Effect of HVOF sprayed TiC+25%CuNi-Cr coatings on sustainability and cavitation erosion resistance of SS316 steel

Cavitation erosion (CE) resistance of thermal spray-coated steel specimens was compared with that of uncoated steel specimens. Titanium carbide (TiC) was deposited along with 25 weight percentage of cupronickel (CuNi) and chromium (Cr) as binding materials over stainless steel (SS316) acting as the substrate, using High Velocity Oxy Fuel (HVOF) thermal spray coating process. Microstructures and morphologies of the above-stated coatings were analyzed by employing Scanning Electron Microscopy (SEM) technique. Surface roughness, microhardness, and cavitation erosion resistance (CER) tests were conducted over prepared samples. Experimentation was carried out using a high velocity water jet test rig machine where specimens submerged in fresh water were pounded by variable high velocity water jet and stand-off distance (SOD) for a predefined set of time. Experimentation was followed by structural analyses of eroded specimens along with the evaluation of the weight of material expunged during the process of cavitation and thus found the extent of erosion. From the data so obtained, it was deduced that HVOF sprayed coatings were very effective in resisting CE and may improve the sustainability of the water handling components in comparison to the uncoated SS316 substrate. Coatings deposited with an adequate amount of cupronickel were found to be more repellent to pressure waves induced during the cavitation process than other uncoated steel specimens. Further, it is also observed that cavitation erosion also depends upon the variability in impingement parameters.