Effect of Laser Remelting on the Microstructure and Erosion-Corrosion Resistance of NbC and Nb2O5 Thermal Spray Coatings

Monday, May 27, 2019: 11:40
Annex Hall/F203 (Pacifico Yokohama)
Prof. Hipólito D C Fals , Universidad de Oriente, Santiago de Cuba, Cuba
Prof. João Batista Fogagnolo , State University of Campinas, Campinas, SP, Brazil
Dr. Leonardo Fanton , State University of Campinas, Campinas, SP, Brazil
Ms. M.J.X. Belém , UNIMEP - Methodist University of Piracicaba, Santa Bárbara d'Oeste, Brazil
Prof. Angel Sanchez Roca , Oriente University, Santiago de Cuba, Cuba
Prof. Carlos R. C. Lima , UNIMEP - Methodist University of Piracicaba, Santa Bárbara d'Oeste, Brazil

Niobium is a largely available ductile transition metal. NbC presents low wear characteristics. Nb2O5 shows high corrosion resistance in several environments. NbC and Nb2O5 do not have so far any restriction related to human toxicology nor as substances of very high concern like Co and W related alloys. Nb2O5 and NbC were deposited by LV-Flame Spray on steel substrates, remelted using a 400 W Power Generated Yerba Fiber Laser in a chamber for argon atmosphere control. For the selection of the remelting parameters, isolated passes were performed using three focal distances and three remelting speeds. Erosion-corrosion tests on a suspension of SBF were performed on a mixing vessel tribometer before and after remelting. The surfaces and cross sections of the coatings were characterized by Optical and Scanning Electron Microscopy, accompanied by microanalysis  and X-ray diffraction. In the cross section analyzes, it was verified that the Laser remelting reduced the porosity of the layers, and eliminated the defects of the coating/substrate interfaces. It was found that the dilution of the coating with the substrate formed a gradient of chemical composition and consequently of mechanical properties that result in an increase in erosion-corrosion resistance of both coatings after the Laser remelting process.

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