Thermally sprayed coatings rely on mechanical anchoring as the main bond mechanism, which depends on previous surface preparation, i.e. cleaning, roughening and preheating. In this work, aluminum oxide (Al 2 O 3 ) grit was used to blast surfaces in order to show the influence of the abrasive reuse on the decrease in granulometry, surface roughness, cleanliness and consequently on the coating adhesion strength. SEM images illustrate the difference in grain sizes and EDS was used to study the contamination of the abrasive with the substrate elements. To understand the granulometry reduction, the samples were blasted and after each cycle the abrasive was classified with different sieves, and then the mass was measured. The abrasive was mixed and the process was repeated for five cycles. Sa, Sz, Ssk and Sku were the parameters chosen for the roughness characterization and were compared to the grain size decrease, showing a significant correlation between them. Lastly, the adhesion strength of the coatings was measured according to ASTM-C633 and compared to both the roughness and blast cycle. The results show that a small fraction of abrasive with finer grit reduces the roughness significantly. However, the adhesion strength was not affected.

Aluminum coatings applied by thermal spraying are widely used for protection against marine corrosion. The HVOF process produces aluminum coatings with high particle velocity, at a higher temperature for longer, permitting a high adhesion among the deposited particles. The objective of this work was to analyze how the microstructure of the aluminum coating sprayed by HVOF was formed on different complex surfaces. The influence of different deposition process parameters on the coating, varying the angle of incidence during deposition, substrate preheating and nitrogen flow was studied. Outer corner and convex surfaces presented greater uniformity in the formed microstructures. The angle of incidence was the most influential parameter on the coatings, filling complex profiles better, with 60° of incidence, although the 90° of incidence increased the adhesion. The potentiodynamic polarization test was performed to evaluate the corrosion resistance of coatings. The higher preheating and lower angle of incidence increased the corrosion resistance of coatings. Corrosion tests in salt spray are in progress in order to compare with continuous results.

The HVOF process is characterized by the deposition of a low porosity and oxide content coating and the particles projected by this process have high kinetic energy, resulting in a high density coating. However, the presence of non-melted particles can affect the porosity, tensile adhesion, hardness and surface finishing. In this article, the influence of the shot peening treatment on morphology, porosity, tensile adhesion and roughness of some FeMnCrSi(Ni/B) HVOF coatings have been studied. High carbon steel particles with spherical geometry were used for shot peening. The results show that the shot peening reduces the porosity, mainly in the coatings with higher porosity level, and generates an increase of hardness with no phase transformations. The increase in adherence is also a benefit generated by the treatment. The surface quality analyses show a significant roughness reduction. With shot peening a compressive residual stress state was achieved in the coating, improving mechanical properties.