Faculty Publications

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Author: search.filters.author.Ramesh, M.R.Subject: search.filters.subject.Carbides

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    Tribological Performance of Fe-Based Composite Coatings Under Elevated Temperature Conditions
    (Springer, 2025) Chandramouli, T.V.; Joladarashi, S.; Ramesh, M.R.
    The present study investigated the tribological performance of Fe-based coatings reinforced with carbides onto a maraging steel substrate using the HVOF spray technique. These materials are widely used in manufacturing various components in the aerospace and energy sectors. Commercially available SS316L and 17-4PH are reinforced with WC–Co feedstock powders to deposit these composite coatings on maraging steel substrate. The dry sliding wear tests were conducted using the ball-on-disc tribometer at varying temperatures (25 and 300 °C) with 10 N normal load using an alumina ball (Al2O3) as the counter body. The study includes micro-hardness, porosity, density, bond strength, and surface roughness of the coatings. The samples subjected to wear testing were analyzed using SEM/EDS and XRD techniques, and the wear scar volume was measured using a 3D profilometer to calculate the volume metric loss. The wear rate of SS316L30%WC–Co is 64.46% lower than that of 17-4PH30%WC–Co at room temperature and 67.33% lower at 300 °C under a load of 10 N. At room temperature, the worn surface exhibited abrasive wear, while at 300 °C, adhesive wear and oxidative wear were observed owing to the formation of protective layers. Therefore, SS316L-30%WC–Co demonstrates superior wear resistance compared to 17-4PH-30%WC–Co and offers enhanced mechanical strength, particularly in challenging environments. The deposition of these coatings effectively protects the maraging steel substrate. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
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    High temperature corrosion behaviour of HVOF sprayed WC-CrC-Ni coatings
    (Inderscience Publishers, 2016) Somasundaram, B.; Kadoli, R.; Ramesh, M.R.; RAMESH, C.S.
    The present work aims to study the hot corrosion resistance of high velocity oxy-fuel (HVOF) sprayed WC-CrC-Ni coating developed on three types of boiler tube materials such as SA213-T22, MDN-310 and Superfer 800 H steels. Hot corrosion studies were conducted in a molten salt environment of Na2SO4-60%V2O5 at 700°C and thermogravimetric analysis was used to establish kinetics of corrosion. Corrosion kinetics of coated steels followed nearly parabolic behaviour and showed a lower corrosion rate in comparison to uncoated alloys. It is concluded that corrosion is restricted to the external surface of the coating and the formation of thick scale composed of oxides of Cr, Ni and their spinel oxides, acts as a diffusion barrier to the transportation of corrosive species into the coating. The carbides of tungsten and chromium uphold the strength of the coating. © © 2016 Inderscience Enterprises Ltd.
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    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.
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    Investigation on the performance of AlCrN and AlTiN coated cemented carbide inserts during end milling of maraging steel under dry, wet and cryogenic environments
    (Elsevier Ltd, 2019) Varghese, V.; K, A.; Ramesh, M.R.; Dupadu, D.
    The present study investigates the machining performance of AlCrN and AlTiN coated cemented carbide inserts during end milling of MDN 250 maraging steel. The mechanical and metallurgical characterization is carried out to determine the properties of the PVD coatings developed. The end milling experiments under dry, wet and cryogenic environment is carried out using coated uncoated inserts (UC) at different spindle speeds to evaluate the machining performance in terms of tool life, surface roughness and cutting forces. The coated inserts showed higher tool life, better surface finish, and low cutting forces during machining at different spindle speeds. It is found that the AlCrN coating had a better wear resistance and machining performance in comparison with AlTiN coating. The cryogenic environment reduced the surface roughness & cutting force and improved the tool life of the cutting tool compared to conventional dry and wet environment. It is revealed that coated tools along with cryogenic cooling can be employed for high-speed machining applications. © 2019 The Society of Manufacturing Engineers
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    Tribological performance of wire arc additive manufactured 347 austenitic stainless steel under unlubricated conditions at elevated temperatures
    (Elsevier Ltd, 2020) Duraisamy, R.; Subramaniyan, S.; Kannan, A.; Siva Shanmugam, N.; Sankaranarayanasamy, K.; Ramesh, M.R.
    Wire Arc Additive Manufacturing (WAAM) is an effective metal additive manufacturing process. In this research, 347 Austenitic Stainless Steel (ASS) walls were manufactured with ER347 consumable material. The microstructure of the WAAM processed 347 plate is entirely heterogeneous with changing grain morphology along the building direction and this is attributed to the complex cyclic thermal history during WAAM process. The microstructure is composed of columnar, cellular and equiaxed structures at various regions. The hardness decreased gradually from bottom to top along the building direction. The volume fraction of ferrite ranged from 0.5% to 4.2% at various regions and the presence of niobium carbide (NbC) was confirmed. The aim of the current work is to provide an outline of the WAAM processed 347 steel under dry sliding conditions at elevated temperatures. The elevated temperature wear mechanism has mild oxidative wear characteristic due to the formation of tribo-oxides on the wearing and sliding surfaces. However, the average coefficient of friction (COF) is lower for the WAAM processed 347 compared to 347 substrate. In all cases after initial running-in, the wear debris from the wearing and sliding surface forms mechanically mixed composite layer of tribo-oxides (Fe2O3, Fe3O4 and Al2O3). The worn surface at 200 °C presents different wear behavior compared to the samples at 400 °C and 600 °C. The wear at 200 °C is a typical adhesive wear, while the wear at 400?600 °C is mild oxidative wear. The increase in the percentage of Fe3O4 helps to heal the wear surface by forming a mechanically mixed composite layer. The characteristics of mild oxidative wear were elucidated. © 2020 The Society of Manufacturing Engineers
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    Characterization and Sliding Wear Behavior of Iron-Based Metallic Coating Deposited by HVOF Process on Low-Carbon Steel Substrate
    (Springer, 2020) Prasad, C.D.; Jerri, A.; Ramesh, M.R.
    The main aim of this work is to improve the sliding wear resistance of boiler steel material. The iron-based or Metco 41C metallic feedstock was deposited over the ASTM-SA213-T11 steel substrate using high-velocity oxy-fuel spraying process. The resultant deposits were subsequently characterized for microstructure, density, hardness, porosity and surface roughness. These characterizations were carried out with the help of XRD, SEM and Vickers’s microhardness tester. The sliding wear performance of the substrate and coatings were investigated by varying normal loads of 10 N and 20 N at temperatures of 200 °C, 300 °C as well as room conditions by employing pin-on-disk tribometer. The friction coefficient, volume of wear loss and wear rate were being found out. The wear results were compared among the substrate and coating. The formation of additional carbide phases such as Fe2C and SiC in Metco 41C coating led to higher hardness results in better wear resistance compared with the substrate. © 2020, Springer Nature Switzerland AG.
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    Comparison of Microstructural and Sliding Wear Resistance of HVOF Coated and Microwave Treated CoMoCrSi-WC + CrC + Ni and CoMoCrSi-WC + 12Co Composite Coatings Deposited on Titanium Substrate
    (Springer Science and Business Media B.V. editorial@springerplus.com, 2020) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.
    CoMoCrSi-WC + CrC + Ni and CoMoCrSi-WC + 12Co composite coatings are coated on titanium substrate by high velocity oxygen fuel method (HVOF). Prior to spraying, CoMoCrSi feedstock are processed through high energy ball milling (HEBM) in order improve the intermetallic laves phases and to reduce its particle size. The processed feedstock exhibits amorphous nature by improving laves phases and particle size of 60.12 ?m. Microwave heating energy is utilized as post heat treatment technique to improve the mechanical and metallurgical properties of as-sprayed coatings. Fused coatings reveals better properties in terms of surface roughness, porosity, microhardness and adhesion strength compared to as-sprayed coatings. Metallurgical bonding is observed in case of fused coatings due to diffusion of substrate elements. Frictional and wear behaviors have been investigated by a pin on disc apparatus at temperatures of 200 °C, 400 °C, and 600 °C under normal loads of 10 N and 20 N. Both wear trace and friction coefficients of the fused coatings are smaller than as-sprayed coatings and substrate at all test temperatures. The wear traces of fused coatings decreased with increasing the surface temperature due to the lubricant effect of cobalt oxides formed on the sliding surface. As a result, cobalt based cermet coatings are highly recommended as a durability improvement coating for the protection of sliding surface, such as high speed spindle. © 2020, Springer Nature B.V.
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    Effect of Microwave Hybrid Heating on High-Temperature Adhesive Wear Behavior of High-Velocity Oxygen Fuel-Sprayed WC-CrC-Ni and WC-Co/NiCrFeSiB Coatings
    (Springer, 2023) Medabalimi, S.; Ananthu, M.R.; Gudala, S.; Ramesh, M.R.
    HVOF-processed coatings are chemically inhomogeneous and are not metallurgically bonded to the substrate. As a result, components coated with HVOF experience considerable material degradation during sliding wear. Microwave hybrid heating (MHH) is a novel surface modification technique for modifying the as-sprayed properties of the coating. Hence, this paper investigates and compares the wear and frictional behavior of HVOF as-sprayed coatings against MHH samples of WC-CrC-Ni and WC-Co/NiCrFeSiB coatings at elevated temperatures. MHH had a significant impact on wear rate and coefficient of friction by optimizing the porosity, integrated oxide phases and intersplat cohesion strength of the coatings. A modified domestic oven was used to perform MHH on HVOF-coated samples for 5 min at 1200 °C. Wear tests were performed using a pin-on-disk tribometer from room temperature to 200, 400, and 600 °C with Al2O3 disk as a counterface. SEM/EDS and XRD were utilized to examine the microstructural characterization of the coatings and substrate. Both the coatings showed higher wear resistance than the substrate at all temperatures. The WC-Co/NiCrFeSiB coating produced an oxide layer on the worn surfaces and integrated WC, CoWO4, and Fe2SiO4 splats, enhancing wear resistance. The MHH WC-CrC-Ni coating formed Cr2O3 and NiWO4 phases on the worn surfaces, increasing the intersplat cohesion strength between matrix and carbide splats, lowering the overall wear rate. After MHH, the wear rate of a substrate and WC-CrC-Ni coating was 3.5 and 1.12 times more at room temperature and 8.07 and 2.92 times more at 600 °C than WC-Co/NiCrFeSiB coating. © 2022, ASM International.
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    Effect of Impact Angles and Temperatures on the Solid Particle Erosion Behavior of HVOF Sprayed WC-Co/NiCr/Mo and Cr3C2-CoNiCrAlY Coatings
    (Springer, 2023) Behera, N.; Medabalimi, S.; Ramesh, M.R.
    Extreme erosion wear from elevated temperature caused by the impact of entrained solid particles in the fluid stream primarily affects aerospace components and marine parts. This work focuses on increasing the base material erosion resistance by applying thermally sprayed carbide-based coatings. A high-temperature Solid particle erosion behavior of WC-Co/NiCr/Mo and Cr3C2-CoNiCrAlY coatings deposited by the HVOF process on a titanium-31 was evaluated using an air-jet erosion tester. The erosion test was conducted utilizing alumina erodent of grit size 35-50 µm. The effects of impact angles (30°, 60°, and 90°) and temperatures (200-800 °C) on the erosion performance of two coatings are compared. The feedstock powder and as-sprayed coatings were characterized for micro-structure phase composition, porosity, density, micro-hardness, and adhesion strength. SEM/EDS and a 3D optical profilometer were used to examine eroded samples further to determine the erosion mode. The Cr3C2-CoNiCrAlY coating shows a brittle mode behavior of erosion at 200-400 °C and ductile mode behavior of erosion at 600-800 °C. In contrast, the WC-Co/NiCr/Mo coating shows brittle mode behavior of erosion at 200-400 °C and 600-800 °C, a mixed mode behavior of erosion. The erosion loss in volume of Cr3C2-CoNiCrAlY is lower than WC-Co/NiCr/Mo for all temperatures and impact angles. The development of carbide and oxide phases on the eroded surfaces demonstrates increasing erosion resistance at high temperatures. The optical profilometer measures the volumetric erosion loss, compares it with the weight loss method, and finds consistency between them. © 2023, ASM International.
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    Characterization and evaluation of carbide-based composite coatings for high-temperature wear resistance on Titanium substrate
    (SAGE Publications Ltd, 2025) Behera, N.; Ramesh, M.R.
    Titanium alloys are used in the automotive and aerospace industries, but perform poorly at high temperatures due to inadequate wear and friction properties. This study investigates Cr3C2-25%CoNiCrAlY and WC-CoCr coatings applied via High-velocity oxygen Fuel on a titanium-31 substrate. Coatings were evaluated from 200–800?°C under 20?N and 30?N using a ball-on-disc tribometer. Characterization techniques included scanning electron microscope, X-ray diffraction, microhardness, porosity, and bond strength. WC-CoCr coating showed higher hardness and bond strength than Cr3C2-25%CoNiCrAlY. Both coatings exhibited reduced wear rates until 600?°C, after which the wear rates increased at 800?°C due to enhanced oxidation. The coefficient of Friction decreased with increasing temperature. At 600?°C, oxide phases helped reduce wear and friction. WC-CoCr coating shows better wear resistance than Cr3C2-25%CoNiCrAlY coating and the substrate. Wear mechanisms changed from abrasive and fatigue at 200?°C to oxidative and adhesive at 800?°C. Volumetric ball loss was higher for WC-CoCr due to its greater hardness. © The Author(s) 2025