bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Temperature-Functionalization of Surfaces: Drag Reduction and Self-Cleaning
Authors: Wilden J. , Jahn S. , Drescher V.E. , Schaaf P.
Published: September 2022

Increasing requirements on technical components for high-temperature-applications (e.g., turbine blades) demand for new developments in surface engineering. The selective combination of materials with positive and negative thermal expansion coefficients (NTE) will lead to a reversible activation of the surface depending on surface temperature: The generation of a riblet structure (“shark skin”) in operation condition by thermal expansion of the matrix and shrinkage of the NTE-ceramic and self-cleaning of the surface at cool down as a result of the reversal of the process. Due to its hygroscopicity the chosen NTE-ceramic Y2W3O12 needs to be embedded into a binder matrix. Therefore a feedstock powder consisting of MCrAlY, WO3 and Y2O3 is mechanically alloyed in a high-energy ball mill. The powder is deposited on substrates by thermal spraying (VPS and HVOF) and laser cladding as well. After coating process a lateral- and depth-selective ion implantation of tungsten, yttrium and oxygen will force nucleation in predefined areas. A following heat treatment of the specimens supports the in-situ-formation of Y2W3O12.
Influence of Air Pressure and Plasma Remelting in the Microstructure and Cavitation Resistance of the Arc Thermally Sprayed Cobalt Stainless Steel
Authors: Pukasiewicz A. , Capra A. , Paredes R.
Published: September 2022

Many studies have investigated methods to reduce cavitation damage in hydraulic turbines and reduce residual stresses after coating deposition. In this work, a cobalt stainless steel was applied by arc thermal spraying. The influence of air pressure deposition and plasma remelting on the microstructure, oxide volume fraction, porosity, microhardness, and cavitation resistance were studied. Microstructures and properties of the AS895HY cobalt stainless steel coatings were investigated by x-ray diffraction, optical microscopy, scanning electron microscopy, microhardness testing, and ultrasonic cavitation testing (ASTM G32-93). The increase in air pressure, 280 to 550 kPa, modified the oxide fraction from 10.9±1.8% to 24.1±2.8% in the samples. The mass loss results in the cavitation tests were 13.8, 19.2, and 15.0 mg/h for the samples with 280, 410, and 550 kPa, respectively. The remelting of the sprayed coatings eliminated the oxides and porosity. Austenite formation was observed in the two remelted layers with decreases in microhardness; for the first layer, this occurred because of the AWS309L substrate dilution. The PTA remelting reduces the mass loss rate to 0.497 mg/h, with 8.02 hours incubation period. Phase transformations were observed in the remelted coating, but not verified in the arc thermal sprayed coatings.
Industrial Technology of Laser Assisted Direct Metal Deposition
Authors: Thivillon L. , Pervushin D. , Bertrand P. , Smurov I.
Published: September 2022

Laser assisted direct metal deposition (or simply DMD) belongs to the family of laser cladding. This is flexible and efficient method for elaboration of diverse coatings including functionally graded, multi-layered, etc. The coatings are characterized by excellent adhesion (metallurgical contact), low porosity and variable thickness up to several millimeters and even centimeters. Actually DMD technology is under intensive development. The most important objective is to increase product quality, process stability and reproducibility along with the simultaneous decrease of risks, failures and defects both on processes and on end-products. The use of the TRUMPF 505 DMD machine with 5 kW CO2 laser allowed to scale-up the technology to an industrial level. The targeted applications are related to petrol, chemical and plastics industries where wear resistance is improved by deposition of a hard-phase coating; in aeronautics DMD is used for near net shape manufacturing from Inconel alloys.
Sealing up the Holes by Gas Dynamic Spraying
Authors: Buzdygar T. , Kashirin A. , Klyuev O. , Shkodkin A.
Published: September 2022

High density and low porosity of gas dynamic sprayed coatings may provide gases and liquids impermeability. But jet deflection and stagnation in the narrow splits and reach-through holes prevent from sealing up the deep substrate defects by gas dynamic spray. The correct choice of powder blend makes the gas dynamic spray process applicable to the splits and holes sealing up. The approaches to the defects sealing up by gas dynamic spray and some applications are presented and discussed.
Characteristics and Heat Treatment of Cold-Sprayed Al-Sn Binary Alloy Coatings
Authors: Kim H.J. , Ning X.J. , Jung D.J. , Lee C.
Published: September 2022

In this study, Al-Sn binary alloy coatings were prepared with Al-5wt.%Sn (Al-5Sn) and Al-10wt.%Sn (Al-10Sn) gas atomized powders by low pressure and high pressure cold spray process. The microstructure and microhardness of the coatings were characterized. The as-sprayed coating were heat treated at 150, 200, 250 and 300 °C for 1 hour, respectively. The effect of heat treatment on microstructure, microhardness and content of Sn phase of the coatings were investigated. The bonding strength of as-sprayed and heat treated Al-Sn coatings were also studied. The results show that the dense and well-bonded Al-10Sn coating can be deposited by low pressure with helium gas while Al-5Sn coating by high pressure cold spray with nitrogen gas. The content of Sn for both Al-5Sn and Al- 10Sn in as-sprayed coatings are consistent with that in feed stock powders. The coarsening and/or migration of Sn phase in both coatings were observed when the annealing temperature exceeds 200 °C. Furthermore, the microhardness of the coatings decreased significantly under the annealing temperature of 250 °C. EDAX analysis shows that the heat treatment has no significant effect on content of Sn phase in Al-5Sn coatings. Bonding strength of as-sprayed Al-10Sn coating is slightly higher than that of Al-5Sn coating. Annealing under 200 °C can increase the bonding strength of Al-5Sn coatings.
Mechanical Properties of WC/Co Coatings Prepared by Cold Spraying
Authors: Kitamura J. , Sato K. , Aoki I. , Sakaki K. , Takahata M. , Shimizu Y.
Published: September 2022

Wear properties of WC/Co cermet coatings have been investigated prepared by cold spraying. Influence of cobalt contents (12~25wt.%), WC particle size (0.2 and 1.8 µm) and agglomerated-and-sintered powder size (-20+0 and - 45+15 µm) on abrasive wear resistance, micro hardness and coating structure is studied, in detail. It has been found that both smaller WC particle and decrease of cobalt content are effective to produce dense, hard and highly wear resistant coating. Smaller powder size is also favorable to make a coating with high mechanical properties. As a result, the cold sprayed coating from WC(0.2 µm)/12wt.%Co with powder size of -20+0 µm has best mechanical properties within this study. This coating has high uniformity and high density with little pores compared to conventional HVOF sprayed coatings. Abrasive wear resistance of the cold sprayed coating, investigated using Suga-abrasion tester, has been almost comparable to HVOF sprayed coating prepared from same feedstock. Strong correlation is also seen between Vickers hardness and abrasive wear resistance. Microstructural analysis suggests that further improvement of coating uniformity by decrease of small pores with the size of sub micron and homogeneous dispersion of WC grains in the cobalt matrix is required to improve the mechanical properties.
Influence of Interface Temperature and Strain Gradients on Impact Energy Model of Soft Particle on Hard Substrate in Kinetic Spraying
Authors: Ji Y. , Yoon S. , Bae G. , Kumar S. , Lee C. , Choi H.
Published: September 2022

In this study, individual particle impact behaviors of soft particle on hard substrate were observed. The ratio of bonds was compared to the difference between adhesion and rebound energies. To improve the existing model, the equation for effective yield strength was modified and finite element analysis was applied to estimate the temperature and strain gradients. The energy difference was derived from the strain and temperature of the elements and compared to the experimental ratio of bonds.
Microstructure Observation on the Interface between Warm Spray Deposited Titanium Powder and Steel Substrate
Authors: Kim K.H. , Watanabe M. , Mitsuishi K. , Kawakita J. , Wu T. , Kuroda S.
Published: September 2022

Titanium particles were deposited on a steel substrate by the impact of high velocity in warm spraying. In the process, nitrogen gas at various flow rates was mixed to control the temperature of a supersonic gas flow generated by combustion. TEM and other techniques were used to analyze the microstructure of the interface between the titanium coatings and the substrate. At the lower nitrogen flow rate, thick oxide double layers in the interface region were observed. The adhesive strength of the coating was high even at lower particles’ velocity possibly because the mechanical interlocking between the titanium particle and the substrate could be enhanced by the high deformability of heated particles. As the nitrogen flow rate increased, however, just a little oxide and a very thin oxide layer covering on the titanium splats were locally detected. The highly localized pressure and the resultant intensive shear stress generated within a titanium particle by the impact could reveal the fresh metal surface through break-up of the thin oxide films on the particle and the substrate. As a result, the metallic bonding between the deposited particle and the substrate was formed and increased the adhesive strength remarkably beyond a certain impact velocity.
Characterization of Low Pressure Type Cold Sprayed Aluminium Coatings
Authors: Ogawa K. , Ito K. , Ichimura K. , Ichikawa Y. , Shoji T.
Published: September 2022

Aluminium alloys are widely used for transportation facilities, because of light weight and high corrosion-resistance. If there are some cracks in transportation, sometimes they repair by welding. However, it is difficult to weld aluminium materials. Because, Aluminium has high specific thermal conductivity and high coefficient of thermal expansion compared with that of steel. The cold spray technique is known as a new technique not only for coating but also for thick depositions. It has many advantages, i.e. dense coating, high deposition rate and low oxidation. Therefore, it has a possibility to apply the cold spray technique instead of welding to repair the cracks. What seems to be lacking, however, is deposition mechanisms and mechanical properties of deposition produced by low pressure type cold spraying. This is a very important issue for applying the cold spray to repair some structures. In this study, elucidation of deposition mechanisms and evaluation of mechanical properties for the low pressure type cold sprayed aluminium depositions were investigated. As a result of elucidation of deposition mechanisms, it can be clear that the particle deposition needs to activate the surface by several impingements. Furthermore, as a result of evaluation of mechanical properties, the cold sprayed specimen showed higher strength than the monolithic specimen in the case of compressive loading to the coating.
PSI: An Innovative Method to Determine and to Classify Particles during the Thermal Spray Process
Authors: Zimmermann S. , Landes K. , Schein J.
Published: September 2022

Coatings produced by thermal spray processes are determined by particle parameters, which can be investigated using various diagnostic systems. With the newly developed PSI (Particle Shape Imaging) four (velocity, size, shape and position) important particle parameters can be measured and evaluated. The data acquisition system consists of two separate optical setups, thus a single particle produces two pictures in the lower and upper area of an ICCD-Camera. These pictures are evaluated by assigning specially developed shape and size parameters to the particles, which in combination with the velocity can be used to predict the coating quality. This instrument can be used to determine the optimum spray parameters (i.e. find the optimal distance between substrate and thermal spray system) and to survey the coating process. A newly developed, mobile PSI-System will allow operation at industrial and research thermal spray facilities.
The Application of Cr3C2-NiCr Coatings to Improve the Corrosion and Wear Properties of an AA7050 Alloy
Authors: Magnani M. , Suegama P.H. , Benedetti A.V. , Espallargas N. , Dosta S. , Guilemany J.M.
Published: September 2022

The Cr3C2-NiCr coatings were sprayed on an AA 7050-T7 alloy by HVOF Thermal Spray Process using AMPERIT 586.054 powder. The substrate was refrigerated during the sample preparation using liquid nitrogen in a device specially designed for this purpose. The spray conditions were also performed increasing the carrier gas flow or the oxygen flow. The XRD and SEM studies showed well-bounded coating/substrate interface, pores, metallic matrix, chromium oxides, carbides, and carbides dissolution into the matrix. The structure comparison between the samples showed a denser structure due to the increase in the carrier gas velocity and the highest carbide dissolution due to the high temperature achieved during the spray process. All samples showed similar wear abrasive behavior, and all of them showed wear rates 7 times higher than the aluminum alloy. All samples also showed corrosion resistance much higher than the AA7050 alloy in NaCl solution.
Microstructure and Wear Resistance of Plasma-Sprayed Carbides and Ceramic Coatings Deposited on an Invar Alloy Surface
Authors: Turbil M. , Rosso M. , Giolli C. , Rizzi G. , Scrivani A.
Published: September 2022

Invar alloy (Fe – 36%Ni) is used in industrial applications which require high dimensional stability because of its exceptionally low thermal expansion coefficient. Purpose of this work is to enhance the performance of molds for the production of carbon fiber reinforced plastic (CFRP) components. Four different kinds of commercial powders were coated on an Invar substrate: Al2O3 - 12TiO2, Cr2O3 and ZrO2 - 8Y2O3 by Air Plasma Spray (APS) and WC - CoCr by High Velocity Oxygen Fuel (HVOF). Metallographic microscopy observation and SEM analysis were carried out and microhardness and fracture toughness were evaluated by means of the micro - indentation method. Friction behaviour and wear resistance were evaluated in dry sliding conditions with Pin On Disk apparatus for not coated Invar substrate and for the different coated substrates. Chromium oxide and tungsten carbide coatings exhibited higher mechanical characteristics respect to the other coatings: chromium oxide had the higher hardness value and tungsten carbide the higher fracture toughness. Tungsten carbide coating had the lower average coefficient of friction and together the chromium oxide the lower wear mass loss and wear rate. Among APS ceramic coatings, Cr2O3 exhibited the best mechanical and tribological behavior while the HVOF cermet coating exhibited the best behavior among all the coatings.
The Jet Characteristics of Supersonic Plasma Jet Spraying System
Authors: Yang H. , Wang L.
Published: September 2022

The jet characteristics of supersonic plasma jet spraying (SPJS) system were studied. Comparison of jet property was made between conventional plasma spray system and SPJS system. The results showed that the characteristics of the SPJS system are superior to the latter system. The particles velocities in the range of 400~800 m/s are obtained for supersonic plasma jet guns with 4.5 mm diameter nozzles and 60 l /min total gas flow rates, SPJS operate about 36 KW. The particle velocity is more than two times as much as conventional plasma jet spraying. The supersonic plasma jet is much longer than that of the conventional torch. It can bring about improvement for flying powder heated and accelerated and also prolong spray distance.
Influence of Microstructure on Ionic Conductivity of Plasma-Sprayed Yttria-Stabilized Zirconia Coatings
Authors: Xing Y.-Z. , Li C.-J. , Li C.-X. , Wu H.-L. , Li R.-T. , Zhang Q.
Published: September 2022

During plasma spraying, high substrate temperature contributes to increase the interface temperature between flattening droplet and substrate and subsequently promotes the through-lamella grain growth in the coating. In this study, yttria stabilized zirconia (YSZ) coatings are prepared by atmospheric plasma spray (APS) on the stainless steel substrate preheated to different temperatures from room temperature to 1100°C. The microstructure of the coatings is characterized from polished and fractured cross sections by SEM. The ionic conductivities of the coatings are measured using both DC and AC methods, and the relationship between ionic conductivity and microstructure of coatings is examined. SEM observation shows that the coatings exhibit different microstructures with different substrate temperatures. With the increase of substrate temperature, the columnar grain growth continuously across lamellar interfaces is enhanced and subsequently the intersplat bonding ratio in the coating is increased. The ionic conductivity of YSZ coatings at the direction perpendicular to coating surface is significantly increased through the microstructure development by increasing deposition temperature.
Thermal Cyclic Behavior of Plasma-Sprayed YSZ/AI2O3 Thermal Barrier Coatings
Authors: Saral U. , Ustel F. , Toplan N.
Published: September 2022

Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The coating comprised of YSZ – 0, 20, 50 and 80 wt % Al2O3; NiCrAlY bond coat; and AISI 304L stainless steels substrate. Thermal shock tests were performed over the specimens, at 1000 °C and 1200 °C for 5 min and then forced air quenching. The samples were directly pushed into a tube furnace at 1000 °C and 1200 °C. The results were prominent in forced air quenching tests at 1000 °C , where the lives of the TBCs were observed more than 66 cycles. It was noticed that with increase of Al2O3 content the thermal shock life of the specimens decreased. Further, the coating roughness decreased by Al2O3 addition. It was observed that with decrease in coating roughness, the thermal shock life decreased slightly.
Mechanisms of Residual Stress Generation in Plasma-Sprayed Hydroxyapatite Coatings
Authors: Yang Y.C.
Published: September 2022

From the past studies of the residual stress occurred during the plasma spraying, the different results were obtained; the arguments of these previous works were not only in the value of residual stress but the stress state existed in the HACs. The residual stress generation theory stated in these literatures appear to be oversimplified, hence a more basic study is needed to explore the contention on the residual stress state in HA coating during plasma spraying. In this study, in order to obtain the whole and accurate residual stress value and state, the residual stress was measured by using the material removal method. For the purpose of inferring the generation mechanism of residual stress, the particular forms of the substrate holder and various cooling system were employed. The results show that the difference between the HAC and substrate temperature is the main factor that dominates the residual stress state. HAC/Ti-substrate on the hollow rotational holder with the back cooling system would lead to the higher temperature in coating than substrate during plasma spraying and result in the tensile residual stress in the HAC. On the contrary, HAC with the front cooling system displayed much lower temperature than the Ti-substrate that fixed on non-hollow holder and hence the compressive residual stress occurred. These could be attributed to the differences of volume shrinkage between the HAC and Ti-substrate that from different initial temperature to room temperature. In another word, the residual stress state is depended on the spraying program not always tensile or compressive state.
New Developments in the PROTAL Process for the Coating of Cylinder Bores
Authors: Costil S. , Liao H. , Danlos Y. , Coddet C.
Published: September 2022

To avoid the constraints due to the conventional surface preparation before thermal spraying (degreasing and sand-blasting), the PROTAL process was developed implementing a Q-Switched Nd:YAG laser with a very short pulse duration to prepare the surface simultaneously to the coating buildup. Until now interesting results were obtained both from the adhesion and economical points of view. Specific parameters were developed according to the spraying process (APS, HVOF, wire arc), the powder (Cu alloy, Al2O3, WC-Co, ...) as well as the part nature (Ni alloy, Magnesium, steel, aluminium alloys, etc.). Considering the wide development of thermal spray applications in the automotive industry, new developments of the PROTAL process were considered in order to reach the feasibility of an internal laser treatment of the parts. After a presentation of the implementation of a new laser head in the thermal spray environment, some results concerning the case of a metallic coating (ferrous alloy) on a metallic part (aluminium alloy) will be presented.
New Industrial Applications for Cold Spraying
Authors: Hartmann S.
Published: September 2022

Since the first installation of a cold spray system at OBZ Innovation GMBH in 2002 the application areas of cold spraying have increased greatly. Cold spraying has developed into a safe and reliable process that is used successfully in various areas of industry. In this presentation current applications and new project developments at OBZ Innovation GMBH are demonstrated. Furthermore within an outlook the new possibilities with the latest cold spray technology, the KINETICS-8000-HP, are demonstrated. With this unit it is possible to increase the deposition rate compared to previous cold spray systems and expand the material spectrum usable for cold spraying to include higher refraction materials – all while cutting costs, increasing quality and maintaining excellent process reliability.
Relationships Between Coating Microstructure and Thermal Conductivity in Thermal Barrier Coatings – a Modelling Approach
Authors: Tano I. , Gupta M. , Curry N. , Nylén P. , Wigren J.
Published: September 2022

Fundamental understanding of relationships between coating microstructure and thermal conductivity is important to be able to understand the influence of coating defects, such as delaminations and pores, on heat insulation in thermal barrier coatings. Object-Oriented Finite element analysis (OOF) has recently been shown as an effective tool for evaluating thermo-mechanical material behaviour, because of this method’s capability to incorporate the inherent material microstructure as an input to the model. In this work, this method was combined with multi-variate statistical modelling. The statistical model was used for screening and tentative relationship building and the finite element model was thereafter used for verification of the statistical modelling results. Characterisation of the coatings included microstructure, porosity and crack content and thermal conductivity measurements. A range of coating architectures was investigated including High purity Yttria stabilised Zirconia, Dysprosia stabilised Zirconia and Dysprosia stabilised Zirconia with porosity former. Evaluation of the thermal conductivity was conducted using the Laser Flash Technique. The microstructures were examined both on as-sprayed samples as well as on heat treated samples. The feasibility of the combined two modelling approaches, including their capability to establish relationships between coating microstructure and thermal conductivity, is discussed.
Influence of Helium and Nitrogen Gases on the Properties of Cold Gas Dynamic Sprayed Pure Titanium Coatings
Authors: Wong W. , Irissou E. , Legoux J.-G. , Yue S.
Published: September 2022

This study investigated the effect of the type of gas used, nitrogen and helium, during cold spraying of titanium coatings. In all conditions, the propelling gases’ temperature and pressure were attuned to attain three similar particle velocities for each gas. Coatings were characterized by SEM and XPS. Deposition efficiency, coating microhardness, and porosity were evaluated for all conditions. Results show that for the same particle impact velocity, the deposition efficiency and coating density were mostly the function of the surface temperature, which in turn was influenced by spray parameters. It is shown that loosely-bonded particles at the surface can be detached by the passage of high pressure supersonic gas stream. In addition, a thick and fully dense cold sprayed titanium coating was achieved with optimized spray parameters with He and the corresponding average particle velocity was measured at 1173 m/s.
Correlation of Wear Resistant Functions of HVOF and Warm Sprayed WC-Co Coatings with In-Flight Particle Characteristics
Authors: Sato K. , Kitamura J. , Raman G. , Watanabe M. , Komatsu M. , Kuroda S.
Published: September 2022

WC-Co thermal sprayed coatings are mainly used for wear protecting functions in various industries, for which high velocity oxy fuel (HVOF) spray is considered to be the best suited process. However, WC-Co HVOF coatings still have some defects as compared with sintered bulk, such as decarburization of WC and porous structure. Recently, experiments of WC-Co coatings using warm spray (WS) and cold spray processes have demonstrated some improvements in reduction of these defects. In particular, WS process seems to be a more promising process for WC-Co coatings from the previous work. In this study, wear resistant functions of WC-12%Co coatings prepared by HVOF and WS were investigated by abrasion and erosion tests. In addition, in-flight particles were captured and their characteristics such as the amount of decarburization, crystal phase, particle strength and particle size distribution were investigated to clarify the difference between HVOF and WS processes. The result shows that the wear resistances of the WC-Co WS coatings are comparable or superior to those of the HVOF coatings, which can be attributed to the difference in the amount of W2C and coatings porosity revealed by the in-flight particles and the coating microstructure. The result of the in-flight particle analysis also indicates that wear resistance of WS coatings can be further improved by optimizing the powder shape and chemical composition.
Plasma Sprayed LSCF Oxygen Electrode for SOFC
Authors: Ansar A. , Soysal D. , Ilhan Z. , Wagner N.
Published: September 2022

La1-xSrxCo0.2Fe0.8O3-δ deposits, of different stoichiometry, were fabricated for SOFC oxygen electrode using atmospheric plasma spraying (APS) with TriplexPro gun. The spraying conditions were developed by correlating, plasma jet characteristics (enthalpy and velocity), in-flight particle properties (temperature and velocity) and deposit quality (phase composition, porosity, coefficient of thermal expansion, electrochemical testing). The optimal cathode deposits exhibited a porosity of about 20 vol.%. The CTE in air flow at 800 °C was, however, 15.6 x 10-6 K-1 and it was independent of the processing conditions. Electrochemical tests for cathodes were conducted on SOFCs that were produced following metal supported design and had YSZ as electrolyte and NiO+YSZ as anode. At 800 °C, power densities of above 640 mW/cm2 at 0.7 V were recorded with H2/air for cell having La0.60Sr0.40Co0.2Fe0.8O3-δ as cathode. Cells consisting of La0.58Sr0.4Co0.2Fe0.8O3-δ and La0.78Sr0.2Co0.2Fe0.8O3-δ had 479 and 496 mW/cm2 under similar conditions. Using equivalent circuit diagrams the contribution of different polarizations on the cell performance were separated and cathodes were compared. La0.60Sr0.40Co0.2Fe0.8O3-δ was found to have the best electrochemical performance followed by La0.58Sr0.40Co0.2Fe0.8O3-δ and La0.78Sr0.20Co0.2Fe0.8O3-δ.
The Next Step in Intelligent Gun Technology – EvoLink for Plasma Spraying
Authors: Koller M. , Kilchenmann A.
Published: September 2022

As the requirements placed on thermal coatings become increasingly stringent, being able to acquire more accurate data more quickly is becoming increasingly important. To achieve this, process variables must be measured close to or even inside the gun. This paper introduces a new product which measures process variables directly inside a thermal spray gun. It explains the advantages of measuring the process variables inside the gun, but also why it is important to have gun-relevant data stored on the gun itself.
Measurement of Particle Parameters in Detonation Spraying
Authors: Smurov I. , Pervushin D. , Chivel Yu. , Laget B. , Ulianitsky V. , Zlobin S.
Published: September 2022

Measurement of the particle temperature and velocity in detonation spraying is significantly complicated by the pulsed character of the process. In the present study, these parameters are measured for powders with strongly different nature and properties such as WC/Co, Inox and Ti. Experiments are performed using an original computer-controlled detonation spraying (CCDS) installation developed by the authors. The system is distinguished by the mode of powder feeding into the gun barrel which is pulsed in time and localized in space. Evolution of the particle-in-flight velocity and size is examined by an original CCD-camera-based diagnostic tool developed by the authors. A significant spatial separation of the particles along the detonation plume is observed during their acceleration: 15 μm fine particles overtake 45 μm coarse particles by more than 10 plume diameters. For this reason, distributed scanning over the plume length is applied in order to obtain adequate results. A previously developed mathematical model of the process is experimentally validated. Calculations are found to be in a qualitative agreement with the experimental results. As far as particle-in-flight velocity is concerned, the agreement is even quantitative.
Measurement of Particle Emissions Generated by Arc Spray and Flame Spray Processes
Authors: Billières D. , Bémer D. , Subra I. , Lecler M. , Régnier R. , Morele Y. , Gutha J.
Published: September 2022

Thermal spray of Zn, Zn/Al, or Al is extensively used to make anticorrosion coatings on steel structures. Twin arc spray and wire flame spray are the two most practised processes to achieve such coatings. This paper presents measurements of particle emissions generated by these two processes. Sampling and analysis of aerosols generated by both processes have been carried out inside the exhaust ductwork using various instruments: an ELPI impactor, a CNC (Condensation Nucleus Counter), a TEOM microbalance and sampling filters allowing sampling for SEM observations. Electric arc spraying produced much more fumes of ultra fine particles than flame spraying. Aluminum spraying also produces large fume quantities compared to the Zn spraying under the same conditions. The aerosol comprised submicron particles and 95% of the numerical particle size distribution was less than 100 nm. The nanometric nature of the fume particles was confirmed by observations on the SEM. The strong dilution caused by compressed air has the effect of strongly limiting particle coagulation and, in turn, the size of the agglomerated particles. Electric arc spray has taken market share versus wire flame spray for Zn, ZnAl, or Al spraying, but this study shows that it generates much more particle emissions.
Study of the Influence of Pre-Heated Al6061 Substrate Temperature on Al Coatings Deposited by Cold Spray
Authors: Rech S. , Trentin A. , Vezzù S. , Legoux J.-G. , Irissou E. , Guagliano M.
Published: September 2022

In this work, the influence of the substrate temperature on the deposition efficiency and on the coating properties and residual stress was investigated. Pure Al coatings were deposited on Al 6061 alloy substrates using CGT Kinetics 3000 deposition system. The substrate temperature was ranged between 20°C (room temperature) and 375 °C and was kept nearly constant during the deposition while all the other deposition parameters were unchanged. The deposited coatings were quenched in water (within one minute from the deposition) and then characterized. The residual stress was determined by Almen gage method (Ref 1, 2, 3), Modified Layer Removal Method (Ref 4, 5, 6), and XRD (Ref 7) in order to identify both the mean coating stress and the stress profile through the coating thickness from the surface to the coating- substrate interface. The residual stress results obtained by these three methods were compared and discussed. The coating morphology and porosity were investigated using optical and scanning electron microscopy.
Comparative Study of the Electrical Properties and Microstructures of Thermally Sprayed Alumina and Spinel Coatings
Authors: Toma F.-L. , Scheitz S. , Berger L.-M. , Sauchuk V. , Kusnezoff M.
Published: September 2022

In the present work, APS and HVOF processes have been used to prepare alumina (Al2O3) and magnesium aluminate spinel (MgAl2O4) coatings designed for electrical insulating applications. The microstructures and the phase compositions of the sprayed coatings were evaluated by microscopic and XRD analysis. The electrical characteristics electrical resistance, electrical resistivity and dielectric breakdown strength were investigated using different methods: direct current (DC) measurements, electrochemical impedance spectroscopy (EIS) and dielectric breakdown testing. The electrical resistance was measured at room temperature at different humidity levels. Differences in the insulating properties due to the different natures of the coating materials, microstructures and the measurement methods used for electrical characterisation are discussed.
Microstructures of Metallic NiCrBSi Coatings Manufactured via Hybrid Plasma Spray Process
Authors: Serres N. , Hlawka F. , Costil S. , Langlade C. , Machi F.
Published: September 2022

This paper deals with coating alternatives to hard chromium plating. Indeed, thermal spraying is already used in industry, but results are not always satisfactory for reasons of porosity and microstructures. In this study, atmospheric plasma spraying (APS) and in situ laser irradiation by diode laser processes were combined to modify the structural characteristics of thick NiCrBSi alloy layers. The microstructure evolution was studied and results show that in situ laser remelting induces the growth of a dendritic structure which strongly decreases the porosity of as-sprayed coatings and increases the adhesion on the substrate. Moreover, no phase transition after laser treatment is observed. At least, a mechanical investigation demonstrates that the combination between the plasma spraying and in situ melting with a diode laser can result in the improvement of mechanical properties. The hybrid process appears to be a possible alternative to hard chromium plating, in order to protect mechanical parts, because of the good mechanical behaviour of NiCrBSi layer. Moreover, the increase of the laser incident power causes an increase of the mean contact pressure, along with coatings hardness.
Tungsten-Based Coatings to Increase the Lifetime of Permanent-Mold Casting Molds
Authors: Wilden J. , Drescher V.E.
Published: September 2022

Molten metals are extremely corrosive against steel-made molds. In addition to alternating thermal loads and erosion by hard particles the lifetime of molds in the permanent-mold casting industry is rather short. Tungsten-based pseudoalloys are able to increase the lifetime of these molds significantly, but, by now, their use is limited to sintered inlays at the mostly stressed parts of the mold. Coating the whole mold with these materials offers an increase of the lifetime and at the same time a reduction of the amount of deployed feedstock. Within this research project it was possible to increase the lifetime of a kernel in used in casting brass by a factor of 20 by cladding it with tungsten-based pseudoalloys. The metallurgical behaviour of the tungsten-based pseudoalloys is quite complex. By modifying the coating process different shapes and amounts of tungsten precipitations in the nickel-iron-binder can be realized. The different microstructure within the coating does strongly affect the mechanical and anti-corrosion properties of the coating.
Extension of Erosion Life of Turbine Housing for Ship by Thermal Spray
Authors: Sonoya K. , Nakamura M. , Ishida K.
Published: September 2022

The blast erosion-resistance properties of HVOF thermal spray Cr3C2 type coating system and aluminized material were examined to improve erosion-resistance of turbine housings of compressors used in turbochargers for marine diesel engines. As a result, the erosion life of aluminized material is as same as that of the substrate, on the other hand the erosion life of thermal sprayed coating is ten times of that of the substrate. Therefore, erosion life of turbine housing can be extended by the surface treatment procedure. This technology is applicable to actual products.
Wear Properties of Ni-Based Composite Coatings Sprayed by HVAF
Authors: Wu C. , Zhou K. , Liu M. , Deng C.M. , Deng C.G.
Published: September 2022

In order to explore wear properties of Ni-based coating on the copper substrate, the coatings with different composition were designed. Ni-based coating, Ni-based/Al2O3 and Ni-based/Al2O3/WC coatings were sprayed by HVAF on the copper substrates. Wear properties of different composite coating were measured at different loads at room temperature. The experimental results indicate that all the coatings have high wear resistance. Adding Al2O3 in sprayed powders has little effect on the microstructures and wear properties of coating. The wear resistant is improved by the addition WC-12Co obviously. The best wear resistant is obtained when optimum WC-12Co content is added.
Coating of Aluminum Components with Iron-Based Nanocrystalline Solidifying Materials to Improve Wear Resistance
Authors: Wilden J. , Drescher V.E. , Lehmann O.
Published: September 2022

Conventional processes of gas shielded metal arc welding (GMAW) do not offer directly the possibility for cladding heat sensitive materials such as aluminum with iron-based materials due to intermetallic Al/Fe phases form. This paper deals with the first evaluated cladding results of aluminum components with iron-based nanocrystalline solidifying materials by controlled shielded metal arc welding processes to improve wear resistance. In the present work, the design of experiments and data evaluations are systematically applied to get the first results about the dependence between controlled arc welding process parameters and the iron-based coatings of aluminum substrate. In particular, the effect of the chosen parameters such as wire feed speed, welding speed, frequency and further factors on the heat input, welding penetration, micro hardness, rate of welding penetration and width of intermetallic phases in the interface zone are investigated. Optical and scanning electron spectroscopy provide input for further statistical evaluation. The experiments were carried out using various controlled arc technologies which offer different control over the heat input to the substrates. Different power supplies were used.
Velocity Diagnostics for Gas Velocity Distributions in Cold Gas and Plasma Spraying Using Non-Resonant Laser Scattering
Authors: Lange S. , Sieber M. , Forster G. , Marqués J.L. , Schein J.
Published: September 2022

In cold spray and thermal spray applications, one of the primary factors affecting coating deposition is the location where particles are injected into the gas jet. Therefore, a detailed knowledge of the gas flow distribution is required. Non-resonant laser scattering allows to spatially resolve the distribution of drift velocity and mass density within the flow, particularly at locations close to the injector. Based on laser scattering, this paper presents a new diagnostic that locally measures drift velocity, as well as a relative mass density distribution of a gas stream. Its application is mainly focused on cold gas flows, where velocity measurements in a supersonic nozzle, obtained by means of laser scattering, correlate well with theoretical calculations and particle image velocimetry (PIV) experimental results.
Thermal Spray Forming of High-Efficiency, Metal-Foam Heat Exchanger Tubes
Authors: Tsolas N. , Chandra S. , Salimjazi H. , Pershin V.I. , Mostaghimi J.
Published: September 2022

Thermal spray coating processes have been employed in the current study to deposit well-adhered, dense skins on the surfaces of open-cell nickel foams. Using foam with 10 and 40 PPI (pores per inch) pore sizes, square channels were made with a height of 20mm and having a length of 250mm. In a unique process that prevents the deposited skin from penetrating the foam substrate via a paste comprised of a thermoset resin and powder particles, a dense stainless steel skin with an average thickness of 400 μm is applied to the exterior of the foam sample. The result is a channel that consists of a Ni foam core and a stainless steel skin wall that can be used as a compact heat-exchanger by directing the coolant flow through the foam. To study the feasibility of the metallic foam heat-exchangers, hydraulic and heat-transfer characteristics were investigated experimentally. The local wall and fluid temperature distribution and the pressure drop along the length of the heat exchanger were measured for heat-flux of 1540.35 – 9627.38 W/m2. Experiments were conducted using air as the coolant and varying flow velocity from 10 – 80 L/min. For non-Darcy flow with inertia effects in the porous media, the Dupuit and Forchheimer modification is employed with the experimental results to determine foam characteristics such as permeability (K), Ergun coefficient (CE) and the friction factor (f). To measure the heat-transfer performance of the metal foam filled channels, a length average Nusselt number is derived based on the local wall and fluid temperatures. Heat transfer was shown to have nearly doubled compared to that of a channel without a foam core.
Challenges for Plasma Spray Deposition of Decomposition-Prone Perovskite Coatings
Authors: Jarligo M.O. , Mauer G. , Mack D. , Vassen R. , Stöver D.
Published: September 2022

Processing of powder feedstock materials often influences the deposition behavior and ultimately, the properties of the atmospheric plasma spray (APS) deposited coatings. The necessity of materials design and the control of deposition parameters are therefore, of high importance. Feedstock from promising ceramic thermal barrier coating materials with Ba(Mg1/3Ta2/3)O3 and La(Al1/4Mg1/2T1/4)O3 perovskite structures (λ~ 2 W/m-K and α~11x10-6 /K at 1473 K) were prepared through solid state and conventional spray drying techniques. The powders were then deposited on metallic substrates by APS process. Monitoring of in-flight particle characteristics and splat formation as well as characterization of deposited coatings, were conducted. It was found that these types of perovskite materials tend to lose constituents during deposition by atmospheric plasma spraying. This paper reports on the challenges of powder feedstock design and the control of critical deposition parameters to prevent or minimize the non-stoichiometric deposition of decomposition-prone perovskite coatings by APS process.
The Structure and Properties of Plasma Sprayed Fe Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors
Authors: Puranen J. , Lagerbom L. , Hyvärinen L. , Kylmälahti M. , Vuoristo P.
Published: September 2022

Manganese cobalt oxide spinel doped with Fe2O3 was studied as protective coatings on alloyed metallic interconnect plates for solid oxide fuel cell applications. Chromium alloying causes problems at high operation temperatures in oxidising conditions, on the cathode side of the fuel cell. The formed chromium oxide layer tends to form a thin layer of chromium trioxide or chromium hydroxide which evaporates at certain oxygen partial pressures more easily than chromium oxide and thus poisons the cathodes active area causing the degradation of the solid oxide fuel cell. Thermal spraying is regarded as a promising way to produce dense and protective layers on top of ferritic steels to lower the degradation processes and extend the lifetime of the SOFC device. In the present work, the ceramic Co-Mn-oxide spinel coatings were produced by using the atmospheric plasma spray process. The structures and compositions of the coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) was used to study the phase structure in as-sprayed and heat treated coatings and mechanical properties were examined by using micro hardness tester. Coatings with low thickness and micro structurally dense structures were produced by using optimal deposition conditions.
Expansion of the Applicable Range of HVOF Process Conditions
Authors: Wank A. , Schwenk A. , Liu M. , Zhou K.S. , Deng C.M. , Deng C.G.
Published: September 2022

A conventional GTV K2 kerosene fuel HVOF spraying system has been modified with the aim to expand the applicable range of process conditions in order to also cover the presently existing gap between conventional HVOF and cold gas spraying. Different measures have been applied in order to reduce heat transfer and increase momentum transfer to spray particles. Increase of momentum transfer results both in reduced particle temperature as a consequence of reduced dwell time in the hot flame area and high particle velocities. In detail expansion nozzles with conical shape that provide improved expansion of combustion gases, combustion chambers with reduced critical diameters that provide increased combustion chamber pressures and the injection of coolant media water and / or nitrogen into the combustion chamber are applied. The effect of modified spraying conditions on the process characteristics and coating properties have been studied for a variety of materials. Besides copper, titanium alloys and MCrAlYs also WC/Co(Cr) and Cr3C2/Ni20Cr have been sprayed and respective coatings have been analysed concerning their microstructure, gas content, microhardness and wear resistance. In particular a moderate increase of oxygen content in dense titanium alloy coatings compared to the powder feedstock from 0.41 to 0.59 wt.-% proves the high potential of the undertaken measures to expand the application field of HVOF spraying. Thereby existing systems only need relatively small modifications to achieve this expansion.
Evaluation of Boron Carbide Based Thermal Sprayed Coatings for Tribological Applications
Authors: Lima C.R.C. , Rosales M.J. , Camargo F.
Published: September 2022

The superior mechanical properties of Boron Carbide make it very attractive for use as a wear resistant coating in tribological applications. Boron carbide is the hardest non-oxide ceramic produced in large quantities. It offers a high erosion and abrasion resistance, high chemical and outstanding heat resistance. B4C can be formed on a suitable substrate by thermal spray process as an alternative to high wear carbide coatings. The objective of this work was to investigate and to characterize the mechanical properties of a boron carbide based coating applied by HVOF spraying using a non commercial powder for corrosion and abrasion applications. The produced coatings were evaluated by metallographic procedure, microhardness, porosity and roughness measurements as well as adhesion and wear tests. The results are promising and signal good applications for such coatings.