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