Browsing by Author "Mathapati, M."

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Cyclic oxidation behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere coating
(2018) Mathapati, M.; Ramesh, M.R.; Doddamani, M.
Components working at elevated temperature like boiler tubes of coal and gas fired power generation plants, blades of gas and steam turbines etc. experience degradation owing to oxidation. Oxidation resistance of such components can be increased by developing protective coatings. In the present investigation NiCrAlY-WC-Co/Cenosphere coating is deposited on MDN 321 steel substrate using plasma spray coating. Thermo cyclic oxidation behavior of coating and substrate is studied in static air at 600 �C for 20 cycles. The thermo gravimetric technique is used to approximate the kinetics of oxidation. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray mapping techniques are used to characterize the oxidized samples. NiCrAlY-WC-Co/Cenosphere coating exhibited lower oxidation rate in comparison to MDN 321 steel substrate. The lower oxidation rate of coating is attributed to formation of Al2O3, Cr2O3, NiO and CoWO4 oxides on the outermost surface. � 2018 Author(s).
Cyclic oxidation behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere coating
(American Institute of Physics Inc. subs@aip.org, 2018) Mathapati, M.; Ramesh, M.R.; Doddamani, M.
Components working at elevated temperature like boiler tubes of coal and gas fired power generation plants, blades of gas and steam turbines etc. experience degradation owing to oxidation. Oxidation resistance of such components can be increased by developing protective coatings. In the present investigation NiCrAlY-WC-Co/Cenosphere coating is deposited on MDN 321 steel substrate using plasma spray coating. Thermo cyclic oxidation behavior of coating and substrate is studied in static air at 600 Â°C for 20 cycles. The thermo gravimetric technique is used to approximate the kinetics of oxidation. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray mapping techniques are used to characterize the oxidized samples. NiCrAlY-WC-Co/Cenosphere coating exhibited lower oxidation rate in comparison to MDN 321 steel substrate. The lower oxidation rate of coating is attributed to formation of Al2O3, Cr2O3, NiO and CoWO4 oxides on the outermost surface. Â© 2018 Author(s).
EFFECT of LASER POST-TREATMENT on MICROSTRUCTURAL and SLIDING WEAR BEHAVIOR of HVOF-SPRAYED NiCrC and NiCrSi COATINGS
(World Scientific, 2022) Naik, T.; Mathapati, M.; Prasad, C.D.; Nithin, H.S.; Ramesh, M.R.
In this study, NiCrC and NiCrSi coatings are deposited on the MDN 310 steel using High-Velocity Oxy-Fuel (HVOF) process. Laser Surface Melting (LSM) post-heat treatment is carried out on as-sprayed coatings using Laser Engineered Net Shaping (LENSTM) with a power of 300W. The characteristics of both coatings in terms of mechanical and metallurgical properties have been investigated. The thicknesses of the as-sprayed NiCrC and NiCrSi coatings are in the range of 170-200μm. Laser-treated NiCrC and NiCrSi coatings exhibit a thickness range of 162-185μm, respectively. The microstructure of laser-treated NiCrC-300W coating clearly shows a dendrite-like structure, whereas the laser-treated NiCrSi coating exhibits hard layer and columnar homogeneity. Microhardness of as-sprayed NiCrC coating is 515±15 HV0.3 and that of NiCrSi coating is 645±25 HV0.3. Microhardness of laser-treated NiCrC coating is 720±30 HV0.3 and that of NiCrSi coating is 890±15 HV0.3. Dry sliding wear tests are conducted at room temperature (RT) and 400°C with 10-N and 20-N loads. The wear rates at 400°C temperature of laser-treated NiCrC and NiCrSi coatings produced are slightly below (1-2.2)×10-3mm3/m and (0.8-1.6)×10-3mm3/m, respectively. Laser-treated coatings produced better dry sliding wear behavior compared with as-sprayed coatings owing to dense microstructure. Formation of SiC phase in NiCrSi coating imparts high wear and frictional resistance compared to the NiCrC coating. © 2022 World Scientific Publishing Company.
Evaluation of mechanicalProperties of EN31 steel heat treated using biodegradable oils
(Research India Publications subscription@ripublication.com, 2015) Harichandra, B.P.; Prashanth, M.; Mathapati, M.; Prakash, S.V.
Heat treating is the controlled heating and cooling of metals to achieve the desired physical and mechanical properties without changing the product shape. Most of the researches reveal thatthe commonly used quenchants is water, but petroleum based quenchants are utilized as quenching medium when lower cooling rates and more uniform cooling is desired for better distortion control and crack prevention. In order to overcome some of the disadvantages of petroleum quenchants such as poor biodegradability, toxicity, flammability and non-renewability, an attempt has been made to find an alternative ie., biodegradable, nontoxic oil and renewable such as Gingelly oil and Soybean oil as quenchants in the heat treatment of high carbon EN31 steel and the evaluation of mechanical properties such as hardness, tensile strength, yield strength has been carried out in both untreated and heat treated condition and compared with the properties of petroleum based SF(super-fast quench) oil as quenchant. © Research India Publications.
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.
High temperature tribological studies of cold sprayed nickel based alloy on low carbon steels
(Elsevier Ltd, 2019) Padmini, B.V.; Mathapati, M.; Niranjan, H.B.; Sampathkumaran, P.; Seetharamu, S.; Ramesh, M.R.; Mohan, N.
The boiler steels of grades SAE213 T11 and T22, find extensive applications in heat exchanger tubes, paper and pulp, chemical industries and refineries. Further, these steels are also used in shafts, cylinders, bearings, and in automotive transmission parts and these aspects are less explored. They experience low wear life in specific components, both at room and slightly higher temperature regimes. In order to protect them from these damages, coatings are deployed involving many techniques like HVOF, Plasma spray, Cold spray etc. so that the life of the components get extended. In cold spray coatings, the powders are fed at very high impact velocities of up to 1200 m/s on the substrate and undergo plastic deformation during the impact. There is no oxidation of the powder takes place during the process, as the coating is done at very less temperature and this is one of the lead characteristic of cold spray technique. This particular work mainly focuses on evaluating the tribological behaviour of nickel based super alloy powder on T11 and T22 low alloy steels by cold spray method, using pin on disc machine both at room temperature as well as at 200, 300 and 400 Â°C. The associated tests such as hardness, porosity, and microstructure have been undertaken to support the wear data. The wear damage assessment has been carried out using scanning electron microscope to arrive at the mechanism and also to give credence to the wear data. Â© 2019 Elsevier Ltd.
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.
Investigation of microstructural and tribological behavior of Metco 41C+WC-12Co composite coatings sprayed via HVOF process
(CRC Press, 2021) Prasad, C.D.; Mathapati, M.; Ramesh, M.R.; Joladarashi, S.
The present work deals with developing an elevated-temperature sliding, wear-resistant, iron-based (Metco 41C) composite coating on the boiler steel substrate using high-velocity oxy fuel (HVOF) system. Prior to coating, Metco 41C (70%) and WC-12Co (30%) were mixed mechanically using ball milling process. Later, feedstock was employed into the HVOF system to develop the coating. The coating samples were subjected to metallurgical and mechanical characterization techniques under required conditions. Further substrate and coating were taken for wear test without employing lubrication through pin on disc apparatus. Wear test was carried out by selecting 10 and 20 N loads at room temperature, 200°C, and 300°C parameters. The sliding distance and the velocity were kept constant. The worn-out samples were analyzed for microstructural changes and formation of phases using SEM and XRD methods, respectively. The wear properties of friction coefficient, wear rate, and loss of volume were calculated. Deposited coating exhibited hard phases such as Cr3C2, Ni3C, W2C, Fe2C, and SiC along with intermetallic phases like Mo2C and Co3W3C. The result is improvement in hardness and better wear resistance with respect to the substrate. © 2022 selection and editorial matter, Lalit Thakur, Hitesh Vasudev. All rights reserved.
Lightweight and sustainable materials for coating applications
(Elsevier, 2023) Mathapati, M.; Ramesh, M.R.; Doddamani, M.
This chapter deals with the development of Cr3C2-25NiCr/cenosphere/MoS2/CaF2, Cr3C2-25NiCr/cenosphere/MoS2/CaSO4, and Cr3C2-25NiCr coatings through plasma spraying on MDN 321 steel substrate. Methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) are used for coating phase composition and microstructure analysis. Sliding wear behavior of substrate and coatings is tested at 200°C-600°C by utilizing a pin-on-disk tribometer. Owing to the existence of cenospheres and action of solid lubricants, frictional coefficient and wear rate of fly ash cenosphere-based Cr3C2-25NiCr/MoS2/CaF2 and Cr3C2-25NiCr/MoS2/CaSO4 compositions are reduced in comparison with Cr3C2-25NiCr coating and substrate at all test parameters. The characterization of the coatings’ worn-out surface reveals lubrication at 200°C by MoS2. At elevated temperature, CaF2 with CaMoO4 formed through tribochemistry further aids lubrication. Micrographs of worn surfaces demonstrate plowing and delamination as the main wear mechanism. © 2023 Elsevier Ltd. All rights reserved.
Microstructure and tribological behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere/solid lubricants composite coatings
(Elsevier B.V., 2018) Doddamani, M.; Mathapati, M.; Ramesh, M.R.
Present investigation deal with NiCrAlY/WC-Co/Cenosphere/MoS2/CaF2, NiCrAlY/WC-Co/Cenosphere/MoS2/CaSO4 and NiCrAlY/WC-Co/Cenosphere coatings deposited on MDN 321 steel using atmospheric plasma spraying. Tribological properties of MDN 321 steel and coatings are evaluated from room temperature (RT) to 600 °C under dry lubrication conditions using a pin on disc high-temperature tribometer. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) are used to characterize the coatings. Presence of cenospheres in these coatings might effectively reduce wear acting as localized regions accumulating wear debris. The result shows that wear rate of all the coatings are lower as compared to MDN 321 substrate at all the test conditions. NiCrAlY/WC-Co/Cenosphere/MoS2/CaF2 and NiCrAlY/WC-Co/Cenosphere/MoS/CaSO4 coatings registered lower friction coefficient as compared to NiCrAlY/WC-Co/Cenosphere coating and MDN 321 substrate. Characterization of the NiCrAlY/WC-Co/Cenosphere/MoS2/CaF2 and NiCrAlY/WC-Co/Cenosphere/MoS2/CaSO4 coatings worn out surface suggests that MoS2 provides lubrication at 200 °C and formation of CaMoO4, MoO3 through tribo chemistry reaction at higher temperature provides lubrication at 600 °C. SEM micrograph of worn surface demonstrates that the main wear mechanism is plowing and delamination. © 2018 Elsevier B.V.
Microstructure and tribological characteristics of APS sprayed NiCrBSi/flyash cenosphere/Cr2O3 and NiCrBSi/flyash cenosphere/Mo composite coatings at elevated temperatures
(Institute of Physics Publishing helen.craven@iop.org, 2019) Nagabhushana, N.; Rajanna, S.; Mathapati, M.; Ramesh, M.R.; Koppad, P.G.; Reddy, N.C.
In the present investigation NiCrBSi/flyash/Cr2O3 and NiCrBSi/flyash/Mo composite coatings are developed using atmospheric plasma spray technique on superni 76 alloy. Coatings are characterized in terms of microstructure, phase analysis, and microhardness. Tribological properties of the coatings are evaluated using a pin on disc tribometer. Test is conducted under dry sliding conditions at room temperature, 200 °C, 400 °C, and 600 °C respectively. Microstructure and worn surfaces of the coatings are analyzed by utilizing Scanning Electron Microscope (SEM) where in phase analysis is carried out using x-ray diffractometer (XRD). XRD results revealed the presence of ?-Ni as primary phase along with Ni3B, Cr7C3, SiO2 and Al2O3 as minor phases in both the NiCrBSi/flyash/Cr2O3 and NiCrBSi/flyash/Mo coatings. Among the two coatings, Mo composite coating exhibited lower porosity and higher microhardness. The friction coefficient of both the coatings decreased with increasing temperature. The wear rate is found to decrease at lower temperatures but increased at a higher temperature (>400 °C) for Cr2O3 composite coating wherein Friction coefficient is decreased with increase in the temperature for Mo composite coatings. The worn surface analysis conducted revealed abrasive wear at lower temperatures while the transition from abrasive to adhesive is observed at higher temperatures. © 2019 IOP Publishing Ltd.
Plasma sprayed Cr3C2-NiCr/fly ash cenosphere coating: Cyclic oxidation behavior at elevated temperature
(Institute of Physics Publishing helen.craven@iop.org, 2018) Doddamani, M.; Mathapati, M.; Ramesh, M.R.
Oxidation is one of the major degradation phenomena observed in components subjected to higher temperatures like in thermal power plants (boiler tubes), steam and gas turbines blades etc. Developing protective coatings for such components mitigate oxidation. In the present study, plasma spray technique is utilized to deposit the Cr3C2-NiCr/Cenospheres coating on MDN 321 steel substrate. Thermo cyclic oxidation test is conducted at 600 °C (20 cycles) on both the coating and MDN 321 steel substrate. The thermogravimetric methodology is employed to estimate the oxidation kinetics. Energy Dispersive Spectroscopy (EDS), x-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and x-ray mapping technique is employed to characterize the oxidized samples. Cr3C2-NiCr/Cenosphere coating displayed lower rate of oxidation as compared to substrate implying its suitability in high-temperature applications. Protective oxides like Al2O3, Cr2O3, and NiCr2O4 are observed on the uppermost layer of the coating lowering the oxidation rate in the developed coating. © 2018 IOP Publishing Ltd.