Faculty Publications
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Item High temperature erosion behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere coating(Elsevier B.V., 2017) Mathapati, M.; Ramesh, M.R.; Doddamani, M.High temperature erosive behavior of plasma sprayed NiCrAlY-25WC-Co/cenosphere coating deposited on MDN 321 steel is investigated in the present work. Coating is characterized using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Microhardness, porosity, adhesion strength, fracture toughness and ductility of the coating are quantified. Solid particle erosion test is conducted at 200, 400 and 600 °C with 30 and 90° impact angles using alumina erodent. Optical profilometer is used to evaluate erosion volume loss. Erosion resistance of the coating is observed to be higher than the substrate for the test temperatures chosen and noted to be more prominent at lower impact angle and higher temperature. High temperature stability of mullite, alumina and oxide layer assists in increasing erosion resistance of coating. The eroded coating surface morphology reveals the brittle mode of material removal. © 2017 Elsevier B.V.Item High-Temperature Erosive Behavior of Plasma Sprayed Cr3C2-NiCr/Cenosphere Coating(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Mathapati, M.; Doddamani, M.; Ramesh, M.R.This research examines the deposition of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings on MDN 321 steel through the process of plasma spray. In this process, the solid particle erosion test is established at 200, 400, 600 °C with 30° and 90° impact angles. Alumina erodent is adopted to investigate the erosive behavior of the coating at higher temperatures. The properties of the Cr3C2-NiCr/cenosphere coating are established based on the microhardness, the adhesive strength, the fracture toughness, and the ductility. To quantify volume loss as a result of erosion, an optical profilometer is used. At higher temperature, decrease in the erosion volume loss of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings is observed. The erosion-resistive property of Cr3C2-NiCr/cenosphere coating is higher than that of MDN 321 steel by 76%. This property is influenced by high-temperature stability of mullite, alumina, and protective oxide layer that is formed at elevated temperatures. The morphology of eroded coating discloses a brittle mode of material removal. © 2018, ASM International.Item Elevated temperature solid particle erosion behaviour of carbide reinforced CoCrAlY composite coatings(Institute of Physics Publishing helen.craven@iop.org, 2018) Nithin, H.S.; Desai, V.; Ramesh, M.R.CoCrAlY+WC-Co and CoCrAlY+Cr3C2-NiCr coatings are deposited on nickel based alloy using atmospheric plasma spray technique. Mechanical properties such as microhardness, adhesion strength and fracture toughness of coatings are evaluated. Elevated temperature solid particle erosion behaviour of these coatings are investigated at 600 °C using alumina erodent at 30 and 90° impact angle. Coatings are characterized utilizing Scanning electron microscope (SEM), x-ray diffraction (XRD) and Energy dispersive spectroscopy (EDS). CoCrAlY+WC-Co coating shows higher hardness, adhesion strength and fracture toughness than CoCrAlY+Cr3C2-NiCr coating. CoCrAlY+WC-Co coating exhibited approximately 3 times higher erosion resistance than CoCrAlY+Cr3C2-NiCr coating at 90° and 30° impact angles. SEM images of eroded surfaces of coatings reveals the combination of ductile and brittle fracture. CoCrAlY+Cr3C2-NiCr coating shows severe cracks, craters, carbide pull out and chipping than CoCrAlY+WC-Co coating. High temperature erosion is a combination of simultaneous building up of material by oxidation and removal of material by erosion process. Thus reforming the erosion process to oxidation modified erosion process. © 2018 IOP Publishing Ltd.Item Evolution of Microstructure and High-Temperature Tribological Performance of Self-Lubricating Nickel-Based Composite Tungsten Inert Gas Coatings(Springer, 2021) Gudala, S.; Ramesh, M.R.; Siva Shanmugam, S.S.The present study aims to assess the effect of Ag/BaF2 solid lubricant encapsulation in the nickel-based composite coatings for high-temperature tribological applications. The composite coatings (NiCrSiB/WC and NiCrSiB/WC/Ag/BaF2) have successfully been fabricated on the titanium 31 substrate by tungsten inert gas (TIG) cladding technique. The influence of the TIG processing current on the microstructure, microhardness, and fracture toughness was investigated. Mechanical characteristics of the coatings were further correlated with the microstructural morphologies. The coating fabricated at 70 A exhibited significantly higher hardness than other coatings. The tribological performances of the NiCrSiB/WC/Ag/BaF2 composite coatings were superior to those of the NiCrSiB/WC coatings at both low (200 °C) and high (600 °C) temperatures. The synergistic lubrication effect of the Ag/BaF2 solid lubricant combination provided lubrication at a wide range of temperatures. The addition of these solid lubricants in the nickel-based coating helped achieve the low coefficient of friction of 0.2 and lower wear rates. Particularly, oxide phases (such as NiO, TiO, Ni3Ti3O, and W3O) formed on the worn surface at 600 °C, and the lubricant phases (Ag, Ag2F, and Ba (TiO3)) provided excellent resistance to wear. © 2021, ASM International.