bluuebunny/crossref_metadata_2025 huggingface dataset:
Adapting to Involuntary, Radical, and Socially Undesirable Career Changes
Authors: Rudolph Cort , Zacher Hannes
Published: May 2021

Career adaptability is a psychosocial resource that aids in coping with current and anticipated tasks, transitions, and traumas that people experience in their occupational roles. Although there is a great deal of evidence that career adaptability relates to important career outcomes, the role that it is perceived to play in involuntary, radical, and socially undesirable career changes is understudied. Grounded in career construction theory, we conducted a study with an experimental vignette methodology to ascertain whether career adaptability moderates the influence of different types of career transitions on ratings of hypothetical employees adapting effectiveness. Findings suggest that career adaptability can be seen as an important resource for managing radical career changes. This is one of the first papers to test a key tenet of career construction theory—that career adaptability is efficient for managing career related transitions and traumas. Moreover, we extend the scope of this tenet to include the notion that people can readily identify qualities of career adaptability in others.
Racism, Posttraumatic Stress Symptoms, and Racial Disparity in the U.S. COVID-19 Syndemic
Authors: Zhou Xiang , Nguyen-Feng Viann N , Wamser-Nanney Rachel , Lotzin Annett
Published: May 2021

The COVID-19 syndemic, with a disproportionately higher adverse impact on communities of color (i.e., COVID-19 infection and death), will likely exacerbate the existing health disparities in trauma-related symptoms between people of color (POC) and White Americans. However, no studies have examined the racial disparities in posttraumatic stress symptoms (PTSS) during COVID-19. Grounded in ecological theory and racial trauma framework, we investigated rates of racial disparities in PTSS and three possible mechanisms, 1) COVID stress, 2) direct racism, and 3) indirect racism, for these discrepancies using a large U.S. national sample (N = 2,019). Results indicated that POC reported higher levels of PTSS than White Americans (d =.21). The PTSS racial disparity was accounted more by direct and indirect racism than by the COVID-19-specific stressors, after controlling for age, gender, education, income, parent status, adverse childhood experiences (ACEs), and intimate partner violence (IPV). Additional fine-grained analyses for Hispanic/Latinx Americans (n = 283), Black/African Americans (n = 279), and Asian American and Pacific Islanders (n = 123) by and large corroborated the above findings. Our findings highlighted the deleterious impact of the ongoing racism pandemic on the POC community as a public health crisis in addition to the COVID-19 pandemic.
Chasing the Tail: A Generalized Pareto Distribution Approach to Estimating Wealth Inequality
Authors: Kennickell Arthur B.
Published: May 2021

Since the work reported in Vermeulen [2018], a literature has developed on using the simple Pareto distribution along with “rich list” information to make improved estimates of the upper tail of the wealth distribution measured in surveys. Because the construction of such external data is typically opaque and subject to potentially serious measurement error, it may be best not to depend exclusively on this approach. This paper develops an alternative approach, using the generalized Pareto distribution (GPD), of which the simple Pareto is a subset, extending an estimation strategy developed by Castillo and Hadi [1997]. The greater flexibility of the GPD allows the possibility of modeling the tail of the wealth distribution, using a larger set of data for support than is typically the case with the simple Pareto. Moreover, the elaboration of the estimation method presented here allows explicitly for the possibility that the extreme of the observed upper tail is measured with error or that it is not captured at all. The approach also allows the incorporation of external data on total wealth as a constraint on the estimation. For the applications considered here using Austrian and U.S. micro data, the model relies on an estimate of total household wealth from national accounts, rather than rich-list information. The results suggest that where sufficiently comparable and reliable estimates of aggregate wealth are available, this approach can provide a useful way of mitigating problems in comparing distributional estimates across surveys that differ meaningfully in their effective coverage of the upper tail of the wealth distribution. The approach may be particularly useful in the construction of distributional national accounts. (Stone Center on Socio-Economic Inequality Working Paper)
Re-Conceptualizing Inclusive Pedagogy in Practice in Higher Education
Authors: Livingston-Galloway Marcia , Robinson-Neal Andree
Published: May 2021

Twenty-first-century classrooms are becoming increasingly culturally, ethnically, and racially diverse and are looking more and more like microcosms. Consequently, students and some educational stakeholders are demanding the inclusion of race, culture, justice, and equality in the curricula and pushing the envelope for more inclusive pedagogy. Central to the concept of inclusive pedagogy are the values of fairness and equity. Proponents of inclusive pedagogy have indicated that numerous variables influence pedagogy, particularly inclusive pedagogy. These values have elicited concerns throughout the educational system regarding how instructors and facilitators serve all learners academic needs in their academies. However, there is no consensus on what constitutes inclusive pedagogy in higher education (HE) or if inclusive pedagogy even exists in that space. Therefore, educational institution leaders need to re-conceptualize their thoughts on inclusive pedagogy. This paper reviews some of the existing literature applicable to inclusive education and inclusive pedagogy. It proposes inclusive pedagogy dimensions that instructors in HE need to consider to effectively implement inclusive pedagogy practice (IPP) in the classroom. It concludes with a conceptual framework for inclusive pedagogy in practice (IPIP) in HE and suggestions of how administrators, faculty members, and course designers can advance the IPIP framework across their campuses.
The Ephesians 4:15 Rule: A Socratic Approach to Political Correctness
Authors: Azarvan Amir
Published: May 2021

In the Apostle Paul’s words, we should “[speak] the truth in love” (Eph. 4:15). Many of us are good at doing one (i.e., speaking the truth) or the other (i.e., speaking in love). But few of us excel at doing both at the same time. I argue that this “Ephesians 4:15 Rule” is relevant to the many contemporary political debates that revolve around the concept of political correctness and push us into joining one or the other extreme ideological camp. In this essay, I lay out my Socratic approach to explaining to students what I take to be the proper approach to this somewhat elusive concept.
Urbanizaciones y espacios públicos en Lima: San Isidro, Chorrillos y Miramar. 1919-1930
Authors: Quispe Fredy
Published: May 2021

La ciudad de Lima tuvo un acelerado desarrollo urbano durante el Oncenio de Leguía (1919-1930). El área urbana se duplicó y el triángulo conformado entre Lima, Callao y Chorrillos se empezó a ocupar. Las avenidas Leguía, El Progreso y Costanera consolidaron el desarrollo urbano y se proyectaron más de treinta urbanizaciones. San Isidro, Chorrillos y Miramar se construyeron en este periodo y estuvieron orientadas a distintos niveles socioeconómicos. La urbanización San Isidro se encuentra rodeando el bosque del Olivar, la urbanización Chorrillos tiene como referente al morro solar y la urbanización Miramar se presenta frente al océano Pacífico Sur. Las urbanizaciones desarrolladas durante este periodo no proyectaban nuevas áreas destinadas a espacios públicos ni áreas verdes y pueden explicar, en parte, la actual ausencia de plazas, parques, zonas recreación y espacios de afirmación ciudadana que adolece la capital.
Thermal Spraying of High Performance Thermoplastics
Authors: Lugscheider E. , Herbst C. , Fischer A.
Published: May 2021

Thermally sprayed coatings of high performance thermoplastics are of interest especially for the chemical industry for anti-corrosion applications at elevated temperatures. In this paper coatings of polyetherether-keton (PEEK) and polyphenylen-sulphide (PPS) have been produced by simple flamespraying. They have been investigated by optical metallography, FT-IR analysis and DSC-analysis. Among the coating properties also the "in-flight" particles have been studied by wipe-tests and FT-IR analysis in order to assess possible decomposition effects during spraying.
Resistance of Thermal Sprayed Duplex Coating Composed of Al and Ni-Cr Alloy Against Aqueous Corrosion
Authors: Ishikawa K. , Suzuki T. , Tobe S. , Kitamura Y.
Published: May 2021

The development of corrosion resistant sprayed coating without sealing is required to increase reliability of the thermal spray coating method and to expand the field of application for the wet corrosion environments. The conventional wire flame sprayed Al coating on the steel substrate without sealing has poor resistance against aqueous corrosion, so as to be restricted in use in practical fields. A duplex coating composed of sprayed Al on a 80Ni-20Cr alloy undercoat was proven to have sufficient resistance in a hot, near neutral aqueous environment through a trial use in a vegetable oil process. In this paper, mechanism of the corrosion resistance of the duplex coating is clarified by electrochemical measurements of the corrosion potential and the anodic polarization characteristics.
A Study of Oxidation Behaviour of WC-Co, Cr3C2-NiCr And TiC-Ni-Based Materials in Thermal Spray Processes
Authors: Berger L.-M. , Vuoristo P. , Mantyla T. , Gruner W.
Published: May 2021

In this paper the oxidation behaviour of WC, Cr3C2, and TiC and their composites with binder metals is compared on the basis of literature data and some oxidation experiments. It was found that the oxidation mechanisms in air, which are more or less equal to service conditions of coatings, seem to be totally different from those in the spray process in the case of WC, but similar in the case of TiC and Cr3C2. Oxide layer scale adhesion strengths and, possibly, the high volatility of WO3 seem to be responsible for this difference. It can also be assumed, that the problem of oxidation of TiC-based materials and Cr3C2-NiCr is that of local oxidation on the surface of the spray powder particles during the spray process. Cr3C2-NiCr and TiC-based materials are characterized by a high oxidation resistance in air. Plain WC-Co oxidizes readily in the temperature range 400-600°C, but alloying with Cr, as for instance in WC-CoCr and WC-(W,Cr)2-Ni spray powders increases the oxidation resistance.
Assessment of HVOF Coatings for Wet Corrosion Protection
Authors: Dvorak M. , Heimgartner P.
Published: May 2021

Until now the use of thermal sprayed metallic coatings for wet corrosion protection is limited to applications where the coating (Al-alloys, Zn-alloys and their mixtures) acts as an anode to protect the substrate or special cases, where thick cold sprayed metallic layers give good results. Other atmospheric cold sprayed layers made of corrosion resistant Ni, Co, Cu or Fe base alloys have their limitations due to the process related discontinuities like pores and oxide films. In more aggressive environments thermal sprayed and fused layers made of so called self-fluxing Ni and Co based alloys are commonly applied. Also in some applications the use of specially designed gas shrouds or of spraying techniques running in inert gas atmospheres or vacuum can yield protective coating solutions. However, these techniques have high investment or service costs or the size of the parts to be coated is restricted. Recent developments in HVOF-spraying open new possibilities in applying cold sprayed coatings on site with good corrosion resistance. The aim of this paper is on one hand to give a comparative overview about the wet corrosion behaviour of thermally sprayed metallic coatings using different spraying techniques related to the performance of the corresponding bulk materials and on the other hand to demonstrate the potential of a new generation of coatings to protect or repair structures exposed to aggressive environments. Keywords: corrosion behavior, thermal sprayed metallic coatings, cermet coatings HVOF, HVIF, PTAW.
Microstructure and Wear-Resistance of Fe-Cr-B Alloy Coatings Fabricated by Detonation Gun
Authors: Jin H.-W. , Park C.G. , Kim M.C.
Published: May 2021

Amorphization induced by sliding wear and consequent wear resistance have been investigated in relation with the microstructure of Fe-Cr-B alloy spray coatings. The Fe-Cr-B spray coated layer exhibited much higher wear resistance and significantly lower friction coefficient in comparison with that of low carbon steel substrate thanks to the amorphous surface film formed during the dry sliding wear. Electron microscopy on the cross-section of the coated layer exhibited intra-particle segregation associated with rod-shape Cr rich (Cr,Fe)xB particles in the matrix of Fe-Cr solid solution phase. From the observations using TEM and EDS, Fe-Cr solid solution phase with super-saturated B and Si content was confirmed to be the phase which mainly contribute to the crystalline-to-amorphous transition induced by sliding wear. The formation of oxide inclusions seems to impede the crystalline-to-amorphous transition by lowering the solute content in Fe-Cr solid solution phase. Keywords : microstructure, wear-resistance, Fe-Cr-B alloy, amorphization, detonation gun
Influence of Surface Microstructure of Ceramic Coatings on the Initiation and Development of Scuffing Phenomena
Authors: Antoszewski B. , Zorawski W.
Published: May 2021

This paper presents the results of a study on the scuffing behavior of thermally sprayed ceramic coatings. The progress of building up of seizure is related and evaluated for a set of ceramic coatings embodying a diversity of granulations of Al2O3TiO2 and Cr2O3 plasma sprayed on steel, the IHI8N9T steel and carbon-graphite when tested on a roller-block machine. The greatest antiscuffing resistance was recorded for Cr2O3/carbon-graphite pair. An analysis of regression approximating friction force was carried through.
Wear Behaviour of HVOF and HVAF Sprayed WC-Cermet Coatings
Authors: Jacobs L. , Hyland M. , De Bonte Μ.
Published: May 2021

The tribological behaviour of WC-Co-Cr coatings deposited by HVOF and HVAF and WC-Co coating deposited by HVAF was investigated in pin-on-disc tests. Wear rates were determined and wear tracks on the coatings and counterbodies were investigated in SEM. The HVAF sprayed coatings showed greater wear resistance compared to the HVOF coatings. The main wear mechanism in the WC-Co coatings was adhesive wear. The cobalt matrix is lubricious, resulting in very low wear rates and low debris generation. The main wear mechanisms in the WC-Co-Cr coatings were adhesive and abrasive wear. Adhesive wear results in pull-outs that are trapped in the contact zone and act as a third-body abrasive. Particle pull-out of the coating significantly increases the wear rate of the coated specimen. The HVAF WC-Co-Cr coatings proved to have a better resistance to particle pull-out which reflected in a considerably lower wear rate than the HVOF WC-Co-Cr coatings.
The Structure Property Relationship of Erosion Resistant Thermal Spray Coatings
Authors: Tucker R.C. , Ashari A.A.
Published: May 2021

Thermal spray coatings are widely used for erosion resistance, but the relationship between the microstructure of the coatings and their erosion resistance is not well understood. In this paper the performance of several commonly used coatings at ambient and elevated temperatures is reviewed in light of the coatings' structure and compared with a new coating. Two high temperature industrial applications, solid particle erosion in steam turbines and alumina-based erosion have been chosen to illustrate the significance of a coating's structure on its performance.
Effect of Powder Type on the Relationship between Spray Parameters and Properties of HVOF Sprayed Cr3C2-NiCr Coatings
Authors: Li C.J. , Ji G.-C. , Wang Y.-Y. , Sonoya K.
Published: May 2021

The effects of powder types and HVOF spray systems used to produce Cr3C2-NiCr coating on the relationships between spray parameters and wear performance were investigated based on the effect of fuel gas conditions on abrasive wear and erosion wear. The relationships between spray parameters and wear properties were obtained by orthogonal regression experimental design method. Four types of powders and two HVOF spray systems were used. It is found that with the increase in fuel gas flow or pressure the abrasive wear and erosion of Cr3C2-NiCr coatings change following a concave curve. The Cr3C2-NiCr coating with the best wear performance will be deposited under intermediate fuel gas condition. It is experimentally confirmed that by different types of powders and HVOF systems applicable to HVOF spraying of Cr3C2-NiCr coating, although the optimized fuel gas conditions to deposit coating with the best wear performance will be influenced by types of starting powders.
Effects of Powder Composition on the Erosion, Corrosion and Erosion-Corrosion Properties of HVOF Sprayed WC Based Coatings
Authors: Berget J. , Bardal E. , Rogne T.
Published: May 2021

Different WC-based coatings have been sprayed by the HVOF process and characterised by different methods. The influence of different powder characteristics on the wear and corrosion performance was investigated. Powder characteristics investigated include: i) average WC particle size, ii) matrix composition and iii) powder grain size distribution. The results show that the coating properties are affected by the different powder characteristics. Small WC particles were found to be beneficial as regards the erosion and erosion-corrosion resistance. An increase of the Cr and Mo content increased the corrosion and erosion-corrosion resistance. Powders with narrow grain size distributions gave coatings of higher quality than powders with wider grain size distributions.
Optical Diagnostics and Modeling of Gas and Droplet Flow in Wire Arc Spraying
Authors: Kelkar M. , Hussary N. , Schein J. , Heberlein J.
Published: May 2021

There is widespread industrial interest in wire arc spraying as it has proven to be a relatively inexpensive alternative providing high quality coatings in many applications. Modeling and experimental studies have been conducted with different nozzle geometries to study the influence of fluid dynamics on the behavior of the particles which form the coating. Schlieren optical diagnostics and image analysis are used to study flow patterns obtained with different nozzle geometries. Supplementary measurements are made with static and total pressure probes. A particle breakup model is used to predict the trajectory and breakup of molten particles in the jet. This investigation indicates that nozzle designs that minimize or eliminate shock formation before the atomizing gas reaches the wire tips result in lower coating porosity and a more uniform particle size distribution.
3D Modelling of Thermal Spray Droplet Splashing
Authors: Bussmann M. , Aziz S.D. , Chandra S. , Mostaghimi J.
Published: May 2021

Various models exist of the 2D impact of a molten thermal spray particle onto a flat solid surface. Such models, however, cannot be used to examine 3D effects such as the asymmetric splashing and breakup which are common under thermal spray conditions. The focus of the present work is on such effects. A 3D model of droplet impact has been developed which predicts splashing and the subsequent formation of small satellite droplets. The model is a 3D version of RIPPLE (LA12007- MS), an Eulerian fixed-grid finite volume code utilizing a volume tracking algorithm to track the droplet free surface. Simulations are presented of the impact and splashing of a molten tin droplet, and the results compared with photographs. A simple model, based on Rayleigh-Taylor instability theory, yields an estimate of the number of satellite droplets which form during impact. Finally, a simulation of droplet impact under thermal spray conditions demonstrates breakup, although in the form of a corona which separates from the bulk of the fluid.
Mathematical Modeling of a Plasma Jet Impinging on a Flat Structure
Authors: Bolot R. , Coddet C. , Imbert M. , Monin V.
Published: May 2021

A mathematical model of the impingement of a plasma jet on a flat structure is proposed. This model can be used to predict temperature and velocity fields in the jet and in the near substrate region, but also to estimate thermal exchanges at the surface of this substrate. Different options were tested concerning the modeling of the near wall region and results indicate that a boundary layer calculation is necessary to predict the energy flux transferred to the substrate with a good accuracy. Nevertheless, the influence of the presence of the substrate on temperature and velocity fields was found to be important only in the near substrate region, indicating that the flow fields calculated from free jet modeling are accurate over the major part of the domain.
The Effect of Substrate Preheating and Surface Organic Covering on Splat Formation
Authors: Li C.J. , Li J.-L. , Wang W.-B.
Published: May 2021

The splashing usually occurs when a droplet impact on a substrate surface during thermal spraying, which results in the formation of splat with irregularly complicated morphology. In present study splats are formed on polished stainless steel substrate surface covered with different organic substances with different boiling points by plasma spraying under different preheating temperature of substrate in order to clarify the factors which control the splashing during droplet flattening in thermal spray process. The droplet materials used are aluminum, nickel, copper, Al2O3 and molybdenum. Three kinds of organic substances used are xylene, glycol and glycerol which are brushed on the surface of substrate before spraying. It is found that when the preheating temperature exceeds 50°C over the boiling point of organic substance brushed on substrate surface the regular disk type splats are formed in the case that no substrate melting occurs by molten droplet. When the flattening of droplet causes the melting of substrate such as the combination of Mo droplet with stainless steel substrate, the preheating of substrate has no influence on splat morphology. The evaporated gas induced splashing and substrate surface melting induced splashing models are proposed to interpret the formation of the annulus-ringed splat.
Comparison of the Behaviour of Copper, Cast Iron and Aluminum Alloy Substrates Heated by a Plasma Transferred Arc
Authors: Leylavergne M. , Valetoux H. , Coudert J.F. , Fauchais P. , Leroux V.
Published: May 2021

PTA (Plasma Transferred Arc) reclamation of aluminum alloys by hard materials with a much higher melting temperature is very difficult. This is due to the high thermal diffusivity of these al1oys. Below a critical heat flux φc nothing happens and over φc the substrate melts very rapidly contrarily to what is observed with steel substrates. That explains probably why PTA is mainly used for steel reclamation. Thus the knowledge of heat flux transferred to the anode is a critical point to develop PTA reclamation on aluminum alloys and this is the aim of this paper. An experimental set-up was built to study the heat transferred to three substrates made of different materials : cast iron for reference, aluminum alloy and copper for its high thermal conductivity. The plasma torch was a Castolin Eutectic gun and allowed to inject a sheath gas around the plasma column. The copper, aluminum alloy and cast iron substrates, easily interchangeable, were the top of a water-cooled calorimeter allowing to determine the variation of the received heat flux with the working parameters : arc current, stand off distance, plasma forming gas momentum, sheath gas composition and momentum. The determination of the arc electric field allowed to calculate the arc diameter which was compared first with pictures taken with a video camera and second, with wear traces left on the anode material. Several correlations have been established to characterize the arc voltage and the anode heat flux.
Droplet Flattening During Thermal Spraying at Off-Normal Angles
Authors: Sobolev V.V. , Guilemany J.M.
Published: May 2021

Analytical correlations between the flattening characteristics and the Reynolds number and the spraying angle are obtained. The final splat thickness is shown to decrease and the final splat radius is found to vary nonuniformly with a decrease in the spraying angle. Analytical formulae are obtained describing the pressure distribution in a flattening droplet along the droplet-substrate interface during thermal spraying at off-normal angles. The magnitudes of droplet-substrate microadhesion, deformation of the substrate surface and the coating porosity depend upon the spraying angle. The spraying angle 45° can be recommended as a reasonable limit for off-normal thermal spraying for achieving the quality coatings. The theoretical results obtained on flattening characteristics agree with those of the experimentally observed tendencies of thermal spraying at off-normal angles. The theoretical results for % relative porosity are in a reasonable agreement with experimental observations at off-normal angles between 30° and 90°.
Peening Action and Residual Stresses in HVOF Thermal Spraying of 316L Stainless Steel
Authors: Kuroda S. , Tashiro Y. , Yumoto H. , Taira S. , Fukanuma H.
Published: May 2021

316L stainless steel powder was sprayed by a high-pressure HVOF process. Effects of powder size and the pressure in the combustion chamber on the velocity and temperature of sprayed particles were studied by using an optical instrument firstly at the substrate position. A strong negative correlation between the particle diameter and temperature was found whereas the correlation between the diameter and the velocity was not significant. The pressure in the combustion chamber affected the velocity of sprayed particles significantly whereas the particles' temperature remained largely unchanged. In-situ curvature measurement was employed in order to sturdy the process of stress generation during HVOF spraying. From the measured curvature changes, the intensity of peening action and the resultant compressive stress by HVOF sprayed particles were found to increase with the kinetic energy of the sprayed particles. The results were further used to estimate the stress distribution within the coatings.
Analysis of Residual Stress Generated During Plasma Spraying of Glass Coatings
Authors: Bao Y. , Zhang T. , Gawne D.T.
Published: May 2021

An investigation has been undertaken on the analysis of residual stress in glass coatings during plasma spraying. Theoretical analysis and in-situ experimental measurements show that the residual stresses in glass coatings are particularly sensitive to the heat input from the plasma flame, since this can raise the temperature to above the glass transition temperature. Control of the spraying parameters enables the quench stress of splats to be relaxed by the end of the spraying and the only significant remaining source of stress derives from the differential contraction between the coating and substrate during cooling. The analysis also shows that a stress transition occurs during cooling and that the sign of the final residual stress depends upon the expansion coefficient of the glass. The residual stresses are shown to govern the critical coating thickness for cracking and the coating adhesion.
High Damping Capacity Iron-Chromium-Aluminium Based Coatings for Surface Vibration Control
Authors: Karimi A. , Giauque P.H. , Sagradi M. , Barbezat G. , Salito A.
Published: May 2021

The ability of high damping iron-chromium-aluminium alloys and coatings to absorb noise and vibrations has been investigated over a wide range of frequencies and amplitudes. The damping capacity was determined using a cantilever method based on the modal analysis technique of the flat beams and was found to be very sensitive to internal stress of specimens. Heat treatment usually enhanced the loss capability, but only an optimised annealing restored the maximum damping capacity. The influence of vibration amplitude evidenced by appearance of a maximum around ε = 10-4”, while the vibration frequency did not influence 'damping behaviour significantly. The position of the maximum damping was shifted towards lower strains with annealing time and temperature. The structure of magnetic domains was observed using the magneto-optical Kerr effect and their modification following to an applied stress or magnetic field was associated with different values of the damping capacity. Accordingly, the beneficial effect of annealing on damping capacity arises on the one hand from improved mobility of unpinned domain walls and on the other hand from growth of 90° domains considered as the principal responsible of damping. Addition of aluminium between 1-8 wt%. improved the damping values notably around 4 wt%.
Modelling of Elastic Constants of Plasma Spray Deposits with Spheroid-Shaped Voids
Authors: Leigh S.-H. , Lee G.-C. , Berndt C.C.
Published: May 2021

The five independent elastic constants of plasma spray deposits were calculated from constitutive equations and the microstructural information (void aspect ratios and porosity) were gained from stereological analysis. The voids within the deposit were assumed to be a spheroidal shape. The structure of the deposit was considered to be transversely isotropic with respect to the spray direction, which requires five independent elastic constants of a stiffness tensor. Solid mechanics models containing spheroid-shape voids were applied to obtain the five independent elastic constants of the deposits. The calculated elastic constants were compared to the experimentally determined values.
Microstructure Study of Spinel Plasma Coatings
Authors: Lallemand G. , Fayeulle S. , Treheux D. , Esnouf C.
Published: May 2021

Spinel powders of different compositions were fabricated for their good properties of chemical resistance. These powders were plasma sprayed on steels and their microstructure was investigated by scanning electron microscopy (SEM), microanalysis, X-ray diffraction and transmission electron microscopy (TEM). Due to the powder fabrication process, coatings were very heterogeneous in composition, but had the spinel structure. TEM observations pointed out that splat solidification occurred with a cooling rate gradient leading to different crystallization inside a lamella. Young's moduli by the coatings were measured by the resonant frequency method and the correlation with coating microstructure was discussed.
Characterization and High Temperature Behaviour of Thermal Sprayed Coatings used in Boilers
Authors: Higuera Hidalgo V. , Carrilez Menendez A. , Belzunce Varela F.J.
Published: May 2021

CrNiAlTi, NiCrBSi and WC-Ni coatings have been thermal and plasma sprayed projected over a stainless steel surface in order to protect it against heat and erosion actions encountered in power plant boilers. Their microstructure, porosity and microhardness have been measured. High temperature oxidation under an atmosphere similar to service conditions in power plants and thermal fatigue tests have also been performed in our experimental combustion chamber and, finally, the adhesion between the substrate and the coating layer has been evaluated by means of tensile tests. The obtained results have been discussed paying especial attention to the microstructural materials evolution due to thermal effects and coating projection methods.
Thermophysical and Mechanical Properties of PYZ Thick Thermal Barrier Coatings
Authors: Schwingel D. , Taylor R. , Haubold T. , Wigren J. , Gualco C. , Ladru F. , Lugscheider E. , Gourlaouen N.
Published: May 2021

Within a Brite Euram project thick thermal barrier coatings for combustor applications were produced by plasma spraying of yttria partially stabilised zirconia (ZrO2 + 8 wt.% Y2O3). The material properties of such coatings strongly depend on their microstructure which can be altered by manipulating the parameters controlling the plasma spraying process. Covering a variation of possible microstructures, the coatings considered had a thickness of about 2 mm and were six to eight times thicker than the coatings currently in service. This investigation was concerned with an evaluation of the thermophysical and mechanical properties of these coatings and their correlation with the microstructure and the plasma spray parameters. Particular attention was paid to the influence of coating segmentation, microcracking and porosity. The experimental work included the measurement of the thermal diffusivity using the laser flash technique, thermal expansion measurements, and the determination of flexural strength and Young's modulus by means of a specially constructed four-point bend rig. Since some of the samples considered were sprayed according to a partially factorial test plan a statistical evaluation of the material data was possible yielding the correlation between process parameters and material properties.
On the Behavior of Thick and Porous Copper Deposits Under Compressive Stress
Authors: Verdy C. , Montavon G. , Coddet C.
Published: May 2021

Pure copper thick deposits were vacuum plasma sprayed in such a way that several porosity levels were obtained. Mechanical compressive tests permitted to assess the mechanical behavior of these materials and to study the associated pore microstructural changes. A linear porosity level decrease was observed during the first stages of the compressive squeezing, until the stress reached a specific value corresponding to a transition between pore contraction and copper splats deformation. Stereological measurements showed that the pore squeezing was isotropic.
High Corrosion Resistant Iron-Based Amorphous Coatings Obtained by Thermal Spraying
Authors: Otsubo F. , Era H. , Kishitake K. , Matsumoto H.
Published: May 2021

Fe-Cr(-Mo) alloy coatings were thermal sprayed by different processes of LPPS, HVOF and HPS. The as-sprayed coating by LPPS is perfectly amorphous and coatings by other processes contain partly crystalline phases. The amorphous phases crystallize at 773 K or more and shows a high hardness of about 1000 to 1400 DPN just after crystallization. The anodic polarization curves of the coatings shift from active to passive state in 1N H2SO4 and 1N HCl solutions. The coatings obtained by LPPS indicate the lowest active and passive current densities and possess the best corrosion resistance. The corrosion resistance of the coatings obtained by other processes are better than a SUS316L stainless steel coating. The LPPS coating of Fe-Cr-C-P alloy is not attacked on immersion test in 6% FeCl3·6H2O solution containing 0.05N HCl at the corrosion potential, while large pit corrosion is developed in a SUS316L stainless steel sheet.
Compressive Behaviour of Plasma Sprayed High-Alloy Steels
Authors: Volenik K. , Novak V. , Dubsky J. , Chraska P. , Neufuss K.
Published: May 2021

The mechanical properties of plasma sprayed metals and alloys are important in most applications. It a posttreatment by forming of plasma deposited coatings is required, their response to compressive loading is decisive. This paper is concerned with the compressive behaviour of two high-alloy steels sprayed by a water stabilized plasma gun. Martensitic (13.2 % Cr) and austenitic (19.6 % Cr, 11.6 % Ni) steels were plasma sprayed onto plain steel substrates. Small cube-shaped test samples were cut out of thick coatings by an electrospark technique. Compressive load was applied along axes parallel and perpendicular to the substrate and coating surfaces. In addition, comparative samples of bulk steels produced by conventional metallurgy were tested. The compressive behaviour of the as-sprayed martensitic steel was anisotropic at room temperature, i.e. dependent on the orientation of the compression axis. As a result of compression, the splat shapes changed in a manner depending on the orientation of the compression axis. The room temperature compression tests showed that the yield stress of this steel was decreased and the anisotropy was reduced by annealing after plasma spraying. At room temperature, the anisotropy of the as-sprayed austenitic steel and the effect of annealing were less pronounced in comparison with the martensitic steel. Very low values of the yield stress were observed in both steels compressed at the annealing temperature. In spite of the presence of oxide films enveloping each splat, the coatings were prone to considerable plastic deformation, in particular if compressed along the axis perpendicular to the surface.
Comprehensive Methods for Studying Microinhomogeneity in Thermal Spray Coatings with Amorphous-Crystalline Structure
Authors: Grigorenko G. , Borisova A.
Published: May 2021

An integrated approach was developed for investigation of thermal spray coatings with the amorphous-crystalline structure. The new approach combines methods of metallography, differential thermal and X-ray phase analysis, scanning electron microscopy and X-ray microanalysis. This makes it possible to reveal structural, phase and chemical heterogeneity, determine the degree of amorphization of coatings, temperature and heat of crystallization of the amorphous phase during heating. The new integrated approach was used to study amorphous-crystalline coatings of the Ni-P, Fe-Ni-B and Fe-B systems produced by thermal spraying.
Effect of WC-Co Addition on the Adhesion of HVOF Ni-Based Coatings
Authors: Li C.J. , Li H.
Published: May 2021

Self-fluxing nickel based materials are widely used as hard coating materials. HVOF process is promising to produce dense coating with high adhesion. In present study the effects of HVOF spray conditions, and WC-Co addition into self-fluxing nickel based material (NiCrBSi) and the introduction of HVOF WC-Co bond coat on the adhesion of HVOF NiCrBSi coatings are investigated. With regarding to NiCrBSi material, the spray conditions are optimized by orthogonal regression experimental design method with adhesive strength. The adhesive strength is estimated by tensile test. The results show that the adhesive strength of the NiCrBSi coating sprayed at the optimized conditions reaches to about 40MPa. It is found that the addition of WC-Co material through mechanical blending can improve the adhesion of HVOF NiCrBSi coating. The adhesive strength is increased with the increase in WC-Co content in the composite powder. The introduction of HVOF WC-Co bond coat between NiCrBSi coating and substrate can improve the adhesive strength. The multiply enhancing effect on the adhesive strength of HVOF nickel based coating is recognized by applying HVOF WC-Co bond coat to NiCrBSi-WC-Co composite coating.
Microstructure Development During Plasma Spraying of Molybdenum Part 2: Coating Microstructure and Properties
Authors: Jiang X.Y. , Sampath S. , Vardelle A. , Vardelle M. , Fauchais P.
Published: May 2021

This is part II of the two part paper based on international collaboration between the University of Limoges, France and the State University of New York, Stony Brook, USA, aimed at fundamental understanding the relationship between processing condition and microstructure development and properties of thermally sprayed materials. In this study, the effects of deposition temperature on the microstructure and properties development of molybdenum coating was investigated. It is found that with the increase of steel substrate temperature, the molybdenum splat morphology changes from fragmented to more contiguous disk-like shape. The splats on molybdenum substrate show predominantly disk shape. With the increase in deposition temperature, the coating exhibits better lamellar structure with less interlayer pores and debris. The fracture characteristics changes gradually from interlamellar to trans-lamellar and, thermal conductivity is enhanced. Higher deposition temperature improves dramatically the adhesion and bonding of the splats, therefore the physical and mechanical properties of coatings.
Physico-Chemical Aspects of Plasma Spray Coatings
Authors: Klinskaya N. , Jilyaev V. , Pankratov A.
Published: May 2021

The results of an investigation into compound, structure and some properties of composite plasma coatings based on stellite with an addition of titanium nitride are presented. It is shown that the coating formed in a gas-air plasma is characterized by better wear resistance and resistance to scaling. The results of industrial test lend support to wide use of such coatings in machine parts and units that work under the simultaneous influence of impact, abrasive wear and high temperature.
In-Flight Particle Concentration and Velocity Measurements in Thermal Spraying Using a Non-Intensified CCD Camera
Authors: Vattulainen J. , Lehtinen T. , Hernberg R. , Knuuttila J. , Mantyla T.
Published: May 2021

Plasma spraying is a complicated process involving many partly interdependent parameters, which are in industrial spray environments difficult to optimise without laborious and time consuming experiments. In this work a non-intensified CCD camera without any external illumination is used for in-flight particle visualisation. Particle visualisation is based purely on the spontaneous light emitted by the hot particles. The motivation for this work is to outline the possibilities to develope a CCD based, low cost and rugged in-situ measurement system suitable also for industrial use. The measurement method has been tested with Plasmatechnik A3000S plasma spraying equipment using fused and crushed Al2O3 powder. Using digital image processing techniques relative particle concentrations and particle velocities have been calculated from the acquired images. These results have been correlated with wear resistance and deposition efficiency of the coatings produced with different powder feed rate and powder port adjustments. Coatings were also produced using both new and worn electrodes. The benefits and limitations of the method are discussed and the measurement results are compared against measurements made using laser sheet illumination, which can give information concerning also the colder and/or smaller particles not visible for the passive CCD system.
Plasma Spraying Using Ar-He-H2 Gas Mixtures
Authors: Janisson S. , Vardelle A. , Coudert J.F. , Pateyron B. , Fauchais P. , Meillot E.
Published: May 2021

In dc plasma spray guns, the properties of the plasma forming gas largely control the characteristics of the plasma jet and the momentum and heat of the particles injected into the flow. This paper examines the effect of Ar-He-H2 mixtures on the dynamic and static behavior of plasma jets expressed in terms of arc voltage and gas velocity. Correlations between these parameters and operating variables (arc current, gas flow rate, volume composition) were established from a dimensional analysis and supported by the calculation of the thermodynamic and transport properties of the gas mixtures used in the study.
Oxidation Control in Atmospheric Plasma Spraying: Comparison Between Ar/H2/He and Ar/H2 Mixtures
Authors: Denoirjean A. , Lagnoux O. , Fauchais P. , Sember V.
Published: May 2021

Plasma spraying of metals and metallic alloys performed in controlled atmosphere or soft vacuum results in coatings with a low oxidation level and excellent thermomechanical properties. Unfortunately, the spraying cost is drastically increased by one or two orders of magnitude compared to air plasma spraying (APS). Thus the minimisation of oxidation during APS is a key issue for the development of such coatings. Oxygen concentrations sucked into plasma jets have been measured by an enthalpy probe linked to a mass spectrometer. This technique allows to determine simultaneously plasma composition, temperature and velocity distributions within the plasma plume. Results have been compared to those obtained with a two-dimensional turbulent flow model. The obtained results have shown that surrounding air entrainment is reduced when using adequate Ar/H2/He mixtures which viscosity is higher than that of Ar/H, mixtures, limiting the turbulence in the jet fringes and pumping of the surrounding atmosphere.
Influence of Injector Geometry on Particle Trajectories: Analysis of Particle Dynamics in the Injector and Plasma Jet
Authors: Vardelle M. , Vardelle A. , Dussoubs B. , Fauchais P. , Roemer T.J. , Neiser R.A. , Smith M.F.
Published: May 2021

The conditions of particle injection into the side of plasma jets play an important role in determining the microstructure and properties of sprayed deposits. However, few investigations have been carried out on this topic. The current work presents the results of an experimental and computational study of the influence of injector geometry and gas mass flow rate on particle dynamics at injector exit and in the plasma jet. Two injector geometries were tested: a straight tube and a curved tube with various radii of curvature. Zirconia powders with different particle size range and morphology were used. A possible size segregation effect in the injector was analyzed from the space distribution of particles collected on a stick tape. The spray pattern in the plasma jet was monitored from the thermal radiation emitted by particles. An analysis of the particle behavior in the injector and mixing of the carrier-gas flow with the plasma jet was carried out using a 3-D computational fluids dynamics code.
Absolute Coating Porosity Measurement Using Image Analysis
Authors: Mailhot K. , Gitzhofer F. , Boulos M.I.
Published: May 2021

This paper describes the procedure that has been developed for absolute porosity measurement using Image Analysis (IA). Because of the crumbly nature of the composite substrate, it was not possible to proceed with standard method. The IA conducted on Optical Microscopy did not show enough contrast between pores and other features to be automated. The IA conducted on Scanning Electron Microscopy (SEM) with back scattered electron imaging gives enough contrast for automatic threshold determination. The SEM magnification is a parameter to be considered because it filters the information. Three frames at 500X magnification are enough for measuring the porosity of homogeneous supersonic induction plasma sprayed 18 mm samples (thickness 50-100 µm). The established calibration almost shows a 1 to 1 ratio for the image analysis as measured porosity versus the Archimedean porosity. Application of this absolute porosity determination by IA can be found in the Functionally Graded Materials (FGM) which composition is not constant over the layer thickness.
The Place of Thermal Spraying in Industry Today and the Prospects for the Future
Authors: Huchin J.P.
Published: May 2021

In 1913, in the dawning years of the 20th century, Doctor Schoop published a process for "depositing metal under an air flow" in the Scientific American, opening new horizons to surface treatment techniques. Therefore, surface treatments were taken into account right from the design stage by engineers, and their performances became input for devising objects right from the time they were conceived. There is a constant acceleration in the means employed, ever greater system automatisation and a continuous broadening in the applications