem for some applications. Among different possibilities existing to cool down a specimen during spraying, the use of liquid CO 2 is one of the most attractive. However, care has to be taken to obtain good results due to the specific characteristics of CO 2 . Moreover, there are still some remaining problems which limit the growth of such system. One of the most important is the condensation of air humidity at the exit of the atomising nozzle. Therefore, a new design of the nozzle has been developed. This design avoid ice building up and can be easily fixed on any kind of spraying set up. Examples of working conditions are presented.