bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual Stress Distribution in HVOF Inconel 718 Coatings for Aerospace Repair Applications
Authors: Lyphout C. , Nylén P. , Manescu A. , Pirling T.
Published: September 2022

Residual stress build up in thick thermal spray coatings is a property of concern. The adhesion of these coatings to the substrate is strongly influenced by the residual stress generation during the coating deposition process. In the HVOF spray process, due to lower processing temperature and higher particle velocity as compared to plasma spraying, significant peening stresses are generated during the impact of semi molten particles on the substrate. The combination of these peening stresses together with quenching and cooling stresses that arise after deposition can be of significant importance. In this paper both a numerical finite element analysis (FEA) method, to calculate peening, quenching and cooling residual stresses, and experimental methods, as Modified Layer Removal Method (MLRM) and Neutron Diffraction analysis, are applied. The investigation is performed for thick Inconel 718 coatings on Inconel 718 substrates. Combined, these numerical and experimental techniques yield a deeper understanding of residual stress formation and a tool for process optimisation. The relationship between the stress state and deposit/substrate thickness ratio is given particular interest.
In Situ Visualization of Impacting Phenomena of Plasma-Sprayed Zirconia: From Single Splat to Coating Formation
Authors: Shinoda K. , Murakami H. , Kuroda S. , Oki S. , Takehara K.
Published: September 2022

Understanding the impacting phenomena of yttria-stabilized zirconia (YSZ) particles and following coating formation in plasma spraying process is of importance to control and design the microstructure of coatings such as thermal barrier coatings. To this aim, recently, the authors have developed a novel in situ monitoring system for particle impacts under atmospheric dc plasma spraying conditions. This system utilized a high-speed video camera coupled with a long-distance microscope and was capable of capturing the particle-impinging phenomena at one million frames per second. To understand the coating formation mechanism, two approaches were attempted, that is, observation of the single splat formation and the following coating formation as the integration of splats. In the former case, the deformation and cooling processes of YSZ droplets impinging on substrates were captured successfully. In the latter case, multiple-droplet-impacting phenomena were observed as an ensemble treatment. Representing coating process, the tower formation (1- dimensional) and bead formation (2-dimentional) were observed under typical plasma spray conditions for thermal barrier coatings. By using a triggering system coupled with the motion of a robot, impact events were recorded for every pass. The obtained images clearly showed the coating formation resulted by the integration of single splats.
Analysis of Plasma Spray Particle State Distribution for Deposition Rate Control
Authors: Wroblewski D. , Ghosh O. , Lum A. , VanHout M. , Basu S.N. , Gevelber M. , Willoughby D.
Published: September 2022

Plasma spray for depositing thermal barrier coatings features large distributions of particle states that result in significant variations in coating quality. These variations arise from distributions of particle sizes, large spatial gradients of plasma thermal-fluid fields, and temporal variations of the arc and jet. This paper describes a simplified approach for studying how particle state distributions are influenced by torch conditions and powder distributions, and the implications for deposition rate monitoring and control. The approach combines a simplified jet model with a more detailed particle model. The important fluid-thermal spatial gradients in the plasma jet are captured using a three zone model: a core region, modeled by growth of a turbulent shear layer around a laminar core, a transition region and a similarity region. Plasma-particle momentum and thermal interactions, particle phase transitions, internal particle temperature gradients, and collapse of in-flight hollow particles have been modeled using a multi-lumped particle model. Effects of distributions of particle size, particle morphology, injection velocity, and carrier gas flow were studied for YSZ spray in an Ar-He plasma. The results provide guidance on sensor design and operation and on approaches for plume location control.
A Combined Numerical and Experimental Analysis of the Cold Spray Process
Authors: Samareh B. , Dolatabadi A. , Lüthen V. , Stier O.
Published: September 2022

The two-phase flow properties of copper particle laden nitrogen are measured and compared to computational fluid dynamic calculations, determining the achievable degree of consistency between model and reality. Two common, commercial nozzles are studied. A two-way coupled Lagrangian scheme along with the RSM turbulence model is used to track the particles and to model the interactions between the gas and the particulate phase. Significant agreement is found for the geometrical gas flow structure, the resulting particle velocities, and the dependence of the two-phase flow on the particulate phase mass loading. The particle velocities decrease with increasing mass loading, even for modest powder feed rates of less than 3 g/s. The velocity drop occurs even when the gas flow rate is kept constant. Adiabatic gas flow models neglecting the energy consumption by the particles are thus inaccurate, except for very dilute suspensions with low technical relevance. For the cases modeled, the experiments evidence the high predictive power of the chosen approach.
Microstructure and Creep Behaviour of Plasma Sprayed Yttria Stabilized Zirconia Thermal Barrier Coatings
Authors: Soltani R. , Coyle T.W. , Mostaghimi J.
Published: September 2022

The purpose of this study was to determine the creep/sintering characteristics of thermally sprayed zirconia coatings and attempt to understand the influence of microstructure on the creep resistance of deposits. The major modification, compared with more typical practice, was employment of powder feedstock with agglomerated sub-micron size particles (Nanox), which is compared to one of the best commercially available powders (HOSP). Thick plasma sprayed coatings were prepared and their physical and mechanical properties were characterized. Creep/sintering experiments were then conducted to investigate the response of the materials when exposed to high temperatures under load. The results showed that it could be possible to correlate the splat thickness to the creep behaviour of the coatings.
Microstructure of Plasma Sprayed La2O3 Modified YSZ Coatings
Authors: Liu Y. , Tao S.Y. , Zhou X.M. , Gao Y.F. , Li W.D. , Luo H.J. , Ding C.X.
Published: September 2022

Yttria stabilized zirconia coatings (YSZ) have received great attention as a good candidate for thermal barrier coatings (TBCs). However, the grain growth and phase transformation, within applied coatings particularly under temperatures higher than 1473 K limit its further applications to great extent. In our present study, in order to develop better understanding of aforementioned phenomena and explore effective methods to conquer this challenge, TBCs using traditional and La2O3 modified YSZ powders were deposited by atmospheric plasma spraying and their microstructures were investigated. Results show that the La2O3 addition can effectively alleviate the grain growth of coatings under high temperature.
Issues and Requirements for Developing a Plasma Spray Deposition Rate Sensor for Real-Time Control
Authors: Gevelber M. , Wroblewski D. , Vattiat B. , Ghosh O. , VanHout M. , Basu S.N.
Published: September 2022

This paper investigates the need and requirements for developing an improved sensing scheme for plasma spray, which would aid in compensating for the large variations in deposition rate. Experimental evaluation of a variety of current sensors reveals poor correlation with deposition rate. Important issues that explain these results include reconsidering what particle state characteristics should be measured and determining what sensing characteristics are required to achieve better correlation with deposited mass. A new particle flux sensor is proposed that meets these challenges is evaluated.
Spreading of Plasma-Sprayed Molybdenum on Grit-Blasted Glass
Authors: McDonald A. , Chandra S. , Moreau C.
Published: September 2022

Plasma-sprayed, molten molybdenum particles (~55 µm diameter) were photographed during impact on grit-blasted glass surfaces that were maintained at either room temperature or at 350°C. Droplets approaching the surface were sensed using a photodetector and after a known delay, a fast charge-coupled device (CCD) camera was triggered to capture time-integrated images of the spreading splat from behind the glass. A rapid two-color pyrometer was used to collect the thermal radiation from the spreading droplets to follow the evolution of their temperature and calculate the splat cooling rates. It was found that as the surface roughness increased, the maximum spread diameters of the molten molybdenum droplets decreased, while the splat cooling rates increased. Impact on non-heated and heated roughened glass with similar roughness values produced splats with approximately the same maximum spread diameters, skewed morphologies, and cooling rates. On smooth glass, the splat morphologies were circular, with larger maximum spread diameters and smaller cooling rates on non-heated smooth glass. An established model was used to estimate the splat-substrate thermal contact resistances. On highly roughened glass, the thermal contact resistance decreased as the glass roughness increased, suggesting that splat-substrate contact was improved as the molten metal penetrated the spaces between the large asperities.
Particle Temperature Fluctuations in Plasma Spraying
Authors: Goutier S. , Nogues-Delbos E. , Vardelle M. , Fauchais P.
Published: September 2022

In a DC plasma spray torch, the dynamic behaviour of the arc attachment at the anode nozzle results in fluctuations of arc voltage and the resulting plasma jet instabilities affect the treatment of the particles injected in the plasma flow, and thus, the coating quality. However it is not clear if the experimentally-observed fluctuations of particle temperatures are a major phenomena and if their frequencies are always in unison with those of voltage. In this study, two on-line techniques are used to investigate respectively the time-variation of particle temperatures and their correlations with voltage variations; the first technique makes it possible to analyse plasma voltage instabilities and the second one to investigate the instabilities of particle temperatures. Both allow determining the frequencies and amplitude variations of voltage and particle temperatures. The experiments are carried out with two plasma torches (F4-type and 3MB-type) using respectively argon-hydrogen or nitrogen–hydrogen mixtures as plasma-forming gases. A good correlation between arc voltage and particle temperature fluctuations is observed when the plasma torch is operating with argon-hydrogen while that's not the case when the torch is operating with nitrogen-hydrogen.
Substrate Properties Influence on the Coating Deposition by DYMET Technology
Authors: Shkodkin A. , Kashirin A. , Klyuev O.
Published: September 2022

The heating of the substrate by the jet may influence on the process of coating deposition by DYMET technology. It can be observed as deposition efficiency variation at various nozzle transverse speeds. Experimental investigation of the deposition efficiency variation for different jet stagnation temperatures and different substrate thermal properties is presented and discussed. The suppression of substrate influence on the deposition process with the coating thickness growth is demonstrated.
Low Pressure Cold Gas Dynamic Spray and Post-Spray Heat Treatment of Composite Coatings
Authors: Maev R. , Beneteau M. , Birtch W. , Villafuerte J. , Sastry K.Y. , Leshchynsky V.
Published: September 2022

This paper describes the influence of post-spray heat treatment parameters on mechanical properties of Ni-TiC composite coatings. Thin Ni-TiC composite coatings were produced by low pressure cold gas dynamic process (also referred as cold spray or kinetic spray process) on an Inconel alloy substrate. In the coating process, mechanically mixed micron-sized Ni-TiC powders (~50 µm) were injected into a de-Laval nozzle propelled by a supersonic gas stream to high velocity (>300 m/s) to impinge upon a substrate. The coatings are formed subsequently as the metallic particles are severely deformed plastically and bonded to both the substrate and to one another. However the tensile adhesion strength levels were determined to be in the range of 10-14 MPa. A subsequent post-spray heat treatment in vacuum was found to enhance the bond strength of the coated particles with the substrate due to good metallurgical bonding caused by diffusion mechanism.
Microstructure and Mechanical Properties of Low-Pressure Cold Sprayed (LPCS) Coatings
Authors: Koivuluoto H. , Lagerbom J. , Kylmälahti M. , Vuoristo P.
Published: September 2022

In low-pressure cold spray (LPCS) process, compressed air is used as a process gas. The most important process parameters are the gas (air) preheating temperature and the gas pressure. Maximum preheating temperature of air is 650ºC and pressure is 9 bar in the LPCS system used in the present study. Powders used in LPCS process contain hard particles (Al2O3) with metallic powders. LPCS is the method to spray soft metallic coatings with ceramic hard phase for different application areas. For example LPCS opens a way to produce thick coatings for electrical and thermal conductive applications and for corrosion protection. Aim of this study was to investigate microstructural properties such as microstructure and denseness of LPCS coatings. Also mechanical properties (hardness and bond strength) were studied. One interest of this study was to clarify the effect of hard phase on different coating properties. Coating materials were Cu, Ni, and Zn. Substrate material were carbon steel and copper. LPCS coatings seemed to be dense according to SEM studies but corrosion tests were needed to identify existence of porosity. Through-porosity was observed in the structures of the LPCS coatings during the corrosion tests. Bond strengths of LPCS Cu and Zn coatings were found to be reasonable and furthermore, hardnesses were quite high indicating reinforcement effect of hard phase and work hardening.
Influence of Laser Irradiation on Formation of Low-Pressure Cold Sprayed Coatings
Authors: Kulmala M. , Koivuluoto H. , Vuoristo P.
Published: September 2022

In cold sprayed coatings, the technical properties are besides the coating material itself also highly determined by the integrity of interparticle boundaries and coating to substrate interface. One possibility to affect these boundaries is a simultaneous laser irradiation during the cold spray process. It is expected that laser-assisted low-pressure cold spraying could be an effective method to improve the low-pressure cold sprayed coating denseness and adhesion. The purpose of the additional energy from the laser beam is to create denser and more adherent coatings, enhance deposition efficiency and increase the variety of coating materials. In this study copper and nickel powders with additions of alumina powder were laser-assisted low-pressure cold sprayed (LALPCS) on carbon steel. Coatings were sprayed using nitrogen or air as process gas. A 6 kW diode laser or 4 kW Nd:YAG laser and low-pressure cold spraying unit were used in the experiments. The influence of laser energy on coating microstructure, denseness and deposition efficiency was studied. The coating microstructure was characterized by a scanning electron microscope (SEM). The coating denseness was tested with open cell potential measurements and salt spray tests. Results showed that laser assistance made coatings denser and also enhanced deposition efficiency.
Axial Injection Plasma Spraying using Micro and Nanopowder Slurries to Produce Dense Ceramic Coatings
Authors: Tang Z. , Yaroslavski I. , Hartell P. , Bogdanovic N. , Burgess A.
Published: September 2022

Plasma spraying was successfully applied for Thermal Barrier Coatings (TBCs), which typically possess a lamellar structure with a porosity of 5-20%. Control of the plasma process presents a big challenge when the goal is to achieve fully dense coatings, as required for some emerging applications such as solid oxide fuel cells (SOFCs) and dense TBCs. Fine powders produce finer lamellae, and result in denser coatings. However, powders finer than 10 microns are very difficult to feed consistently into a plasma torch. Liquid slurries offer a means to deliver fine particles to thermal spray torches. In this paper, an automatic slurry feed system was developed to consistently deliver micro and nano powder slurries. The slurries were injected axially into a high energy/high velocity plasma torch to generate dense coatings. The effects of plasma parameters and different feedstocks on coating microstructures are investigated; dense coatings for various applications are demonstrated.
Plasma Spray Processing of Nanostructured Partially Stabilized Zirconia for a Strain Accommodating Inter-Layer – Splat Characteristics
Authors: Guru D. , Heberlein J.
Published: September 2022

Build up of strain within thermal barrier coatings has been identified as one of the main reasons for coating failure. The large volume fraction of grain boundaries in nanostructured materials has been predicted to partially relieve the strain in a coating structure. In this study, the difference in morphological characteristics of regular PSZ (r-PSZ) particles and nano-agglomerate PSZ (n-PSZ) particles have been investigated to improve our understanding of the stresses and strains within a coating. The Triple Torch Plasma Reactor, a reduced pressure plasma spray system along with a pair of tungsten and molybdenum apertures was used to isolate spray particles from the plume to deposit splat sample. Cross sections of the splat samples were prepared. Image analysis techniques were used on scanning electron microscopy (SEM) images to characterize both the surface and the cross sectional features of the splat samples. Semi-molten structures were found to be the defining characteristic of the n-PSZ samples. Peak height distribution (PHD) was defined to quantify the distribution of the height of semi-molten structures. PHD was estimated for different samples and was found to track the changes in the morphological characteristics as a function of the deposition conditions.
Research of Properties of Nanostructured Cr2O35SiO23TiO2 coatings by plasma sprayed
Authors: Li Z. , Yu Y. , Zeng K. , Song X. , Zhou H. , Wu C.
Published: September 2022

Plasma sprayed chromium oxides coatings have been widely applied in anilox rolls and pump seal for many years. This paper is researching the effect of nanostructured Cr2O35SiO23TiO2 composite powder preparation when adding nano-size SiO2 and TiO2 powder in Cr2O3 powder, to prepare for through spray drying, high temperature sintering and flame density. The microstructure of powder and plasma sprayed coating are analyzed by SEM and XRD, compared with pure Cr2O3 powder and METCO 136F powder. The Microhardness of the coatings are measured by 402MVATM Vickers hardness tester. Fracture test is used to analysis the ductility of coatings, and the fracture appearance is analyzed by SEM. The result indicates that the mechanical behaviors of nanostructured Cr2O35SiO23TiO2 coating has better performance in the nature of hardness and ductility.
The Effect of Surface Chemistry and Morphology on the Properties of HVAF PEEK Single Splats
Authors: Withy B.P. , Hyland M.M. , James B.J.
Published: September 2022

Thermal spray of polymers has had limited investigation due to the narrow processing windows that are inherent to polymer powders, especially their low temperatures of thermal degradation. The polymer poly aryl ether ether ketone (PEEK) has a high thermal degradation temperature and high resistance to alkaline and acidic attack. These properties led to PEEK being selected for investigation. To minimise thermal degradation of the particles, the high velocity air fuel (HVAF) technique was used. To investigate the effect of substrate pre-treatment on single splat properties, single splats were collected on aluminium 5052 substrates with six different pretreatments. The single splats collected were imaged by scanning electron microscopy (SEM) and image analysis was performed with ImageJ, an open source scientific graphics package. On substrates held at 323°C it was found that substrate pretreatment had a significant effect on the circularity and area of single splats, and also on the number of splats deposited on the substrates. Increases in splat circularity, area, and the number of splats deposited on the surface were linked to the decrease in chemisorbed water on the substrate surface and the decrease of surface roughness. This proved that surface chemistry and roughness are crucial to forming single splats with good properties, which will lead to coatings of good properties.
Ceramics as Wear and Corrosion Protection on Hydraulic Piston Rods
Authors: Kraak T. , Coolegem G. , Herlaar W.
Published: September 2022

The application of thermal sprayed coatings has a broad industrial scope, not only applied where it concerns repairing but also as a preventive means. This article focuses on the applications of ceramics as wear and corrosion protection on hydraulic piston rods. It begins with a concise description of the different forms of wear and their mechanisms with some typical examples of worn surfaces. This is followed by an overview of the available coating techniques for enhancing metal surfaces. Next, the article discusses the principle and applications of thermal sprayed coatings. Then, it presents the scope and protection measures of thermal sprayed coatings to failure mechanism. Further, the article discusses the properties, quality control, and testing criteria of the coatings. It describes the chemical composition and chemical analysis of quality control spray powder. Finally, the article ends with a discussion on the examples of thermal sprayed coatings in OEM applications.
New Structure of APS Sprayed AI2O3 Coatings Investigated by Cu-Electroplating
Authors: Adachi M. , Takabatake T. , Ohmori A. , Kremer M.
Published: September 2022

A copper electroplating method revealed that recently developed commercial Al2O3 thermal spray coatings did not have the well-known lamellar structure but instead had a structure that was made up of tightly bonded particles, with many vertical microcracks in the coating. The coating in the study was prepared by the atmospheric plasma spray system. The copper electroplating method was applied to observation of the Al2O3 thermal spray coating structure. Spray coating specimens were electroplated in an aqueous solution containing CuSO4, H2SO4, CuCl2, and additives so that copper was deposited in small pores and narrow cracks in the coatings. Copper in the Al2O3 coatings was observed clearly by scanning electron microscopy, which also revealed the coating’s structure (boundaries of flattened particles and vertical cracks). The coating did not have a lamellar structure (horizontal apertures between flattened particles) and it was dense in spite of the many microcracks.
Thermal Failure of Nanostructured Thermal Barrier Coatings with Cold Sprayed Nanostructured NiCrAlY Bond Coat
Authors: Zhang Q. , Li Y. , Zhang S.-L. , Wang X.-R. , Yang G.-J. , Li C.-X. , Li C.-J.
Published: September 2022

Nanostructured YSZ is expected to exhibit a high strain tolerability due to its low Young’s modulus and consequently high durability. In this study, a porous YSZ as the thermal barrier coating was deposited by plasma spraying using an agglomerated nanostructured YSZ powder on a Ni-based superalloy Inconel 738 substrate with a cold-sprayed nanostructured NiCrAlY as the bond coat. The heat treatment in Ar atmosphere was applied to the cold-sprayed bond coat before deposition of YSZ. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured YSZ. The results showed that YSZ coating was deposited by partially melted YSZ particles. The nonmelted fraction of spray particles retains the porous nanostructure of the starting powder into the deposit. YSZ coating exhibits a bimodal microstructure consisting of nanosized particles retained from the powder and micro-columnar grains formed through the solidification of the melted fraction in spray particles. The oxidation of the bond coat occurs during the heat treatment in Ar atmosphere. The uniform oxide at the interface between the bond coat and YSZ can be formed during isothermal test. The cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of TBCs mainly occurred through spalling of YSZ within YSZ coating. The failure characteristics of plasma-sprayed nanostructured YSZ are discussed based on the coating microstructure and formation of TGO on the bond coat surface.
Single Impact Erosion Studies of Cr3C2-NiCr Coating: The Role of Microstructure Variation
Authors: Matthews S. , Hyland M. , James B.
Published: September 2022

Cr3C2-NiCr thermal spray coatings have been extensively applied to mitigate erosion in high temperature applications such as aircraft and power generation turbines. Much laboratory based erosion research has been conducted under ambient temperature and mild erosion conditions. However, little has been presented about the coating response under the high temperature, high velocity erosion conditions typically experienced in industrial applications. This work presents the mechanisms of high velocity erosion based on experiments conducted under realistic service conditions. Single impact studies were carried out on a range of Cr3C2-NiCr coatings to assess the variation in erosion mechanism with phase degradation and starting powder morphology. Comparisons were made between the coating response in the as-sprayed state and after long-term heat treatment to determine how the erosion response changes as a function of exposure time in-service. Erosion of the as-sprayed coatings was heavily influenced by splat boundary related mass loss mechanisms. This was accentuated by in-flight carbide dissolution in the coatings based on agglomerated/sintered powders. Heat treatment led to splat sintering and a transition in the erosion response towards more microstructural based erosion mechanisms. The variation in erosion response as a function of microstructural development with heat treatment and starting powder type is presented.
Evaluation of Intermetallic Coatings Processed by PTA
Authors: d'Oliveira A. , de Christo A. , Vaz D.S.
Published: September 2022

Plasma Transferred Arc hardfacing (PTA) is an excellent tool for surface tailoring as it allows for the manipulation of coatings chemical composition. In particular in-situ alloy development can be achieved during the deposition of different powder mixtures. In this work powder mixtures of Ni-Al, Nb-Al and Fe-Al were deposited by PTA. Coatings were characterized for their mechanical features at room temperature evaluated by Vickers microhardness under 300gf load, nano- (0.04gf) and macro- (10kgf) scratch tests and pin-on-abrasive disc tests under 1kgf. Results showed very high dilution for the processed coatings with Vickers microhardness varing with the chemical composition of the deposited powder, mixtures, with the Fe based deposits exhibiting the lower hardness (below 400Hv) and the Nb-based deposits reaching 900HV. Scratch hardness followed Vickers micro hardness only for the Nb based coatings. Abrasion mechanism also varied for each alloy system and within each alloy system, the harder the coating the better the abrasive wear resistance. However when comparing the full set of coatings the Nb based coatings exhibited a superior performance and the Ni based deposits the poorer wear resistance.
Thermally Sprayed TiO2-Cr2O3 Coatings with Multifunctional Properties
Authors: Stahr C.C. , Berger L.-M. , Thiele S. , Saaro S.
Published: September 2022

Thermally sprayed titanium suboxide (TiOx) coatings are widely used in industrial applications due to their good tribological properties and their electrical conductivity. These properties are mainly dependent on the amount of oxygen in the crystal lattice. Oxygen defects lead to the formation of so-called Magnéli phases. The range of applications is limited by the fact that TiOx tends to reoxidize in many service conditions, especially at elevated temperatures. Also, the extreme conditions in the flame or torch used in the thermal spray process lead to undefined phase changes and defects. In the TiO2-Cr2O3 system, Magnéli phases are also formed, but it is assumed that the properties do not change due to oxidation during spraying and subsequent use. This work shows the possibilities of the new coating materials. Powders with different TiO2 and Cr2O3 contents and prepared by different technologies were used for the investigation of coating properties. Experimental powders with defined phase compositions were prepared. The powders were thermally sprayed and the coatings investigated in terms of phase composition, microstructure, hardness, and abrasion wear resistance.
Mechanically Activated Synthesis of Composite Powders for Thermal Spraying
Authors: Ilyuschenko A.F. , Belyayev A. , Talako A. , Letsko A. , Borovick D.
Published: September 2022

Known methods of production of composite powders have a series of deficiencies. The method of self-propagating high-temperature synthesis which has appeared recently has conclusive advantages. The method allows forming in a single work cycle micro and a macrostructure of a composite particle. The present work is devoted to viewing of questions targeted mechanical activated synthesis of composite powders for thermal spraying of function coating of various applications. Results of synthesis of powders Ti and Cr carbides in oxygen atmosphere are given.
Structure and Properties of Powders of Quasicrystalline Alloy AlCuFe Alloyed by Cr and Sc
Authors: Borisova A. , Borisov Y. , Adeeva L. , Tunik A. , Karpets M. , Doroshenko L.
Published: September 2022

Development of thermal spraying of quasicrystalline coatings is connected with development of new powders for produced from alloyed quasicrystalline alloys. Powders of AlCuFe alloyed by Cr and Sc were produced by high – pressure water atomization of melt. Phase composition, microstructure, morphology, flowability of the powders were investigated. Resistance of powders to oxidation in air was studied using thermography. It was determined that doping of AlCuFe – alloy by 0,265 and 0,440 at.% Sc and by 8 at.% Cr significantly increases in them content of quasicrystalline phases. Annealing of AlCuFeCr at 550°C leads to transformation quasicrystalline phase into crystalline approximant of decagonal quasicrystalline phase.
Influence of Process Parameters in the Microstructure and Cavitation Resistance of the Fe-Mn-Cr-Si Metal Cored Wire Developed for Arc Thermal Spraying
Authors: Pukasiewicz A. , Capra A. , Paredes R.
Published: September 2022

The deposition of cavitation-resistant materials coatings in turbine blades is an important way to reduce cavitation damage. Fe-Cr-Mn-Si is a cavitation-resistant steel with many deoxidation elements, which can be important for arc thermal spraying materials. The influence of air pressure, arc tension, and chemical composition on the microstructure, area fraction oxide, porosity, microhardness, and cavitation resistance were studied. Microstructures and properties were investigated by XRD, optical and electronic microscopy, microhardness testing, and ultrasonic cavitation testing per ASTM G32-93. Chromium addition promotes an increase in area fraction oxide, and reduces the porosity, changing the microhardness. An increase in air pressure raised the oxide fraction in the SMA_A and 2 alloys. The SMA_A mass loss rates were 31.8, 25.8, and 37.2 mg/h, respectively, for the samples with 280, 410, and 550 kPa of air pressure. For the SMA_3 samples, the increase in the arc voltage reduces the oxide fraction, changing the mass loss rate to 43.8, 32.4, and 29.4 mg/h for 25, 30, and 35 V, respectively. Phase transformations occurred in the arc thermal spray, for all coatings, during cavitation tests. The SEM analysis verified that the mass loss in arc thermal spray coatings occurred because of the oxide fracture and delamination of the splats.
Study of Copper and Copper-Alumina Cold-Sprayed Deposits
Authors: Rech S. , Trentin A. , Stoyanova V. , Vezzü S.
Published: September 2022

For years, special attention has been paid to study and to develop innovative copper alloys and composites, with improved mechanical behaviour in respect to pure copper and preserving its excellent electrical and thermal properties. In this work different copper/alumina blends have been prepared and then deposited by cold spray at different gas carrier temperatures. The deposition efficiency and the content of embedded alumina have been determined by means of image analysis using SPIP software. Optimized deposition temperature results 450°C: the coatings exhibit compact, pore-free microstructure and very low oxidation. Microhardness and friction coefficient have been evaluated of both pure copper and composite coatings. An increase of microhardness from 65HV0.015 to 150HV0.5 has been observed while a progressive reduction of friction coefficient as a function of alumina content has been reported. Further characterizations to determine thermal and electrical properties of copper/alumina composites are in progress.
Preparation of Multimodal Structured WC-12Co Deposits by Cold Spraying
Authors: Gao P. , Yang G. , Li C.
Published: September 2022

Micro-structural design had attracted increasing interests in modern developments of hard coatings. The ability of cold spray process to retain the feedstock microstructure into coating makes it possible to design coating microstructure through feedstocks for development of different coating properties. In this study, a multi-size modal WC-12Co powder containing nano-sized WC particles was designed to deposit WC-Co deposition with multi-sized WC. Multimodal WC-12Co powders were prepared with ball-milling of a commercial WC-12Co powder, cold-compacting, sintering in hydrogen atmosphere and crushing. WC particle size in the powder exhibits a distribution with two peaks in tens of nanometers and several micrometers. The multimodal WC-12Co deposition was prepared by cold spraying using helium as driving gas. The multimodal size of WC particles in the powders was retained into the deposit. The micro-hardness and fracture toughness of the multimodal structured WC-12Co deposit was compared with bulk WC-12Co. It was found that the multimodal deposition exhibits a comparable hardness to nano-sized WC-12Co and a high fracture toughness compared with micro-sized WC-12Co. The simultaneous strengthening and toughening of WC-12Co can be realized through the bimodal microstructure design of WC-Co.
Deposition Characteristics of Fe/Al Composite Coating Fabricated by Cold Spraying
Authors: Wang H. , Li C. , Yang G. , Li C. , Gao P. , Zhang Q.
Published: September 2022

FeAl Intermetallic compounds have excellent wear resistance and high temperature oxidation resistances. The low temperature brittleness makes intermetallic compound materials more suitable to be applied in the form of coating to protect materials from high temperature oxidation and wear. In the present study, a iron/aluminum composite coating was produced by cold spraying of iron and aluminum powder mixtures and then was annealed at different temperatures to aim at forming an iron aluminide intermetallic based coating. The deposition behavior of iron and aluminum powder mixtures and microstructural characteristics of the as-sprayed deposit were examined by scanning electron microscopy (SEM). The kinetics of the phase transformation of the as-sprayed iron/aluminum composite deposit to iron aluminide was characterized by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed that after heat treatment at a temperature of 600°C, intermediate phase Al5Fe2 coexisted in the deposit with remaining Fe and Al. With increasing heat treatment temperature to 900°C, the deposits consisted of mainly FeAl phase and a trace of remaining Fe phase.
Fabrication of TiO2 Coating by Cold Spraying and Evaluation of Its Property
Authors: Yamada M. , Wada H. , Sato K. , Fukumoto M.
Published: September 2022

Titanium dioxide (TiO2) is a promising material for photocatalyst coating. However, it was difficult to fabricate TiO2 coatings which have excellent photocatalyst property by thermal spray processes. Because anatase phase of TiO2 transforms into rutile phase under high temperature i.e. the photocatalyst property of TiO2 declines by heating. In this study, TiO2 photocatalyst coatings were fabricated by cold spraying. Agglomerated TiO2 powder with 100% anatase phase was injected into nitrogen or helium gas stream and deposit onto steel substrate. It was possible to fabricate TiO2 coatings with anatase phase and dense microstructure. The deposition efficiency was increased with gas temperature. The photocatalytic property of the coatings was evaluated by NOx elimination test. From the results, it became clear that cold sprayed TiO2 coatings had excellent photocatalyst property.
Influence of Powder Porous Structure on the Deposition Behavior of Cold-Sprayed WC-12Co Coatings
Authors: Gao P.-H. , Li Y.-G. , Li C.-J. , Yang G.-J. , Li C.-X.
Published: September 2022

The carbide decomposition and the dissolution of carbide into the binder accompanying with thermal spraying of cermets can be eliminated during cold spray deposition of WC-Co. However, the limited deformation of hard impacting cermet particles and impacted coating makes it difficult for conventional thermal spray powders to continuously build up on impact in cold spraying. The porous structure of WC-Co powders provides the powder particles with certain deformability on high velocity impact, which benefits the continuous building-up of coating. In this study, three nano-structured WC-12Co powders with different porous structures and apparent hardness were employed to deposit WC-Co coatings on stainless steel substrate by cold spraying. The deposition characteristics of three powders of different porosity levels of 44%, 30% and 5% were investigated. It was found that WC-Co coating is easily built-up using the porous powders with WC particles bonded loosely and a low hardness. The microhardness of WC-12Co coatings varied from Hv400 to Hv1790 with powders and spray conditions, which depends on the densification effects by impacting particles. With porous WC-Co powders, the fracture of particles on impact may occur and low deposition efficiency during cold spraying. The successful coating building up at high deposition efficiency depends on the design of powder porous structure.
Formation of NiTi Intermetallics by Heat Treatment of Cold-Sprayed Precursor Coating
Authors: Wang H.-T. , Li C.-J. , Yang G.-J. , Li C.-X. , Gao P.-H. , Zhang Q.
Published: September 2022

Nickel titanium is promising cavitation erosion resistant material. Using NiTi in bulk for components might not be feasible due to its poor workability, as well as the high material and processing costs. Surfacing components with its coating is effective for utilizing the good erosion properties of NiTi intermetallic compounds. In this study, a method to prepare NiTi intermetallic compound coatings in-situ through annealing of the cold-sprayed Ni(Ti) metastable coating was investigated. A nanostructured Ni(Ti) solid solution alloy powder was prepared by ball-milling process. The cold sprayed Ni(Ti) alloy coating was used as the precursor coating. The effect of annealing temperature on the microstructure in-situ evolution of Ni-Ti intermetallic compound in cold-sprayed coating was investigated. The morphology and phase composition of the powders milled for different durations and the microstructure of the as-sprayed coating were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that after annealing at 950°C the Ni(Ti) alloy was transformed to intermetallic phases. NiTi, Ni3Ti and NiTi2 intermetallic phases coexisted in the annealed coating.
Effect of Substrate Roughness on the Deposition Behavior of Kinetic Sprayed Copper Particles on Copper Substrate
Authors: Kumar S. , Bae G. , Yoon S. , Kim J. , Lee C.
Published: September 2022

In this work, effect of substrate roughness on the deposition behavior of the particles through kinetic spray technology is studied. Finite element analysis program, ABAQUS 6.7-2 was used to estimate the results. Particle impact on the planar and roughened substrates were analyzed and compared. Interface temperature, contact area and contact time were found to be higher for the particle impact on roughened surfaces than that of the planar one for constant spray condition. These factors are significant for bonding mechanism. Experiments were performed on the polished and grit blasted surfaces in order to compare the results. The deposition efficiency and the bond strength values were used to evaluate the effect of surface roughness.
Impact Behavior Characterization of Engineering Metals in Kinetic Spraying
Authors: Bae G. , Kumar S. , Yoon S. , Kang K. , Lee C.
Published: September 2022

In this study, three kinds of engineering metals, which are aluminum (1100-H12), commercially pure titanium and mild steel were combined as particle/substrate and classified into four cases, i.e., soft/soft, hard/hard, hard/soft and soft/hard, according to their physical and mechanical properties respectively. Based on finite element modeling, impacting interface elements of four cases were analyzed and impact behaviors were numerically characterized. For soft/soft and hard/hard cases, the maximum temperature at the substrate side, which approached melting point, is higher than that of particle side when the shear instabilities occur. In particular, the different size of thermal boost-up zone was numerically estimated and theoretically discussed for these two cases. Meanwhile, for soft/hard and hard/soft cases, the specific aspect of shear instability, which has very high heat-up rate, was always observed at the relatively soft impact counterpart, and a thin molten layer was expected as well. Thus, the successful bonding of the above mentioned four cases can be predicted as a result of the synergistic effect of localized shear instability with interfacial melting.
A Combined Process: Cold Spraying of Heterogeneous Coatings Followed with their High Energy Treatment
Authors: Solonenko O. , Kosarev V. , Golovin A. , Neronov V. , Korchagin M. , Poluboyarov V.
Published: September 2022

Presently, the self-propagating high-temperature synthesis (SHS) has found wide use in the production of compacts and powder materials, and also in the fabrication of end products. Yet, a disadvantageous feature of the standard SHS process, which can be overcome in part by running the synthesis reaction under pressure, is that it fails to provide the possibility of obtaining high-density materials and products. It is therefore of interest to develop a combined process which would allow one to apply a two-component Ni-Al coating with prescribed stoichiometric composition by cold spraying of a nickel-aluminum powder mixture followed by self-propagating high-temperature synthesis of a target intermetallide (Ni3Al or NiAl) by treating the surface layer of the cold sprayed coating with a highly-concentrated energy flux (argon plasma jet). Preparation methods for nickel-aluminum powder mixtures (in particular, mechanochemical activation) intended for cold spraying process are discussed. Computational experiments were performed to substantiate the choice of stationary, traveling and pulsed energy sources for subsequent initiation of SHS in the heterogeneous layer deposited onto a steel substrate. A model was developed to predict the local phase state of the material synthesized in the coating; this model involves the state diagram of the Ni-Al system. The characteristics of sprayed coatings were examined. The developed approach is shown to offer much potential in practical applications.
A Side-by-Side Comparison of Particle Temperature (Tp), Particle Velocity (Vp) Data Collected using the Accura G3 and the DPV-2000
Authors: Hall A. , Williamson R. , Urrea D. , Mccloskey J. , Beatty D. , Roemer T. , Hirschfield D.
Published: September 2022

A Sulzer-Metco 6P Powder Flame Spray Torch spraying an alumina-titania ceramic powder RX60 6-axis robotic was characterized using an Accura G3(Tecnar Automation; Quebec, Canada) and a DPV-2000 (Tecnar Automation; Quebec, Canada). The two sensors were mounted side-by-side and a robot was used position the torch in relation to each sensor. Process gas flows were set using laminar flow element mass flow controllers. Accura and DPV measurements of particle temperature (Tp) and particle velocity (Vp) were made in succession at each operating condition without changing torch operating conditions. Data for a single designed experiment was collected with both sensors allowing for comparison of the two sensors across the operating space of a typical powder flame spray process.
Asymmetric Melting Behaviour in Twine Wire Arc Spraying with Cored Wires
Authors: Tillmann W. , Abdulgader M. , Vogli E.
Published: September 2022

Asymmetric melting behaviour of the electrodes is a process related feature of the twin wire arc spraying (TWAS) technique since the heating of the negative connected wire is different from that of the positive connected wire. Due to these differences in melting behaviour a tracking of particle velocity and temperature for both electrodes individually is very important. Particle velocity and temperature have been recorded from anode and cathode by positioning the tracking device on each side of the spraying gun. To draw the whole picture of the spraying jet particles have been tracked also from the top side of the spray gun. The goal of this study is to have an experimental data set-up for model building and simulation of depositing process in TWAS. Corresponding measuring devices have been employed to investigate the TWAS process by spraying of massive and cored wires.
Gas Flow Drift Velocity Measurement on Plasma Spray Torches
Authors: Lange S. , Forster G. , Schein J.
Published: September 2022

In thermal spray processes fast gas flows are used to accelerate and melt the coating compound materials. The kinetic energy transferred to the particles by the gas flow depends on the velocity of the jet, which thus becomes an important parameter for coating formation. This paper describes a non-contact technique for measuring the drift velocity in those flows. This technique is based on the additional wavelength shift induced by the gas flow for non resonant light scattering. This shift of the order 1 pm is detected by an interferometer composed of two mechanical tilted plates, such that the wavelength of the scattered light can be easily obtained from the location of the maxima in the corresponding Airy profile paired with an MCP-CCD camera, to enhance sensitivity and processing speed. The experimental setup will be described and first results shown.