bluuebunny/crossref_metadata_2025 huggingface dataset:
In-vitro Compatibility of Some Native Isolates of Trichoderma spp. with Commonly used Pesticides
Authors: Budha C B , Shrestha S M , Manandhar H K , Baidya S
Published: August 2022

Trichoderma is an effective bio-control agent against a wide range of disease-causing pathogens of various crops and potential to be integrated into the disease management program. The study was conducted to find out the compatible pesticide/s with Trichoderma for integrated pest management (IPM). This study includes in-vitro evaluation of four chemical fungicides (carbendazim, copper-oxychloride, captan and tebuconazole + sulphur), three chemical insecticides (malathion, imidachlorpid and chlorpyriphos + cypermethrin) and one botanical insecticide (azadirachtin) for compatibility with seven different native isolates and two known species of Trichoderma through poisoned food technique. Copper-oxychloride was found compatible with all the tested isolates. In contrast, carbendazim and tebuconazole + sulphur were found incompatible. The insecticides, malathion, imidachlorpid, chlorpyriphos + cypermethrin, azadirachtin and the fungicide, captan showed some degree of compatibility. It is concluded that the tested Trichoderma isolates and the given species could be used together in combination with the given compatible fungicide such as copper-oxychloride and the given insecticides. These results would be helpful to set out the possibility of combining Trichoderma spp. as a biocontrol agent with pesticides to be used through IPM approach.
Comparison of Plasma Sprayed High Entropy Alloys with Conventional Bond Coat Materials
Authors: Ang Andrew S.M. , Berndt Christopher C. , Sesso Mitchell L. , Anupam Ameey , Ravi Sankar Kottada Praveen. S. , Murty B.S.
Published: August 2022

High entropy alloys (HEAs) are a new class of alloys that have multiple principal elements in an equiatomic ratio and that exhibit novel phase structures. HEAs are known for their high temperature microstructural stability, enhanced oxidation and wear resistance properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimize the appropriate thermal spray parameters and spray deposits were prepared. Subsequently, the microstructure and mechanical properties of two HEAs coatings of different composition were characterized and compared to conventional plasma spray NiCrAlY bond coats.
Manufacturing of Thick, Crack-Free Wear Protective Coatings on Complex Geometries for Gas Turbine Parts
Authors: Riedel Marcus , Duda Thomas
Published: August 2022

This paper analyses the influence of specific coating parameters such as robot velocity, spray distance and part cooling on the risk of crack formation within Chromium- Carbide / Nickel-Chromium coatings. To understand the effect in more detail, metallographic investigations were conducted. These also provide sufficient data to examine other important coating characteristics such as porosity, mechanical stresses and homogeneity. As an additional analytical method Element Mapping is utilised to show the level of oxidation and its impact on the coating microstructure. The methods X-ray diffraction (XRD) and In-situ coating property (ICP)-Sensor are used to investigate the development of stresses in different coatings. With the information from all these examinations a concept was derived to achieve thick, crack-free wear protective coatings.
Microstructure and Properties of Porous Abradable Alumina Coatings Flame-Sprayed by Semi-Molten Particles
Authors: Li Chang-Jiu , Zou Jiao , Huo Hui-Bin , Yao Jian-Tao , Yang Guan-Jun
Published: August 2022

High efficiency gas turbine needs high temperature sealing by abradable porous ceramic coatings. In this study, porous Al2O3 coatings were deposited by flame spraying through controlling melting of spray powder particle in a semi-molten state. The effect of melting degree of spray particles changed via spray conditions on coating microstructure and porosity was investigated. The melting degree of spray particles was characterized by using 3D confocal laser microscopy. The porosity of the coating was estimated by image analysis. The results showed that the melting degree of alumina particles can be changed from 80 down to 30% and thus the coating porosity can be increased from 30% up to about 60%. The standard hardness test yielded no effective data for the porous coatings deposited by spray particles of a melting degree less than 60%, and hardness of 32-75 HR15Y for Al2O3 coatings deposited by spray particles with a melting degree higher than 60%. The pin-on-disk abrasion test of Inconel 738 nickel-based superalloy spherical pin of 5 mm in diameter at room temperature against porous alumina coating was conducted to evaluate abradability of porous Al2O3 coatings. It was found that for the coatings of hardness less than 32HR15Y and porosity over 40% the wear weight loss of the IN738 pin became negligible despite high wear rate of the coating. It is evident that the flame-sprayed porous alumina coatings of high porosity by the present approach are promising abradable coatings applicable to gas turbine operating at high temperature.
Process-Property Correlation of Heat-Treated Aluminium 6061 Cold Spray Coatings
Authors: Loke Kelvin , Kwok Richard , Koh P.K. , Lim T.C. , Cheang Philip
Published: August 2022

Cold spray Aluminium 6061 coating samples were produced with variations of cold spray gas temperatures from 300°C, 400°C, 500°C, 600°C and 700°C, with all other spray parameters constant. The tensile adhesive strengths of the coatings were found to be decreasing with increasing spray temperature, with a marked 70% drop from 400°C to 500°C. A 72% increase in the average coating adhesive strength was observed after T6-heat treatment of non-grit blasted coating samples although the average coating adhesive strength decreased by 9% after stress-relief heat treatment. A 64% increase in the average coating adhesive strength was observed after T6-heat treatment of grit blasted coating samples although the average coating adhesive strength decreased by 20% after stress-relief heat treatment. Coatings were also sprayed at 40° and 60° and subjected to stress-relief and T6 heat treatment. However there were no significant variations in the coating adhesive strengths after heat treatment.
Spall Resistant HVOF Coatings
Authors: Webb David , Straten Richard Vander , Martin Brad , Montgomery Ron
Published: August 2022

The Under Secretary of Defense mandated all DoD facilities reduce or eliminate Hexavalent Chrome from all processing environments. The USAF Landing Gear Systems Engineering located at Hill AFB Utah is converting all line of sight EHC plating to High Velocity Oxygen Fuel (HVOF) applied tungsten carbide-cobalt (WC/Co) and/or tungsten carbide-cobalt chrome (WC/Co/Cr) coatings. The original HVOF coating thickness of 0.015 inch has been reduced to 0.010 inch due to spallation concerns. This has resulted in the condemnation of many expensive assets due to this coating thickness reduction. ES3 is developing an HVOF applied spall resistant coating for the USAF that may be applied up to 0.030 inch for High Strength Steels (HSS) above 200 KSI stress levels. Material test data and recommendations for use are detailed in this paper.
Thermal Phase Stability of Various Plasma Sprayed TBCs
Authors: Li Li , Peterson Benjamin
Published: August 2022

The thermal phase stability of plasma sprayed TBC is presented and discussed. TBC phase transformation after various isothermal heat treatment processes was studied via Xray diffraction (XRD) and Raman Spectroscopy methods. The YSZ-Gd-Yb and 20YSZ TBCs demonstrated superior thermal phase stability as compared with the high and standard purity 8YSZ TBCs, although higher purity also helps delay the tetragonal to monoclinic phase transformation. The phase transformation appears to be suppressed by cooling at higher rates. This data presents a qualitative phase stability comparison between the various coatings. However, cooling rate has to be taken into consideration in determining the extent of phase instability during the coating design of aero turbine applications.
A Damage Based Finite Element Simulation of Cold Spray Coating under Indentation Loading
Authors: Moridi A. , Hassani-Gangaraj S.M. , Guagliano M.
Published: August 2022

For well over a hundred years, hardness testing has provided engineers a quick measure of the mechanical properties of a material or coating. However, the technique has also been fraught with potential artifacts, many of which are related to a phenomenon known as the “indentation size effect”. Unlike bulk materials, experimental studies on the hardness measurements of cold spray coatings in different load regimes shows strong dependency on the indentation size in a manner different from the Nix–Gao model. In cold spray coating additional parameters such as porosity and cohesive strength between cold sprayed particles affect the hardness measurements. As a result the hardness loss was observed by increasing the indentation load. To interpret the experimental observation, a two dimensional model was developed taking into consideration the inter particle damage. Ductile damage initiation in combination with the linear damage evolution model has been used. The deviation of load-displacement curves in the material with inter particle defects in comparison to bulk material was studied to explain the mechanism involved in hardness loss.
A Novel Coaxially Laser-Assisted (COLA) Cold Spray System
Authors: Allen C.M. , Marrocco T. , McNutt P. , Koivuluoto H. , Latokartano J. , Vuoristo P. , Olsson R.
Published: August 2022

Laser-assisted cold-spray has been recognized for over a decade as a technique capable of depositing high quality coatings. By laser heating (and hence softening) the surface being coated, deposition can occur at particle velocities lower than those normally associated with the cold spray process. This can be used to increase deposition rate. However, it can also be used to facilitate the deposition of higher hardness material combinations, normally more out of the reach of the conventional cold spray process. Laser heating can also reduce the requirements of the process on gas usage and gas heating for a given combination, making it more cost-effective. In the work reported below, the capability of a novel co-axially laser-assisted system (COLA) to deposit higher hardness materials, relevant to a range of different industrial applications, has been evaluated. This system can be retrofitted to conventional cold spray equipment.
A Three-Dimensional Analysis of the Suspension Plasma Spray Impinging on a Curved Substrate
Authors: Pourang K. , Moreau C. , Dolatabadi A.
Published: August 2022

Obtaining a uniform coating on curved mechanical parts such as gas turbine blades is one of the industrial challenges in suspension plasma spraying. Through a three dimensional numerical analysis, this study is aimed at providing a better understanding of the effect of substrate curvature on in-flight particle temperature, velocity and trajectory. The high temperature and high velocity plasma flow is simulated inside the plasma torch using a uniform volumetric heat source in the energy equation. In addition, yttria stabilized zirconia (YSZ) suspension is molded as a multicomponent droplet while catastrophic breakup regime is considered for simulating the secondary break-up when the suspension interacts with the plasma flow. A two-way coupled Eulerian-Lagrangian approach along with a stochastic discrete model was used to track the particle trajectory. Particle size distribution in the vicinity of the substrate at different stand-off distances has been investigated. The results show that sub-micron particles may obtain higher velocity and temperature compared to the larger particles. However, due to the small Stokes number associated with sub-micron particles, they are more sensitive to the change of the gas flow streamlines in the vicinity of a curved substrate
Comparison of Impact Crater Shape and Splat on Various Targets for Estimating Projectile Velocity
Authors: Sakata K. , Tagomori K. , Sugiyama N. , Oka D. , Shinya Y. , Sasaki H. , Akahoshi Y. , Norimatsu K. , Fujimura Y. , Fukuda Y. , Koura T.
Published: August 2022

In order to clarify the bonding mechanism and to control the quality of cold-sprayed coatings, it is necessary to accurately measure the in-flight velocity and impact velocity of a projectile. In this study, the in-flight velocity of an aluminum alloy (A2017) 1 mm sphere shot from a small two-stage light gas gun was measured as being 1 km/s using a laser-cut velocity measurement technique. So as to estimate the impact velocity of the projectile, the projectile was caused to impact targets made of aluminum (A1050), copper (C1012), mild steel (SPCC), and stainless steel (SUS304). After the impact tests, the impact crater shapes of the targets was measured using scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy (EDS), and laser microscopy. The impact velocity of a projectile was estimated from obtained crater depth of the targets. In addition, microstructures of the interface between projectile and target were analyzed by EDS, electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM).
Controlling the Twin Wire Arc Spray Process Using Artificial Neural Networks (ANN)
Authors: Hartz-Behrend K. , Schein J. , Schaup J. , Zierhut J.
Published: August 2022

One approach for controlling the twin wire arc spray (TWAS) process is to use optical properties of the particle beam like length or brightness of the beam as input parameters for a process control. The idea is that changes in the process like eroded contact nozzles or variations of current, voltage and/or atomizing gas pressure can be detected through observation of optical properties of the particle beam. It can be assumed that if these properties deviate significantly from those obtained from a beam recorded for an optimal coating process the spray particle and so the coating properties change significantly. Thus, the goal is to detect these optical deviations and compensate occurring errors by adjusting appropriate process parameters for the wire arc spray unit. One cost effective method for monitoring optical properties of the particle beam is to apply the process diagnostic system PFI (Particle Flux Imaging): PFI fits an ellipse to an image of a particle beam thereby defining easy to analyze characteristic parameters by relating optical beam properties to ellipse parameters. Using artificial neural networks (ANN) mathematical relations between ellipse and process parameters can be defined. Thus in the case of a process disturbance through the use of an ANN-based control new process parameters can be computed to compensate particle beam deviations. In this paper, it will be shown that different process parameters can lead to particle beams with the same PFI parameters.
Development of the Microstructure and Mechanical Properties of Cold-Sprayed IN718 Alloy Coating by a Novel In-Situ Shot Peening Process
Authors: Luo Xiao-Tao , Yao Meng-Lin , Li Cheng-Xin , Yang Guan-Jun , Li Chang-Jiu
Published: August 2022

In this study, in-situ shot-peening approach was introduced by mixing large stainless steel (SS) shots with diameters over 150 μm with IN718 spray powders to aim at developing a novel approach to achieve dense coating. Effect of mixed stainless steel shot content on the microstructure and mechanical properties of the IN718 coating was examined. Results show that IN718 coating can be deposited without any shot peening particle inclusions for their relatively low velocity. It was revealed that the deposition efficiency of the IN 718 powders is improved by the in-situ shot peening effect. With increasing shot fraction in the powder mixture from 0% to 50 vol.%, the coating porosity decreased from 5.6% to 0.2% only by using N2 accelerating gas. Remarkable work hardening induced by impact of the shot peening particles was detected.
Eddy Current Measurement Technique for Bi-Layer Thermal Barrier Systems
Authors: Smith Gregory M. , Erb Nicholas , Hansson Mats-Olov , Johansson Jimmy
Published: August 2022

Non-destructive eddy current evaluation is a practical and well-established tool in aerospace and other industries, used to find or identify material defects not otherwise detectable. It can also be employed to measure the thickness of various coatings, although it is not yet fully optimized for multi-layer thermal spray systems, such as thermal barrier coatings (TBCs). The first part of this paper aims to look at the underlying mechanisms of the eddy current thickness measurement technique and uses a Design of Experiment (DoE) study to identify key characteristics related to thickness measurement of thermal barrier coatings. The second part of the paper is a case study on the application of the findings into general production, showing the achieved improvements in accuracy and repeatability of thickness measurements.
Effect of Alloying Active Elements of Powder on Spreading Behaviour of Plasma Spray Splats
Authors: Zhang Yongang , Hyland Margaret , Tran A.T.T. , Matthew Steven
Published: August 2022

In the formation of plasma sprayed splats, the spreading behaviour of molten droplet is essential for forming desirable lamella with good adhesion to substrate. To understand the effect of active element chromium on droplet spreading, pure Ni and Ni-20Cr alloyed powders with the size of 45~63μm were plasma sprayed on mirror polished 304 stainless steel heated to different temperatures (below 200°C) through electrical resistance heaters. The substrate heating resulted in very little change in the surface roughness. However, there was a measureable change in the surface chemistry of the outermost few nanometers, which became increasingly enriched in Fe at higher temperatures. The splat morphologies were characterised and the transition temperatures were estimated. The results show that the transition from splashed to disk splats was not solely dependent on the temperature of the substrate. In some cases, splashing still occurred to a measureable extent even at relatively high substrate temperatures, even above temperatures at which adsorbates (water) were totally removed from the surface. The splashing behaviour could be correlated to a combination of the change in the surface chemistry of the substrate and the presence of active elements in the coating materials.
Elastic Isotropy of Cold Sprayed Coatings
Authors: Cizek J. , Dlouhy I. , Seiner H. , Landa M. , Huang R.
Published: August 2022

Resonant ultrasound spectroscopy was applied to analyze the elastic anisotropy of thick copper, aluminum, titanium, and nickel coatings prepared by cold spraying and to determine the respective elastic moduli. The results show that the coatings exhibit only weak deviations from perfect isotropy, and the obtained elastic moduli are comparable with those of the corresponding polycrystalline bulks. The increased internal friction observed in some of the studied coatings may indicate grain refinement and consequent grain boundary sliding.
Evaluation of the Influence of Flame Spraying Parameters on Microstructure and Electrical Conductivity of Al-12Si Coatings Deposited on Polyurethane Substrates
Authors: Ashrafizadeh H. , Mertiny P. , McDonald A.
Published: August 2022

The influence of flame spraying parameters on coating microstructure and electrical conductivity of aluminum- 12silicon coatings deposited on polyurethane substrates was studied. In order to evaluate the effect of the spray parameters on temperature distribution and its corresponding effect on coating characteristics, an analytical model based on a Green’s function approach was employed. It was found that the addition of air to the flame decreased the temperature within the substrate. Dynamic mechanical analysis (DMA) of the PU substrate revealed that the PU softened as the temperature increased. Therefore, by increasing the pressure of the air injected into the flame spray torch from 35 kPa to 69 kPa, the particles impacted a stiffer substrate. This led to increased deformation of the particles into splats upon impact, improved interlocking, and the overall coating had lower porosity and lower electrical resistance. The results obtained indicated that coating properties are sensitive to both thermal spraying parameters and temperature distribution within the substrate when depositing on elastomeric materials. The effect of torch stand-off distance on coating properties was also evaluated. It was found that higher air pressure can cool the substrate and, therefore, allow for a decrease of the stand-off distance. As a result of shorter stand-off distances, a coating with lower porosity and electrical resistance was deposited.
Evolution of Microstructure and Wear Behavior of Heat-Treated and Fused Arc-Sprayed Coatings Containing Fe2B Crystals Dispersed in Different Steel-Based Matrices
Authors: Dallaire S.
Published: August 2022

Thermally sprayed coatings are mechanically bonded to the substrate and present porosities and a lamellar microstructure that make them less attractive in applications requiring high coating toughness and impermeability to gas and liquids, these properties been obtained with more technically advanced overlaying processes. This paper presents the research work carried out to increase the erosion resistance of arc-sprayed coatings containing hard Fe2B crystals dispersed in mild and alloyed steel-based matrices. These arc-sprayed coatings were a) heat-treated in furnace up to 1000°C and b) fused with an oxy-acetylene torch. The sprayed specimens were tested in a particle erosion device at the impact angles of 25° and 90°. The evolution of microstructure was done by SEM and wear damage by Time- Domain Optical Coherence Tomography. It was shown that both the heat treatment and fusing processes considerably enhanced the erosion resistance of coatings particularly at the impact angle of 90°. This increase in erosion resistance is attributed to the disappearance of stringers between sprayed lamellae. Liquid phase sintering is the mechanism responsible for the homogenization of arc-sprayed coatings containing Fe2B. Grain growth observed in arc-sprayed coatings heat-treated up to 1000°C or fused with an oxyacetylene torch does not have a detrimental effect on erosion resistance.
Fatigue Performance of TBCs on Hastelloy X Substrate during Cyclic Bending
Authors: Musalek Radek , Medricky Jan , Pala Zdenek , Kovarik Ondrej , Tomek Libor , Curry Nicholas , Bjorklund Stefan
Published: August 2022

Our previous experiments with low-cost steel substrates confirmed that individual steps of conventional thermal barrier coating (TBC) deposition may influence fatigue properties of the coated samples differently. In this study, testing was carried out for TBC samples deposited on industrially more relevant Hastelloy X substrates. Samples were tested after each step of TBC deposition process: as-received (non-coated), grit-blasted, bond-coated (NiCoCrAlY) and bondcoated + top-coated (yttria-stabilized zirconia - YSZ). Conventional atmospheric plasma spraying (APS) with gas stabilized plasma torch was used for deposition of both bond coat and top coat. In addition, for one half of the samples, bond coat was prepared by consecutive combination of HVAF (High Velocity Air Fuel) and APS processes. Samples were tested both in as-sprayed condition and after 100 hours annealing at 980 °C, which simulated in-service conditions. Obtained results showed that different fatigue performance may be expected for various stages of the TBC deposition as well as due to the variation of the deposition process and sample temperature history.
Fracture Behavior and Lifetime Performance of Thermal Barrier Coatings in Thermally Graded Mechanical Fatigue Environments
Authors: Lu Zhe , Myoung Sang-Won , Jung Yeon-Gil , Zhang Jing , Paik Ungyu
Published: August 2022

The effects of bond coat species on the fracture behavior and lifetime performance were investigated in thermal barrier coating (TBC) systems through thermally graded mechanical fatigue (TGMF) tests. Two types of process, air-plasma spray (APS) and high-velocity oxygen fuel (HVOF), were employed to prepare the bond coats of about 300 μm thickness, and then the top coat of about 600 μm thickness was coated on the both bond coats by APS process. The TGMF tests with two tensile loads of 100 and 150 MPa were performed until 900 cycles at a surface temperature of 850 and 1100 °C for a dwell time of 10 min, and then the sample was cooled at the room temperature for 10 min at each cycle. When the tensile load applied in TGMF tests was 100 MPa at 850 °C, the TBC with APS bond coat showed delamination phenomena at the interface between the top and bond coats and small cracks on the surface after about 250 cycles, while the TBC with HVOF bond coat showed a long crack at interface between the top and bond coats without delamination phenomena until 900 cycles. As the tensile load in TGMF tests was increased to 150 MPa at 850 °C, delamination and/or cracks were created at the relatively low cycles, after about 130 and about 279 cycles for the TBCs of the APS and HVOF bond coats, respectively. When the tensile load applied in TGMF tests was 100 MPa and the temperature increase to 1100 °C, the TBC with APS and HVOD bond coats were delaminated after about 65 and about 110 cycles, respectively. These evidences indicate that the TBC with HVOF bond coat is more efficient in improving lifetime performance than that with APS bond coat in the thermal and mechanical environments.
Influence of Grit Blasting on the Interface Roughness and Adhesion Strength of Cold Sprayed Copper Coatings
Authors: Maev R.Gr. , Leshchynsky V. , Strumban E. , Dzhurinskiy D. , Maeva E.
Published: August 2022

Surface preparation is very important for reliable adhesive bonding of cold sprayed coatings to the substrate. In this work, the grit blasting of low-carbon A516 steel substrates with Al2O3 particles was studied and the roughness parameters Ra and Rt of the grit blasted surfaces were then measured. The influence of alumina grit size on the roughening of the A516 steel substrate, and the resulting effect on the roughness of the Cu coating – steel interface were studied. The results showed that variations of the grit blast size had significantly affected the resultant surface roughness of the substrate. The adhesive strength of the formed copper coatings on A516 steel substrates depends on the surface roughness and hardness of the base material. The adhesive strength about 110-200MPa was achieved. The specific features of the Cu coating-A516 steel interface topography were examined and discussed.
Influence of Microstructure on Thermal Properties of Columnar Axial Suspension Plasma Sprayed Thermal Barrier Coatings
Authors: Ganvir Ashish , Curry Nicholas , Markocsan Nicolaie , Nylen Per , Vilemova Monika , Pala Zdenek
Published: August 2022

Suspension Plasma Spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings. This technique enables the production of a variety of structures from highly dense, highly porous, segmented or columnar coatings. In this work a comparative study is performed on six different suspension plasma sprayed thermal barrier coatings which were produced using axial injection and different process parameters. The influence of coating morphology and porosity on thermal properties was of specific interest. Tests carried out include microstructural analysis with SEM, phase analysis using XRD, porosity calculation using Archimedes experimental setup, pore distribution analysis using mercury infiltration technique and thermal diffusivity/conductivity measurements using laser flash analysis. The results showed that columnar and cauliflower type coatings were produced by axial suspension plasma spraying process. Better performance coatings were produced with relatively higher overall energy input given during spraying. Coatings with higher energy input, lower thickness and wider range of submicron and nanometer sized pores distribution showed lower thermal diffusivity and hence lower thermal conductivity. Also, in-situ heat treatment did not show dramatic increase in thermal properties.
Influence of the Plasma Radiation Scattered by Inflight Particles on Temperature Measurement in Suspension Plasma Spraying
Authors: Aziz Bishoy , Moreau Christian
Published: August 2022

The temperature of in-flight particles in plasma spraying is one of the main parameters affecting the coating microstructure. Temperature measurement has been carried out before for inflight particles in air plasma spray (APS) and other thermal spraying processes. Suspension plasma spray (SPS) is an emerging coating deposition technology that permits the deposition of nanostructured coatings with unique structural characteristics. The aim of this work is to evaluate the influence of radiation emitted by the plasma and metallic vapors on temperature measurement of SPS particles performed by two-color pyrometry. To do so, spectroscopic analysis in the visible to near-infrared range is carried out on the jet stream when suspension of 20wt% YSZ particles in ethanol is sprayed. The analysis takes into account the radiation scattered by the particles (Mie scattering) as well as the radiation directly detected from the jet stream, and it was found that the effect of the scattered radiation by the particles on temperature measurement is 1 degree at its melting point (2700°C) and 16 degrees at 2500°C.
Investigation of Alumina and Yttria Coating Microstructures Manufactured by Suspension Plasma Spray
Authors: Aubignat E. , Planche M.-P. , Montavon G. , Allimant A. , Billieres D.
Published: August 2022

Alumina and yttria coatings, manufactured by suspension plasma spraying, were investigated to understand the “material effect” in the coating building. Some particle image velocimetry measurements were carried out to evaluate the particle velocities into the plasma. Some particle collections were performed to get information on their molten state. Splats were observed by scanning electron microscopy (SEM) and their dimensions were measured with an interferometric profilometer. Coating cross sections were finally observed by SEM and porosity rates were evaluated by image analysis and ultra-small angle X-scattering. This study revealed no real difference between the two materials concerning particle velocity. However, splat analyses highlighted a better flattening ratio for yttria particles, due to a lower difficulty to melt of this material. This property seems to enhance particle vaporization whose condensates are found on coating surface. These observations explain the difference of pore size distributions observed for both coatings.
Investigation of the Interface of Overlapping Splats for a WC-Based Cermet
Authors: Hussong B. , Lünnemann V. , Tillmann W.
Published: August 2022

In this investigation, the behavior of overlapping HVOF-sprayed WC-Co splats is analyzed. Samples are sprayed and documented in several steps with a low density of splats. This method enables to distinguish between several splats in areas where overlapping clusters of splats occur. The splats are sorted according to their chronological order of impact. With this information, cross sections are made of these clusters to study the porous structure, developing in the center and at the boundaries of the splats. An ion-polishing method was employed to avoid the corruption of small pores and structures by mechanical force. It turns out that pores in HVOF coatings are initiated by the overlapping regions at the edges of the splats. Splats impacting directly onto each other show very dense microstructures at the interface in the center region of the impact.
Joining of Dissimilar Materials by the Cold Spray Process
Authors: Champagne Victor Kenneth , West Michael K. , Reza Rokni M. , Curtis Todd
Published: August 2022

This paper presents a concept to develop a practical method to join dissimilar materials by the cold spray process currently not possible with conventional technologies. The novel aspect of the process includes the development of a joint design using cold spray as the enabling technology to join dissimilar materials. The emphasis in this study will be on the method used in the joining of cast ZE41A-T5 magnesium and wrought 6061 aluminum by the cold spray process (CSP) in combination with friction-stir welding (FSW) and the subsequent materials characterization. Microstructural analysis by electron and optical microscopy, along with mechanical test results will be presented. Comparisons will be made to conventional joining techniques and the importance, as well as the applications of this technique, will be discussed.
Low Cost Suspension Plasma Spraying of YSZ Coatings
Authors: Shahien Mohammed , Suzuki Masato
Published: August 2022

Suspension plasma spraying (SPS) process is showing promising improvements for the Thermal barrier coatings (TBCs) performance. This study will focus on the development of a low cost suspension plasma spray system with an axial feeding of yttria stabilized zirconia (YSZ) coatings. A unique twin-cathode plasma spray gun with three plasma torches; P-torch (reversed polarity: cathode nozzle and anode), and two N-torches (normal polarity: anode nozzle and cathode) was used. During operation, the electric power is supplied between P-torch anode and N-torches cathodes to maintain the plasma jet. The system requires only argon as plasma gas, since the enthalpy of plasma jet is enough high for melting ceramic powders, which makes it as cost reduction system. Moreover, the p-torch electrode is hollowed anode and therefore commercial dual tube nozzle was used for the axial feeding to increase the deposition efficiency. It was possible to fabricate dense and/or porous 8YSZ coatings with using only Ar plasma gas through using the twin cathode plasma spray system and the axial injection. The coating microstructure and porosity level can be controlled by appropriate changes in the solids amount in the suspension and the spraying parameters. To control the microstructure the main factor is controlling and adjusting the splat size.
Mechanistic Study and Characterization of Cold Sprayed Ultra-High Molecular Weight Polyethylene-Nano Ceramic Composite Coating
Authors: Ravi Kesavan , Ichikawa Yuji , Ogawa Kazuhiro , Deplanke Tiana , Lame Olivier , Cavaille Jean-Yves
Published: August 2022

The cold spray deposition of ultra high molecular weight polyethylene (UHMWPE) powder mixed with nano alumina, fumed nano alumina and fumed nano silica was attempted on two different substrates namely polypropylene (PP) and aluminum (Al). Approximately 4mm and 1mm thick coating were observed on Al and PP substrates respectively with UHMWPE and fumed nano alumina mixture. The nano ceramic particles played an important role as a bridge bond between the particles. The coatings with nano alumina, fumed nano alumina and fumed nano silica were very contrasting in terms of coating thickness. Gas temperature and pressure played an important role in the deposition. The differential scanning calorimetry (DSC) results of the coatings showed that UHMWPE was melt crystallized after the coating. The substrate properties also affected the deposition mechanism greatly.
Modeling of the Self-Assembly of Nanoparticles into Branched Solid Aggregates for a Suspension Droplet
Authors: Zhang He , Shan Yanguang
Published: August 2022

In the suspension plasma spray, nanosized particles are suspended in a liquid and the suspension is injected into the plasma to deposit coatings. The structure of the highly branched solid aggregates has significant influence on the microstructure and performance of the coating. In this paper, we investigate the formation of branched nanoparticle aggregates resulting from the evaporation of nanofluid droplets. A kinetic Monte Carlo (KMC) approach is used to simulate the drying process of a nanofluid droplet in a circular domain. It is found that the two-dimensional lattice-gas-based Monte Carlo model can describe the self-assembly of nanoparticles into a highly branched solid aggregate. The results reveal that the fingering contact line instabilities can emerge under a given condition and force the formation of a branched nanoparticle structure. The results also show that the initial chemical potential of boundary and the rate of chemical potential change have significant influence on the resulting patterns and the finger number.
Preparation and Characterization of Transparent Hydrophobic Al2O3 Surface by Vacuum Cold Spray
Authors: Li J. , Zhang Y. , Li C.-X. , Pan X.-D. , Yang G.-J. , Li C.-J.
Published: August 2022

Transparent hydrophobic materials have broad application prospects in industry and daily life due to its transparent and super-hydrophobic characteristics, while its performance will be significantly influenced by the materials and its surface morphology. Hydrophobicity and transparency are competitive properties from the viewpoint of surface roughness. However, there are still a lot of problems to be solved to satisfy hydrophobicity and transparency simultaneously in the prepared surface. A novel and simple method to fabricate transparent hydrophobic surface is introduced in the present paper. Micron and sub-micron mixed Al2O3 powders were deposited on the glass and plastic substrate by vacuum cold spray. The coatings were modified by 1,1,2,2- Tetrahydroperfluorodecyltrimethoxysilane (FAS) to reduce the surface energy. The surface morphology was characterized by scanning electron microscopy (SEM) and 3D laser microscopy (LSM). The transmittance of the coating was also investigated. The results show that the as-sprayed surfaces exhibit submicron structure. After FAS absorbing treatment, the contact angle of water droplets on the coatings ranged from 108° to 136° depending on the local surface morphology, and the transmittance of Al2O3 coatings are all above 80% in the range of visible light.
Stress Formation within the First Layer in Plasma Sprayed Coatings
Authors: Mutter Markus , Mauer Georg , Mücke Robert , Vaßen Robert , Back Hyoung Chul , Gibmeier Jens
Published: August 2022

The residual stresses within plasma sprayed coatings are an important factor which can influence the lifetime of the coatings. The investigation of the evolving stresses during deposition and post-deposition cooling of YSZ coatings by measuring in-situ the specimen’s curvature with the so-called ICP sensor is a powerful tool to identify the different stress generation factors. Under certain spray conditions one can observe that the first torch pass leads to a significantly higher increase in specimen´s curvature than the following deposition passes, which indicates significantly higher stresses within the interface coating region. The reason for this steep curvature increase was investigated. It is suggested to be a combination of a stronger bonding of those splats being connected directly to the substrate and the relief of compressive stress within the substrate. The slope of this increase depends on the spray parameters as well as on the substrate conditions, which was investigated also.
Taguchi Design and Analysis of 3D-Computer Fluid Dynamic (CFD) Experiments (TDACE) for the Optimization of Air-Cap Configuration in Arc Spraying
Authors: Tillmann W. , Abdulgader M. , Anjami N. , Bezerra D.
Published: August 2022

The computational fluid dynamic approach is adopted in this work, using L16-Taguchi matrix, to study the effect of different secondary atomization gas outlet configurations on the gas velocity, jet divergence, and pressure distribution at cap outlet. The spraying process variables that are integrated in this study are primary and secondary atomization gas pressure, PG and SG respectively. In addition, the geometrical variables of the SG air-cap like the position, the number and the angle of the outlet holes for SG are a part of the L16-Taguchi matrix. The effect of the process variables and geometrical design variations are analyzed on the obtained gas flow characteristics. Increasing the number of the SG outlet holes leads to a higher gas velocity at the cap outlet. The amount and the angle of the SG outlet holes have a direct effect on the plume divergence. The SG outlet angle determines the distance between the flow intersection point (PG-flow and SG-flow) and the air-cap outlet. Increasing the SG outlet angle leads to a reduction of the gas velocity. The use of Design of Experiment (DoE) in the optimization of the air-cap design by implementing CFD-simulation was proved to be a very useful and efficient tool to design high performance air-caps of twin-wire arc-spraying.
The Many Facets and Complexities of 316L and the Effect on Properties
Authors: Miller Ingrid Hauer
Published: August 2022

One of the most widely accepted and versatile materials used with many coating deposition methods is austenitic stainless steel 316L. This is due to the combination of good corrosion and mechanical properties that are suitable for numerous varying applications. As a result of our familiarity with 316L we assume the properties achieved will be within the expected frame as described in the literature. Deposition techniques and component size and shape have an impact on the heating and cooling variations which will then affect the microstructure of the final coating. This in turn will result in variations in the properties achieved. Some of these numerous factors such as: deposition technique, component geometry and size, impurities in the substrate and chemistry of the substrate will be considered. The influence of these factors on the microstructure and the definitive properties of 316L will be presented.
The Shear Test According to DIN EN 15.340—Advantages, Disadvantages, Improvements, and Important Directions
Authors: Hartmann S.
Published: August 2022

The shear test developed within a European research project has important advantages compared to the coating strength test mainly in use today, the adhesion strength test according to DIN EN 582 or ASTM C 633. One of the main advantages is that no glue is used avoiding any possible influences of the glue. Furthermore the test is a rapid process compared to the adhesion strength test as there is no gluing procedure. However a number of very important directions have to be obeyed in order to make sure that the shear test is correct and comparable results can be reached. This is very important as in many cases it is not possible to control after the test if the directions had not been correctly obeyed. A number of further rules need to be followed to make sure the test results are correct. Within this presentation these direction will be summarized and essential hints will be given to make sure the test is carried out in the correct way. Finally a comparison will be given between the tensile adhesive test and the shear test from the practical and economical point of view of obz innovation gmbh, a thermal and cold spray job shop.
Tribological Performance of Cold-Sprayed Nanocrystalline and Conventional Cu-Al Coatings
Authors: Liu J.C. , Zhang Jishan
Published: August 2022

Cryomilled Cu-Al powder and the Cu/Al mixture were sprayed onto aluminum substrate using the cold spraying process. This study focused on the wear properties of the nanocrystalline (NC) Cu-Al coating in comparison to its coarse-grained (CG) Cu/Al counterpart. The results showed that the as-sprayed deposit presented a dense microstructure. Investigations on the worn surface of the NC coating revealed that the plastic deformation with grooves and some debris were prominent with no visible cracking. Nanocrystalline Cu-Al coating showed a good wear resistance with a low friction coefficient. The enhancement of the wear properties of the NC Cu-Al was attributed to the grain refinement and the superior hardness.
Effect of MCrAlY Bond Coat Temperature on Thermal Cyclic Lifetime of Plasma-Sprayed Thermal Barrier Coatings
Authors: Dong Hui , Li Chang-Jiu , Ding Hang , Yang Guan-Juan , Li Cheng-Xin
Published: August 2022

Gradient thermal cycling test was performed on atmospheric plasma sprayed (APS) thermal barrier coatings (TBCs) to examine the influence of the bond coat temperature on the thermal cyclic lifetime. The TBC system consisted of Inconel 738 substrate, cold-sprayed NiCoCrAlTaY bond coat (BC) and plasma-sprayed yttria-stabilized zirconia (YSZ) top coat. Every thermal cycling test included 70s heating, 50s holding and 120s cooling. The temperature of top YSZ surface was about 1150 °C, while the bond coat temperatures were 900°C, 950°C and 1000°C, respectively. Results indicated that the lifetime of APS TBCs is significantly affected by bond coat temperature. A model to predict the relative thermal cyclic lifetime of TBCs at different bond coat temperature was established by taking account of main factors affecting the lifetime of TBCs. It was found that the predicted results are consistent with the observed results. As a result, the change of lifetime of APS TBCs mainly depends on the growth rate of thermally grown oxide (TGO), elastic modulus of YSZ and thermal expansion mismatch difference between YSZ and substrate caused by different bond coat temperature.
Effect of Thermally Grown Oxide Layer Thickness on Isothermal Cyclic Lifetime of Plasma-Sprayed YSZ Thermal Barrier Coatings
Authors: Ding Hang , Dong Hui , Li Chang-Jiu , Yang Guan-Juan
Published: August 2022

This paper investigates the effect of the thickness of the thermally grown oxide (TGO) layer on the isothermal cyclic lifetime of plasma-sprayed yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs). The TBCs were prepared with different initial TGO thicknesses through pre-oxidation. The results showed that the lifetime of the TBCs decreased significantly as the TGO thickness increased. There was a critical TGO thickness of 5 μm, beyond which the TBCs failed rapidly. The failure mode of the TBCs also changed with the TGO thickness, with cracking primarily occurring along the YSZ lamellae interfaces for TGO thicknesses below the critical thickness, and through the TGO or the interface between the TGO and YSZ coating for TGO thicknesses above the critical thickness.
A Method for Mechanical Characterization of Cold Spray Sputter Targets in PV Manufacturing
Authors: Vlcek Johannes , Hardikar Kedar , Juliano Daniel R.
Published: August 2022

In this work the Brazilian disc test technique is applied to mechanical characterization of cold-sprayed Cu-In-Ga deposits. The main advantage of the test is that the material can be tested in its end product form while naturally attending to the distribution of micro-structural phases and flaws by choosing an appropriate specimen size. The stress state of the test specimen can be obtained in analytical closed form and testing can be readily extended to obtain the stress-strain curve. While limited to low ductility materials the Brazilian disc test appears ideal for testing as-sprayed cold spray deposits due to their typically brittle nature.