bluuebunny/crossref_metadata_2025 huggingface dataset:
Solidification and Homogenization Modeling of High Entropy Alloys
Authors: Hope Adam T. , Chen Hai-Lin , Pedro Oliveira João , Fink Carolin
Published: March 2024

High entropy alloys (HEA) are an exciting new class of alloys composed of several metallic elements with equiatomic or near-equiatomic composition to maximize configurational entropy, leading to desirable properties. However, during solidification, as in casting or welding processes, elements segregate, creating local regions of distinct composition. In conventional alloy systems, homogenization heat treatments are used to remove this segregation effect. This study examines the conditions of the heat treatment needed in HEA alloys. First, the solidification behavior of equiatomic alloy composition AlCoCrCuFeNi is modeled using the Scheil module within Thermo-Calc along with the TCHEA2 database. Energy dispersive spectroscopy (EDS) is performed across the dendrite arms of the as-melted HEA to compare with the Scheil calculations. The resulting dendritic and interdendritic compositions are used as inputs in Thermo- Calc to determine the stable phases as a function of temperature. Selected heat treatments are conducted on the as-melted HEA to compare with the calculation results.
A Match of Material and Process—A Slip for Downhole Isolation Tools Made of a Cast Iron by Surface Hardening Treatments
Authors: Yang Xiangtong , Liu Hongtao , Wang Lei , Xu Jianhui , Liu Yu
Published: March 2024

In the design of a downhole isolation tool for multi-stage fracturing in the oil and gas industry, a setting component, called slip, was used to set the tool in the casing prior to the hydraulic fracturing operation. The material of the slip is made of gray cast iron with surface hardening requirement. This study investigated the performance of slips treated by induction hardening versus flame hardening. The slip treated by induction hardening produced low hardness and insufficient affected layer. On the other hand, flame hardening generated satisfactory results of case hardening layer by 0.762 mm (0.030 in.) thickness with 50 HRC minimum hardness. The Type E graphite in the raw material was transformed to Type A in the flame hardening process, which is favored in the case hardened layer. The effect of different treatment processes on the affected layer and their microstructural response in gray cast iron was discussed in this study. The isolation tool using the slip treated by flame hardening, together with other proven components, showed successful performance of 82.7 MPa (12 ksi) pressure holding at 177 °C (350 °F) for high pressure and high temperature downhole applications.
Preventing Plant/Process Shutdowns Related to Momentary Short Circuits in Heat Treat Furnaces
Authors: Bako Thomas
Published: March 2024

The purpose of this presentation is to outline challenges faced by the Heat Treat Industry related to momentary short circuits when electrical furnaces are used in the production process. The common causes of the problem will be outlined along with some examples of the types of equipment and processes that are impacted by these phenomena. The heat control loop, focusing specifically the power control and semiconductor protection will be analyzed and discussed. Newly developed technologies to overcome these issues and the benefits of such technologies will also be discussed. Some common causes of SCR Power control failures and technologies related to integrated thermal protection and diagnostics, and how these technologies are in line with Industry 4.0 will also be presented.
A New Test Method to Characterize Heat Transfer Coefficient Distribution in Industrial Gas Quenching Systems
Authors: Lu Yuan , Yu Haixuan , Sisson Richard D.
Published: March 2024

Gas quenching is drawing increasing attention within the heat treat industry. The heat transfer coefficient (HTC) for gas quenching can reach 2000 when using high pressure and high velocity nitrogen, helium, or mixtures of these gases. The HTC in water quenching is between 3000 and 4000. The lower HTC of gas quenching may result in workpieces with less distortion and residual stress after quenching. Compared to water, polymer, and oil quenching, gas quenching is environmentally friendly, and the surface of the part is clean after quenching.
Identification of the Important Process Parameters to Control Distortion and Residual Stress During Heat Treating
Authors: Yu Haixuan , Lu Yuan , Zhou Tianyi , Sisson Richard D.
Published: March 2024

A finite element (FE) method was used to determine the important heat treating process parameters that impact the residual stress and distortion in steel. The FE model combines a commercially available heat treatment software DANTE to the finite element analysis software ABAQUS. A thermomechanical FE model was developed to model the evolution of microstructure, the volumetric changes associated with the kinetics of martensitic phase transformation and the formation and distribution of residual stress during quenching of steel. Alternative quenching parameters such as different steel grades, quenching orientation, immersion speed, quenching agent, quenching temperature, austenitizing temperature and part geometry were ranked based on their impact. The main purpose of this paper is to provide processing guidelines to control residual stress and distortion.
An Experimental Study on Blade Curving due to Quenching in the Japanese Sword
Authors: Arimoto Kyozo , Iyota Muneyoshi
Published: March 2024

Blade curving due to quenching in the Japanese sword has been recognized by swordsmiths through the ages. In the late 1920s, Hattori noted that the sword curving is induced from not only martensitic transformation expansion in the near-edge region but also non-uniform elastic and plastic strains distributed in the section, based on his experimental results using cylindrical specimens. Our research for an updated explanation on the subject prepared Japanese sword (JS) type specimens made of the same steel and process as the Japanese sword, and model JS (MJS) type specimens with the almost same shape as the JS type specimens, which were machined from commercial carbon steel and austenite stainless steel bars. All specimens quenched by a swordsmith using the traditional way showed a usual curved shape with different curvatures. Curving, temperature, hardness, metallic structure and residual stress measurements for the specimens were performed to prepare their future simulation works.
Quenching and Partitioning in Hot Stamped Steels
Authors: Ramón-Reyna Claudia , Álvarez-Elcoro Ignacio , Mercado-Solís Rafael , Leduc-Lezama Luis , Salinas-Rodríguez Armando , García Rincón Omar
Published: March 2024

The present work is the first stage of an ongoing research project concerning with integration of quenching and partitioning heat treatment into the traditional hot stamping process, for 22MnB5 alloy, high Si and high Mn steels, last two proposed for the research with a special chemical composition to enhance Quenching and partitioning (Q&P) process. The above, in order to produce a microstructure containing retained austenite and martensite to improve the ductility of resultant components. The investigations of quenching and partitioning process were made by means of dilatometry and hot stamping plus quenching and partitioning (HS - Q&P) process experiments by a special experimental tool. The resulting microstructure was examined using light optical and scanning electron microscope as X-ray diffraction too. Some results obtained shown that compared with conventional hot stamping samples, the HS-Q&P process improves elongation effectively and maintains high-strength at the same time.
Corrosion Resistance of Niobium and Vanadium Carbide Layers Produced by Thermoreactive Diffusion Treatments on Spheroidal Cast Iron
Authors: Soares Carolina , Edson Mariani Fábio , Corrêa Rêgo Galtiere , Satoru Takeya Gustavo , Edward Totten George , Carlos Casteletti Luiz
Published: March 2024

In the present study unalloyed spheroidal graphite iron was compared with a sample alloyed with copper and nickel (Cu- Ni). Samples of those materials were treated in salt bath (a composite of sodium borate, aluminum, iron-niobium and/or iron-vanadium) at 1000 °C for 2 hours. This resulted in layers of niobium carbide (NbC), vanadium carbide (VC) and ternary carbide of niobium and vanadium (NbVC2). Characterization of these layers was obtained by optical microscopy, X-ray diffraction and microhardness Vickers. The microhardness and the thickness results were statistically analyzed by the two factors variance analysis method. The efficiency of the layered surface in increasing corrosion resistance was demonstrated by submitting it to potentiodynamic polarization corrosion tests.
Alternative Surface Activation Techniques When Nitriding Stainless Steels
Authors: Nousir Saadia , Kalucki Jack A.
Published: March 2024

Because of its qualities such as surface uniformity and high load density, controlled gas nitriding is recognized as one of the best nitriding techniques available. It guarantees greater dimensional and surface morphology stability and, therefore, is applied to a variety of stainless steels components. Classical depassivation methods often contribute to a decreased corrosion resistance. In certain applications, alternative methods may be used to achieve the same extent of surface uniformity and similar results, without the use of classical halogen activation methods.
Uphill Quenching of Aluminum Alloys—A Progress Report
Authors: Mattos Wellington da S. , Ferreira Thiago , Totten George E. , Canale Lauralice de Campos F.
Published: March 2024

This paper describes the uphill quenching process which is applied in the heat treatment of aluminum alloys. This lesser known process was developed by Alcoa and first applied more than 50 years ago for aluminum alloys of several thicknesses. Uphill quenching has been reported to reduce residual stresses by > 80%. Typically, uphill quenching is applied after quenching and before aging of aluminum alloys. Uphill quenching consists of the immersion of the part in a cryogenic environment and after equilibration, the part is transferred immediately to a fixture in a superheated steam chamber to obtain a temperature gradient sufficient to maintain the improved mechanical properties gained with heat treatment that result in low residual stresses and superior dimensional stability. Assuming that most of the stresses that appear in aluminum alloys during heat treatment are due to the quenching process, then this intermediate treatment becomes a potentially effective tool for the heat treatment of aluminum alloys. The aim of this paper is to present an overview of recent work showing tensile test results obtained with uphill quenching relative to conventional quenching processes.
Effect of Post Weld Heat Treatments on Electron Beam Welded SAE 5137 Steel
Authors: Bhavar Valmik , Kattire Prakash , Thakare Sandeep , Mane Santosh , Patil Sachin , Pawar Vinayak , Singh RKP
Published: March 2024

Though electron beam welding (EBW) causes minimum destruction to the base metal, significantly different microstructure exists at weld zone. Rapid heating and cooling during electron beam welding results in dendritic microstructure, which lowers mechanical properties. In order to recover the original mechanical properties, post weld heat treatments (PWHT) needs to be performed after EBW. This paper presents effect of PWHTs on mechanical and microstructural properties of electron beam welded SAE 5137 H steel. Welded steel plates were processed through different heat treatments like stress relieving, normalizing and hardening & tempering. Micro-structural and mechanical testing were performed to characterize these specimens. It was perceived that, different PWHT’s can be employed and selection depends on final mechanical property requirement from the weld joint.
A New, Innovative Approach to Designing a Vacuum Furnace Hot Zone
Authors: Jones William R. , Fradette Réal J.
Published: March 2024

A new high strength and energy efficient graphite board (HEFVAC) was introduced in fall 2016 as a vacuum furnace insulation package, which has evolved with the goal of further reducing power consumption. The unique features of the HEFVAC material offer a new approach to the design and construction of a vacuum furnace hot zone. Our presentation will document the thermal advantages of the HEFVAC board as well as introduce a new hot zone design that integrates the board into a self-supporting structure. This new design offers greatly improved thermal efficiency, resulting in reduced power usage compared to current vacuum furnace hot zones.
Low Pressure Carburizing Distortion Data Comparing Oil and High Pressure Gas Quenching
Authors: Lelong Vincent , Beauchesne Dennis
Published: March 2024

This presentation will discuss data on parts tested in Low Pressure Carburizing using oil and gas quenching. We will present data on metallurgy, distortion and load design to optimize each quenching media. As we know oil and gas quench respond differently, we will explore the evolution of high pressure gas quenching as it exist in today’s market. Low Pressure Carburizing has been growing among OEM’s and now Tier 2 suppliers as well as heat treaters in the Automotive and Aerospace markets. These details should help show the audience that they also can take advantage of the clean environment from Low Pressure Carburizing and just in time processing along with possible distortion control for all their parts currently being atmosphere carburized.
Multiple Chamber Vacuum Furnaces vs. Single-Chamber Vacuum Furnaces—A Review
Authors: Bernard Benjamin T. , Bernard William J.
Published: March 2024

A review of vacuum processing in a multiple-chamber vs. single-chamber vacuum furnace and the advantages and disadvantages of both design concepts will be presented. Cycle calculations will be shown to illustrate the differences in the floor-to-floor time, heating energy required to process and cooling power to quench a normalized load. Additionally, the presentation will discuss the differences in residual atmosphere for a given vacuum level for the two furnace concepts. Differences in operation and maintenance between the two concepts and appropriate processes to run in each will also be discussed.
Optimizing Cycle Time and Process Flexibility Using Vacuum Sealed Quenching
Authors: Marteeny Don , Korecki Maciej
Published: March 2024

Hardening and case hardening are among the most common types of heat treatment processes, which can be performed in either atmosphere or vacuum furnaces. These processes, followed by oil quenching, are carried out in batch sealed quench and continuous furnaces such as pusher, roller, or rotary hearth types. Atmosphere heat treatment technology and equipment was developed more than 60 years ago with little new product innovation or change since. However, in this time period the needs of manufacturing have changed dramatically, driven by global competitiveness and the drive for lower unit cost. As such the heat treatment solutions must be capable of achieving higher productivity (through shorter cycle times), increased flexibility (with respect to material and process/cycles) and meet higher product quality standards. In addition, today’s manufacturing requires absolute process reproducibility and integration with other manufacturing processes, all done using energy efficient and environmentally friendly equipment. The solution to this situation is modern vacuum furnace technology and vacuum equipment that easily adapts to stringent specifications and changing industry standards. In this discussion, two case studies of this technology are presented. The first includes a two-chamber sealed oil quench vacuum furnace to case harden a SAE 5120 component to a surface hardness of 61 HRC using a Low - Pressure Carburizing (LPC) process. The result was a 30% savings over traditional atmosphere carburizing integral quench furnace owned by a commercial heat treater. The second study involves the use of a three-chamber sealed oil quench vacuum furnace to case harden SAE 5115 steel automotive steering components to an effective case depth of 0.9 mm minimum and a minimum surface hardness of 60 HRC. Using LPC these parameters were easily achievable. By, using a three-chamber sealed oil quench furnace, the potential for up to 600 kg/hr throughput was demonstrated, while maintaining costs comparable to a traditional atmosphere style integral quench furnace. Together, both studies show that sealed oil quench vacuum furnaces can improve process time and quality over a traditional atmosphere integral quench furnace while maintaining the process costs needed to remain competitive.
Comparative Investigation of Standard WC-Co and a New WC-FeCrAl Feedstock Powder
Authors: Hussong B. , Pfeiffer J. , Lehmert B. , Wojarski L. , Tillmann W.
Published: March 2024

This study investigates the HVOF spraying characteristics of a new WC-FeCrAl powder as compared to a standard WC-Co feedstock. Significantly higher particle temperatures were recorded for the WC-FeCrAl powder during spraying, presumably an effect of phase reactions during particle dwell time in the jet. XRD graphs revealed W2C and δ-Fe2O3 formations. Gibbs free energy calculations propose that energy is being released during the formation of these phases. Comparable correlations between in-flight particle measurements and splat morphologies were found for both powders. Coating hardness was also found to be comparable, although porosity was significantly lower in the WC-FeCrAl samples. This is attributed to the smaller carbide grain size of the new powder, which might help explain the lower viscosity of the molten particles at impact. A response surface analysis of XRD measurements indicates that W2C formation occurs in the spray jet, and it is assumed that δ-Fe2O3 formation occurs on the surface of the substrate after particle deposition.
Deposition and Oxidation of Oxide-Dispersed CoNiCrAlY Bondcoats
Authors: Okada M. , Vaßen R. , Karger M. , Sebold D. , Mack D.E. , Jarligo M.O. , Bozza F.
Published: March 2024

This study compares the deposition and oxidation behavior of two oxide-dispersed CoNiCrAlY powders, one commercially obtained, the other prepared in a high-energy attrition ball mill using CoNiCrAlY and nanosize α-alumina powders. The custom powder was deposited by HVOF spraying using two sets of parameters, one optimized for CoNiCrAlY powder, the other for fine alumina. Coatings produced under the latter conditions were found to be porous, which can be attributed to a low degree of melting in the dispersed alumina. Isothermal oxidation testing at 1373 K for up to 1000 h in air caused oxidation not only at the surface, but also inside the coatings due to the movement of oxygen through the pores. The coatings deposited under the other set of parameters, i.e., at higher power levels, were free of pores. Isothermal oxidation tests were also carried out on coatings produced from the commercial powder, in this case, by HVOF and as well as vacuum plasma spraying. The coatings obtained by HVOF spraying were found to have a thinner thermally grown oxide layer than not only the VPS coatings, but also conventional metallic bond coats. Internal oxidation in the HVOF coatings is due to insufficient cohesion of the spray particles. Furnace cycling tests were conducted on specimens with an additional ceramic thermal barrier coating. Specimens with VPS bond coats produced from commercial oxide-dispersed powder achieved almost same number of cycles to delamination as specimens with conventional metal bond coats.
Mechanical Properties of Plasma Sprayed YSZ Coatings Measured Using TAT and TCT Test
Authors: Ming Ang Andrew Siao , Berndt Christopher C.
Published: March 2024

This investigation employs tensile adhesion tests (TAT) and tubular coating tensile (TCT) tests to measure the adhesion and cohesion bond strength of plasma sprayed YSZ coatings. Tensile adhesion testing measures the bond strength of the YSZ-bond coat system perpendicular to the spray direction, while tubular coating tensile testing measures the intersplat strength of the YSZ coating parallel to the spray direction. In both cases, the failure strength of the coatings can be approximated to a Weibull distribution, indicative of anisotropic behavior as verified by Knoop microhardness indentation tests. The average coating strength parallel to the spray direction is shown to be about 1.5 times greater than the bond strength perpendicular to the spraying direction.
Y2O3 and Yb2O3 Co-Doped Strontium Hafnate as a New Thermal Barrier Coating Material
Authors: Ma W. , Li P. , Dong H.-Y. , Bai Y. , Zhao J.-L. , Fan X.-Z.
Published: March 2024

This study investigates the phase stability and thermophysical properties of Y2O3 and Yb2O3 co-doped SrHfO3 (SHYY) powder and bulk material along with the phase stability and microstructure evolution of as-sprayed SHYY coatings during annealing. The powder was synthesized by a solid-state reaction at 1450 °C, showing good phase stability up to 1400 °C. Dilatometry measurements revealed no abnormal changes in the coefficient of thermal expansion over a temperature range of 200-1300 °C. The thermal conductivity of the bulk material was found to be 16% lower than that of SrHfO3. Free-standing SHYY coatings deposited by air plasma spraying were also tested. The coatings consisted of SHYY and a minor amount of secondary phase Yb2O3 and exhibited good phase stability during heat treatment at 1400 °C for 288 h. Coating samples examined after 216 h still exhibited a columnar microstructure.
A Novel Modification for Twin Wire Arc Spraying to Improve the Variety of Application
Authors: Tillmann W. , Abdulgader M. , Hagen L.
Published: March 2024

Various approaches are presented in this paper to adapt conventional twin wire arc spraying (TWAS) for the production of smooth and finely structured coatings. Higher particle velocities were achieved by modifying spraying nozzle geometry. New geometries that incorporate a Laval shape produced the highest particle velocities while also eliminating overspray and extending the high-velocity region. This led to a more focused spraying plume and a change in optimal spraying distance, which was found to be more than 200 mm based on coating roughness. Some of the new nozzles exhibited evidence of particle deposition on the inner walls, which can restrict plume flow if not addressed. The problem is related to the position of the Laval throat in the spray plume as well as changes in gas pressure.
High-Temperature Oxidation-Resistant Thermal Spray Coatings Based on MoSi2 for Furnace Applications
Authors: Schuberth S. , Uhlig T. , Pokhmurska H. , Rupprecht C. , Lampke T.
Published: March 2024

The aim of this work is to optimize molybdenum disilicide coatings for high-temperature oxidation protection of metallic surfaces. Agglomerated and sintered MoSi2 powder was deposited on test substrates by atmospheric plasma spraying. The powders and coatings were characterized by means of optical and scanning electron microscopy. Various tests were carried out to determine the influence of powder size and spray parameters on coating porosity, hardness, and adhesive pull strength.
Effect of WC-Co-Cr Powder Properties on Coating Characteristics by Recent HVAF Spraying
Authors: Sato Kazuto , Miyajima Hidenori , Kato Masami , Kitamura Junya , Sakaki Kazuhiko
Published: March 2024

This study investigates the density, hardness, and wear behavior of WC-Co-Cr coatings produced by high-velocity air fuel (HVAF) spraying. The results indicate that coating hardness, density, and wear performance are improved by increasing gas velocity and using powders composed of fine CoCr particles.
Investigation of HVOF-Sprayed Hardmetal Coatings for Static Friction Applications
Authors: Berger L.-M. , Spatzier J. , Gräfensteiner M. , Vidner J. , Leidich E. , Schiefer S. , Gröger S. , Gerlach M.
Published: March 2024

This study investigates the static friction properties of HVOF-sprayed Cr3C2-NiCr coatings. Measurements of the static coefficient of friction (CoF) of as-sprayed coatings show their potential for use in frictionally engaged joints. The form, orientation, and geometric characteristics of Cr3C2-NiCr friction surfaces are assessed as well and slipping curves are determined. The results show a standard deviation in the static CoF depending on nominal contact pressure, but it is not yet possible to establish a correlation with coating properties such as carbide grain size and geometrical parameters such as coating roughness.
Corrosion Protection of a 5xxx Series Aluminum Alloy by Cold Spray Process
Authors: Sridharan K. , Maier B. , Hauch B. , Devan D.
Published: March 2024

In this investigation, 5083 aluminum alloy coatings were deposited on substrates of the same material by high-pressure cold spraying. Spray trials were carried out using powders with size ranges of 5-20 µm and 20-44 µm, gas temperatures of 673 K and 773 K, and nitrogen and helium process gases. Coatings and coating-substrate interfaces were evaluated primarily by SEM and EDS, while XRD was used to examine coating stresses and oxidation effects. Corrosion protection was assessed by electrochemical potentiodynamic measurements in synthetic seawater and Knoop indentations tests were conducted as a measure of work-hardening and mechanical integrity of the coatings. Test results are presented and correlated with spray parameters.
Investigation on Microstructural & Mechanical Properties of Cold Sprayed & P/M Processed Composites
Authors: Chandanayaka T. , Azarmi F.
Published: March 2024

In this study, nickel-matrix composites reinforced with nickel-aluminide particles are produced by cold spraying and powder metallurgy techniques. A powder mixture of 80 vol% Ni and 20 vol% Ni3Al is used in both processes. Optical microscopy, SEM, and EDX analysis are used to evaluate the microstructural uniformity of the as-fabricated composites, while hardness and Young’s modulus are determined by microindentation tests. Microhardness tests are also conducted after each step of the P/M process in order to evaluate corresponding changes in hardness. The findings are presented and explained.
Comparison of Microstructures and Mechanical Properties between Thermal and Kinetic Sprayed Thick Fe Deposits on Fe-Si Alloy Sheets
Authors: Kim Jaeick , Bae Gyuyeol , Won Juyeon , Lee Changhee , Jun Teasung , Choi Jongkyo
Published: March 2024

In this study, plain carbon steel wire and pure iron powder are deposited on grit-blasted Fe-Si alloy substrates using thermal (electric arc, plasma, and HVOF) and kinetic spraying techniques. The coatings obtained were then heat treated. Coating microstructures and mechanical properties were investigated and compared focusing on oxidation, delamination, and Si dilution from the substrate to the coating.
Preparation and Characterization of TiO2 Scattering Layer for Plastic Dye-Sensitized Solar Cells by Vacuum Cold Spray
Authors: He X.-L. , Yang G.-J. , Li C.-X. , Li C.-J. , Fan S.-Q.
Published: March 2024

Plastic dye-sensitized solar cells (DSCs) are a promising photochemical solar technology owing to their light weight, flexibility, and suitability for low-cost roll-to-roll production. In order to improve cell efficiency, a light scattering layer was prepared on the surface of nanocrystalline (NC) TiO2 by vacuum cold spraying (VCS) at room temperature using submicron-sized TiO2 particles. The influence of the scattering layer and its connection with the underlying TiO2 was investigated to understand the improvement in cell efficiency. For comparison, two scattering layers were prepared by spray deposition using ethanol-based suspensions with either submicron Al2O3 or TiO2 particles. All three layers exhibited a higher light-reflecting capacity than the TiO2 nanocrystalline layer, although dark current test results showed that the biggest efficiency improvement was achieved in the NC-VCS-TiO2 cells.
Dust Explosion Properties of Aluminum, Titanium, Zinc and Iron Based Alloy Powders Used for Cold Spray
Authors: Sakata K. , Tagomori K. , Sugiyama N. , Sasaki S. , Shinya Y. , Nanbu T. , Kawashita Y. , Narita I. , Miyahara H.
Published: March 2024

In this study, the dust explosion properties of aluminum, titanium, zinc, and iron based alloy powders were evaluated by JIS Z 8818: “Test method for minimum explosible concentration of combustible dusts,” IEC 61241-2-3 (1994-09) Section 3: “Method for determining minimum ignition energy in dust-air mixtures,” and JIS Z 8817: “Test method for explosion pressure and rate of pressure rise of combustible dusts.” The test are described and the results are presented and discussed.
Design and Development of High-Pressure Warm Spray Gun
Authors: Katanoda H. , Sun B. , Ohno N. , Fukanuma H. , Kuroda S. , Watanabe M. , Ohashi O.
Published: March 2024

A new high-pressure warm spray gun was designed with the aim of increasing particle velocities to 1000 m/s for 30 µm Ti particle at 1000 °C or below. Nozzle geometry and combustion chamber pressure were optimized based on one-dimensional simulations. The flow rate of nitrogen gas injected into a mixing chamber was determined by calculation. The fuel injector was developed experimentally, its geometry optimized to spay small well-diffused droplets of kerosene into a 4 MPa chamber.
Mechanical Properties of Cold Sprayed Al Coatings Reinforced by Ceramics
Authors: Ko K.H. , Choi J.O. , Lee H.
Published: March 2024

This work investigates the effect of feedstock size on the hardness and wear resistance of metal-matrix composite coatings produced by cold spraying. Feedstocks consisting of Al and Al2O3 powders were prepared for the study. The feedstocks, which differ in regard to Al2O3 particle size (100, 50, 10 µm) and composition (25-50 vol%), were accelerated by compressed air through a Delaval-type nozzle positioned 10 mm from the target substrate. The morphology of the coating resembled that of an Al matrix with embedded Al2O3 particles. Optical microscopy showed that large Al2O3 particles (> 50 µm) fractured into small pieces and embedded in the matrix. It is likely that some of the fragmented particles bounced off, rather than adhering. These collisions (tamping effect) increase coating hardness and density. In the case of the feedstock with 10 µm Al2O3, particle sizes were unchanged during spraying and the benefits of work hardening were not achieved.
Influence of Carrier Gas Composition on Microstructures and Mechanical Properties of Cold-Sprayed Titanium Coatings
Authors: Ichikawa Y. , Ogawa K. , Nose N. , Nomura Y. , Takahashi M. , Amano H.
Published: March 2024

This study investigates the effects of gas composition on cold-sprayed titanium coatings deposited under nine different spray conditions. Experiments show that higher levels of gas purity translate to higher particle velocities and measurable improvements in bending strength. The influence of gas temperature, pressure, and chemical composition is considered in the study along with interactions between carrier gases and sprayed particles. In addition to bending strength, the resulting coatings are assessed in terms of porosity and oxygen content.
Anisotropic Mechanical Properties of Cold Sprayed Copper Coatings
Authors: Watanabe Y. , Atsumi K. , Yamada M. , Fukumoto M.
Published: March 2024

Cold spraying is a promising process to fabricate functional coatings. Because of the solid-state particle deposition, the electrical and chemical properties of the coatings are similar to those of bulk materials. This is not the case with mechanical properties, however, which differ between the coating and bulk due to severe plastic deformation in the particles. The residual stress and bonding state of particles in cold-spray coatings are investigated in this study as to their influence on mechanical anisotropy. Bending tests on cold spray copper coatings show that loading direction has a significant effect, which may be related to the distribution of microvoids and pores. Traverse patterns and process gas temperature are also examined and are shown to play a role.
Splat Formation and Adhesion Mechanisms of Cold Gas Sprayed Al Coatings on Al2O3
Authors: Wielage B. , Drehmann R. , Grund T. , Rafaja D. , Schucknecht T. , Manygoats K.
Published: March 2024

In this study, aluminum is deposited by cold gas spraying on smooth and rough alumina substrates. SEM examination of single particle splats on polycrystalline Al2O3 suggests that mechanical interlocking is the primary bonding mechanism for cold gas sprayed metals on rough ceramic surfaces. Coating cross-sections on monocrystalline, atomically smooth sapphire substrates were examined by means of high-resolution TEM, revealing nanosized Al grains close to the interface, which could be an indicator of recrystallisation induced by local heating and the deformation energy stored in the particle during impact.
Analysis of Thermal History and Residual Stress in Cold Sprayed Coatings
Authors: Arabgol Z. , Assadi H. , Schmidt T. , Gärtner F. , Klassen T.
Published: March 2024

It is generally believed that residual stresses in cold spray coatings are caused by particle impact and deformation and are hence predominantly compressive, as opposed to thermal spraying where thermal effects, particularly solidification, play the lead role. This study aims to provide a preliminary review of this notion through finite element analysis, distortion measurements on copper-coated steel, and the consideration of thermal history. The dimensions and elastic properties of the coating and substrate are key factors in the study along with heat input. Based on the review, a simple model is proposed to predict the final state of residual stress and distortion in flat surfaces coated by cold spraying.
Multi-Scale Analysis between Microstructure and Absorbing Performance of Thermal Sprayed Fe-(β-SiC/SiO2) Coatings
Authors: Yuan Xiaojing , Zha Bailin , Wang Hangong
Published: March 2024

This paper describes how effective medium theory and fractal analysis are used to investigate nonlinear microstructure-property relationships in HVOF-sprayed composite coatings produced from nano Fe-(β-SiC/SiO2) agglomerate powders in order to optimize microwave absorption performance. The powder used in the study was prepared by spray granulation and deposited on Fe substrates. The microstructure of the powder and coatings was examined by SEM, the phase structure was determined by XRD analysis, and electrical permittivity and permeability were measured. To simplify calculations, electromagnetic absorption phases in the coating were assumed to be periodically distributed cubes. The results of the study indicate that multi-fractal diffraction in the coating microstructure facilitates the absorption of microwaves and is optimized when the mass fraction of nano βSiC in the composite is 28 wt%.
Influence of Surface Contamination on the Adhesion Strength of HVOF Coatings
Authors: Barr J. , Estrada C. , White B.
Published: March 2024

Base metal surfaces are typically prepared for thermal spraying by chemically cleaning followed by grit blasting. In common practice, HVOF coatings are applied within 2-4 h or the entire cleaning process is repeated to prevent in-service adhesion failures. This study was initiated to assess the effect of long wait times on the adhesion strength of WC-Ni coatings. Test coupons were chemically cleaned, grit blasted, and then set out in shop conditions for up to 48 hrs. Some were also subjected to different forms of contamination including dirty fingerprints, grease, penetrating oil, surface rust, tape residue, and paint. Pull test and metallographic examination results show that none of the contaminants had an influence on the adhesion strength of the HVOF coatings.
Development and Characterization of B4C Reinforced Detonation Sprayed Al Coatings
Authors: Tillmann W. , Hollingsworth P.S. , Fischer G. , Nellesen J.
Published: March 2024

This paper describes the development of detonation-sprayed aluminum-matrix composite coatings reinforced with boron carbide. The goal is to achieve a homogeneous coating structure with low porosity, low oxide content, and high concentration of embedded carbides. Tensile tests of various types were conducted and different stages of deformation were analyzed using micro computed tomography, a 3D imaging technique that reveals the formation of cracks in real time.
Current Activities for Standardization on Indentation Method to Evaluate Adhesion Strength of Thermal Spray Coatings in Japan
Authors: Yamazaki Y. , Suzuki M. , Arai M. , Miyashita Y. , Waki H.
Published: March 2024

Adhesion strength of thermally sprayed coatings is usually measured in accordance with the tensile method specified by ISO 14916. A major limitation of the method, however, is that it cannot measure adhesion strengths greater than that of the glue used to prepare the test specimen. Indentation testing, by virtue of its simplicity and practicality, is a promising alternative in such cases. Collaborative work has been conducted by members of the Japan Thermal Spray Society (JTSS) to establish a standard method for measuring coating adhesion using a conventional Vickers indenter. This paper provides an overview of the experimental and theoretical work that was done and describes the criteria proposed to quantify adhesion strength based on standardized test procedures.
Friction Evolution of WC-CoCr Thermally Sprayed Coatings during Dry Sliding in Different Environments
Authors: Wesmann J.A. , Johnsen R. , Espallargas N. , Herland J. , Twist D.
Published: March 2024

Gate valves used in oil and gas production undergo stringent qualification before going into service. During qualification there is no external lubrication, leaving contact surfaces susceptible to friction evolution and wear. The work presented in this paper was carried out to better understand the changes that can occur during qualification and where and when the limit for mild wear and stable friction is reached. Ni-Cr alloy gate valve components were coated with WC-CoCr by HVOF spraying and dry sliding wear tests were conducted in nitrogen and in air. The coatings were then evaluated by means of SEM, EDX, and XRD analysis, nanoindentation and surface roughness measurements, and compression tests on micropillars milled out by FIB. Similar tests and analyses were performed on gate valves returned from the field. Examination of the valves that had been in service revealed the presence of oxygen rich layers on polished surfaces due to opening and closing of the gate. Such layers were also observed in coating samples following tribological testing. Initial surface roughness was found to play a role in the development of the oxygen rich layers as well as friction evolution.
Influence of Surface Pre-Treatment on Aluminum Alloy Mechanical Behavior
Authors: Lamraoui A. , Costil S. , Langlade C.
Published: March 2024

This study analyzes the mechanical properties of aluminum alloy substrates, in particular, changes in flexural behavior of laser-textured surfaces. Bending tests are conducted on samples treated by laser texturing and by conventional methods such as chemical degreasing and sandblasting. A comparison of flexural strengths caused by the different surface pre-treatments method is presented.
Microstructure and Mechanical Properties of Plasma Sprayed Nanostructured and Conventional Al2O3-13TiO2 Coatings
Authors: Żórawski Wojciech , Góral Anna , Bokuvka Otakar , Berent Katarzyna
Published: March 2024

This work evaluates the tribological properties of conventional and nanostructured Al2O3-13TiO2 coatings obtained by atmospheric plasma spraying. The structure and composition of the composite coatings and powders were analyzed by SEM, TEM, and x-ray diffraction. Nanoindentation and ball-on-disc tests were conducted and surface topography was examined by noncontact 3D profiling. Coating samples of both types were polished and their friction coefficients were measured. The coefficient of friction for nanostructured coatings was 0.51, while that of conventional coatings was 0.62.
Surface Hardening of HVOF Sprayed Stainless Steel Coatings by Plasma Nitriding and Nitrocarburizing
Authors: Park Gayoung , Bae Gyuyeol , Lee Changhee
Published: March 2024

This study compares the effects of plasma nitriding and nitrocarburizing treatments on HVOF sprayed stainless steel coatings with different crystal structure. The treatments were conducted at 550 °C for 10 h in a gas mixture of N2 and H2 for nitriding and N2, H2, and C2H2 for nitrocarburizing. Optical microscopy, SEM-EDS, and XRD show that the treatments produced thick nitride layers consisting of a compound layer and a nitrogen diffusion layer. The treatments increased not only the surface hardness, but also the load bearing capacity of the coatings due to the formation of CrN, Fe3N, and Fe4N phases. Plasma nitrocarburized 410 stainless steel had the highest microhardness and load bearing capacity because of the precipitation of Cr23C6 on the surface.
Abrasive Wear Resistance of Thermal Surfacing Materials for Soil Tillage Applications
Authors: Dizdar Senad , Maroli Barbara
Published: March 2024

This study ranks a number of common thermal surfacing materials for soil tillage applications based on the results of dry-sand rubber-wheel testing for abrasion resistance. Test specimens were prepared by plasma transferred arc (PTA) and powder welding deposition of a nickel-based self-fluxing matrix with and without tungsten carbide (WC) additions. For comparison, PTA coated M2 tool steel and quenched and tempered spring steels were also tested. PTA and PW deposition produced coatings with a similar level of abrasive wear resistance. Hardfacing with M2 and nickel-based 1560 deposited by PTA showed ~30% and ~15% wear respectively compared to the reference steels, while nickel-based grades with additions of 50% carbide showed only ~5% wear. Moreover, by increasing the amount of WC from 50 to 60 wt%, abrasive wear resistance was increased by 25%.
Increasing Durability of a Multilayer Oxidation Protection System for Gamma-TiAl
Authors: Bobzin K. , Kopp N. , Warda T. , Linke T.F.
Published: March 2024

Lightweight gamma titanium aluminide (γ-TiAl) intermetallic alloys have recently found application in low-pressure turbine blades in the aviation industry, but their use is currently limited to around 700 °C due to oxidation. This study evaluates the potential of various multilayer coating systems to increase the operating temperature range of γ-TiAl. The coating systems tested are based on a CoNiCrAlY topcoat for oxidation protection and a YSZ diffusion barrier, both applied by atmospheric plasma spraying using a three-cathode torch. Two bond coats, NiCrBSi and CoNiCrAlY, were also tested. Test specimens with bond coats withstood 1000 h of exposure at 900 °C without delamination and no detectable oxygen at the coating-substrate interface. Samples produced with varying feed rates showed that graded coatings can be achieved using the APS process.
MCrAlY Bondcoats by High Velocity Atmospheric Plasma Spraying
Authors: Mauer G. , Sebold D. , Vaßen R.
Published: March 2024

Atmospheric plasma spray parameters were developed for a three-cathode torch with a high-velocity nozzle and MCrAlY powders of different particle size fractions. The main objectives of the work are to achieve bond coats with low oxygen content and porosity. Other goals are achieving sufficient surface roughness at high deposition rates and efficiencies. The oxidation behavior of the sprayed coatings was characterized by thermal gravimetric analyses and isothermal heat treatments.
Comparison Study of Three or Two Dimensional Analytical Model for Simulation of Thermal Conductivity in Thermally Sprayed Ceramic Coatings
Authors: Yang G.-J. , Xie Y.-C. , Xie H. , Li C.-X. , Li C.-J.
Published: March 2024

This study compares the accuracy of 2D and 3D models for determining the thermal conductivity of thermally sprayed ceramic coatings. Although the overall dependency of relative thermal resistance on microstructural parameters is similar for the two models, the detailed dependency is quite different and is more accurate in the 2D model. With increasing unit size and decreasing splat thickness and bonding ratio, the 2D model is more effective than the 3D model due to its more appropriate assumption of splat thickness relative to the distance between cracks.
Tribological Characterization of Plasma Sprayed CoNiCrAlY-BN Abradable Coatings
Authors: Irissou E. , Dadouche A. , Lima R.S.
Published: March 2024

The processing conditions, microstructural and tribological characterizations of plasma sprayed CoNiCrAlY-BN high temperature abradable coatings are reported in this manuscript. Plasma spray torch parameters were varied to produce a set of abradable coatings exhibiting a broad range of porosity levels (34-62%) and superficial Rockwell hardness values (0-78 HR15Y). Abradability tests have been performed using an abradable-seal test rig capable of simulating operational wear at different rotor speeds and seal incursion rates. These tests allowed determining the rubbing forces and quantifying the blade and seal wear characteristics for slow and fast seal incursion rates. Erosion wear performance and ASTM C633 coating adhesion strength test results are also reported. For optimal abradability performance, it is shown that coating hardness needs to be lower than 70 and 50 HR15Y for slow and fast blade incursion rate conditions, respectively. It is shown that the erosion wear performance, as well as, the coating cohesive strength is a function of the coating hardness. The current results allow defining the coating specifications in terms of hardness and porosity for targeted applications.
Friction Coefficient Improvement of Cold Sprayed Al-Al2O3 Coatings
Authors: Ko K.H. , Choi J.O. , Lee H.
Published: March 2024

This study investigates the effects of various reinforcement materials and solid lubricants on cold spray aluminum composite coatings. The wear resistance and friction coefficient of the coatings were very different with and without a reinforcement and solid lubricant. It was found that Al2O3 greatly improves wear properties, Mo results in better dispersion hardening, and MoS2 reduces the friction coefficient.
Numerical Simulation of Heat Transfer in Thermal Spray-Formed Metal Foam Heat Exchangers
Authors: Taheri M. , Chandra S. , Mostaghimi J.
Published: March 2024

A numerical investigation of fluid flow and heat transfer through thermal spray formed metal foam heat exchangers is presented. Experimentally obtained fluid flow and heat transfer parameters are used in the simulations. Analytically obtained values of effective thermal conductivity are used to model heat transfer. A 3D CFD model was created for a metal foam heat exchanger with a square cross-section. The external walls were deposited on the foam using a wire-arc process. The channel walls of the foam were exposed to a constant temperature of 400 K and an air flow with an inlet velocity of 2 m/s. The model was verified by comparing sample results to experiments. The effect of the foam on heat transfer was then studied by varying thermal conductivity values.
Modeling the Influence of Solution Properties on Precipitations of Vaporizing Droplets in Plasma Gases
Authors: Xu L.S. , Shan Y.G.
Published: March 2024

Solution droplets injected into a plasma jet experience a sequence of thermal, physical, and chemical processes. These include droplet breakup and collisions, solvent vaporization, solute precipitation and pyrolysis, formation of the product particles, sintering, and perhaps melting. Depending on plasma conditions, solution concentration, and the properties of the solvent and solute, different particle morphologies are produced. In this paper, a heat and mass transfer model for vaporizing solution droplets was used to investigate the influence of solvent type, initial salt content, and concentration. Temperature and composition dependent thermo-physical properties were used. Temperature and concentration distributions and variations of precursor droplets (cerous nitrate and zirconia acetate in water and ethanol) were predicted.