bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Substrate Properties on the Formation of Plasma-Sprayed Alumina Splats
Authors: Pershin V. , Pasandideh-Fard M. , Mostaghimi J. , Chandra S.
Published: June 2022

The effect of substrate characteristics on the formation of plasma-sprayed alumina splats was studied using both experiments and numerical simulation. Knowledge of the particle and substrate conditions is critical in understanding coating formation and in validating computational models. The size, velocity and temperature of the alumina particles prior to impact were measured using a particle in-flight diagnostic system. Experiments were performed on two substrate materials: stainless steel and glass. Substrate temperatures were varied in a range of 20-500°C and controlled with an electric heater. For each substrate material, a transition temperature was observed above which there was no fingering/splashing and the splats had a circular disk shape. A 3D computational model of free surface flows with heat transfer and solidification was used to simulate the impact of alumina particles in conditions given by the experiments. The splat shapes from numerical model were comparable to those of the experiments for hot stainless steel substrate. For a cold substrate, the numerical model did not show any fingering/splashing. In the experiments, however, we observed two types of splat shapes: intensive splashing with no central core and circular disk splat. Substrate surface contamination, not considered in the numerical model, was the probable cause of droplet splashing on the cold substrate.
Oxidation of Iron Particles During APS: Effect of the Process on Formed Oxide; Wetting of Droplets on Ceramic Substrates
Authors: Espié G. , Fauchais P. , Labbe J.C. , Vardelle A.M. , Hannoyer B.
Published: June 2022

Investigations have been carried out to study the influence of Atmospheric Plasma Spray process (APS) on the in-flight oxidation of pure iron particles. After collecting the molten droplets in-flight, XRD, SEM and Mössbauer spectroscopy are used to determine the amount and distribution of formed oxides. The results indicate that the Wüstite, Fe0.95O, is the only oxide formed during the APS. In the jet core and at the beginning of its plume, oxidation is controlled by convection within molten droplets and then for the downstream of the plasma by diffusion where the solubility of oxygen through the external oxide layer governs the growth of Wüstite. Calculations have shown that the convective movement is due to the drastic velocity difference between the plasma jet and particles. Wüstite granules can be distinguished within the particles due to the immiscibility between Fe and FeO in liquid phase. This oxide phase represents about 13 wt% of the collected particles at 100 mm stand-off distance in an Ar-H2 plasma jet (50:10 SLM) with 18 kW effective power. The amount of oxide decreases when the H2 volume percentage of the plasma, the internal diameter of the anode nozzle and the effective power increase. Sessile drop studies of molten iron on ceramic substrates are carried out to simulate the wetting of oxidized iron particles during coating formation. It is found that the oxidation state of iron particles during APS has a significant effect on the observed contact angles. A strong decrease of the contact angle is observed in the case of oxidized iron particles. In-flight oxidation of iron particles allows a better splat covering.
Splat Morphology and Graphite Formation in Plasma-Sprayed Cast Iron
Authors: Morks M.F. , Tsunekawa Y. , Okumiya M. , Shoeib M.A.
Published: June 2022

Fundamental aspects of a plasma sprayed cast iron coating on an aluminum alloy substrate are investigated in the present study: focusing on the effects of preheat substrate temperature (TS) and chamber pressure (PC) on the splat morphology, the adhesive strength of splats, the formation of a reaction layer and graphite. Splash-type splats appear at low TS but disk and star-shaped splats arise at high TS. Deformed substrate ridges, mainly due to the slight surface melting, are formed adjacent to the splat periphery at high TS. At low TS, pores are observed at the splat/substrate interface, which cause a decrease in the adhesion of splats. In contrast, a reaction layer composed of iron, aluminum and oxygen is ready to form at high TS. The amount of graphitized carbon increases in cast iron splats with TS. At a low PC of 26.3 kPa, disk-type splats are in the majority at a constant TS of 473 K. As PC increases, star-shaped splats appear along with disk splats. The flattening ratio of disk splats decreases with the increase of PC, because of a decrease in the kinetic energy and temperature of molten droplets. An interfacial oxide layer composed of iron, aluminum and oxygen is ready to form at high PC. The number of pores intensively increases with PC, which leads to a decrease in the adhesive strength of splats. The amount of formed graphite in cast iron splats slightly increases with PC, however, that of a rapidly solidified phase of Fe-Si-C decreases because of lowering of the solidification rate.
Splat Morphology in Spray Pattern of Plasma Spraying
Authors: Oki S.
Published: June 2022

New method for characterization of coating microstructures and for evaluation of coating property by means of surface morphology has been proposed. In this paper, the distribution of shape and dimensions of splat was examined using quantitative analysis of scanning electron microscope images from the surface of spray pattern as well as the surface of coating. Results obtained in this study indicate that it is necessary to analyze the spray pattern as well as the surface morphology in order to estimate the coating property by means of the distribution of splat which composes the coating. Moreover, the splats, which are in the interface between the substrate and the coating, should have the same morphology as those of the coating surface. Therefore, the analysis of the surface morphology is important even for the evaluation of coating adhesion behavior.
Microstructure Simulation of Thermally Sprayed Particles
Authors: Wilden J. , Frank H. , Müller T.
Published: June 2022

A large expansion of the applicability of thermally sprayed coatings will be achieved, if there is success in tailoring the coatings structure. This is particularly necessary for functional coatings with special electrochemical or electromechanical properties. The coating structure is determined by the solidification of the sprayed particles on the substrate respectively the earlier deposited particles. In addition to the particle parameters - particle size, velocity, degree of melting and temperature of the melt, the substrate surface conditions - roughness, temperature, activity - influence the spreading and subsequently the solidification of the particles and the formation of the coating. Theoretical parameter studies show the particular influence of the above mentioned parameters on the coatings microstructure. The influence of the remelting of deposited particles caused by the following particles is regarded. The amount of remelted volume depends on the particle feed rate, particle size distribution, heat content and substrate temperature. By controlling these parameters even directionally solidified coatings can be produced. The calculations are in good agreement with the experiments.
Computer Simulation of Shrouding on the Profile of a Plasma Jet
Authors: Zhang T. , Liu B. , Bao Y. , Gawne D.T.
Published: June 2022

Jets produced in conventional atmospheric plasma spraying are inevitably heterogeneous due to the mechanics of a rapid gas flow entering a stagnant environment. The resulting high air content together with considerable velocity and temperature variations will adversely affect the quality of coatings. This paper applies a CFD code to simulate the effect of a solid shield and a gas shroud on the characteristics of a plasma jet. The computational results show that the geometry and gas flow rates of the shrouding systems have an important influence on the quality of the plasma flow. The work shows that shrouding can substantially reduce the entrained air content and the temperature and velocity gradients in the jet. The model is applied to predict the optimum shrouding conditions for plasma spraying.
Calculated and Measured Oxygen Contents in the Gas Flow of a Shrouded Thermal Spray Process
Authors: Jamais S. , Creaven M. , Rinaldi C.
Published: June 2022

Shrouding a thermal spray process to reduce the oxidation of particle stream is not a new concept. Nevertheless the actual use of this idea is not very widely used in practice, due to some problems arising. In this paper the results of the study performed to optimize two shrouding devices for thermal spray are presented. Gas flows inside the device and in between its outlet and the target were modeled by Computational Fluid Dynamics both for an arc-wire and a plasma system. To validate the modeling methodology measurements were performed of the oxygen content using a gas sampling probe and a paramagnetic O2 analyzer. A good agreement between calculated and measured O2 values was obtained. Modeling results in different conditions could suggest the best shroud configuration and shielding gas flows necessary to reduce the oxygen content around the particle stream at very low values. Coatings with very low defect contents can now be produced.
Modeling of the Natural Gas HVOF Process
Authors: Bolot R. , Planche M.P. , Coddet C.
Published: June 2022

A supersonic external flow and high particle velocities, which lead to low porosity coatings, characterize the High Velocity Oxygen Fuel (HVOF) process. A numerical study of this process is proposed in the present work. In a first step, the PHOENICS CFD code is used for the computation of the flow inside a CDS gun and within the supersonic external jet: a two-dimensional axisymmetric geometry is used. The combustion model assumes chemical equilibrium whereas the turbulence effect is taken into account using the Chen-Kim k-ε model, which is appropriate for the computation of round jets. In a second step, an in-house code is used in order to simulate the flow/particles interactions. Finally, numerical results obtained on in-flight particle characteristics are compared with measurements obtained with the DPV2000 system.
Computer Simulation and Control of Plasma Spraying Processes
Authors: Kundas S. , Ilyushenko A.
Published: June 2022

Integrated technological complex for computer simulation, experimental study and practical realization of plasma spraying processes was created. Main features of development are possibility of simulation of all plasma spraying stages (moving and heating particles in plasma jet, coating structure formation, heat transfer and strained-stress state of coating-substrate system) separately and in the mode of end-to-end; data base with material and gas properties; possibility of experimental measurement of main plasma spraying parameters and entering them in the computer in the real time mode; graphic visualization of simulation and experimental measurement results; computer control of plasma spaying equipment; fabrication of initial lots of products according to developed technology. Complex is designed on the base of VPS «Plasmatechnik» equipment. Experimental measurement of particle temperature, velocity and coating temperature were conducted with original optoelectronics system. All technological and measurement equipment are connected with computer with special interfaces and working under computer control.
3-D Modeling of Gas Flow and Particle Spray Jet in Plasma Spraying
Authors: Mariaux G. , Baudry C. , Vardelle A.M.
Published: June 2022

This paper presents a numerical simulation of the plasma spraying of alumina particles using a three-dimensional commercial fluid dynamics code ESTET 3.4 . The objective of this study is to investigate the effect of (i) turbulence model and turbulence radial profiles at the torch exit on plasma flow and particle behavior, (ii) particle injection conditions on particle trajectories and heating and (iii) plasma jet fluctuations on temperature and velocity flow fields. The comparison of predictions with experimental measurements of gas and particle velocity and temperature, makes it possible to determine the influential parameters and set them to pertinent values.
Mathematical Modeling of Deformation and Solidification of Molten Droplet on a Flat Substrate in a Plasma Spray Process
Authors: Ilyuschenko A. , Lakubenya A. , Gromyko G. , Zayats G.
Published: June 2022

In the present paper mathematical model of the deformation behavior of a liquid spherical particle upon its impingement onto a solid surface, including flattening and simultaneous solidification is developed. Particle-substrate interactions are investigated for typical thermal spray process. Numerical simulation for the complete Navier-Stokes equations is based on the finite-difference method on rectangular mesh in cylindrical coordinates. The energy equation is solved for both particle and substrate regions using the adjoint conditions for the temperature. In this paper main attention is paid to investigation of the temperature in contact of the particle with substrate. In connection with the oxide films effect on the surface substrate taking onto account thermal resistance of oxide is simulated. Heat transfer process in particle and substrate has been modeled by 2-D problem of heat conduction with influencing hydrodynamic processes into molten particle. Particle solidification and the movement of the solidification front have been described by means of one-dimensional Stefan problem. Numerical results for the heat transfer process and the effect of some important processing parameters such as particle diameter, viscosity, oxide films and temperature of plasma on the flattening and solidification of a single liquid particle have been discussed. Numerical algorithms were realized in the form of applied programs complex.
Microstructural Evaluation of Plasma Sprayed Coatings Using Fractal Characterization
Authors: Bianchi L. , Llorca-lsern N. , Bertran G.
Published: June 2022

Depending on working parameters, plasma spraying process allows to achieve original metallic and/or ceramic coating microstructures varying from quite dense to high porosity materials. Combined to the versatility of the process in terms of coating shaping, this leads to an extended field of applications. For instance, porous coatings are required for stress accommodation or filtering applications due to their high specific area, whereas dense coatings are needed for the electrolyte in S.O.F.C technology. Past works have shown that porosity is not a convenient parameter to describe completely coating microstructure and that the main difficulty is to find a unique parameter capable to describe the microcrack network and pores distribution. In this paper we propose a fractal approach of coating microstructure based on confocal microscopy of fluorescent impregnated coatings. Fractal dimensions as well as porosity data are given and analyzed for various plasma-spayed coating microstructures. This work is a contribution to characterize plasma-sprayed coatings. Coatings properties are related to the microstructure which depends on the spraying process.
Influence of Coating Thickness on Fatigue Properties of Sprayed Co-Based Self-Fluxing Alloy with Fusing Treatment
Authors: Oh J. , Shimizu M. , Komotori J.
Published: June 2022

Fatigue strength and fracture mechanism of a medium carbon steel having carbon content of 0.35%C with gas flame thermally sprayed Co-based alloy coatings were investigated by rotating bending tests. After fusing treatment, machining was done to make three kinds of specimens having 0.3mm, 0.5mm and 1.0mm in coating thickness. The fatigue strength of all coated specimens was much higher than that of the substrate and that of the grit blasted ones. Especially, it was found that the fatigue strength of the specimens with 1.0mm coating was remarkably higher compared to those with 0.3mm and 0.5mm coatings. That is, fatigue characteristics depend on coating thickness, and fatigue strength increases with the increase of coating thickness. The result showed that at lower stress levels, the fatigue cracks were initiated only inside the substrate of 0.3mm and 0.5mm coated specimens (Internal failure in the substrate). At higher stress levels the fatigue cracks were initiated at the coating layer, originated from the porosity located in coating layer of all coated specimens (Coated layer failure). But no fracture mode transition was noticed for the case of 1.0mm coated specimen. The cause of the fracture mode transition depending on the coating thickness was discussed on the basis of the results from calculation of the stress at the location where the fatigue fracture was initiated.
The Influence of the Process Parameters on the Properties of Detonation Sprayed WC-12Co Coatings
Authors: Sivakumar G. , Ramakrishna L. , Jain V. , Srinivasarao D. , Sundararajan G. , Reddy G.M.
Published: June 2022

In recent years, the thermal spray technique has emerged as the most useful method for developing a wide variety of coatings which enhance the performance and durability of engineering components exposed to diverse forms of wear. Among the thermal spray techniques, detonation spray coating (DSC) has retained its position as one of the best available techniques for obtaining dense, wear-resistant coatings. Notwithstanding the advantages of the DSC technology over other thermal spray variants, the understanding of the fundamental aspects of this technology is still extremely limited. In view of the above, a major programme has been undertaken in this laboratory to assess the parametric impact of the key DSC process variables (oxy-fuel ratio, spray distance, powder feed rate and shot frequency) on the mechanism of coating formation and the properties of the resulting coating. As a part of the above exercise, the key DSC process variables have been varied systematically employing a statistical design and the properties of the WC-12Co coatings so obtained have been evaluated. The results of such a study are presented in this paper. In particular, it has been demonstrated that useful conclusions regarding the influence of process parameters on the properties of the WC-12Co coating cannot be reached unless the scatter in the experimentally measured coating property data is also simultaneously taken into account.
Wear Resistance of HVOF-Sprayed Carbide Coatings
Authors: Rodríguez M.A. , Klisans J. , Bavaresco L. , Scagni A. , Arenas F.
Published: June 2022

The cermet materials have been developed to protect surfaces against wear and corrosion. In cutting tools technology as well as chromium replacement, WC coatings have been used to improve life and performance at higher temperatures. This work compares the abrasion and adhesion resistance of a WC-Co mixed in a x:y relation with a NiCrBSiW alloy deposited by High Velocity Oxy-Fuel (HVOF) process using a JP-5000 gun in two conditions: as sprayed and thermally treated. Abrasion and adhesion tests were performed according to ASTM G-65 and ASTM C-633 respectively. The microstructure and composition of the coatings, failure and worn surface were evaluated using Optical (OM) and Scanning Electron Microscopy (SEM) as well as X-Ray energy Dispersive Spectroscopy (EDX) and X-Ray diffraction (XRD). Vickers microhardness under a 500g load has been averaged from 8 indentations per sample. The results showed that the coatings studied presented a similar microhardness as well as good abrasion resistance. The best behavior of the post-heated coating could be attributed to a lower porosity, better distributions and effective cohesion between hard phases. Partial recrystallization of the amorphous phase produced during the thermal spray process into sub-carbides could be related to the improvement in abrasion resistance of the post-treated coating.
Ceramic and Metallurgical Composite Coatings With Advanced Tribological Properties Under Dry Sliding Conditions
Authors: Gadow R. , Scherer D.
Published: June 2022

In mechanical engineering there is an increasing demand for lightweight design and materials engineering from the view points of weight reduction, reduction of consumed energy and upgrading of performance. One major drawback of light metal alloys is their poor tribological properties concerning friction and wear under high surface loadings. This study focuses on the development of combined coatings on light metal substrates which show high wear resistance and low friction coefficients under dry sliding conditions. The combined coatings consist of a thermally sprayed ceramic or metallurgical primary coating to provide the wear resistance. Subsequently a coating with dry lubricating ability is deposited to achieve a low friction coefficient, either by application of a lubricant lacquer containing microscale solid lubricant particles (e.g. PTFE, MoS2), by cathode sputtering of MoS2 or by deposition of pure carbon containing coatings (a-C:H) by plasma assisted CVD.
Effect of WC Content on the Wear Resistance of Ni-Base Alloy Spray Fusing Overlays
Authors: Ding Z. , Zhao H. , Wang J.
Published: June 2022

This paper gives an account of pin-on-disc low stress abrasive wear and erosion wear tests on the specimens made by oxy-acetylene flame spray-fusing technology to explores the effect of WC content on the wear resistance of oxy-acetylene flame spray-fusing overlays. In the test, Ni60, NiWC25 and NiWC35 three kinds of various WC content Ni-base self-fluxing alloys were used as the typical wear resistance materials compared with 16Mn material and high Cr cast iron arc surfacing overlay. In pin-on-disc wear tests, SiC, Al2O3 and SiO2 different abrasive were used, and in erosion wear tests 30° and 90° erosion wear tests were performed. This paper also analyzed the wear mechanisms of spray-fusing overlays that possess different WC content by means of hardness tests and overlay's structure analysis. The results show that WC content influences the wear resistance of spray-fusing overlays greatly, but in various wear type and conditions, its effect's degree and tendency are quite different.
Study of Slide-Wear Resistance of Ultrasonic Arc Sprayed TiAl Alloy Coatings
Authors: Wang H. , Li P. , Guo Q. , Yang H.
Published: June 2022

By use of homemade arc spraying system patented, which could make melted metal droplets atomized fully and make its flying velocity achieve ultrasonic velocity, TiAl alloy coatings were manufactured on the aluminum alloy (LY12) substrate surface. The slide wear resistance of TiAl alloy coatings was investigated. The effect of spraying parameters, coatings' chemical composition and microstructure on the slide-wear resistance of coatings was examined. Then the slide-wear mechanism of the coatings was discussed. The results showed that the slide wear resistance of TiAl alloy coatings by ultrasonic arc sprayed is 17 times higher than it of the aluminum alloy (LY12) substrate under the condition of dry slide-wear.
Tribological Behaviour of Abradable Coatings Obtained by Atmospheric Plasma Spraying (APS)
Authors: Guilemany J.M. , Navarro J. , Lorenzana C. , Vizcaino S. , Miguel J.M.
Published: June 2022

Actually abradable coatings obtained by thermal spraying are currently used in aeronautical industry. They improve the turbines tightness increasing in that way, their yield. The most relevant property of this kind of coatings is its easy machinability. They have good friction properties due to the lubricant phases such as graphite or polyester and could be used for surface engineering. To optimizate abradable coating It is necessary to study the wear mechanics implied in tribological processes. In the Thermal Spray Center of the Universitat de Barcelona, AlSi-Polyester, AlSi-Graphite and Ni-Graphite coatings have been studied. Their tribological study includes Ball on Disk (BOD) test (according to ASTM G99-90) to determinate the coating friction coefficient. The wear mechanism is determined by the study of the wear track by means of scanning electron microscopy (SEM) and Scanning white light interferometry (SWLI). Main common wear parameters are reported and compared to the steel substrate.
Investigation of Composite Powders with a Carbide Phase for Plasma Spraying of Wear Resistant Coatings
Authors: Ilyuschenko A. , Shevtsov A.I. , Okovity V.A. , Steinhauser S.
Published: June 2022

Conducted are investigations of powders for plasma spray of wear resistant coatings. Studied are shape, relief and particle size of NiCr-Fe+50(80)%Cr3C2, NiCr-Fe+50(80)%SiC powders using scanning electron microscopy. Investigations is supplemented by the results of X-ray structural studies. Investigations serve to develop coatings with the improved oil trap capability, increased hardness and wear resistance, sprayed by a plasma jet. The developed coatings will be used to restore and strengthen machines components
Microstructure Characteristics and Corrosion Behaviour of HVOF Sprayed Metallic Coatings
Authors: Sturgeon A.J.
Published: June 2022

The application of HVOF spraying to deposit high quality coatings of corrosion resistant alloys for protecting an underlying steel substrate against corrosion in seawater has received much interest over the past few years. Despite the attainment of low levels of porosity and oxide, the coatings to not appear to offer the same level of corrosion resistance as the corresponding bulk materials. The aim of the work reported here is to demonstrate the level of corrosion performance that can be expected from coatings of corrosion resistant alloys deposited using the HVOF spraying process. Three alloy types are considered, a stainless steel with a composition similar to 316L, a nickel alloy with a composition similar to 625 alloy, and commercially pure titanium.
A Summary of Recent Developments of HVOF Sprayed Ceramic-Metallic Coatings for Corrosion and Wear Resistance
Authors: Berget J. , Rogne T.
Published: June 2022

In recent years Norwegian industries together with SINTEF and NTNU have run several projects dealing with development of thermally sprayed ceramic-metallic coatings for corrosion and wear applications. The mechanisms of erosion, corrosion and combined actions have been studied. The coatings studied are of the metal-carbide / metallic binder type sprayed by the High Velocity Oxygen Fuel (HVOF) process. The influence of powder properties like carbide particle size, powder grain size distribution, chemical composition (i.e. type of carbide and composition of the metallic binder) together with the influence of spray systems and parameters have been studied. The studies have demonstrated how optimization of powder and spray parameters improve corrosion and wear behavior of the coatings. Attention has also been paid to methods used for manufacturing powders for thermal spraying. This is very important from a corrosion point of view. The manufacturing methods should make sure that metallic binders are sufficiently alloyed to achieve the necessary corrosion resistance. The results from the work done in these projects are valuable for suppliers of thermal spray powders, spray companies and end users of coatings.
Arc Sprayed Ti-N Coatings for Protection Against Corrosion and Wear
Authors: Bach Fr.-W. , Babiak Z. , Tegeder G.
Published: June 2022

TiN reinforced Ti coatings were produced by using the arc spraying process. TiN hard phases were synthesized during spraying using Ar/N2 reactive atomizing gas. The spray process was realised in an air atmosphere with a shrouded gun and in a chamber with closed loop Ar/N2-gas atmosphere. The content of TiN phases in Ti-coatings was increased by rising the N2-amount in atomizing gas during spraying. Sprayed coatings obtained a graded hardness ranging from 450HV0.1 near the substrate up to 650HV0.1 near the top (mean values). TiN-particle precipitations exhibited micro hardness up to 1350HV0.1. Structure investigations of manufactured coatings proved that they consist of pure titanium, titanium nitrides and small amounts of titanium oxides. Wear resistance of the coatings, tested by Taber Abraser and Pin on Disc, decreases from the coating surface to the substrate. According to Kesternich test, Ti/TiN-arc sprayed coatings exhibit good corrosion resistance.
Extensive Characterization of Dense and Corrosion Resistant Coatings Produced by Improved Shrouded Techniques
Authors: Rinaldi C. , Ferravante L. , Uberti-Paci F. , Bianchi P.
Published: June 2022

In a BRITE-EURAM Project gas shroud devices were developed for arc-wire and air plasma spraying processes to obtain cost effective coatings with high density, low defect contents and high corrosion resistance. To test the two devices FeCrAl, NiCrAl and NiCrTi coatings sprayed by shrouded arc were studied for boiler application; AMDRY 995 coatings sprayed by shrouded plasma were analysed for gas turbine blades. In this paper the results are presented of the extensive characterization performed by CESI on the coatings produced with the innovative techniques developed by the other partners. The coatings were sectioned and analysed by metallography and image analysis to determine oxide and porosity contents (total defect levels were less than 5%). Hardness and adhesion were measured following the ASTM standard procedures. On FeCrAl, NiCrAl and NiCrTi coatings sprayed by shrouded arc-wire technique both thermal cycling and corrosion tests were performed. A sulphidizing gaseous atmosphere was used to simulate boiler environment burning sulphur rich fuel as Orimulsion. The corrosion behavior after 1000h at 450°C resulted to be as good as that of an HVOF sprayed similar coating. Moreover coated tubes survived to thermal cycling tests without any delamination. Hot corrosion "Dean tests" were performed on AMDRY995 coatings sprayed by shrouded plasma onto two Ni-base superalloys (Ud 529 and In738). The environment was typical of hot parts in gas turbines; the corrosion resistance results after 1750h at 850°C were comparable to those typically obtained on the same material sprayed by vacuum plasma spray technique. The applicability of the shrouded plasma technique to the field of gas turbines was confirmed.
Corrosion Properties of HVOF Sprayed and Nd-YAG Laser Remelted High-Chromium Nickel-Chromium Coatings
Authors: Tuominen J. , Vouristo P. , Mäntylä T. , Ahmaniemi S. , Vihinen J. , Andersson P.H.
Published: June 2022

Thermal spray processes are widely used to deposit high-chromium nickel-chromium coatings to improve high temperature oxidation and corrosion behaviour. However, in spite of the efforts made to improve the present spraying techniques, such as HVOF and plasma spraying, these coatings may still exhibit certain defects such as unmelted particles, oxide layers at splat boundaries, porosity and cracks, which are detrimental to corrosion performance in severe operation conditions. Due to low process temperature only mechanical bonding is obtained between the coating and substrate. Laser remelting of the sprayed coatings was studied in order to overcome the drawbacks of sprayed structures and to markedly improve the coating properties. The coating material was high-chromium nickel-chromium alloy, which contains small amounts of molybdenum and boron (53.3%Cr- 42.5%Ni - 2.5%Mo - 0.5%B). The coatings were prepared by high-velocity oxy-fuel spraying onto mild steel substrates. High power fiber coupled continuous wave Nd-YAG laser equipped with large beam optics was used to remelt the HVOF sprayed coating using different levels of scanning speed and beam width (10 mm and 20 mm). Coating remelted with the highest traverse speed tended to suffer cracking during rapid solidification inherent to laser processing. However, choosing appropriate laser parameters, non-porous, crack-free coatings with minimal dilution between coating and substrate were produced. Laser remelting resulted in the formation of dense oxide layer on top of the coatings and full homogenization of the sprayed structure. The coatings as-sprayed and after laser remelting were characterized by optical and electron microscopy (OPM, SEM). Dilution between coating and substrate was studied with EDS. The properties of the laser remelted coatings were directly compared with properties of as-sprayed HVOF coatings.
Non Destructive Testing for the Estimation of the Adhesion of Plasma Sprayed Coatings
Authors: Costil S. , Coddet C. , Rosa G. , Psyllaki P. , Oltra R.
Published: June 2022

In this study, a new laser based technique was evaluated for the characterization of plasma-sprayed oxide coatings. It uses the contactless laser generation and detection of ultrasonic waves in the bi-layered systems. For this purpose, a nanosecond pulsed Nd:YAG laser (λ : 1064 nm, τ =14 ns) was used for irradiating the ceramic coating, whilst the longitudinal displacements of the rear surface of the metallic substrate were detected at the epicenter using a laser heterodyne interferometer. The acoustic signal recorded at the rear surface of the substrate was found to be characteristic of the different events taking place within the irradiated system. In this way, the longitudinal wave velocity, the porosity, as well as the Young's modulus of the coatings can be easily determined, whilst the coating/ substrate adhesion strength can be calculated, taking into account both the thermal, as well as the acoustic effects of the laser radiation. The proposed technique was applied to alumina coatings deposited onto stainless steel coupons by Atmospheric Plasma Spraying and the results were found to be in accordance with those obtained by the techniques commonly used for testing thermal spray coatings (interfacial indentation test, porosity measurement, etc.).
Properties of Thermal Sprayed Coatings Characterized by Lock-in Thermography
Authors: Wielage B. , Hofmann U.
Published: June 2022

The control of the coating quality becomes more and more important. Infrared methods are well introduced in industry for several types of inspections. The lock-in thermography is based on modulated heat flux and is proved for composite materials and electronic components. In combination with an IR-camera seems to meet the requirements of a modem quality control system. The off-line measurement takes about 3 up to 5 minutes depending on the geometry of the surface. The paper gives an overview on the principle, the technical details of the measurement and the correlation of the detected signals and the coating properties will be discussed. The accuracy concerning the thickness is determined for different coatings (e.g. WC-Co).
Quality Assurance for Thermal Spraying by Implementation of New QM Standards and Regulations for Personnel Qualification
Authors: Böhme D.G.F. , Huber R.
Published: June 2022

Quality management (QM) standards, used as a support to safeguard product quality, show the way to implement a quality management system and/or to adapt and revise an already existing QM system. This article describes the quality requirements for thermal spraying companies and qualification requirements for spraying personnel. In addition, it provides the guidelines for the education and examination of spray personnel.
Integrated Thermal Spray Systems—Some Practical Considerations
Authors: Tucker R.C.
Published: June 2022

Industrial demands for higher quality, yet lower cost thermal spray coatings have driven the development of highly automated and fully integrated thermal spray systems. These systems include computer control of the powder, gas, electrical power, and cooling fed to the spray device, auxiliary cooling of the part, and motion of the part spray device. The subsystems may include closed-loop control of particular parameters such as the powder feed rate. More fundamental closed-loop or "intelligent" processing systems are under development. A key element in such systems is the ability to sense critical parameters that are indicative of the coating's properties in such a manner that changes in the process can be made to maintain its properties while the coating is being deposited. For example, it is widely recognized that the temperature, velocity, and size distribution of the powder particles during flight are largely responsible for the properties of the resultant coating. A variety of sensor systems have been developed recently that can measure one or more of these properties. At least one such system is capable of measuring all three parameters for the full cross section of the spray. Computer controls, closed loop systems, and intelligent processing cannot compensate for poorly designed, manufactured, or maintained equipment. Nor can they compensate for unsatisfactory preparation of the surface, feedstock (powder, gas, power), finishing equipment or materials, or training of operators. Sufficient attention to all of these factors may even make the investment in some more sophisticated systems questionable for some applications. This paper will attempt to provide an overview of the currently available highly automated and integrated thermal spray systems used for intelligent processing and consider some criteria for its selection and use.
New Developments in Thermal Spray Gas Supply Systems
Authors: Cole M. , Gabzdyl J.
Published: June 2022

An important aspect in the successful commercialisation of thermal spray processing is a safe and cost efficient gas supply system. As coating techniques such as High Velocity Oxygen Fuel spraying, (HVOF) High Pressure Plasma spraying (HPPS), High Pressure High Velocity Oxygen Fuel kerosene based systems (HPHVOF) and the recent developments in Cold Gas Dynamic spraying become more prominent, so the requirements on existing standard gas delivery systems designed for less demanding applications such as flame and plasma spraying need to be up-rated and improved. This work highlights recent developments in gas safety supply equipment dedicated to the thermal spray sector, the use of gas detectors in thermal spray workshops, more cost efficient gas delivery systems for fuel gases such as hydrogen, LPG propane, propylene and acetylene, and also covers improvements in gas delivery systems for the process gases such as oxygen, nitrogen and argon. The paper looks at various gas supply options, comparing compressed gas cylinders, liquid gas cylinders and bulk liquid supply vessels outlining the benefits and limitations of each systems in relation to the individual spray techniques. The higher pressures and flow rate associated with the growth of kerosene based fuel guns has resulted in an increased demand on the conventional compressed oxygen supply systems making them less cost effective and unworkable in a production environment. The paper covers new liquid oxygen supply cylinders and novel bulk tank systems that reduce cylinder holdings while reducing gas wastage due to lack of pressure. With the increase in higher thermal energy systems, necessity to more closely control the temperature of sprayed the component has outstretched the demands on conventional compressed air cooling systems. In the past, the use of cryogenic cooling gases such as carbon dioxide has been restricted by increased cost. However it has been shown in a number of cases that often the hidden costs of running air compressors, including the use of moisture traps, and oil filters can be greater than using clean, high purity cryogenic liquid gases such as carbon dioxide and nitrogen. The paper outlines the details of such cooling systems. The commercial success of Cold Gas Dynamic spraying may in future rely on a cost efficient, high pressure and high volume gas delivery systems for either helium or nitrogen. The paper describes a novel high pressure supply system presently used in another application suitable for Cold Gas Dynamic spraying with nitrogen able to generate pressure in-excess of 30 bar and flow rates above 120m3/hr from a liquid vessel.
What Influence Does the Purity of Industrial Gases Have on the Quality of Thermal Spraying?
Authors: Krömmer W. , Heinrich P.
Published: June 2022

Being able to offer a consistently high level of spray coatings on a global scale has become more and more the trend in thermal spraying. For this reason it is extremely important that auxiliary materials such as industrial gases or spray materials of a high quality are provided world-wide. In connection with their respective applications, industrial gases must always be available at a specified purity level. In order to ensure such a purity, industrial gas producers invest a great deal of time and energy in analysis and supply concepts which guarantee this purity from the tank or cylinder through to the transfer point. This paper will provide an overview of state-of-the-art supply and purity concepts, as seen by the gas industry, and the influence of fluctuating gas quality. Examples will also be given for the differing gas qualities in individual countries.
Plasma Spray: The Job Shop Perspective
Authors: Bhusari M.
Published: June 2022

The plasma spray process is one of the oldest and most useful thermal spray processes used in industry today. The principles of plasma spray are complex. The many factors that affect plasma spray make understanding and manipulating the process a difficult task. Although it is impossible to isolate each of those factors, the understanding of the way they affect the quality of the coating can help the sprayer make an improved judgement for coating development and application. This paper is an attempt to identify the various factors, including plasma spray equipment configurations, plasma gases, feedstock and manipulation, and discuss their effect on a particular plasma spray coating application from a job shop perspective. Also, plasma spray coating applications are discussed.
SHS Powder Materials for Protective Coatings in Power Industry
Authors: Ilyuschenko A. , Vitiaz P. , Beijaev A. , Talako T.
Published: June 2022

This article investigates composite powder materials based on double chromium and titanium carbides with nickel-chromium binder produced using self-propagating high-temperature synthesis. It focuses on the hypersonic velocity oxygen fuel coatings from the synthesized powders. Laboratory tests were focused on the solid particle erosion which occur in energy production systems such as fluidized bed combustors, advanced pulverized cool boilers, and entrained coal gasifiers. Tests were conducted at elevated temperature in a blast nozzle type of tester using bed or fly ashes retrieved from the operating CFB boilers. It was observed that, when adjusting carbide phase composition and chromium content in titanium carbide solid solution, one can control the oxidation kinetic and wear resistance of the material. Fine-grained structure and high cohesion strength of the composite materials formed during synthesis provide their excellent elevated temperature erosion performance in a wide range of test conditions.
PROTAL Processing of Titanium Alloys as an Alternative to Degreasing and Grit-Blasting Prior to Thermal Spraying
Authors: Coddet C. , Montavon G. , Verdier M. , Costil S. , Barbezat G.
Published: June 2022

Titanium alloys exhibit high specific strength characteristics. They are for this reason widely used by aeronautical engineers mostly to design airframes and gas turbine components. Very often, surface treatments are applied to locally increase the surface properties, especially to obtain a better resistance against wear. Thermal spraying is largely used to manufacture these coatings. This technology requires a specific surface preparation prior to the spraying stage. This surface preparation conventionally consists in surface degreasing and grit-blasting which has some drawbacks, among them a significant decrease of the components fatigue resistance due to the notch-sensitive behavior of these alloys. The PROTAL process consists in combining surface cleaning based on laser ablation to the deposition stage thus avoiding grit-blasting. This paper aims to present an overview of the possibilities offered by this process for the coating of titanium alloys; the criticality of the different processing parameters is studied and discussed.
What is Scanning Probe Microscopy, and How Can it be Used in Failure Analysis?
Authors: Tangyunyong Paiboon , Campbell Ann
Published: June 2022

Scanning probe microscopy (SPM) refers to a suite of techniques that measure the interaction between a fine probe or tip and a sample in contact or close proximity. These interaction measurements allow the study of properties such as topology, magnetic and electric fields, capacitance, temperature, work function, and friction. The information obtained from SPM plays an important role in IC failure analysis.
Case History: Passive Voltage Contrast Technique for In-Line Characterization and Failure Isolation During Development of Deep-Submicron ASIC CMOS
Authors: Liang Victor , Sur Harlan , Bothra Subhas
Published: June 2022

Passive voltage contrast (PVC) has traditionally been used by semiconductor engineers for end-of-line post-mortem analysis. PVC distinguishes between open and short structures and is both nondestructive and noncontact. When applied during process development for in-line characterization, it allows wafers to be examined at multiple points, where electrical probing might not be feasible. This provides feedback on the cumulative effect of the process on critical parameters such as oxide integrity and can reduce development cycle times because wafers do not have to be deprocessed in order to determine the exact location of failures. Two case studies are presented in this article, demonstrating the use of PVC in a process development environment.
SEM for General Purpose Failure Analysis: "Little Used but Very Useful"
Authors: Devaney John R.
Published: June 2022

Scanning electron microscopes can be used to analyze almost anything that conducts electricity and is prone to failure, including relays, coils, inductors, capacitors, resistors, transistors, diodes, IGBTS, MOSFETS, and hybrid circuits. As the author of the article explains, SEMs are one of the most versatile tools for failure analysis if used to the full extent of their capabilities. Their operating modes include emissive imaging, backscattering, voltage contrast, EBIC or specimen current, and conductivity resistive mapping. The author describes each operating mode and presents examples of the various ways they can be used.
DUV Microscopy for Wafer and Mask Inspection and Metrology
Authors: Vollrath Wolfgang
Published: June 2022

This article provides an overview of deep ultraviolet (DUV) microscopy, the factors that led to its development, and the types of applications for which it is suited in semiconductor device manufacturing, testing, and inspection. It also includes several images demonstrating it capabilities relative to visible light microscopy.
MEMS Failure Analysis Engineer’s Toolbox (Part 1)
Authors: Walraven Jeremy A. , Peterson Kenneth A.
Published: June 2022

Experiments to assess microelectromechanical systems (MEMS) test their functionality and materials properties. These experiments provide knowledge and insight into MEMS failure modes and potential pathways to improve the lifetime of MEMS devices. This article demonstrates the use of optical microscopy and SEM analysis to determine various causes of failure in MEMS devices.
Laser Voltage Probe (LVP): A Novel Optical Probing Technology for Flip-Chip Packaged Microprocessors
Authors: Yee Wai Mun , Paniccia Mario , Eiles Travis , Rao Valluri
Published: June 2022

Laser voltage probing (LVP), an IR-based technique, facilitates through-silicon signal waveform acquisition and high frequency timing measurements from active p-n junctions on CMOS ICs. The ICs can be in flip-chip as well as wire-bond packages with backside access to the IC. As the article explains, LVP significantly improves silicon debug and failure analysis throughput time compared to electron-beam probing because it eliminates the need for backside trenching and probe-hole generating operations.
Backside Analysis: Anti-Reflection Coatings Increase Performance of Failure Analysis Tools
Authors: Nall Jonathan
Published: June 2022

This article explains how antireflection (AR) coatings can improve the results of IR-laser probing when debugging flip-chip ICs from the backside. It discusses the optical physics involved as well as surface preparation requirements.