Executive Summary : | This project aims to develop a new kind of coating with the same or better performances as hard chrome coatings using combined techniques of the high velocity oxy fuel HVOF technology and arc vacuum PVD technology. In the last decades, the electrodeposited hard chromium coating has been widely used in surface engineering practice to protect a broad range of mechanical components from corrosion and wear but is known to be carcinogenic, and its solution severely pollutes the environment. The HVOF process can deposit a hard multi-component thick 400-500 microns metal-carbide or cermet coatings at a high deposition rate but are porous and have residual stresses. The vacuum arc technology permits a super hard 40- 45 GPa corrosion-resistant nitride-ceramics coating with a low friction coefficient 0.3 and smooth surface finish but is very thin and brittle. In the proposed work, composite PVD coating such as AlCrN/ZrCN are deposited on the HVOF sprayed Carbide-NiCr coatings surface to improve hardness, wear resistance, and anti-corrosive performance. The composite coating is expected to have better adhesion to the steel substrate and a lower probability of cracking. It is essential to emphasize the synergetic effect in combining such different coatings where the lower HVOF sprayed layer is a thick and hard ground for the upper vapour deposited super hard nitride ceramic coating. Also, the vapour deposited coating covers all porous of the lower layer effectively. In application, once the upper layer is worn off, the lower HVOF layer will work as a protective run-in layer. The sliding adhesive wear resistance of the Carbide-NiCr/AlCrN/ZrCN multi-layer system will be evaluated using a Ball-on-disc tribometer. The corrosion resistance of the multilayer coating system will be determined using an electroChemical corrosion setup. Cyclic oxidation tests are conducted at different temperatures to ascertain the kinetics of oxidation. The two-layer coating deposited with reduced thickness 200-250 microns can prevent cracking and possesses better hardness, corrosion and wear resistance than coating developed separately using HVOF and vapour technology. |
Co-PI: | Dr. Ravikiran Kadoli, National Institute of Technology Karnataka (NITK), Surathkal, Karnataka (575025), Dr. Sharnappa Joladarashi, National Institute of Technology Karnataka (NITK), Surathkal, Karnataka (575025) |