bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative Study on HVOF, Vacuum Plasma Spray and Axial Plasma Spray for CoNiCrAlY Alloy Deposition
Authors: Scrivani A. , Groppetti R. , Bardi U. , Lavacchi A. , Rizzi G. 
Published: June 2022

Abstract
In the aerospace field as well as in the stationary gas turbine field, thermal sprayed coatings are used to improve the surface properties of Nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly Yttria partially stabilized Zirconia) In the present study, our purpose was to assess the properties of thermally sprayed bond coat CoNiCrAlY comparing the performance of three different techniques: Vacuum Plasma Spray (VPS), High Velocity Oxygen Flame (HVOF) and Axial Plasma Spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of structural (porosity, oxide concentration, unmelted particles presence) and mechanical characteristics (hardness, adhesion). Furthermore, a study of the surface composition and morphology has been carried out. Specific efficiency trial has been carried out to compare the efficiency of the three examined technologies. We observed that the highest quality films are obtained by VPS, but that also HVOF and AxPS sprayed films have interesting properties which can make their use interesting for some applications in view of the lower cost of HVOF and AxPS.
Analysis of Porosity and Cracks in Cross Sections of Plasma Sprayed Oxide Coatings
Authors: Koschlig T. , Lallement R. 
Published: June 2022

Abstract
Microstructure of plasma-sprayed thermal barrier coating has an influence on the lifetime under service conditions in aero engine. This paper focuses on problems of preparing and comparing ceramic samples and characterising microstructure features such as porosity and cracks within coating cross sections by image analysis. The results can be used for developing standards and best practices for characterization plasma-sprayed coatings. The methodology was evolved to relate coating microstructure to spraying parameters and properties of coating. It would help to develop new ceramics coatings or optimise them.
Microstructural Studies of Thermally Sprayed Deposits by Neutron Scattering
Authors: Keller T. , Wagner W. , Ilavsky J. , Margandant N. , Siegmann S. , Pisacka J. , Matejicek J. , Barbezat G. , Fiala P. , Pirling T. 
Published: June 2022

Abstract
Technological properties of thermally sprayed deposits are to a great extent related to the underlying microstructure. The present project aims to relate macroscopic properties of metallic coatings to their microstructure. For this purpose, thermally sprayed deposits of nickel based alloys (NiCr, NiCrAlY) were manufactured by various spraying techniques - atmospheric and vacuum plasma spraying, flame spraying, high velocity oxygen fuel and water-stabilized plasma spraying. One of the key microstructural features is the void system. This system is usually characterized by the total volume of voids, the so called porosity. An additional characteristic parameter of the void system is the specific surface area. The method of anisotropic Small Angle Neutron Scattering (SANS) in the "Porod Regime" allows the determination of the anisotropic specific surface area of the complex void system that consists of intralamellar cracks and interlamellar pores. In contrast to optical microscopy, the SANS technique is capable of resolving the pore structure down to the nanometer scale, and the measured specific surface area represents a statistically relevant average value for the whole illuminated sample volume which is usually a few mm3. Besides the presence of voids and cracks the performance of thermally sprayed coatings is also significantly influenced by residual stresses. In the present work residual strains were determined by the technique of neutron diffraction as well as by bending tests, i.e. laser profilometry of the substrate before and after the spraying process. The specific surface area and the residual stresses are discussed with respect to total porosity, the presence of secondary phases like oxides and wear behavior. Special attention is drawn to the anisotropy of the apparent surface area, which is discussed with respect to the anisotropy of macroscopic properties like electrical resistance.
Mechanisms of High Hardness in Cr3C2-NiCr Cermet Coatings Formed by Vacuum Plasma Spraying
Authors: Tomita T. , Takatani Y. , Tani K. , Harada Y. 
Published: June 2022

Abstract
Hardness and microstructure of Cr3C2-NiCr coating formed by vacuum plasma spraying process (VPS coating) were investigated in compare with that formed by High Velocity Oxygen Fuel Spraying process (HVOF coating). The results are as follows. (1) The hardness of VPS coatings in as sprayed condition was HV1243 ± 80, which was much higher than that of HVOF coatings, HV958±44, and never went down under HV1100 even after heat treatment at 1273K for 3.6ks. (2) VPS coating presents dense lameller structures composed of Cr2C3, Cr7C3 and γ-NiCr phase, while HVOF coating presents lameller structures with many fine gaps, composed of Cr2C3, Cr7C3, γ-NiCr phase and relatively large amounts of Cr2O3. (3) The reason why such high hardness was obtained in VPS coating, has been considered due to their dense lamella structures.
Effect of Plasma Fluctuations on In-Flight Particle Parameters
Authors: Bisson J.F. , Gauthier B. , Moreau C. 
Published: June 2022

Abstract
The influence of arc root fluctuations in DC plasma spraying on the physical state of the particle jet is investigated by correlating individual in-flight particle temperature and velocity measurements with the instantaneous voltage difference between the electrodes. In-flight diagnostics with the DPV-2000 sensing device involves two-color pyrometry and time-of-flight technique for the determination of temperature and velocity. Synchronization of particle diagnostics with the torch voltage fluctuations is performed using an electronic circuit that generates a pulse when the voltage reaches some specific level; this pulse, that can be shifted by an arbitrary period of time, is used to trigger the acquisition of the pyrometric signals. Unlike what has been predicted by numerical modeling, time-dependent particle temperature and velocity due to power fluctuations induced by the arc movement can be very important. Periodic variations of the mean particle temperature and velocity, reaching ΔT= 600°C and Δv = 200m/s, are recorded during a voltage cycle. Moreover, very few particles are detected during some part of the cycle. The existence of quiet periods suggests that particles that are injected at some specific moments in the plasma are neither heated nor accelerated efficiently. To our knowledge, this is the first time large time-dependent effects of the arc root fluctuations on the particle state (temperature and velocity) are experimentally demonstrated with quantitative measurements.
On-Line Monitoring (SDC) Through Coating Surface Temperature of Residual Stresses in APS WC-Co17wt% Coatings on Hastelloy X
Authors: Renault T. , Vardelle M. , Fauchais P. , Hoffmann H. , Braillard F. 
Published: June 2022

Abstract
During last 10 years, it has been pointed out that the reproducibility and reliability of air plasma sprayed (APS) coatings depend, among other parameters, on the particle velocity and temperature distributions prior to their impacts to the target surface. On-line control systems have been designed to follow these parameters in the harsh environment of booths. However, in spite of significant strides, works have yet to be carried out to establish relationships between deposit properties and in-flight particle parameters and/or surface target temperature, roughness and oxidation stage. The SPCTS laboratory at the University of Limoges has developed the SDC (Spray and Deposit Control) system in collaboration with SNECMA Services. It controls the stability of the spray jet and the mean particle trajectory together with the target surface temperature. It has been used with a device allowing to measure the deflection of a rectangular beam during APS of WC-Co17wt% or ZrO2+8wt%Y2O3 powder on Hastelloy X (Ni base alloy) substrate. The aim of this study was to determine which spray parameters influence the residual stresses, in order to achieve a mean compressive residual stress in the WC-Co17wt% coating on Hastelloy X and to control it with the deposit temperature.
Diagnostic of In-Flight Particle Properties and Resulting Coating Qualities on Atmospheric Plasma Spray Process
Authors: Lugscheider E. , Fischer A. , Koch D. , Papenfuß N. 
Published: June 2022

Abstract
Thermal spray technology became established in various parts of industry (e.g. aircraft industry, medical industry etc.). Some of the applications are highly sensitive, therefore the coating quality plays an important role. Most of the common quality control methods are based on destructive testing methods which are undesirable for economical reasons. In recent years the interest in non-destructive online measurement methods increased and still is growing. More detailed knowledge of the relationship between process parameters can help to improve the coating quality standards and to understand different phenomena in thermal spraying. This will make online process control possible and improves the acceptance of thermal spray technology. In this paper results of fundamental studies on the atmospheric plasma spraying process (APS) are presented. Al2O3 and NiCr powder were sprayed as model materials. In the experiments modem on-line monitoring systems were used to investigate the entire process from gun parameters to the coating quality. The faces in this paper are set on investigations of the in-flight properties of spray particles with the particle sensor DPV 2000 and their relationship with resulting coating properties. A method will be presented to extract characteristic values (velocity and temperature) out of the spray process with DPV 2000. With this method the APS-process was monitored and process parameters were correlated with main coating properties.
Plasma Jet Properties in a New Spraying Process at Low Pressure for Large Area Thin Film Deposition
Authors: Dorier J.L. , Gindrat M. , Hollenstein C. , Loch M. , Refke A. , Salito A. , Barbezat G. 
Published: June 2022

Abstract
This paper describes an experimental investigation of plasma jet properties of a DC torch operated at low pressure (below 10 mbar). A modified enthalpy probe system is described, which allows gas sampling from the plasma jet at pressures down to the mbar range. Measurements of the specific enthalpy, temperature and velocity throughout the jet for different pressures are presented and discussed. In the pressure range investigated, the jet flow is supersonic and compressible theory is used to infer the velocity from the dynamic pressure measured at the probe tip. In addition, optical emission spectroscopy of the plasma jet is used to evidence the differences of these low-pressure plasmas with respect to common, atmospheric pressure thermal jets. These preliminary measurements are the starting points towards a better understanding of plasma jets at low operating pressures in view of new process development and optimisation.
The Relationships Between In-Flight Particles Characteristics and Coating Properties Under Plasma Spraying Conditions
Authors: Planche M.P. , Normand B. , Suzon E. , Coddet C. 
Published: June 2022

Abstract
The effects of the plasma spray process parameters on the microstructure and properties of coatings have been recognized for a long time. It is now clearly proved that the quality and the properties of the deposits are strongly dependent on the in-flight particle characteristics as well as on the splat morphology. The aim of this study was to examine in detail: firstly the interaction between an Al2O3/13%TiO2 powder and the spraying process, secondly the splat formation in order to understand the morphology of the deposits. A good way to reach a better understanding of the particle/ plasma interaction is to determine the particle parameters at impact. The particles parameters: velocity, temperature and diameter, prior to their impact on the substrate were measured by the DPV-2000 diagnostic system. The effect of particle velocity, temperature and size on the splat morphology and deposits properties for different plasma conditions were examined. The splat morphology was characterized using the Sommerfeld dimensionless number, K; the value of which is directly related to the impact mode. These analyses were correlated to microhardness, roughness and to the tribological properties of the coatings.
Visualization of the Impact of Drops on a Substrate in Plasma Spraying: Deposition and Splashing Modes
Authors: Escure C. , Vardelle M. , Vardelle A.M. , Fauchais P. 
Published: June 2022

Abstract
In plasma spraying, the dynamics of droplet deformation and cooling on the substrate determines the geometry of the resulting splat, the porosity formation and the quality of contact between the splat and the underlying layer, thereby controlling the properties of coatings. The process of splat formation depends on the droplet velocity, size, molten state, chemistry and angle of impact, and on the substrate material, roughness, temperature and surface chemistry. This paper concentrates on investigating the way the droplets impact onto the substrate. A fast-imaging camera is used to observe the impact of plasma-sprayed alumina droplets on cold and hot substrates. Three modes of impact are observed: splashing, deposition or rebounding. A droplet is said to splash when it disintegrates totally or partially into secondary droplets after impacting onto the surface while it is said to deposit if the liquid material spreads and solidifies on the surface with a minimum splashing. The results are expressed in dimensionless form as a correlation between the impact mode and the Sommerfeld parameter K. The latter quantifies the importance of the particle parameters at impact (temperature, velocity and size) and viscous and surface tension forces. It is found that, when K is higher than 57.7, the splashing mode prevails as already found in a variety of different fields for droplets impacting on surfaces.
The Interrelationship Between Particle Velocity and Temperature, Splat Formation and Deposition Efficiency in Detonation Sprayed Alumina Coatings
Authors: Sundararajan G. , Sivakumar G. , Srinivasa Rao D. 
Published: June 2022

Abstract
It is well accepted that the morphology and microstructure of the splats have a strong influence on the characteristics and properties of thermally sprayed coatings. McPherson has made pioneering and outstanding contributions in the above area, especially for plasma sprayed coatings. Recently, splat morphology - microstructure - properties correlation has also been attempted in the case of HVOF thermal spray coatings. However, only limited data is available in the case of detonation sprayed coatings inspite of the fact that DS coatings have been available commercially for a long time. In the present work, the influence of particle velocity and temperature on the splat morphology and also area coverage of the splat has been studied for detonation sprayed Al2O3 particles on a mild steel substrate. Further, the effect of two detonation spray process variables namely, oxy fuel ratio and shot frequency on splat morphology and splat area coverage has been evaluated. The above correlation has then been utilized to understand the variation of deposition efficiency of detonation sprayed Al2O3 coatings on mild steel as a function of spray process parameters.
Development of a Coupled Model to Predict Droplet Deformation and Solidification During Splatting
Authors: Hale D.L. , Berry R.A. 
Published: June 2022

Abstract
Thermal spray is a melt-spray process in which material is melted and accelerated to high velocities, impinges upon a substrate, and rapidly solidifies to form a coating. Modeling the deposition dynamics of droplets is a key step towards understanding the evolution of a coating microstructure, since a coating is built up from the successive accumulation of many deformed, solidified droplets. This paper discusses some special effects testing of a particle model being developed by the authors to simulate the mechanics and thermodynamics associated with the simultaneous flattening and solidification of a fully liquid or partially solidified droplet. Rigorous validation of the numerical algorithm must necessarily be performed via this separate effects testing.
Mechanical Properties of Thermal Spray Coatings
Authors: Varis T. , Rajamäki E. , Korpiola K. 
Published: June 2022

Abstract
Under load and stress thermal spray coatings have unique behaviour as compared to the bulk materials. The aim of this study was to define the mechanical properties of thermal spray coatings and consider the effect of external stress on coatings under test conditions. Five HVOF or Plasma spray coatings: NiCr, WC-CoCr, Al2O3-TiO2, Al2O3, and Cr2O3 were studied. Mechanical properties, such as elastic modulus (E), and tensile strength (a) were measured. Behaviour of some coatings in different loading conditions (tension and compressive) was studied.
Bonding Strength Test and Biological Evaluation of Plasma Sprayed HA-Based Composite Coatings
Authors: Zheng X.B. , Ding C.X. 
Published: June 2022

Abstract
To improve the bonding strength of HA coating, several HA-based composite coatings (HA/Ti, HA/ZrO2 HA/ZrO2SiO2 and HA/NiCr composite coatings) have been fabricated via atmospheric plasma spraying. The bonding strengths of fabricated specimens were tested by ASTM C-633 method. The bioactivity of composite coatings was evaluated by examining carbonate-containing apatite formation on their surfaces in simulated body fluid (SBF). In vitro cell cultures were carried out to examine the biocompatibihty of composite coatings. The results obtained revealed that the addition of metal or ceramics in HA improved the bonding strength of coating significantly except HA/ZrO2-SiO2 composite coating. In SBF test, all of these four coatings were covered by carbonate-containing apatite after immersed in SBF, indicating good bioactivity for composite coatings. The results of cell cultures produced the testimony of excellent biocompatibihty for the coatings except that HA/NiCr composite coating possessed cytotoxicity. By comprehensive survey of bonding strength, bioactivity and biocompatibihty, HA/Ti and HA/ZrO2 composite coatings were candidates of prospective biocoatings.
Characterization and Tribological Properties of Electroless Plated Ni-Co on Plasma-Sprayed Cr3C2-NiCr Coating
Authors: Li J. , Ding C. 
Published: June 2022

Abstract
Microstructure of electroless plated Ni-Co coating on plasma-sprayed Cr3C2-NiCr coating which was previously applied onto lCrl8Ni9Ti stainless steel was characterized, and its tribological properties during sliding against different materials were evaluated. It was found that the electroless plated Ni-Co coating on the Cr3C2-NiCr coating had lower cobalt content and a finer structure than that deposited directly on lCrl8Ni9Ti stainless steel. All the self-mated as-sprayed Cr3C2-NiCr coating, the self-mated electroless plated Ni-Co coating on the Cr3C2-NiCr coating, the self-mated electroless plated Ni-Co coating on lCrl8Ni9Ti stainless steel and the frictional pair of the electroless plated Ni-Co coating on lCrl8Ni9Ti stainless steel against the Cr3C2-NiCr coating exhibited higher friction and wear coefficients during sliding. The frictional pair of the electroless plated Ni-Co coating on the Cr3C2-NiCr coating against the Cr3C2-NiCr coating displayed excellent tribological properties with a friction coefficient of 0.10 and a wear coefficient less than 10-6 mm3 Nm-1 during dry sliding in air. The electroless plated Ni-Co coating on the Cr3C2-NiCr coating somewhat reduced friction and wear coefficients during sliding against plasma sprayed TiO2 coating. The above results could be attributed to that the electroless plated Ni-Co coating on the Cr3C2-NiCr coating could weaken the adhesive intensity between the suitable counterpart materials during sliding.
Importance of the Adhesion of HVOF Sprayed Coatings for Aqueous Corrosion Resistance
Authors: Kuroda S. , Kawakita J. , Fukushima T. , Tobe S. 
Published: June 2022

Abstract
Importance of coating adhesion in a corrosive environment was studied experimentally. Tensile adhesion strength of HVOF sprayed 316L stainless steel and Hastelloy C coatings were tested in as-sprayed condition as well as after immersion in seawater. It was found that the adhesion strength of the stainless steel coatings degraded rapidly whereas that of the Hastelloy coatings remained almost intact. Specimens with an artificial defect were also immersed in seawater. The cross sectional observation after the test revealed that the corrosion at the coating-substrate interface proceeded much faster with the stainless steel coating as compared to the Ni-base alloy coating. A model experiment to simulate the galvanic corrosion of a coating-substrate couple was carried out and no significant difference in the galvanic current density was found between the two coatings when coupled with the steel substrate. The tightness of the coating-substrate interface was then tested with a fluorescent dye penetration test. The dye could penetrate the boundary between the stainless steel coating and the substrate whereas the boundary between the Ni-base alloy coating and the substrate was so tight that no penetration occurred. The size of the micro-gaps at the coating-substrate boundary was discussed from the viewpoint of classical Washburn-Ridiel theory. It was concluded that such micro-gaps between the coating and substrate must be eliminated for these barrier-type coatings to be used in corrosive environments. Heat treatment was highly effective for suppressing the preferential corrosion at the coating-substrate boundary.
Relationship of Corrosion Resistance–Coating Structure of HP/HVOF Carbide and Metallic Coatings
Authors: Shmyreva T. , Wang D. , Thorpe R. 
Published: June 2022

Abstract
A study was carried out on the corrosion resistance of the JP- 5000 coatings of Superalloy 625, WC-12%Co, WC-17%Co, WC-10%Co-4%Cr and Cr3C2-25NiCr materials and comparisons made with chrome plating. The coating corrosion resistance was evaluated using the standard salt fog test (ASTM B117) and also by submersion tests in 10% FeCl3 solution (ASTM G48), in 10% HNO3 and in 0.1M H2SO4 + 0.2M HCl solutions. The coating corrosion mechanisms in relationship with the coating microstructure and phase constitutions are discussed. The test results show that the HP/HVOF coating corrosion resistance can be significantly improved through spray parameters and coating structure optimization. All coatings tested herein having optimum microstructure and phase constitutions have shown improved corrosion resistances in comparison with chrome plating.