bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytical Predictions of Thermal Stress in Plasma Spray Coating and in Substrate at Low Temperature Compared with Strains Measurements
Authors: Gassot H. 
Published: July 2021

Abstract
An analytical thermal stress calculation and an in situ thermal stress measurement are developed at low temperatures (from room temperature to liquid helium temperature) on a cylindrical specimen made from an inner bulk niobium wall and a copper alloy VPS coating. This kind of structure is proposed for superconducting cavities in order to reduce the cavity frequency shift due to Lorentz forces. Since the superconducting cavity works at liquid helium temperature (below 4 K) and the niobium thermal expansion ratio is very different from the thermal expansion ratio of copper, thermal stress evaluations during the cool down are necessaries. The experimental approach consists in two series of measurements, the first series of measurements is performed at bulk niobium, bulk copper and thermal sprayed copper since the use of strain gage at liquid helium temperature is unknown from the manufacturer and the behaviour of the strain gage on the copper alloy coating is also unknown, the thermal compensation of strain gage from helium temperature to room temperature is imperative. Then the strain measurements are realized at inner surface (bulk niobium substrate) and outside (copper alloy VPS coating) of the cylindrical specimen. The analytical calculation takes into account non linear thermal expansivities of the materials, the calculated prediction of thermal stress is verified by measurement, a first observation on the copper alloy coating thermal expansion behaviour at low temperatures is established. Key words: thermal spray coating, thermal stress calculation and measurement, liquid helium temperature, superconducting radiofrequency cavities stiffening
Influence of Coating Removal Processes on Residual Stresses of Base Ni Sheet
Authors: Goubot N. , David T. , Baudoin J. , Dhers J. , Ducos M. , Michaud H. 
Published: July 2021

Abstract
Substrates protected by thermal spray coatings are usually found intact after use, making them viable candidates for recycling and reuse. The key is to remove the coating without damaging the component. This requires a process that minimizes the development of residual stresses and the associated distortion. The purpose of this work is to determine the optimal descaling technique for Ni-base sheets with a thermal barrier coating. Test specimens were produced following industry procedures. Thin sheets (&lt;3 mm) of Ni-base superalloy were plasma sprayed with a NiCrAlY bond coat and a Y203-stabilized ZrO2 topcoat. The coating layers were then removed using different methods, including pickling, shot blasting, and water jet descaling, and the substrates were assessed based on X-ray diffraction and chord width measurements. The findings of the study show that water jetting removes all surface materials, particularly the bond coat, without damaging the underlying surface. It also produces the least amount of stress and deformation and is relatively easy to automate.
Variation in Residual Stress Field During Fatigue Failure of Thermal Spray Coatings
Authors: Ahmed R. , Hadfield M. , Tobe S. 
Published: July 2021

Abstract
A non-destructive experimental approach was adapted to investigate the variations in residual stress fields within thermal spray coatings. WC-Co coatings produced by a HVOF technique were considered for concentrated rolling sliding contacts in this study. These coatings were produced in various thicknesses on various substrates. Residual stress measurements were made using an x-ray diffraction technique, along and across the rolling direction. A modified four-ball machine was used to conduct rolling contact fatigue tests under various tribological conditions of contact stress, lubrication and contact configuration. Residual stress measurements were made before and after the tribological tests. Failed rolling elements were analyzed using scanning electron microscopy, electron probe microscopy and surface interferometry. Results indicate that the magnitude of compressive residual stress attenuates during fatigue failure. The magnitude of attenuated residual stress was dependent upon the type of tribological failure. This attenuation of residual stress was attributed to the microcracking of coating under the influence of contact stress.
Properties of TiC-Ni Based Coatings Deposited by Different HVOF Spraying
Authors: Vuoristo P. , Väisänen M. , Mäntylä T. , Berger L.-M. 
Published: July 2021

Abstract
Hardmetal-like coatings of the TiC-Ni system are potential for use as wear, corrosion and heat resistant coatings in various operation conditions. Our previous works [1-12] have shown that these materials are well sprayable using different thermal spray processes such as plasma, D-Gun and HVOF spraying. Since HVOF spraying is today the most important process used to apply carbide based coatings, this study was carried out in order to evaluate more systematically the sprayability of these novel spray powders and the influence of HVOF spray parameters on some coating properties. Coating samples were prepared by using DJ Hybrid gun with propane as a fuel gas, and a CDS gun with hydrogen fuel gas. Oxygen flow rate was varied in both cases for changing the flame temperature. Microstructure, phase composition, hardness, and abrasion wear resistance of the coated samples were investigated. The results showed that both HVOF processes used give satisfactory coating properties and that the use of high oxygen flow rates is beneficial for improving the wear resistance of the coatings. Powders with fine particle size are beneficial in the DJ Hybrid process; the use of coarse powders results in coatings with somewhat higher wear rates. The optimum spray condition for the TiC-Ni system powders differs from that typically used for conventional WC-Co and Cr3C2-NiCr powders by a higher flame temperature.
Effect of Increase in Entrance Convergent Section Length of Gun Nozzle on HVOF Thermal Spray Process and its Application to Nozzle Design for Cold Gas-Dynamic Spray Method
Authors: Sakaki K. , Shimizu Y. 
Published: July 2021

Abstract
Nozzle geometry has a profound effect on HVOF spraying, influencing combustion gas dynamics as well as particle behavior. Nozzle dimensions are also important in cold gas-dynamic spraying (CGDS), particularly the length of the nozzle which affects gas flow temperature and speed. In this study, numerical simulations and experiments were conducted to determine how the length of the entrance convergent section of gun nozzles affects HVOF spraying. Process changes that occur inside the nozzle (as predicted by simulation) were correlated with coating properties. An Al2O3-TiO2 powder was used for the experimental studies. Changes in nozzle length had a significant impact on deposition efficiency, microstructure, hardness, and particle velocity. These relationships (as measured and calculated) were then applied to the nozzle design for the CGDS method.
Characterizaton of Plasma Sprayed Aluminum-Beryllium for Aerospace and Space Application
Authors: Castro R.G. , Thoma D.J. , Vaidya R.U. , Field R.D. 
Published: July 2021

Abstract
There is a continued need within the aerospace and space communities to increase the structural efficiency of launch vehicles in order to increase the payload and/or lower fuel usage. Many of these structures have critical stiffness demands because of deflection, buckling, or acoustic/vibration damping. Aluminum-beryllium (Al-Be) is a candidate material for many such structural components because it has a very high stiffness to weight ratio (second only to pure beryllium) and has superior formability and weldability as compared to beryllium. The strength to weight ratio of commercial Al-Be is superior to aluminum alloys (7050 and 6061-T6) that are currently used for aerospace and space applications. Plasma spray forming of Al-Be alloys is being investigated at Los Alamos National Laboratory for producing axial symmetric components for aerospace and space applications. Plasma spray forming of beryllium and beryllium alloys was investigated during the 1960's and 70's by Union Carbide Speedway Laboratories and the Atomic Weapons Establishment for producing axial symmetric launch vehicle components for defense related applications. Information is presented on the thermal and mechanical properties of plasma sprayed AlBeMet which is a commercial Al-Be alloy produced by Brush Wellman Inc.
Self-Bonding, Exothermically Reactive MCrAlY Composites for Abradable-Clearance Control Coatings
Authors: Hermanek F.J. 
Published: July 2021

Abstract
Ni+Al, Ti+Al, NiCr+AI, and Cr+Al powders react exothermically in the heat zone of thermal spraying systems. Whether such reactions occur between aluminum and superalloy powders is the underlying question of this study. This paper describes composites of this nature and their sprayability to form adherent, metallurgically bonded deposits. Through parametric manipulation, coatings can be produced with a range of properties from dense to open (porous/abradable) structures. The paper also shows how seed particles can be clad with aluminum and sprayed to predictable property limits.
Plasma-Spray-Forming of Alumina Matrix Composite Reinforced with Metal Thin Wire
Authors: Sodeoka S. , Inoue T. , Suzuki M. 
Published: July 2021

Abstract
Alumina matrix composites reinforced with metal thin wire (Inconel-600) were successfully fabricated by plasma spray forming. The atmospheric plasma sprayed matrix layers and wire layers arranged by filament-winding technique were piled up alternately. Though the matrix and the wire were partially bonded only on the side which sprayed particles came flying to, a solid structure was obtained by this technique. Spraying in one direction perpendicular to the substrate made peculiar V-shape pores around the wires, but tilting the torch was effective to reduce the pores. The flexural strength of composite did not increase in spite of some crack deflections on the fracture surface. Owing to the wire pullout, however, the composite exhibited a remarkably higher apparent fracture energy than that of monolithic alumina ceramics.
Novel Bioactive Composites by Thermal Spray Process
Authors: Khor K.A. , Gu Y.W. , Li Y. , Quek C.H. , Lim V.J.P. , Cheang P. 
Published: July 2021

Abstract
This paper compares two types of hydroxyapatite (HA) composite coatings, HA/Ti-6Al-4V and HA/Y-ZrO2. The powders used in the study were prepared using a slurry process then deposited by plasma spraying. The resulting coatings were characterized based on their microstructure, mechanical properties, and biocompatibility. Both composite coatings performed better than pure HA coatings in tensile adhesion and indentation tests. Testing also revealed that the HA/Y-ZrO2 coatings had favorable strength and fracture toughness and that the HA/Ti-6Al-4V coatings had good affinity to living tissue and sufficient mechanical strength.
Evaluation of Adhesive Strength of Coating Film on Ni-Base Superalloy for Gas Turbine
Authors: Okazaki M. , Okamoto M. , Harada Y. 
Published: July 2021

Abstract
Methodology to evaluate the adhesive strength between the MCrAlY alloy coating film and the Ni-base superalloy substrate was studied and proposed. By employing the double cantilever beam specimens which were taken from the CoNiCrAlY alloy coated Ni-base superalloy, the fatigue crack propagation tests along the interface were carried out. Through the work particular attention was given to the threshold level to the fatigue crack propagation along the interface as a measure to represent the adhesive strength, based on fracture mechanics approach. The effects of temperature, the surface finishing of the substrate and the long term thermal aging on the adhesive strength were also investigated.
Transferred-Arc Cleaning of Tungsten
Authors: Hollis K.J. , Castro R.G. , Bartram B.D. 
Published: July 2021

Abstract
Transferred-arc cleaning is being investigated as a solvent-free cleaning method for various metallic substrates. With the recent increase in attention given the hazards involved in the storage, use and disposal of organic solvents, cleaning methods which promise comparable cleaning effectiveness with reduced hazards are being sought. Transferred-arc cleaning of tungsten substrates has been studied to identify the effect of processing conditions on cleaning and roughening characteristics. A Box-Behnken response surface designed experiment varying the chamber pressure, substrate standoff distance and plasma torch arc current while observing the transferred-arc voltage, current, surface cleanliness and surface roughness was performed. The results of the analysis show the effect of the various independent variables on the measured responses. Particular difficulties in roughening tungsten are due to its exceptionally high arc voltage for metal arc attachment. The results presented here provide an enhanced understanding of the arcing properties of various cathode materials. Such information is useful in obtaining the desired cleaning and/or roughening of the substrate.
Microstructure and Corrosion Behavior of Arc Sprayed Stainless Steel Coatings
Authors: Tajiri T. , Zeng Z. 
Published: July 2021

Abstract
The microstructure of arc sprayed stainless steel 316L coatings appears mainly in bright white matrix, deteriorated layers (grey), and black pores under optical microscopy. The black pores and the chromium-depleted areas in the deteriorated layers are known as the factors for decreasing the ability of protecting substrate under corrosive environments. Results of experiments in this paper suggests, in the condition of this study besides the factors mentioned above, Fe-Cr oxides should be another factor of dominating the corrosion resistance in the coatings. It also describes that the quantity and the distributions of such oxides are great influence on the corrosion behaviors. In this study, two kinds of coatings were used, one with thick deteriorated layers and another with thin deteriorated layers, which were sprayed on mild steel substrate by air atomization and nitrogen atomization respectively. Salt spray test and salt-water dip test were carried out to investigate corrosion behavior in macro and micro view. An effect of sealing treatment on the performance of the coatings was also examined. Results of metallographic examination and image processing analysis are well supported by a detailed investigation of corrosion behaviors of individual phases.
Arc Sprayed Coatings of Ferroalloy-Base Flux-Cored Wires
Authors: Borisova A.L. , Mitz I.V. , Kleyman A. 
Published: July 2021

Abstract
This paper presents the results an experimental study on ferroalloy-base flux-cored wire coatings. The work conducted shows that it is possible to improve the structure and properties of coatings by adding aluminum to the ferrochromium powder charge and rare-earth elements and calcium to ferroboron. This reduces the oxygen content and porosity of coatings by a factor of 1.5-2. It also reduces residual tensile stresses in outer coating layers and improves coating-substrate adhesion strength as well as abrasive wear resistance.
New Arc Wire Approvals for Aircraft Power Plant Overhaul
Authors: Sampson E.R. , Sahoo P. 
Published: July 2021

Abstract
Arc spray systems are increasingly used in the overhaul of aircraft engine components and auxiliary power units. The increasing use of arc spray over plasma for metallic coatings has created a demand for new wire approvals. The chemistry is already established as a powder and it is a matter of conversion to a wire and the arc spray process. The increasing popularity of the arc spray process is due to its superior bond strength and microstructure that exceed those of plasma. In one case, there is a two and one-half percent porosity requirement for the arc spray and up to 15% is allowed for plasma. This density approaches HVOF quality requirements. This paper will discuss some historical background of the process, what is approved and then move on to the new materials that are submitted for approval. Microstructures and bond strengths will be presented and some information about a proprietary method to solve a coating problem in the aircraft overhaul industry of long standing. The paper will also discuss new advances in arc spray systems and materials, which makes these systems amenable to replacing plasma sprayed coatings.
Influence of Substrate Preheating Monitoring on Alumina Splat Formation in DC Plasma Process
Authors: Pech J. , Hannoyer B. , Denoirjean A. , Fauchais P. 
Published: July 2021

Abstract
This paper is devoted to the study of alumina splats formation and the adhesion/cohesion of alumina coatings on oxidized 1040 steel substrates. When preheating with the plasma torch, a duplex oxide layer is formed with an upper hematite and an under magnetite. Measurements have been performed on oxide layers with 470 nm average thickness corresponding to preheating times of about 10 min. In these conditions, the relative thickness of each sub-layer can be controlled by monitoring the heating rate and the preheating temperature. When the hematite upper layer is thick, it is mostly broken by the droplet impact and correspondingly the resulting coating has a poor adhesion (≈ 34 MPa) the rupture occurring within the oxide layer. When the hematite upper layer is thin, the droplet impact breaks only partly the oxide layers and the rupture of the coating occurs both within the oxide layer and the substrate surface (≈ 40 MPa).
Splats and Coatings of Stainless Steel Particles Coated with an Alumina Shell
Authors: Ageorges H. , Fauchais P. 
Published: July 2021

Abstract
The effect of an alumina shell on stainless steel particles used in plasma spraying has been studied. The mean size of the injected particles is about 65 nm and the thickness of the alumina shell is 3 µm. The composite powder is plasma sprayed using a PTF4 type plasma gun with an internal injection 3 mm upstream of the nozzle exit. The results show that without preheating the substrate splats are extensively fingered and become circular when the substrate surface is preheated over 200°C. EDS analysis of the distribution of the various elements shows that the alumina either uniformly covers the stainless steel splat or is distributed in pieces over the surface. This behavior has been explained by collecting particles in flight and analyzing them. A composite stainless steel/alumina coating sprayed on a rough stainless steel substrate preheated to 400°C has been examined and compared with a pure stainless steel coating. Both hardness and cohesion are improved for the alumina coated particles due to the random distribution of alumina within the steel matrix.
Effect of Melting State of Spray Particles on the Adhesive Strength of HVOF Nickel-Based Alloy Coatings
Authors: Li C.-J. , Wang Y-Y. , Ohmori A. 
Published: July 2021

Abstract
NiCrBSi and Ni-50Cr coatings are deposited using High Velocity Oxygen-Fuel (HVOF) spray process under different spray parameters with two powders of different sizes to clarify the influence of melting state of spray particles on the adhesive strength of the coating. The adhesive strength of coating is estimated according to ASTM C633-79. The melting state of spray droplet is examined from the coating microstructure. It is found that the melting state of spray particles has significant effect on the adhesive strength of HVOF sprayed Ni-based coatings. The significant melting of spray particle does not contribute to the increase in the adhesion of HVOF metallic coatings. On the other hand, the deposition of partially melted large particle contributes to the substantial improvement of adhesive strength of HVOF coating. The subsequent coating presents a dense microstructure and yields an adhesive strength of over 76 MPa, which is doubled compared to the coating deposited with completely molten particles.
Fabrication of SiC Fibre Reinforced MoSi2 Based Composites by Low Pressure Plasm a Spraying
Authors: Baik K.H. , Grant P.S. , Bhatti A.R. , Shatwell R.A. 
Published: July 2021

Abstract
SiC fibre reinforced SiAlON-MoSi2 composites have been manufactured by concurrent fibre winding and low pressure plasma spraying (LPPS), producing multi-layer, circumferentially fibre-reinforced composite rings. LPPS parameters for the powder used were optimised by a two-level experimental design method followed by additional tuning, achieving smooth sprayed surfaces with low matrix porosity and good deposition efficiency. The microstructure of the SiAlON-MoSi2 matrix consisted of a lamellar structure and uniformly distributed SiAlON splats throughout the MoSi2 matrix. The spray/wind composites exhibited 2% porosity and well controlled fibre distribution. Matrix cracking occurred after heat treatment at 1500°C and was attributed to the development of large tensile residual stresses during cooling due to CTE mismatch. Increasing the SiAlON to MoSi2 ratio in the composite solved the problem. Simulations based on residual stresses showed that the maximum permissible fibre volume fraction to avoid matrix cracking was 0.06 for SiC/MoSi2 and 0.23 for SiC/SiAlON(40v/o)-MoSi2.
Improved Wear Performance by the Incorporation of Solid Lubricants During Thermal Spraying
Authors: Marple B.R. , Voyer J. 
Published: July 2021

Abstract
For components that are required to function in sliding or rubbing contact with other parts, degradation often occurs through wear due to friction between the two contacting surfaces. Depending on the nature of the materials being used, the addition of water as a lubricant may introduce corrosion and accelerate the degradation process. To improve the performance and increase the life of these components, coatings may be applied to the regions subject to the greatest wear. These coatings may be engineered to provide internal pockets of solid lubricant in order to improve the tribological performance. In the present study, coatings containing a solid lubricant were produced by thermal spraying feedstock powders consisting of a blend of tungsten carbide-metal and a fluorinated ethylene-propylene copolymer-based material. The volume content of this Teflon-based material in the feedstock ranged from 3.5 to 36%. These feedstocks were deposited using a high velocity oxy-fuel system to produce coatings having a level of porosity below 2%. Sliding wear tests in which coated rotors were tested in contact with stationary carbon-graphite disks identified an optimum level of Teflon-based material in the feedstock formulation required to produce coatings exhibiting minimum wear. This optimum level was in the range of 7-17% by volume and depended on the composition of the cermet constituent. Reductions in mass loss for the couples on the order of 50% (an improvement in performance by a factor of approximately two) were obtained for the best-performing compositions, as compared to couples m which the coating contained no solid lubricant.