Improving corrosion properties of high-velocity oxy-fuel sprayed inconel 625 by using a high-power continuous wave neodymium-doped yttrium aluminum garnet laser |
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Authors: | J Tuominen P Vuoristo T Mäntylä M Kylmälahti J Vihinen P H Andersson |
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Affiliation: | (1) Institute of Materials Science, Tampere University of Technology, FIN 33101 Tampere, Finland;(2) Institute of Production Engineering, Tampere University of Technology, FIN 33101 Tampere, Finland |
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Abstract: | Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite
the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying, these coatings
may in certain service conditions show inadequate performance,e.g., due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding
bulk materials. The main cause for a low bond strength in thermalsprayed coatings is the low process temperature, which results
only in mechanical bonding. Mechanical and corrosion properties typically inferior to wrought materials are caused by the
chemical and structural inhomogeneity of the thermal-sprayed coating material. To overcome the drawbacks of sprayed structures
and to markedly improve the coating properties, laser remelting of sprayed coatings was studied in the present work. The coating
material was nickel-based superalloy Inconel 625, which contains chromium and molybdenum as the main alloying agents. The
coating was prepared by HVOF spraying onto mild steel substrates. High-power continuous wave Nd:YAG laser equipped with large
beam optics was used to remelt the HVOF sprayed coating using different levels of power and scanning speed. The coatings as-sprayed
and after laser remelting were characterized by optical microscopy and scanning electron microscopy (SEM). Laser remelting
resulted in homogenization of the sprayed structure. This strongly improved the performance of the laser-remelted coatings
in adhesion, wet corrosion, and high-temperature oxidation testing. The properties of the laser-remelted coatings were compared
directly with the properties of as-sprayed HVOF coatings and with plasma-transferred arc (PTA) overlay coatings and wrought
Inconel 625 alloy. |
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Keywords: | corrosion HVOF Inconel 625 laser remelting Nd:YAG laser |
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