The objective of this work is to present a model of high pressure turbine blade, made of single crystal superalloy based on nickel. Their leading edges may be privileged sites of damage and crack initiation it is necessary to take into account in the manufacturing of turbine blades. This work consisted, initially to make a theoretical study, the turbine blade is modeled as a Timoshenko rotating beam . In a second step we made a numerical approach to study the effect of crack initiation on natural rotating frequencies, and the effect of cycle number on rigidity. The dynamic showed the variation of mechanical properties under crack propagation. In general, these changes in addition to initial defects of the material structure favoring the spread of cracks under isothermal loads. Finally an experimental study of the fatigue crack growth and the influence on the blade vibration is presented. This helped to highlight mechanical damage and determining the fatigue life predictive of component.

This paper is dedicated to the optimization of magnetic properties of iron based magnetic materials with regard to milling and coating process conditions using artificial neural network methodology. Fe–20wt.% Ni and Fe–6.5wt.% Si, alloys were obtained using two high-energy ball milling technologies, namely a planetary ball mill P4 vario ball mill from Fritsch and planetary ball mill from Retch. Further processing of Fe–Si powder allowed the spraying of the feedstock material using high-velocity oxy-fuel (HVOF) process to obtain a relatively dense coating. Input parameters were the disc Ω and vial ω speed rotations for the milling technique, and spray distance and oxygen flow rate in the case of coating process. Two main magnetic parameters are optimized namely the saturation magnetization and the coercivity. Predicted results depict clearly coupled effects of input parameters to vary magnetic parameters. In particular, the increase of saturation magnetization is correlated to the increase of the product Ωω (shock power) and the product of spray parameters. Largest coercivity values are correlated to the increase of the ratio Ω/ω (shock mode process) and the increase of the product of spray parameters.

Coatings produced by air plasma spraying (APS) are widely used to protect components against abrasive wear C by be reduced. To and corrosion. However, APS coatings contain Porosities and the properties of these coatings may there improve these properties, various methods could be proposed, including post-laser irradiation [1-4]. Firstly, PROTAL process (thermal spraying assisted by laser) has been developed as a palliative technique to degreasing and grit-blasting prior to thermal spraying. Secondly,. thermal spray coatings are densified and remelted using Laser treatment.In this study, a review of microstructure coatings prepared by laser-assisted air plasma spraying will be presented. Mechanical and magnetic properties will be evaluated in relation to changes in the coating microstructure and the properties of such coatings will be compared with those of as-sprayed APS coatings.

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.

In this paper, the FeSiBNbCu and FeSiBNbCu-Al coatings were synthesized using cold spray technique in order to produce ferromagnetic materials. Ultra-fine grain coatings are obtained using FINEMET nanostructured powders mixed with Aluminum. Various percentages of Aluminum characterized by its low hardness were taken in account. The obtaining coatings were formed of Aluminum matrix and randomly distribution of FINEMET particles. Indeed, 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 good soft magnetic properties.

Driven by economical and ecological reasons, thermoplastic-based coatings become a potential solution for anti-wear purpose. Two coating design concepts, flame spraying and printing PEEK (poly-ether-ether-ketone)-based coatings on Al substrate, were introduced in this paper. An amorphous PEEK coating was obtained by these two techniques. After being annealed, the coating presents a semi-crystalline structure. The friction and wear behaviors of PEEK-based coatings were investigated by means of ball-on-disc tests. The results show that PEEK coatings exhibit an excellent tribological performance with a relatively low coefficient of friction and wear rate. The semi-crystalline PEEK coating exhibits a lower friction coefficient and wear rate than the amorphous one. The additions of micron-sized particles such as SiC and graphite in PEEK coating can improve significantly the coating wear resistance.

In this work, the Fe–Si based thermal sprayed coatings were synthesized using HVOF in order to obtain ferromagnetic materials. Ultra-fine grain Fe–Si based coatings were synthesized by HVOF thermal spraying using nanostructured powders obtained from mechanical milling. Magnetic measurements revealed a soft magnetic character for all the coatings. Additions of boron, niobium and copper which can be regarded as non-magnetic inclusions caused a slight increase of coercivity. In order to investigate the stability of the magnetic properties of thermal spray deposits during their application, relaxation heat treatments was carried out. The result shown the high thermal stability in magnetic properties of the deposits and allow to using these deposits in several magnetic applications even to high temperatures.

Flame sprayed PEEK (poly-ether–ether–ketone) coatings, with an amorphous structure, were subjected to isothermal treatments with annealing temperatures from 180 to 300°C and holding times from 1 to 30min. The coating structures were studied by means of differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. All the annealed coatings exhibited semi-crystalline structures. Coexistence of thick and thin lamellae in the spherulites of annealed coatings can be deduced. The Knoop hardness and the interfacial adhesion of the coatings were examined. The annealed coatings exhibit higher hardness than the amorphous one. The formation of the thick lamellae is a determining factor for improving the coating hardness, which could restrict the motions and slippages of the polymer chains. However, the annealed coatings exhibit a weak adherence to the substrate. Some fissures or spherical porosities could be observed, in certain zones, on the coating/substrate interface. The formation of these fissures and porosities could be ascribed to the coating residual stress and the large volume contraction during the crystallization that occurred under the annealing conditions.

The development of amorphous and nanocrystalline materials has attracted significant interest in the field of new materials design. Indeed, the different properties, especially the magnetic properties of materials, are largely enhanced when the size of crystallites becomes nanometric. Besides, the presence of nanocrystalline structure implicates a macroscopic behaviour fairly different from the conventional microstructured materials. In this context, the microstructure and magnetic properties deposits obtained by High Velocity Oxy-Fuel (HVOF) from nanostructured FeSi-based feedstock powders were investigated. Ultra fine grain FeSi-based coatings were synthesised. X-ray analysis shows the formation of amorphous and nanostructured phases in some coatings. Mossbauer measurements confirmed also the presence of the amorphous phase. Magnetic measurements revealed a ferromagnetic character for all the coatings. Though the presence of nanostructure has a significant effect to modify magnetic properties, the results also indicated that the boron, niobium and copper incorporated in the feedstock-milled powders have little effect on these properties. (c) 2006 Elsevier B.V. All rights reserved.

The paper studies the diagnostic, structure, and magnetic properties of FeSi coatings deposited by high-velocity oxy-fuel (HVOF) using microcrystalline powders. Diagnostics of in-flight particles showed that the temperature and velocity particles were sufficient to obtain a good coating with a homogeneous microstructure.X-ray diffraction (XRD) patterns showed that the FeSi coatings were a crystalline structure with basically cubic structure alpha(1)-Fe3Si (DO3) Magnetic measurements showed that FeSi coatings exhibited a good soft ferromagnetic character; its magnetic properties remained stable even at high temperatures. (C) 2004 Elsevier B.V. All rights reserved.

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.

The effect of the HVOF process parameters on coating porosity and magnetic properties of FeNb deposits was studied using artificial neural network methodology. A first artificial neural network was used and optimized to relate process parameters to the magnetic properties of the coating. The effect of process parameters on magnetic properties was quantified by a second network. Predicted magnetic properties correlated with coating porosity were obtained using these optimized network structures. It was then possible to identify the role of porosity with regards to improvement of coercivity and saturation magnetization.

Abstract 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.

Substrate temperature is nowadays recognized as a key parameter to optimise the coating quality in the thermal spraying process. Generally parts being processed are in motion and therefore non contact temperature measurement devices are appropriate. In contrast to thermocouples, optical pyrometers have several advantages. First, they are easy to install and second they do not bring any disturbance to the measured system. Meanwhile, several problems may arise with those devices which are not always considered as they should be and in particular the variation of material emissivity temperature, the effect of the reflection of the external radiation or the attenuation of the optical signal due to the variable transmissivity of the optical path. The aim of this work was to develop algorithms for correcting optical pyrometer temperature measurements during thermal spraying by taking into account emissivity variations and radiation reflexion on the components. Emissivity of some materials with respect to the specific spectral band of the pyrometer and the influence of reflected radiations were measured. Results are discussed in order to point out the influence of each parameter on the temperature value.

The paper studies the effect of high-velocity oxy-fuel thermal spraying parameters, in particular spray distance and oxygen flow rate, on coating porosity and magnetic properties of FeSi and FeSiB deposits using the artificial neural network methodology. The magnetic properties correlated to coating porosity were obtained using an optimized network structure. The predicted results permitted to point out the role of porosity for varying the coercivity and saturation magnetization and the stability of magnetic properties with respect to the considered spray parameters.

We studied the effect of high-velocity oxy-fuel (HVOF) coating process parameters on magnetic properties of FeNb considering the role of coating microstructure. The present study was conducted using artificial neural network methodology. A first artificial neural network was optimized to relate process parameters to coating microstructure features. The effect of process parameters on magnetic properties was quantified by a second network. Predicted magnetic properties correlated to microstructure features were obtained using these optimized network structures. It was then possible to point out the role of microstructure for improvement coercivity, saturation magnetization and remanent magnetization.

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.

The development of amorphous and nanocrystalline materials has attracted significant interest in the field of new materials design. Indeed, the magnetic, chemical and mechanical properties of materials are largely enhanced when the size of crystallites becomes nanometric. In addition, the absence of crystal structure implicates a macroscopic behavior fairly different from that of corresponding to the polycrystalline state, especially, mechanical and magnetic properties.In this work, HVOF and APS thermal spraying were used to produce silicon-iron and niobium-iron alloys coatings. Adjusting the spraying conditions, amorphous coatings were obtained from the FeNb powder. However, for the silicon-iron powder, crystalline deposits were produced in all cases. Boron additives were used to improve the aptitude of the silicon-iron alloy to form an amorphous phase. In this perspective, first principle calculations were elaborated to investigate the electronic structure of crystalline FeNb and Fe3Si. It was shown that the introduction of boron impurities into the alloy matrix lead to the lowering of the structural stability, and made its electronic density of state (DOS) more comparable to the corresponding niobium-iron structure. (C) 2003 Elsevier B.V. All rights reserved.