In this study, we investigated a novel approach using the cold spray process to develop ferromagnetic components. To assess the feasibility and performance of these components, their mechanical and magnetic properties were analyzed through various experiments and measurement techniques. Different FeNi50 powder sizes were considered, and a range of deposition conditions were applied to examine their effects on porosity, deposition efficiency, microstructure of the final structure, and magnetic field properties.

In this study, two sizes of iron and stainless steel powders were binarily mixed into four groups with different weight percent fractions and the various mixtures and single-component powders were cold sprayed onto aluminum substrates. The deposition efficiencies (DE) of the powder mixtures and single-component powders were measured and are compared. The results show that the four binary mixtures exhibit different DE characteristics as a function of stainless steel wt% and that the small size mixtures have higher DE relative to the single-component iron powder. The difference is explained by particle-particle interactions (tamping and retention) that occur upon impact and only in the small size mixtures. The study also finds that changing spray parameters, such as feed rate, stand-off distance, gun travel speed, and gas temperature and pressure, has no effect on particle-particle interactions.

In this study, 43 μm 316L stainless steel and 23 μm commercial purity Fe feedstocks were used. The following coatings were made by cold spray: single component 316L, Fe, and their binary composites with nominal compositions of 20 wt.% Fe (20Fe), 50 wt.% Fe (50Fe) and 80 wt.% Fe (80Fe). The coatings were characterized (microstructure, flattening ratio, composition) and the cold sprayability metrics (DE, porosity, coating cohesion strength) were analyzed. Results show that the single component 316L coating has a much better DE and coating cohesion strength, and a slightly lower porosity as compared with the Fe coating, whereas all the composite coatings have the similar cohesion strength. Moreover, the 20Fe coating features the highest porosity and the lowest DE; 50Fe coating features the lowest porosity; and the 80Fe coating features the highest DE. To characterize the feedstock mixture composition, in addition to the usual approach of weight or volume fraction, the ratio of the 316L and Fe particle numbers in a mixture (i.e. particle number fraction), was calculated. Using this metric, the effects of the feedstock mixing composition on the cold sprayability of bimodal size 316L/Fe powder mixtures can be better explained.

One important trend in thermal spraying is the application of novel Fe-based corrosion/wear protection coating systems. A typical field of application for such corrosion and abrasive wear protection coatings are rotary dryers of paper machines. At the moment, these cylinders are coated by wire arc spraying. A disadvantage of the wire arc sprayed coatings is their high thickness, which has a heat-insulation effect, and their high roughness. Therefore, an expensive post production grinding process is necessary in order to achieve the required surface quality. The goal is to develop a HVAF process that enables the production of thin, dense and near net shape corrosion/wear protection coating systems, which significantly reduce the post-production time and costs. In this study, the HVAF coating process and a novel Fe-based feedstock material are investigated. In the first step the Fe-based powder is analysed thermally using differential scanning calorimetry, to investigate the solidification and melting temperature of the feedstock material. Furthermore, the influence of the spraying distance and the powder feed rate on the microstructure and porosity of the resulting coatings is investigated using light microscopy. Furthermore, the deposition efficiency of HVAF coatings is analysed regarding their economic efficiency.

Three Fe-based powder alloys, Höganäs Fe SP529, Fe SP586 and 6AB, have been deposited by HVOF and HVAF spraying onto mild steel plates. The sprayed samples were first ground and then shot peened using glass shot in order to seal the surface interconnected pores and other surface imperfections. The samples as ground and ground/glass shot peened were tested by salt spray (fog) exposition for 238 h according to ASTM B117/ISO 9227. FeSP586, HVOF and HVAF sprayed and glass shot peening samples achieved surface sealing enough to pass the test with appearance rating RA = 9 according to ISO 10289. All other samples achieved moderate to excessive pitting and/or moderate to excessive staining types of corrosion defects.

In this work, single component 316L and Fe coatings, as well as mixed 316L/Fe coatings with a dual powder feeder to obtain various feedstock compositions, were deposited to measure the deposition efficiency (DE). Individual particle impact tests were performed on single component and composite coatings to understand the particle impact behaviors during deposition. Bond ratio (BR) were determined for the impact tests to correlate with the DE. Results show that the 316L powder has a better DE than Fe, whereas the DE of the mixed 316L/Fe powders increases with increasing feedstock Fe content. The BR results correspond well with the DE of single component powders and mixed powders. The BR of 316L impacts onto composite coatings decreases with increasing Fe content, while the BR of Fe impacts plateaus at a high value regardless of composite coating composition, which leads to the increase of overall mixture DE.

This study compares the wear performance of thermally sprayed iron coatings with that of electrolytic hard chrome (EHC) plating. Three Fe-based alloy powders (FeSP529, FeSP586, 6AB) were deposited on S355 structural steel plates by HVOF and HVAF spraying and the resulting coatings and plating samples were subjected to dry sliding wear tests using a block-on-ring setup. Wear maps for all three Fe-based powder alloys are similar, showing regions of plasticity dominated wear, wear transition, and oxidational wear as a function of sliding velocity. More importantly, the wear rates of the sprayed coatings were ten times lower than those of the EHC plating samples.

In this study, stainless steel powder is mixed with commercially pure iron and cold sprayed on steel in order to produce a metal composite with controlled properties. For these composites, porosity is very low, and annealing at 600-1100°C for an hour reduces it further. Annealing also sinters interparticle interfaces, leading to vastly improved fracture properties. Fully annealed single-component stainless steel exhibits a much higher strength than annealed CP iron, but adding just 20% stainless steel to iron produces a composite with the same fully annealed strength as that of stainless steel.

This study evaluates a new iron-based hardfacing powder alloy. The powder, a FeWCrCB tool steel, is applied to mild steel substrates by plasma transferred arc (PTA) and laser cladding. The clad specimens are examined and tested for weldability, impact and abrasive wear resistance, and wear life. It is shown that the alloy solidifies in a narrow temperature range, first forming a fcc phase followed by a eutectic structure consisting of austenite, carbides, and borides. After solidification, the austenite is transformed to martensite. Impact wear testing shows that the new alloy offers approximately ten times longer life than tungsten-based nickel-matrix composites, but it was outperformed by 50% in abrasive wear tests.

This study investigates the feasibility of forming amorphous iron-based coatings using the cold spray deposition process. Splat tests of cold-sprayed SAM1651 (Fe48Mo14Cr15Y2C15B6 at.%) particles impacting a mild steel substrate were performed using varying gas temperatures and particle diameters. Specimen inspection by scanning electron microscopy revealed splat morphologies that varied from well-adhered particles to substrate craters formed by rebounded particles. Particle flow was analyzed using a finite element model, and impact conditions were predicted using an experimentally validated analytical model, in empirically generating a temperature/velocity window of successful particle deposition as a framework for ongoing work on the formation of cold-sprayed SAM1651 coatings. The results indicate that the unique characteristics of the cold spray process offer a promising means for the formation of metallic glass coatings that successfully retain the amorphous structure, as well as the superior corrosion and wear resistant properties of the feedstock powder.

HVOF and HVAF deposited coatings of three commercial Fe-based powder alloys have been ranked according to ASTM G76 solid particle erosion testing. The reference was electrolytic hard chrome (EHC) plating. The test results at 30 m/s abrasive particle velocity showed that 6AB powder alloy, when HVAF sprayed, Fe SP586 when both HVOF and HVAF sprayed meet the EHC plating reference erosion rate. 6AB HVOF sprayed and Fe SP529 both HVOF and HVAF sprayed powder alloys achieved two to three times higher erosion rate but were still at the same level of magnitude as the EHC plating reference.

In this investigation, particle image velocimetry (PIV) and direct imaging are used to measure particle velocities during cold spraying. Four feedstock powders were sprayed, including Ni, WC-Co, carbonyl Fe, and Cr steel. Multiple exposures at 500 ns intervals were used to measure in-flight particle velocities via direct imaging with a high shutter speed camera. Velocimetry measurements were made with a double-pulse laser and a high-resolution camera. With the minimum frame straddling time set to 100 ns, a maximum particle velocity of 1052 m/s was measured.

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.

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.

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/SiO 2 ) 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%.

In this study, iron-based coatings are deposited on stainless steel substrates by HVOF and HVAF spraying and are evaluated based on SEM examination, hardness measurements, and corrosion and wear testing and by comparison with WC-CoCr and CrC-NiCr reference coatings. The results indicate that corrosion resistance is insufficient if the coating is not fully dense and has open porosity. During spraying, the particles must be totally melted and rapidly solidified to achieve uniform coating composition. Open porosity and nonuniform distribution of alloy elements, particularly chromium, is seen to induce crevice corrosion in iron-based coatings.

New developments in the field of thermal spraying systems (increased particle velocities, enhanced process stability) are leading to improved coating properties. At the same time innovations in the field of feedstock materials are supporting this trend. The combination of modern thermal spraying systems and new material concepts has led to a renaissance of Fe-based feedstocks. Using modern APS or HVOF systems, it is now possible to compete with classical materials for wear and corrosion applications like Ni basis (e.g. NiCrBSi) or metal matrix composites (MMC, e.g. WC/Co or Cr 3 C 2 /NiCr). The work described in this paper focuses on that combination and intends to give an analysis of the in-flight particle and spray jet properties achievable with two different modern thermal spraying systems (kerosene driven HVOF system K2, 3- cathodes APS system TriplexPro-200/-210) using Fe-based powders. The velocity fields are measured with the Laser Doppler Anemometry (LDA). Additionally, resulting coatings are analyzed metallographically with regard to their properties and a correlation with the particle in-flight properties is given. The experimental work is accompanied by computational fluid dynamics (CFD) simulations of spray jet and particle velocities, leading to a comprehensive analysis and characterization of the achievable particle properties with state-of-the-art HVOF and APS systems.

In this paper, an iron/aluminum composite coating was prepared by cold spraying using iron and aluminum powder mixture and then annealed to aim at forming iron aluminides by suitable annealing treatment. The annealed coating was characterized using X-ray diffraction (XRD) to determine the coating phases and scanning electron microscope (SEM) with an EDXA energy dispersive spectroscopy (EDS) to examine the coating microstructure evolution. Results showed that the Fe 2 Al 5 intermetallic layer along some regions of the aluminum-iron boundaries forms after annealing at a temperature of 450°C, where true metal to metal contact had occurred. The content of Fe 2 Al 5 phase increased with raising annealing temperature. It was observed that some cracks were developed in Fe 2 Al 5 layer after annealing treatment at a high temperature of 600°C.

Iron based materials are classified as being more health and environmentally friendly as well as cost-effective (material and machining costs) compared to typical materials used for wear protection applications (e.g. cermets). The advantage which is seen in using very fine powders (< 15 μm), is their potential to spray relatively thin, dense near-net-shape coatings with comparable smooth surfaces. This can lead to lower coating as well as machining costs. In this work fine Fe-based powders (-15+5 μm) have been used in order to produce wear resistant coatings for applications in the printing industry by means of air plasma spraying (APS). With regard to oxidation problems of such fine Fe-based materials a shroud for the air plasma spraying system has been developed and deployed. The resulting coatings have been analysed with respect to the microstructure, micro hardness, chemical and phase composition as well as surface roughness (as-sprayed). The economical aspects have also been considered.

In this study, suspension plasma spraying is used to produce cast iron coatings that benefit from a graphite structure. In order to increase the graphite content, different hydrocarbons in the form of liquid suspension (hexane and toluene) and gas precursor (methane) were injected into the plasma stream along with iron powder. Besides promoting the formation of a soot carbon structure, liquid hydrocarbon injection also prevents in-flight particle oxidation, which is a major concern when spraying metals. In addition, it has been observed that using a shroud during spraying significantly increases the amount of soot carbon in cast iron coatings, which can be transformed into graphite by post annealing.