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.

Atmospheric plasma spray is considered as one of the most efficient methods for forming FeAl intermetallic coatings. But the performance of plasma-sprayed FeAl coatings was remarkably limited because of oxidation and phase transformation during the preparation. In the present work, FeAl intermetallic coatings were prepared by atmospheric plasma spray combined with dry-ice blasting. The microstructure, oxidation and porosity of FeAl intermetallic coatings were investigated. In addition, XRD measurements were also employed to illustrate the lattice-scale performance, e.g., dislocation density. The temperatures during plasma spray were also measured using an infrared pyrometer system. The results show that a denser B2-FeAl coating with a lower content of oxide and lower phase transformation can be achieved because of the cryogenic effect and the mechanical effect of dry-ice blasting. Moreover, the microhardness of FeAl coating was nearly increased by 72%, due to the lower porosity and higher dislocation density.

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.

This paper reports morphological study of coatings microstructure performed on two selected reference abradable materials: AlSi-hBN and NiCrAl-Bentonite. Scanning Electron Microscopy (SEM) was used to obtain adequate micrographs for analysis. The porosity and non-metal particles morphology was assimilated to elliptical inclusions within the metallic matrix. Accordingly, they were described by means of three different geometrical parameters related to the shape, size and orientation distribution, allowing additional statistical analysis on the coatings.

This study was undertaken to investigate the influence of the initial powder particle size on the microstructure development in a Cu-3wt% Ag alloy obtained by vacuum plasma spraying of a mixture of copper and silver powders. Various mixtures of powder particles were used where the copper powder particle size was kept as –80/+40 μm, while the silver powder particle size fraction was varied. Vacuum plasma spraying (VPS) in inert gas atmosphere was used to elaborate thick coatings (2 mm) with limited oxygen contamination. Significant variations in microstructure were obtained depending on the Ag powder size fraction that was used. These differences in behavior are discussed taking into account differences in the solid state precipitation mechanisms in the alloy.

FeAl iron-aluminide based materials with the ordered B2 structure are excellent candidates for use in high temperature applications because of the combination of good mechanical properties, low density, low cost and availability of raw materials, and improved oxidation resistance. The aim of this article is to produce an ultra-fine grained FeAl coating by HVOF thermal spraying of milled powders and characterize the fine scale features of its microstructure. Comparison is made with a more conventional coating obtained by projection of powders obtained by atomization. Starting powders and coatings were investigated using X-ray diffraction and transmission electron microscopy. It was observed that the coating obtained from milled powders had a microstructure essentially characterised by a nanometer grain size and the presence of a disordered FeAl phase.