RESUMO
Cold Spray Additive Manufacturing (CSAM) is a thermal spray technique that is typically used for the repair of metallic components. One of the challenges of CSAM is to improve the geometrical accuracy of the sprayed parts, along with overcoming the inferiority of the mechanical properties of the deposits by tailoring their microstructure with different deposition strategies. For this, Cu, Al, Ti, and Ti6Al4V substrates were reconstructed by two Cold Spray (CS) methods: Traditional (T) and a novel strategy, Metal Knitting (MK). The final geometry, microstructure, and mechanical properties of the reconstructed parts by these two methods were compared. Additionally, we investigated the effects of annealing on the microstructure of sprayed components and its influence on adhesion, resistance to erosion, and abrasive wear. The results indicate that annealing effectively reduces the microstructure defects of the remanufactured parts (up to 30% porosity reduction) and improves the adhesive strength (i.e., below 30 MPa for as-sprayed deposits, and up to 160 MPa for heat-treated Ti4Al4V deposits). Notably, the abrasive and erosive resistance of the Cu and Al annealed deposits sprayed by MK gave very similar results compared to their bulk counterparts, suggesting that it is an efficient method for the reconstruction of damaged parts.
RESUMO
Cold Spray Additive Manufacturing (CSAM) is an emergent technique to produce parts by the additive method, and, like other technologies, it has pros and cons. Some advantages are using oxygen-sensitive materials to make parts, such as Ti alloys, with fast production due to the high deposition rate, and lower harmful residual stress levels. However, the limitation in the range of the parts' geometries is a huge CSAM con. This work presents a new conceptual strategy for CSAM spraying. The controlled manipulation of the robot arm combined with the proper spraying parameters aims to optimize the deposition efficiency and the adhesion of particles on the part sidewalls, resulting in geometries from thin straight walls, less than 5 mm thick, up to large bulks. This new strategy, Metal Knitting, is presented regarding its fundamentals and by comparing the parts' geometries produced by Metal Knitting with the traditional strategy. The Metal Knitting described here made parts with vertical sidewalls, in contrast to the 40 degrees of inclination obtained by the traditional strategy. Their mechanical properties, microstructures, hardness, and porosity are also compared for Cu, Ti, Ti6Al4V, 316L stainless steel, and Al.
RESUMO
Wear processes are always present in components exposed to different work situations. Hydraulic turbines in electric power generation and ship propellers are good examples of components subject to wear and corrosion. One way to protect these components, for example, is the deposition of coatings by thermal spray processes. Indeed, there are several wear or corrosion mechanisms acting simultaneously, and the validation of the mechanisms separately, is not the best way to select the better material. When materials have passivation as protective mechanism against corrosion, the mass loss due erosion can affect the materials selection. This paper study the combined effect of the corrosion on the cavitation mass loss, as well as, the cavitation mass loss influence on the corrosion properties of a chromium carbide Cr3C2-25NiCr coating. Despite of the modification of the erosion mechanism on the cavitated samples under 3,5% NaCl solution, the volume loss did not show any significant alteration. Cavitation mass loss increase the corrosion process, reducing significantly the corrosion potential and raising the corrosion current. It was observed that the cavitation of the Cr3C2-25NiCr HVOF coating influences much more the corrosion kinetics, than the corrosion affects the cavitation resistance.
