This study focuses on the development of thermally sprayed coatings for magnetic data storage. In the con-text of Industry 4.0 and the associated digitization of production, there is more demand than ever for suitable data storage on components in order to be able to automatically identify and process products. The resistance of certain sprayed coatings to harsh environmental conditions, make them a promising alternative compared to other solutions for dynamic data storage such as the RFID chips already available on the market. This area of application results in the requirement for a high stability of the written data against external influences such as temperature, wear or interference fields. These requirements can be met by the tailored choice of material including a sufficient magnetic anisotropy of the sprayed coatings. The influence of the spraying process on the formation of the magnetic material properties in the applied coatings is discussed with the aim of being able to change and optimize them in a targeted manner. The characterization of the produced samples is done by structural and magnetic analysis methods

This paper presents developments in the field of induction capable coatings, mainly used for induction cookware on aluminum or copper base material, based on work by OBZ Innovation GmbH. The aim was to develop a new type of “intelligent” induction coating that influences the magnetic susceptibility depending on its temperature. This not only allows to limit the maximum reachable temperature, but also supports the uniform heat distribution over the bottom of the cookware. Thus, this new type of “intelligent” induction coating regulates such important boundary conditions, independently of undesirable or even unsafe settings of an end-user. Finally, this makes cooking easier, healthier and more durable as it prevents damaged PTFE sealings and safer by reducing the danger of fire because of overheating and burning. Additionally, such coatings can be used in further applications, whenever a passively limited or uniform heat distribution is advantageous, for example when the temperatures are too high or in general an electronic control system is for technical or economical reasons not suitable.

Thermal spraying produces coatings with relatively rough surfaces compared to other deposition methods. In this work, NdFeB coatings were deposited on stainless steel by plasma spraying at various standoff distances. Some of the coatings were also annealed. Surface roughness profiles of as-sprayed and heat-treated coatings were measured by contact profilometry and analyzed via statistical methods. The effect of standoff distance and annealing on roughness is discussed along with the significance of measurement direction and evaluation length.

The aim of this work is to determine whether local disordering plays a role in the bonding of FeAl intermetallic coatings produced by cold spraying. XRD analysis of the powder and coatings revealed superlattice peaks, indicative of an ordered intermetallic structure. Nevertheless, locally disordered structures were detected in the deposits by TEM imaging. This may be related to a deformation induced order-to-disorder transformation due to the high strains involved in cold spraying, which is supported by comparing the magnetic properties of the deposits with those of HVOF sprayed coatings produced using disordered ball-milled feedstock.

In this work, Fe-40Al coatings are produced by atmospheric plasma spraying using a nanostructured feedstock exhibiting a very low degree of order. The as-sprayed deposits consist of fundamental FeAl phases, Fe3Al phases, and oxides and are found to be ferromagnetic due to the low degree of order and the presence of unmelted nanoparticles retained from the feedstock. The magnetic properties of the coatings are shown to be heterogeneous in the parallel and vertical direction.

This study shows that thermal spraying is a viable technique for the deposition of barium hexaferrite layers suitable for microwave absorption applications. More specifically, the study shows that impact quenching of molten BaCoTiFe 10 O 19 hinders the crystallization of the hexaferrite phase. Consequently, when spraying conditions induce near-full melting of the feedstock, the coating mostly consists of spinel and a glassy phase, a state with poor magnetic properties. These phases can be converted to hexaferrite by annealing, but in order to obtain enough crystalline hexaferrite in as-deposited layers, a controlled amount of unmelted material must be preserved. Atmospheric plasma spraying proved to be well suited for this purpose, producing layers with excellent magnetic properties, close to those of pure crystalline BaCoTiFe 10 O 19 . In these coatings, dense regions entrain many unmelted agglomerates of micron-sized particles, effectively preserving the hexaferrite phase.

The cold gas dynamic spray process, or cold spraying (CS), represents a radical departure from conventional thermal spray (TS) methods in that the deposition process relies purely on kinetic energy rather than on a combination of thermal and kinetic components. A potential advantage of this process over TS is the ability to generate dense coatings retaining initial material chemistry and phase composition with a very little oxidation. Also, low temperature process (no bulk particle melting) eliminates solidification stresses and enables thicker coatings. However, hard brittle materials like ceramics can not be sprayed without using ductile binders. In this study, magnetic alloys such as FeSiBNbCu also called Finemet and FeSiBNbCu-Al with various percentages of Aluminum coatings were synthesized using cold spray technique in order to produce ferromagnetic materials. Ultra-fine grain coatings were obtained using FINEMET nanostructured powders mixed with Aluminum as ductile binder in order to improve adherence. Magnetic measurements revealed a soft magnetic character for all the powders and the coatings. 25% of Al was considered as ideal to produce a homogenous coating with suitable magnetic properties.

One of the unique advantages of the kinetic spray process is its ability to mix constituents that would normally react with each other to form coatings. We have used this attribute to produce composite coatings with different rare earth iron alloys (REFe 2 ) and several ductile matrices. Composite coatings of Terfenol-D ((Tb 0.3 Dy 0.7 )Fe 1.9 ) and SmFe 2 were combined with ductile matrices of aluminum, copper, iron, molybdenum, tantalum, and nickel. Evidence of an induced magnetic coercivity was measured for the REFe 2 - Mo and Fe composite coatings. Coatings were produced on flat substrates and shafts. Coating morphology as well as the physical, magnetostrictive and magnetic properties of these coatings will be discussed.

Amorphous metallic alloys can be produced by rapid quenching from the metallic liquid at sufficient cooling rates to suppress the nucleation and growth of crystalline phases. The cooling rates required depend on the alloy constitution; generally the necessary values are in the order of 106 Ks-1[1]. There has been considerable interest in the manufacture of Fe-based metallic glasses because they possess attractive combinations of properties such as high hardness, good abrasive wear resistance together with enhanced corrosion resistance and good magnetic properties. However, in order to achieve these cooling rates in metallic alloy melts, samples less than 50 ƒÝm thick must be suddenly brought into good thermal contact with an efficient heat sink. Hence, these amorphous alloys are frequently produced in the form of ribbon or powder. An alternative approach consists to employ thermal spraying to deposit the alloys directly onto a substrate, in the form of a protective coating about 200 ƒÝm thick. In this study, FeSi powder was chosen as feedstock material. It is characterized by its good magntic properties [2- 7]. In order to control temperature and velocity of the in-flight particles during the coating deposition, on-line measurement of flame sprayed FeSi particles were performed with high-speed two-color pyrometer used especially for the spray forming process. In the same time, a wide band spectral pyrometer (LAND INFRARED) was used to monitor the coating surface temperature to ensure achieving good cooling rates. X-ray diffraction patterns show that the FeSi coatings structure present a crystalline phase and magnetic measurements indicate the soft ferromagnetic character of this last. Abstract only; no full-text paper available.

In this study, the magnetic properties of iron-based coatings obtained by HVOF thermal spraying were investigated. These properties were correlated to alloy type, heat treating temperature and coating thickness using artificial neural network method. Among coating characteristics, porosity is regarded as an influential parameter on the magnetic properties. Therefore, the role of the microstructure was particularly emphasized in this study. Magnetic properties, especially coercivity, showed a weak decrease with the addition of alloying elements. However, these properties remained nearly unchanged at high temperatures and for large coating thicknesses. Porosities are regarded as defects anchoring Bloch walls and consequently promoting an increase of coercivity.

Ultra fine grain Fe-Si based coatings were synthesised by HVOF thermal spraying of nanostructured powders obtained from mechanical milling. Magnetic measurements revealed a soft magnetic character for all the coatings. Additions of boron, niobium and copper were investigated. The thermal stability and the evolution of the coercivity with temperature were observed to be remarkable.

Iron-based alloys were sprayed on a copper substrate using high velocity oxy-fuel process to form amorphous coatings. Two modes of cooling were used, water and air, in order to increase the particles speed solidification. Structures and magnetic properties of FeNb and FeSi deposits have been characterized. X-ray diffraction patterns showed that FeNb coatings present a partially amorphous structure, however, in the case of FeSi alloys, their structure is completely crystalline. The use of the two modes of cooling has given almost the same results for the two types of powders. As a consequence, magnetic properties of this material could be improved by using a heat treatment.

Spinel soft ferrites such as NiZnFe 2 O 4 are of great interest due to their extensive applications in magnetic-optics, microelectronics, and microwave devices. This study deals with the production of thick Ni 0.5 Zn 0.5 Fe 2 O 4 magnetic films (>50 microns) using high velocity oxy-fuel (“HVOF”) thermal spray. With the HVOF process, high density films more than 98% theoretical density were prepared, apparently due to the high velocity of droplets in the process. The influence of the fuel composition on coating structure, deposition efficiency, and magnetic properties of the Ni-Zn ferrite films was investigated. Better magnetic properties were obtained in the as-sprayed film formed with a neutral or oxygen-rich flame. The decomposition of the ferrite material occurred with a fuel-rich flame and resulted in a reduction in magnetic properties. However, the magnetic properties could be improved dramatically after heat treatment. Pellet and toroid samples of these films were produced for evaluation of magnetic properties by saturation magnetization and magnetic permeability. The permeability exhibited a very flat response to high frequencies up to 13 MHz.

The development of amorphous and nanocrystalline materials took a significant part in search on materials these last years. Indeed, the magnetic, chemical and mechanic properties of materials are greatly modified when the size of crystallites becomes nanometric. The absence of crystal structure involves a macroscopic behaviour of the alloy, which is completely different from the same alloy in a polycrystalline state, particularly magnetic and mechanical properties. We have carried out coatings by APS plasma thermal spraying on a copper substrate using three types of powders, FeB (17,5% wt-B), FeSi (6,5% wt-Si) and FeNb (67,2% wt-Nb). Structure of these coatings was characterized by SEM and X-rays. We have also tested the magnetic properties of these deposits. Results obtained showed that the FeNb alloys are amagnetic with a partially amorphous structure, however FeSi and FeB alloys presented a microcrystalline structure with soft magnetic properties.

Coatings with magnetic properties were produced by vaccum plasma spraying of different Nd-Fe-B powders onto stainless¬steel substrates. Microscopic examination of the coatings in a light microscope revealed a low porosity and a good bonding to the substrate. Scanning electron microscope examinations have shown different phases in these coatings. The magnetic properties of the coatings are also presented. Paper text in German.

Physical properties of coatings based on Fe-B, Fe-Ni-B, Fe-Cr-P-C, Fe-Ni-Si-B, Ni-P, Ni-Nb and Co-Fe-B-Si, deposited by the methods of flame, plasma-arc, and detonation spraying were investigated. The coatings have mostly the amorphous structure with the volume content of the amorphous phase equal to 75-95 %. Values of the distribution and temperature coefficients of electric resistance of the coatings, depending upon a method and conditions of spraying, as well as upon their treatment parameters, were determined. Comparative studies of these coatings and thin amorphous strips produced by the melt spinning method were conducted. The amorphous coatings of ferromagnetic iron and cobalt alloys are shown to be magnetically soft materials and are characterized by a high magnetic induction combined with a high magnetic permeability. As compared with the amorphous strips, Curie temperature of the amorphous ferromagnetic coatings is by 50-140 K higher and their anisotropy of magnetic properties is lower.

A diameter of 30 mm polycrystalline diamond film has been deposited by magnet-enhanced DC plasma jet CVD. The diamond film was characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and surface profilograph. Results reveal that under the same depositing parameters, magnetic field can increase purity of diamond film, improve thickness uniformity of diamond film, but no influence on crystal perfection and size of microcrystal of diamond film. A discussion on magnetic effect is presented.