bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Reproducibility of Air Plasma Spray Process and Control of Particle State
Authors: Srinivasan V. , Vaidya A. , Streibl T. , Friis M. , Sampath S.
Published: September 2022

Controlling particle state is important to not only achieve the required microstructure and properties in coatings but also to clearly isolate and understand the role of other clusters of variables (such as the various substrate and deposition conditions) on the aforementioned attributes. This is important to design coatings for high performance applications and in the ongoing efforts towards achieving prime reliance. This study examines the variabilities in particle state and explores a few strategies to control them for improved reproducibility with the aid of in-flight particle and plume sensors. The particle state can be controlled by controlling the torch parameters or by directly controlling the particle state itself via feedback from particle and plume sensors such as DPV2000 & TDS. There exist at least a few control protocols to control the particle state (predominantly temperature and velocity) with judicious choice of critical parameters. In the present case the particle state has been controlled by varying the critical torch parameters in a narrow range using 8% YSZ of angular morphology (fused and crushed) with 10-75 microns size distributions in conjunction with a N2-H2 laminar (non-swirl) plasma. Two important results emerge. (1) The particle state resulting from averaged individual particle measurements (DPV 2000) is surprisingly stable with variabilities in T < 1% and variability in V of < 4%. Ensemble approaches yield a somewhat higher variability (5%). In spite of this the variability in basic coating attributes such as a thickness and weight is surprisingly large. (2) Applying a much simpler control strategy to only control the particle injection and hence the particle trajectory results in reduced variabilities in coating attributes.
Sensing, Control, and Insitu Extraction of Coating Properties: An Integrated Approach towards Establishing Process Maps
Authors: Sampath S. , Srinivasan V. , Vaidya A. , Gouldstone A. , Liu Y. , Nakamura T.
Published: September 2022

Over the last decade there has been an explosion in terms of available tools for sensing the particle spray stream during thermal spray processes. This has led to considerable enhancement in our understanding of process reproducibility and process reliability. However, in spite of these advances, the linkage to coating properties has continued to be an enigma. This is partially due to the complex nature of the build-up process and the associated issues with measuring properties of these complex coatings. In this paper, we present an integrated strategy, one that combines process sensing, with process modeling and extracting coating properties in situ through the development of robust and advanced curvature based techniques. These techniques allow estimation of coating modulus, residual stress and non-linear response of thermal sprayed ceramic coatings all within minutes of the deposition process. Finally, the integrated strategy examines the role of process maps for control of the spray stream as well as design of thermal spray coatings. Examples of such studies for both MCrAlY and YSZ coatings will be presented.
Investigation of Time-Dependent Instabilities of Plasma Spraying Process Using Online Diagnostic Systems
Authors: Weckmann H. , Fiebig S. , Syed A. , Arnold J.
Published: September 2022

Reproducibility of plasma spraying process and resulting deposits is one of the most essential requirements for its application in industrial environment. In most cases, only controlling process input parameters does not suffice for achieving stability and reproducibility of the process. Besides short time plasma instabilities such as arc root fluctuation, process deviations in longer time operations may arise due to electrodes wear and need to be identified by online diagnostics of the plasma spraying process. In this study two online diagnostic systems were employed to investigate the long-term behaviour of a F4-type plasma gun with a convergent and divergent Laval-nozzle. A Plasma Instability Analysis (PISA) system was applied to identify electrode wear and plasma fluctuation phenomena within the gun whereas Particle Flux Imaging (PFI) was used to correlate the electrode wear with the plasma jet characteristics at the nozzle exit. The long-term performance of electrodes was investigated under continuous operation and under periodic reignition of the torch. A good correlation between aberrations in the plasma process observed with PFI and changes in the frequency spectra detected by PISA was found.
Effective Spectral Emissivity Measurement of Thermally Sprayed YSZ Thermal Barrier Coating at High Temperature Using a Wide-Band Single Wavelength Pyrometer
Authors: Moulla L. , Planche M.P. , Coddet C.
Published: September 2022

Single-wavelength pyrometers are widely used as a noncontact temperature measurement tool in material processing, petrochemical and laser-machining industries. In addition, these intensity-based IR sensors are used extensively as a diagnostic and health monitoring in the development and research of advanced high-temperature military and commercial gas turbine engines. In contrast to thermocouples, optical pyrometers have several advantages. First, they are easy to install and second they do not bring any disturbance to the measured system. However, they suffer from some problems, in particular the variation of the material emissivity and perturbations introduced by extraneous radiations. Yttria stabilised Zirconia (YSZ) thermal barriers are known to be more emissive and opaque in the 8-14 µm spectral band, therefore we can take advantage using this spectral band in temperature measurement. Spectral emissivities of an YSZ sample were measured using two commercial pyrometers. And a method for adapting commercial wide-band pyrometers (generally used for low temperature measurements) for high temperature measurements of thermal barrier coatings was tested.
Ultrasonic Testing of the Splat-Substrate Interface
Authors: Ducos M. , Bossuat B. , Walaszek H. , Barradas S. , Jeandin M.
Published: September 2022

The studying of splats in thermal spray is prominent to improve coating properties due to better understanding of coating build-up mechanisms. Most of studies, however, devoted to splats rest on physical aspects of the build-up, which feature the behaviour of a single particle impinging on a substrate. These studies involve the nature, velocity and intrinsic characteristics of the particle. The present work deals with the study of the splat-substrate interface using an ultra-sonic (U.S.) technique. This technique is based on the determining of splat-substrate adhesion (for an elementary splat or a group of splats) to help in the optimising of spraying conditions. APS copper splats were studied for Al-based substrates. This U.S. technique was already tested successfully for adhesion control of thermally-sprayed coatings in Basel, Switzerland. Further development then related to the specific experimental set-up for splat analysis using several transducers. This involved the use of various frequencies, various sizes for the focal spot and various scan velocities. In this study, results from this U.S. technique were discussed in the light of the observation of cross-sections of U.S.- controlled splats. U.S. C-Scan images were shown to fit well with cross-sectional images. In a general conclusion, the work showed the feasibility and efficiency of advanced U.S. control of splats to promote thermally-sprayed coatings whatever the process, i.e. plasma spray, flame spray, HVOF or cold spray.
Deposition of Nickel-Aluminide Coatings by Gaseous Detonation Spraying
Authors: Kharlamov Y.A. , Kharlamov M.Y.
Published: September 2022

The influence of the particle velocity on the formation intermetallic of coatings is discussed. The primary phases of detonation sprayed NiAl coatings are NiAl and Ni3Al, and also a solid solution of Ni in NiAl. The lamellar and homogeneous distribution of Al may be due to the oxidation of the powder particles during their flight in the pulsating high temperature, high velocity jet of the gas detonation process. During heating and melting of the powder particles, an aluminum oxide film is formed. This film takes part in the coating formation and affects the Al distribution. Another important observation is the presence of NiAl and Ni3Al phases in the coating structure. The transition zone between the coating and substrate has a thickness of 10-15 µm. The character of the distribution curves of Al and Ni confirms the lamellar distribution of NiAl and Ni3Al phases in the coating.
Microstructure and Properties of New Abradable Seal Coatings for Compressor Applications
Authors: Bobzin K. , Lugscheider E. , Zwick J. , Ernst F. , Sporer D. , Hopkins N. , Hertter M. , Matejicek J.
Published: September 2022

In modern jet engines, the efficiency of the compressor stages is highly dependent upon the clearance between housing and rotating compressor blades. To control the over-tip leakage, abradable coating systems are applied on the housing. In the high pressure compressor they typically consist of a thermal sprayed multiphase material, comprising a metal matrix combined with a dislocator and/or a solid lubricant as well as a defined level of porosity. In this study, novel material systems have been sprayed via the plasma and flame spray process and compared to reference materials. Resulting microstructures have been analyzed as well as important coating characteristics evaluated, including coating hardness and erosion resistance. Furthermore rig tests were performed to analyse the coatings abradability behaviour under different operation conditions of the compressor.
Characterization of AlCuFeB Quasicrystalline Coatings Sprayed by APS
Authors: Stihle A. , Liao H. , Bertrand P. , Allain N. , Coddet C. , Kenzari S.
Published: September 2022

Plasma sprayed composite coatings were prepared with a mixed powder of AlCuFeB + aluminium. One focus of this study has been the effect of air plasma spraying processing parameters on the characteristics of quasicrystalline composite coating. In this study, Taguchi L9 design of experiments was employed to study the investigated process parameters. Significant effects on the microstructure were observed. For the composite coating (quasicrystal + aluminium) parameters were optimized, considering phase retention and porosity level. Tribological tests were performed with a ball on disk device at room temperature for this composite coating. Results show that quasicrystal phase can be kept in the coating after spraying.
Exploring Thermal Spray Grey Alumina Coating Pore Network Architecture by Combining Stereological Protocols and Impedance Electrochemical Spectroscopy
Authors: Antou G. , Montavon G. , Hlawka F. , Cornet A. , Coddet C.
Published: September 2022

Complex multi-scale pore network architecture characterized by a multi-modal pore size distribution and connectivity develops during the manufacturing of ceramic thermal spray coatings from intralamellar and interlamellar cracks generated when each lamella spreads and solidifies to globular pores resulting from lamella stacking defects. This network significantly affects the coating properties and their in-service behaviors. The De Hoff’s stereological analysis permits the quantification of the 3-D distribution of spheroids (i.e., pores) from the determination of their 2-D distribution estimated by image analysis when analyzing the coating structure from a polished plane. Electrochemical impedance spectroscopy aims at electrochemically oscillating a material surface by frequency variable current and potential and at analyzing the complex impedance. When a coating covers the material surface, the electrolyte percolates through the more or less connected pore network to locally corrode the substrate. The resistive and capacitive characteristics of the equivalent electrical circuit will depend upon the connected pore network architecture. Al2O3-13TiO2 coatings were atmospherically plasma sprayed using several sets of power parameters, the arc current intensity, the plasma gas total flow rate and the plasma gas composition, namely to scan their effects on the pore network architecture. In parallel, particle characteristics upon impact, especially their related dimensionless numbers such as Reynolds, Weber and Sommerfeld criterion, were determined. Analyses permitted the identification of (i) the major effects of power parameters on the pore architecture and (ii) the related formation mechanisms.
Advanced Particle Characterization for Improved Understanding of Spray Coating Quality
Authors: Pirard E. , Campana F. , Janssen J.P.
Published: September 2022

The size and shape of individual particles are essential characteristics to control their behavior during spraying. Thanks to recently available technology in powder image analysis, this paper investigates the correlation between the geometric properties of several thousands of particles and their flowability (Hall flowmeter) and apparent density (Scott volumeter). Four different chromium carbide Cr3C2-NiCr 75/25 powders used for HVOF wear / oxidation resistant coatings are studied. The coating quality obtained for each powder by the HVOF spraying process is further investigated using metallographic image analysis.
Vanadium-Rich Iron-Based Thermal Spray Coatings for Combined Wear and Corrosion Protection
Authors: Wielage B. , Pokhmurska H. , Grund T. , Ahrens S. , Wank A. , Reisel G. , Schnick T.M. , Deppe E.
Published: September 2022

Newly developed iron based hard alloy powders with high chromium and vanadium contents are used for coating production by means of HVOF and LPPS. Crack free and dense coatings with fairly homogeneous microstructure are possible for both spraying methods. XRD analyses of sprayed coatings prove phase compositions similar to those of the powder feedstock when using HVOF systems. In contrast LPPS coatings contain a large share of amorphous phase. Microhardness of LPPS and HVOF coatings is about 1,200 HV0.3 and 800 - 950 HV0.3 respectively. The higher microhardness of LPPS coatings is attributed to the presence of the amorphous phase. However, LPPS coatings are brittle and tend to crack under mechanical load. Wear resistance of coatings is determined by means of corundum grinding disk and ASTM G65 wear test. Corrosion behavior is characterized by means of salt fog test and electrochemical measurements. Cermet and stainless steel 316L coatings are used for comparative purposes in the investigations.
Design and Characterization of a Simulated Environment Erosion Test Bed
Authors: Kosikowski D. , Stanisic J. , Ostrom T. , Mohanty P.S.
Published: September 2022

A simulated environment erosion test platform consisting of a control chamber, a modified HVOF gun, and a programmable logic control module is presented. This robust equipment can vary angles of impingement from 0-90 degrees, erodent velocities up to 300 m/s, and temperatures exceeding 2000°C. The erodent velocity, flow rates and temperatures are directly measured employing a high speed camera, and a DPV/CPS 2000 particle flight diagnostic sensor in contrast to estimates typically reported in the literature. It is demonstrated that, although the gas jet type erosion test apparatuses are frequently used in laboratories, quantitative parameter characterization is essential for setting up a test protocol. Both room and high temperature tests have been performed on this test bed. It is believed that the quantitative characterization of test parameters would greatly assist the designer in choosing and developing the appropriate erosion resistant coatings for their application.
Evaluation of Thermal Stresses in Thermo-abrasive Blasting Nozzles
Authors: Gorlach I.A.
Published: September 2022

Thermo-abrasive blasting is a technique, which combines conventional abrasive blasting and HVAF processes to prepare surfaces prior coating. Thermo-abrasive blasting has a number of advantages over conventional abrasive blasting as the result of a higher nozzle pressure and heat, which helps to remove impurities from the surface. However, practice showed that the short life of blasting nozzles due to thermal stresses and excessive wear is the biggest drawback of this method. Therefore, the correct nozzle geometry and suitable materials are critical for an efficient operation of thermo-abrasive blasting systems. In this study, computational fluid dynamics and finite element analyses were used to obtain the temperature distribution and to evaluate thermal stresses in nozzle materials. The materials investigated include tungsten carbide-cobalt (WC-6wt.% Co), hot pressed dense silicon carbide (SiC) and SiALON (Si3N4-Al2O3-AlN). The analysis and experiments showed that WC-CO nozzles produce the best overall results of thermal shock resistance and wear in thermo-abrasive blasting.
Formation of Pores in Thermal Spray Coatings due to Incomplete Filling of Voids under Solid Particles
Authors: Xue M. , Mostaghimi J. , Chandra S.
Published: September 2022

A three-dimensional, time-dependent numerical model of free-surface flows and heat transfer including phase change has been used to simulate the impact of a liquid droplet on a solid particle and to predict the size of the void under the solid particle caused by incomplete filling by liquid landing on top of it. The solid particle was considered to be a protrusion on the substrate. Fluid flow in the impacting liquid droplet was modeled using a finite difference solution of the Navier-Stokes equations in a 3D Cartesian coordinates assuming laminar, incompressible flow. Heat transfer in the liquid droplet was modeled by solving the energy equation, assuming densities of liquid and solid to be constant and equal to each other. The free surface of the liquid droplet was assumed to be adiabatic. The porosity in this simulation was defined as the volume of the incompletely filled void under the solid particle to the volume of the solid particle. The simulation was repeated with different process parameters, and the results showed that process parameters play significant roles in determining the amount of porosity. A correlation is found to express the porosity as a function of the process parameters.
Nanomechanical Properties of Zirconia- Alumina Plasma Sprayed Nanocomposite Coatings
Authors: Zhao W.M. , Wang J. , Zhai C.S. , Sun B.D.
Published: September 2022

Mechanical properties of micro/nanoscale structures are necessary to design reliable ceramic coatings. Micro/nanomechanical characterizations of novel nanocomposite coatings (NCCs) and micron composite coatings (MCCs) have been studied. Hardness, elastic modulus and creep resistance of these materials were measured by means of nanoindentation. It is found that the nanocomposite coatings exhibit higher hardness, elastic modulus and creep resistance as compared to the micron composite coatings. The nanoindentation tests used in this study can be satisfied to evaluate the mechanical properties of micro/nanoscale structures of ceramic coatings
Ambient and High Temperature Thermal Conductivity of Thermal Sprayed Coatings
Authors: Chi W. , Sampath S. , Wang H.
Published: September 2022

Aside from its importance as a design parameter for thermal barrier coatings, measuring thermal conductivity of thermal sprayed coatings itself provides a unique method to critically characterize the nature, quantity and anisotropy of the defect morphologies in these splat-based coatings. In this paper, we present a systematic assessment of thermal conductivity of wide range of thermal sprayed coatings using the flash diffusivity technique. For the case of plasma sprayed yttria-stabilized zirconia (YSZ), coatings obtained from wide ranging initial powder morphologies as well as those fabricated under different particle states were characterized. Both in-plane and through-thickness properties were obtained. Other material systems that were considered include: metallic alloys, semiconductors and other oxides of interests. Issues such as reproducibility and reliability in measurements were also considered and assessed. Finally, working in collaboration with the Oak Ridge National Laboratory (ORNL) for alternate approaches to characterization of thermal conductivity as well as high temperature measurements was performed.
PTA Hardfacing Material for Earthmoving Equipment Applications
Authors: Jiang X. , Beardsley M.B.
Published: September 2022

Plasma transferred arc welding (PTA) is used to produce coating for wear resistance application in earth moving equipment. The coating is designed to have balanced toughness and hardness, optimal microstructure to perform in the wear modes the components are subject to. 4~ 6 times improvement in wear life compared with hardened steel was achieved as demonstrated in dry sand/rubber wheel test and Caterpillar proprietary abrasion wear test
Laser and PTA Surfacing with TiC-based Materials
Authors: Techel A. , Berger L.-M. , Bretschneider J. , Thiele S.
Published: September 2022

The specific advantages of TiC as a hard material are its low density, high hardness and the high alloyability of the hard phase - binder metal composite. Currently developed agglomerated and sintered core-rim structured TiC-based powders were intensively studied in the last few years for thermal spray coating solutions. In the work described in this paper two different powders with cubic (Ti,Mo)C and (Ti,Mo)(C,N) hard phases and Ni/Co binder, representing the first and second alloying step for the binary TiC-Ni/Co composite, were used together with mechanically mixed NiBSi powder to produce wear resistant coatings by plasma-transferred arc welding (PTA) and laser cladding. Basic process parameters, coating microstructures and properties are described. Coatings with fine grained hard particles were obtained by both processes, while the coating prepared from the nitrogen-containing powder by laser cladding shows a significant smaller hard particle grain size and increased hardness.
Deposition of Thick Wear and Corrosion Resistant Coatings by High Power Diode Laser
Authors: Tuominen J. , Latokartano J. , Vihinen J. , Vuoristo P. , Mäntylä T. , Naumann T. , Scharek S. , Berger L-M. , Nowotny S.
Published: September 2022

High power diode lasers (HPDL) at the level of ? 6 kW are efficient cladding tools in heavy engineering applications where thick (up to 5 mm) wear and corrosion resistant coating layers are required. Large beam geometry makes possible the overlap of thick 20 mm wide cladding tracks side by side without coating defects. Compact size and closed cooling water circulation enable HPDL cladding process to take place also at a site of new or worn high-value machine parts, which have worn in operation or been damaged already during overseas transportation. Instead of moving parts of several tons’ weight, it would be perhaps more cost efficient to transport HPDL cladding unit.
Optimisation of Laser Cladding Process Using Taguchi and EM Methods for MMC Coating Production
Authors: Dubourg L. , St-Georges L.
Published: September 2022

This study investigates the influence of laser cladding parameters on the geometry and composition of metal-matrix composite (MMC) coatings. Composite coatings are made of a Ni-Cr-B-Si metallic matrix and of WC reinforcement with a volume fraction of 50 %. Optical microscopy is used to characterize the coating geometry (height, width and penetration depth) and to determine the real volumetric content of WC. Laser cladding on low carbon steel substrate is carried out using a cw Nd:YAG laser, a coaxial powder injection system and a combination of Taguchi and EM methods to design the experiments. This combination explores efficiently the multidimensional volume of laser cladding parameters. The results, which express the interrelationship between laser cladding parameters and the characteristics of the clad produced, can be used to find optimum laser parameters, to predict the responses and to improve the understanding of laser cladding process.
Scientific, Technological and Economic Aspects of Rapid Tooling by Electric Arc Spray Forming
Authors: Grant P.S. , Duncan S.R. , Roche A. , Johnson C.F.
Published: September 2022

For the last seven years, Oxford University and the Ford Motor Co. have been researching jointly the development of the large-scale spray forming of steel tooling capable for use in mass production, particularly for the pressing of sheet metal in automotive applications. These investigations have involved: comprehensive microstructure and property studies, modelling of shape evolution and heat flow, real-time feedback control of tool temperature to eliminate tool distortion, high speed imaging and particle image velocimetry of droplet deposition on 3D shapes, the testing of full-scale tools for different applications in the production environment, and detailed studies of the cost and time savings realised for different tooling applications. This paper will provide an overview of the scientific and technical progress to date, present latest results, and describe the current state-of-the-art. Many of the insights described have relevance and applicability across the family of thermal spray processes and applications.
Nozzle Modification for Property Improvement of Arc Spray-formed Steel Tools
Authors: Kim J.-H. , Seong B.-G. , Ahn J.-H. , Baik K.-H.
Published: September 2022

Modification of the nozzle of the arc spray equipment was attempted in order to reduce microstructural defects of the spray-formed steel shells since these defects mainly degrade the overall properties of the spray-formed tools. Based on the in-flight particle analysis, a new nozzle design of a gas shrouding concept was proposed. Effects of design factors such as nozzle dimensions and process conditions was investigated by using statistical analysis methods. The results demonstrated that the oxidation of the spray-formed steel shells can be reduced to the one-third levels of the original ones with an optimized design.
Functionally Graded Net-shape Component Fabrication by Hybrid Spray Process
Authors: Kosikowski D. , Ostrom T. , Mohanty P.S.
Published: September 2022

Functionally graded material (FGM) designs aim to combat challenges posed by harsh and conflicting operational requirements. There is a great demand for manufacturing technologies that can fabricate net-shape components incorporating the FGM design concepts. The focus of this paper is on the development of net-shape components incorporating functionally gradient material designs. This novel manufacturing scheme combines the use of re-useable mandrels to generate complex shapes with a unique thermal spray process called “hybrid spray” that can deposit functionally designed materials. This generic hybrid spray process combines arc spraying with either high velocity oxy-fuel (HVOF) or plasma spraying (APS). The resulting benefits are; ability to achieve continuous composition variation, high deposition rates combined with the high coating densities. The multi-material component designs aim to provide cost as well as performance advantages. The geometric resolution and dimensional accuracy of these functional components are presented. This paper also reports results on material compatibility and process parameter development tests. Functional properties such as high temperature resistance and thermal fatigue performance are also reported.
Aspects of Thermal Spray Molding of Micro Components
Authors: Wilden J. , Bergmann J.P. , Luhn T.
Published: September 2022

In this paper the principle of “Thermal Spray Molding” and some application are presented. Micro technology is a very fast growing market nowadays. Metallic micro devices can be produced for example by means of stereo lithography and selective etching. Unfortunately the material range for these processes is limited. The new manufacturing concept of thermal spray molding uses powder or wire as base material, so that an extended material choice for micro parts, for example micro components made of super hard or corrosion resistant steel is possible.
Ni-Cr Coatings Deposited on a Magnesium Alloy Substrate Using the PROTAL Process
Authors: Li H. , Costil S. , Deng S-H. , Coddet C. , Liao H-L. , Richardt K. , Lugscheider E. , Bobzin K.
Published: September 2022

Being the 7th most abundant element on the earth, magnesium and its alloys have become very promising in numerous industrial applications because of some of their distinguished properties, including high thermal conductivity, high strength/weight ratio, good machinability etc. However, some inferior properties especially the poor wear and corrosion resistance have obstructed a widespread use. As one of the most effective solutions, thermal spraying can deposit an adequate protective coating on the substrate, but the necessary grit-blasting operation before spraying leads to high grit-residues on the magnesium surface therefore degrading the deposit performance. The PROTAL® process, combining a laser surface preparation with the deposition stage, can avoid this kind of disadvantage. This paper presents the possibility of employing PROTAL® to prepare a resistant Ni-Cr coating on a magnesium substrate. The coating adhesion and interface microstructure were especially investigated.
Heat Treatment Effects on the Tribological Performance of HVOF-Sprayed Co-Mo-Cr-Si Coatings
Authors: Bolelli G. , Lusvarghi L.
Published: September 2022

The tribological behaviour of HVOF-sprayed Co-28%Mo- 17%Cr-3%Si coatings, both as-sprayed and after heat treatments at 200°C, 400°C, 600°C for 1h, has been studied. Microstructural and micromechanical properties were characterized by SEM, XRD, depth-sensing indentation (microhardness, elastic modulus, indentation fracture toughness); pin-on-disk dry sliding wear tests were performed against 100Cr6 and sintered alumina spherical pins. The as-sprayed coating contains splat boundary oxide stringers and is mostly amorphous (splat quenching). It has low hardness (≈6.7GPa) and toughness (≈1MPa*m1/2); thus, much adhesive wear occurs against 100Cr6 steel. The friction coefficient increases up to ≈0.9, raising the contact point temperature up to a critical coating oxidation value; then, it decreases, increases again and finally settles. Much of the adhesive wear occurs in the first stage of the test. Abrasive wear prevails with the alumina pin: the coating wear rate is lower because the metallic alloy possesses intrinsically good plasticity. Adhesive phenomena still occur, leading to the same thermal effects. After the 200°C and 400°C heat treatments, no major changes occur. The 600°C treatment causes the formation of some submicrometric crystals. The hardness increases (≈8.8GPa), adhesion to steel pin is prevented, and the friction coefficient soon settles at ≈0.8 with no peaks. The coating undergoes no wear loss and the pin wear rate largely decreases. With the alumina pin, coating and pin wear rates remain quite low. However, adhesion is reduced, so that the friction coefficient has no peaks and its final value is lowered (from 0.84 to 0.75).
Effects of Blasting Parameters on Removability of Residual Grit
Authors: Maruyama T. , Akagi K. , Kobayashi T.
Published: September 2022

A carbon steel was blasted by white alumina, and removability of residual grit was investigated. Blasting parameters such as grit particle size were varied. Residual grit was removed from substrate surface by dissolving the substrate in mixed acid solution, and the amount of residual grit was measured. Removal of residual grit was carried out by ultrasonic cleaning. The amount of residual grit was 7-17 g/m2, and penetration depth of embedded grit of most residual grit was 25-40 µm. The amount of residual grit increased with decreasing the grit size. However, the minimum amount of the substrate dissolution required for the grit removal increased with increasing the grit size.
Influence of Substrate Surface Roughness on Adhesive Strength
Authors: Yang H. , Wang H.G. , Cao X.P. , Wang L.
Published: September 2022

The adhesive strength between substrate and sprayed coatings seems to be mainly due to the mechanical interlocking effect. The physical bonding of spray particles to the substrate is the second factor. In this paper, the bonding mechanisms of sprayed coatings were studied on basis of experiments with the substrate at different surface roughness. The substrate surface roughness was quantitatively evaluated using a surface roughness tester. The tensile adhesion strength test method was used to evaluate the adhesive properties. The relationship between surface roughness and adhesive strength was investigated. The adhesive strength of plasma sprayed coating decreased with an increase in substrate surface roughness, as the size of the grit particles for roughening increased. On the contrary, the adhesive strength of arc sprayed coating increased.
Choosing the Right Coating Technology for the Application
Authors: Legg K.
Published: September 2022

With the vast array of coating technologies and materials available in the marketplace, matching the best coating to an application is far from a trivial task. There is a tendency on the part of vendors, for example, to put forward any hard coating as a chrome replacement or any corrosion-resistant coating as an alternative to cadmium. At the same time users often attempt to shoehorn the coatings with which they are most familiar into applications for which they are not well-suited. This paper will discuss how best to match the application to the best technology and material, considering all the critical requirements of fit, form and function, with particular reference to alternatives for chrome and cadmium plating.
Hybrid Plasma Spray – PVD Coatings in Triple Torch Plasma Reactor
Authors: Heberlein J. , Kolman D. , Chen' H.
Published: September 2022

A reactor and process are described that allow the variation of the plasma deposition conditions such that a wide range of coating properties can be obtained. The reactor consists of three plasma torches mounted such that the deposition precursors can be injected centrally into the merging jets. This reactor has been used to deposit the different layers of a solid oxide fuel cell, including the very dense (99.5% density) zirconia electrolyte layer. Investigation of the zirconia layer showed a microstructure which has characteristics of both plasma sprayed coatings and vapor deposited coatings. The region of particle heating and acceleration has been characterized with enthalpy probes resulting in velocity and temperature fields. Calculations have been performed to describe the particle heating histories. The results show that a significant fraction of the particles evaporate and condense at the surface thus contributing to the formation of the dense layer. This hybrid process combines the possibility of obtaining high density coatings as with a PVD process with the rapid deposition rate of a plasma spray process.
Environmentally Safe Alternative Chrome Application Technology for the Automotive Industry
Authors: Sunthankar M.
Published: September 2022

Conventional decorative chrome plating operations are known to be environmentally and occupationally hazardous because of the use of hexavalent chromium and other toxic chemicals. An alternative ArcBright™ chrome technology has been developed to eliminate these hazards and simultaneously simplify manufacturing methods in this industry. The application method presented here uses an organic base coat and a physically vapor deposited (PVD) chrome to replace electroplated copper-nickel-chrome structure. An advanced rapid cycle, high rate PVD chrome coating method has been developed for this application to be able to increase throughput to the levels required in the automotive sector and to minimize application cost. The technology is applicable to many metals, plastics, composites and other solid materials that are not possible by conventional electroplating providing a wider choice of substrates. The PVD chrome process has been characterized and the ArcBright chrome has been qualified to automotive specifications.
Thermal Sprayed Coatings in High-Performance Agricultural Machinery: Properties and Wear-Behaviour Test Routine
Authors: Lugbauer M. , Kroll A. , Badisch E. , Polak R. , Franek F.
Published: September 2022

Cutting tools in agricultural machines have to withstand high wear demands. Longer maintenance cycle intervals of these tools can be achieved using coatings reinforced with hard particles, applied onto tool substrates. This work was done to establish the qualified test procedure to characterize carbide containing spray & fuse coatings for agricultural demands under abrasion and impact. Simulating these field conditions in lab-scale, tests were performed with a standard ASTM G65 dry-sand rubber-wheel tester (3-body abrasion) and a special impeller-tumbler apparatus (combined impact and abrasion wear). The interaction of hardphase content and matrix composition was investigated to assess their response varying impact energy effects. The test procedure described is suited to optimize coatings by combining quantitative mass loss measurement with results of surface profilometry. It is shown, that crucial material criteria of carbide coatings, such as edge stability and wear progress, can be characterized in a way which is able to tailor coatings for targeted wear regimes in agriculture.
Fretting Wear Behavior of Plasma Sprayed Cu-Ni-In Coating and Cu-Ni-In+MoS2 Composite Coatings
Authors: Paul S.N. , More N.S. , Murthy J.K.N. , Roy M. , Venkataraman B.
Published: September 2022

In many aeronautical applications such as in the fan blade / disk dovetail notch, two parts made up of a titanium alloy are in contact and relative motion between them can occur. Titanium alloys like Ti-6Al-4V are promising candidates for tribological application because of their low weight and high specific strength. However, because of the poor tribological behavior of Ti-6Al-4V under self-mating conditions, modification of the surface has become imperative. In this work, we report on the fretting wear of plasma sprayed Cu-Ni- In along with MoS2 solid bonded lubricant and Ti-6Al-4V. Substrate coated pins were tested against a flat plate of Ti- 6Al-4V alloy. The effect of temperature and frequency on fretting wear of Cu-Ni-In, the composite coating and Ti-6Al- 4V was investigated. Wear properties of the coatings and substrate were evaluated. The morphologies of the worn surfaces and surfaces beneath the worn surfaces were characterized with the help of an optical microscope, scanning electron microscope, electron probe micro analyzer and energy dispersive spectroscopy. Results showed that the composite coating exhibited better fretting resistance than the Cu-Ni-In plasma sprayed coating with no additive. It also exhibited lower surface roughness and a lower coefficient of friction than Cu-Ni-In or Ti-6Al-4V under the same testing condition. Therefore, the use of MoS2 solid bonded coating scan be considered as one of the possible simple and cheap approaches for reducing fretting wear.
Frictional Properties of M3B2 Boride Cermet Coating
Authors: Hamashima K. , Tomita N.
Published: September 2022

The boride cermets composed of M3B2 (M: metal)-system complex borides and metals, have attained superiority over carbide cermets in various mechanical properties. However, their sintered materials have been put into only limited use due to the cost. Therefore, thermal spray coating of the boride cermets was investigated. The powders for thermal spray were prepared by low temperature sintering, and the spraying was performed by HVOF. Microstructure of the sprayed layer was finer, and its hardness was superior to that of a body sintered in vacuum having the same composition. It is clarified that these boride cermet coated layers have outstanding sliding properties. Instantly frictional stress between this boride cermet layer and glass at high temperature is extremely low compared to other materials.
Development of Self-Lubricating Coatings for Ti-6Al-4V Dovetails using a High- Velocity-Particle-Consolidation (HVPC) Process
Authors: Aggarwal G. , Walia P. , Segall A.E. , Smid I. , Eden T.
Published: September 2022

Because of their low density, high specific strength, and high stiffness, titanium alloys are one of the prime candidates for structural application often requiring specific tribological properties. However, their relatively high friction coefficients and low wear resistance are limiting their application over a wider range of temperature. Various coating technologies are currently available to enhance the surface by improving wear and friction characteristics. While the most widely used methods (High-Velocity Oxy-Flame (HVOF), Detonation-Gun (D-Gun), Electron-Beam Physical Vapor Deposition (EB-PVD), etc.) can improve wear performance and decrease corrosion damage, the required higher temperatures usually preclude the integration of thermally vulnerable lubricants. In this research, a low temperature, High-Velocity-Particle Consolidation process (HVPC) was investigated for coating Ti-6Al-4V due to its various advantages over conventional thermal spray processes. The optimum feedstock (nickel + solid-lube) for self-lubricating coating has been developed and compared with respect to different particle sizes and particulate composites. The coating characteristics and its microstructural homogeneity were assessed at various operating parameters and feedstock compositions.
Thermal Spray Coatings from WC-Co Powders Produced by Mechanically Activated Synthesis
Authors: Zimakov S. , Peetsalu P. , Pirso J. , Kulu P. , Mikli V.
Published: September 2022

In the present study WC-Co feedstock powder was produced by the process termed mechanically activated synthesis (MAS). The main characteristics of the powder (particle/granules size, size distribution, morphology, chemical composition and granules microstructure) were determined. The material was sprayed by the HVOF process to investigate the properties of the coatings in comparison to standard materials. The microstructure, phase structure, porosity and microhardness values of the coatings were studied. The abrasion wear resistance of the coatings was evaluated by rubber wheel abrasion tests. Results of abrasive wear tests show that the new material has superior properties compared to conventional WC-Co coatings.
Wear Resistance of Cermet Coating Stainless Steel/ Chromium Oxide Plasma Sprayed
Authors: Medarhri Z. , Ageorges H. , Touimi S. , Fauchais P. , Ctibor P.
Published: September 2022

This work is concentrated on plasma sprayed cermet coatings consisting of stainless steel (SS) (17 wt % Cr and 12 wt % Ni) and chromium oxide (Cr2O3). These powders were sprayed simultaneously, however being injected separately to account for the drastic difference in their thermo-physical properties. Chromium oxide was injected internally and stainless steel externally. The plasma parameters (arc current, hydrogen vol %, mass flow rate) were optimized as well as the injector positions. Coatings were achieved with different mass ratios of SS and Cr2O3. All exhibited a lamellar structure with well distributed Cr2O3 and SS lamellae. They were then systematically characterized by their phase content (XRD), composition (EDS), Vickers micro hardness, morphology (SEM), slurry and dry wear resistances. Finally the best dry linear abrasion resistance was obtained for the pure chromium oxide coatings, while the best slurry wear resistance corresponded to coatings with a mass ratio SS/ Cr2O3 of 56/44.
Cladding with New Short Arc Devices
Authors: Wilden J. , Bergmann J.P. , Dyshlovenko M. , Dolles  , Muether R. , Goecke S.F.
Published: September 2022

Innovative short arc technology is gaining high interest for low temperature joining strategies exemplified by the soldering of zinc coated steels and the joining of steel/aluminum hybrid joints. Controlled short arc allows on one hand a very low heat input in the component, so that melting of the base material can be limited. On the other hand it is possible to use low temperature melting filler wires, as for example zinc wire. New development in controlling short arc have been performed in the last year and reached its maturity for welding production (e.g. Cold Metal Transfer (CMT) of Fronius or Cold Arc in EWM). In both cases the short arc is controlled after drop transfer. One way to perform control is a high dynamic wire feed, which allows high dynamic retracting wire end. Another possibility represents a new type of highly dynamic inverter switching, combined with very fast digital current control, to reduce drastically the peak power in the arc when the short arc is reignited. The consequence of this is a no-sputter, low heat processing procedure. The arc is considerably colder due to the power reduction on re-ignition, which means that a lower heat input is possible.
Zinc Oxide Film Deposition by Atmospheric TPCVD
Authors: Ando Y. , Tobe S. , Tahara H.
Published: September 2022

In order to develop a functional film deposition process with high deposition rate, as a basic study, deposition of zinc oxide film by thermal plasma CVD (TPCVD) in the air was carried out. As ingredient, working gas and substrate, ethanol diluted zinc acetate solution, Ar and 430 stainless steel were used. As for deposition condition, Ar gas flow rate was fixed at 20SLM, deposition distance (distance between substrate surface and nozzle outlet of plasma torch) was varied 50 to 200 mm, zinc acetate concentration in the ingredient was varied 20 to 50 vol%, and ingredient feed rate was varied 30 to 200 ml/h. Consequently, with varying deposition distance, not only crystallized film but also amorphous film could be deposited. In the case of crystallized film, photo-catalytic properties could be confirmed in the films by methylene blue decoloration testing and wettability testing. Besides, in this case, film structure could be changed from lamellar to columnar by decreasing zinc acetate/ ethanol ratio. From these results, this process was found to have high potential for high rate functional film deposition process conducted in the air.
Nozzle Developments for Thermal Spraying at Very Low Pressure
Authors: Bolot R. , Sokolov D. , Klein D. , Coddet C.
Published: September 2022

Very low pressure plasma spraying (LPPS) is the objective of numerous studies for the past years. However, numerical simulations and experiments revealed some difficulties such as the presence of successive expansions and constrictions of the plasma jet that has an influence on the deposition efficiency and on the coating structure. Optimization of the plasma gun is thus required and the use of bell-contoured De Laval nozzle extensions seems particularly promising. In this paper, new developments concerning the use of an in-house bell-contoured nozzle extension are presented and both numerical calculations and experiments were performed.
New Functions of Thermal Spray Toolkit—A Software Developed for Offline and Rapid Robot Programming
Authors: Deng S. , Li H. , Liao H. , Coddet C. , Zeng C. , Charles P. , Uriot P.
Published: September 2022

Thermal Spray Toolkit is a developing toolkit for thermal spray applications based on RobotStudio™ software which is developed by Asea Brown Bovrie Ltd (ABB). This toolkit is composed of several functional modules including PathKit, ProfileKit and MonitorKit. PathKit provides numerous methods to create trajectory on different surfaces including square and rectangular surfaces, round surfaces, curved surfaces and rotating workpieces. ProfileKit permits coating surface analysis by importing a surface profile and it can also guide users to select the right spray parameters according to specific materials. MonitorKit can capture the robot displacement in real-time during the spray process. Thermal Spray Toolkit is a toolkit developed to apply robotics in thermal spray applications whose reliability has been confirmed by the experimental results.
The Basic Principles of DYMET Technology
Authors: Shkodkin A. , Kashirin A. , Klyuev O. , Buzdygar T.
Published: September 2022

Dynamic Metallization (DYMET) process is developed to produce thick aluminum, copper, zinc, nickel, cobalt, lead, and tin coatings on any metal or ceramic substrates. It consists of a surface treatment process in which a mixture of solid metal and ceramic powders are accelerated by compressed air at pressures between 0.5 and 0.8 MPa.