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thermal-spray
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Optimal experiment design for plasma thermal spray parameters at bending loads
, Article International Journal of Surface Science and Engineering ; Volume 6, Issue 1-2 , 2012 , Pages 3-14 ; 1749785X (ISSN) ; Moridi, A ; Farrahi, G. H ; Sharif University of Technology
2012
Abstract
Ceramic thermal barrier coatings are applied on gas turbines and diesel engine components to protect metals from heat and this enhances the service lifetime by means of a reduction in working temperature. In the present paper, optimisation of plasma thermal spray parameters, including feed rate and nozzle distance from the specimen surface is performed by using the design of experiment method. Due to factorial approach, by considering two parameters with three variation levels, nine experiments of bending test are needed. The base material is cast aluminium alloy, A356.0-T7. The coating layers consist of a bond coat, Ni-Cr-Al-Y with a thickness of 150 μm and a top coat, ZrO2-8wt%Y2O3 with a...
A comparison between the corrosion resistances of High Velocity Oxy Fuel (HVOF) sprayed coatings and hard chromium coatings
, Article Materials Science Forum, 1 September 2010 through 3 September 2010, Seoul ; Volume 673 , 2011 , Pages 173-178 ; 02555476 (ISSN) ; 9783037850183 (ISBN) ; Khameneh Asl, S ; Vasfpour, R ; Tazesh, F ; Khallagi, P ; Sharif University of Technology
2011
Abstract
HVOF-sprayed coatings (WC-17%Co) and hard chromium coatings corrosion resistances have been compared through electrochemical polarization test in 3.5% NaCl solution. WC-17%Co alloy coatings were deposited on mild steel substrates by High Velocity Oxy-Fuel (HVOF) spray process. The layers of standard and crack free hard chromium coatings were prepared by using Direct Current (DC) and Pulse Current (PC) electroplating process on the mild steel substrates. Hard chromium coatings was characterized as a reference material, to verify whether HVOF-sprayed coatings are suitable as a hard chromium coatings replacement. The microstructure of the coatings was examined by OM, SEM and XRD. Standard hard...
Evaluation and selection of optimal oxygen/fuel ratio for best mechanical properties, oxidation resistance and microstructure of HVOF NiCoCrAlY coatings using AHP–VIKOR method
, Article Oxidation of Metals ; 2017 , Pages 1-23 ; 0030770X (ISSN) ; Ghasemi, B ; Sadrnezhaad, S. K ; Habibolahzadeh, A ; Jafarzadeh, K ; Sharif University of Technology
Abstract
Abstract: This work describes coating of NiCoCrAlY on IN-738LC superalloy by high-velocity oxygen fuel (HVOF) process. Properties of the coatings are significantly influenced by oxygen/fuel ratio and other spraying parameters. The effect of oxygen/fuel ratio on the oxidation behavior, bond strength, hardness, roughness and microstructure including porosity, inclusion formation and unmelted particles are discussed here. The porosity and inclusion in C1 coating are maximal. C2 coating with oxygen/fuel ratio of 2 has the highest bond strength and the lowest unmelted particles. C3 coating with the lowest total porosity and inclusion has the minimal roughness and the highest oxidation resistance...
Cyclic oxidation characteristics of HVOF thermal-sprayed NiCoCrAlY and CoNiCrAlY coatings at 1000 °C
, Article Journal of Alloys and Compounds ; Volume 746 , 25 May , 2018 , Pages 509-519 ; 09258388 (ISSN) ; Salehi Doolabi, M ; Sadrnezhaad, S. K ; Rezaei, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Thermal-sprayed MCrAlY coatings have become widespread in various industries such as power plants, aeronautics, and oil and gas firms. High-temperature oxidation behavior of these coatings is therefore of significance. Spraying of two prevalent MCrAlY powders (NiCoCrAlY and CoNiCrAlY) on Hastelloy substrate by high velocity oxygen and fuel method and exposing them to 1000 °C air for resolving of their cyclic oxidation behavior are presented in this paper. The coatings were characterized by x-ray diffraction, scanning electron microscopy and energy-dispersive x-ray spectroscopy. The obtained oxidation kinetic indicated that at 1000 °C, the thermally sprayed NiCoCrAlY coating has greater...
Evaluation and selection of optimal oxygen/fuel ratio for best mechanical properties, oxidation resistance and microstructure of HVOF NiCoCrAlY coatings using AHP–VIKOR method
, Article Oxidation of Metals ; Volume 89, Issue 3-4 , April , 2018 , Pages 429-451 ; 0030770X (ISSN) ; Ghasemi, B ; Sadrnezhaad, S. K ; Habibolahzadeh, A ; Jafarzadeh, K ; Sharif University of Technology
Springer New York LLC
2018
Abstract
This work describes coating of NiCoCrAlY on IN-738LC superalloy by high-velocity oxygen fuel (HVOF) process. Properties of the coatings are significantly influenced by oxygen/fuel ratio and other spraying parameters. The effect of oxygen/fuel ratio on the oxidation behavior, bond strength, hardness, roughness and microstructure including porosity, inclusion formation and unmelted particles are discussed here. The porosity and inclusion in C1 coating are maximal. C2 coating with oxygen/fuel ratio of 2 has the highest bond strength and the lowest unmelted particles. C3 coating with the lowest total porosity and inclusion has the minimal roughness and the highest oxidation resistance and...
Using molecular dynamic simulation data of calcite in a wide pressure range to calculate some of its thermodynamic properties via some universal equations of state
, Article Molecular Physics ; Volume 106, Issue 21-23 , 2008 , Pages 2545-2556 ; 00268976 (ISSN) ; Shokouhi, M ; Parsafar, G. A ; Sharif University of Technology
2008
Abstract
Molecular dynamics, MD, simulation of calcite (CaCO3) is selected to compare the p-v-T behaviour of some universal equations of state, UEOS, for the temperature range 100 K ≤ T 800 ≤ K, and pressures up to 3000 kbar. The isothermal sets of p-v-T data generated by simulation were each fitted onto some three- and two-parameter EOSs including Parsafar and Mason (PM), Linear Isotherm Regularity (LIR), Birch-Murnaghan (BM), Shanker, Vinet, Baonza and Modified generalized Lennard-Jones (MGLJ) EOSs. It is found that the MD data satisfactorily fit these UEOS with reasonable precision. Some features for a good UEOS criteria such as temperature dependencies of coefficients, pressure deviation,...
Pressureless sintering of 3Y-TZP/stainless-steel composite layers
, Article Journal of the American Ceramic Society ; Volume 91, Issue 11 , 2008 , Pages 3493-3503 ; 00027820 (ISSN) ; Simchi, A ; Tamjid Shabestary, E ; Hartwig, T ; Sharif University of Technology
2008
Abstract
A pressureless sintering method was utilized to fabricate metal/ceramic joints out of yttria-stabilized zirconia (3Y-TZP) and stainless steels (SS). Ultrafine (150 nm) and nanoscale (75 nm) 3Y-TZP particles and micrometric 17-4PH, 316L, and 420 SS (<31 μm) powders were tested. Isothermal and nonisothermal sintering behaviors of the powders and composite layers in hydrogen, argon, and vacuum atmospheres were examined. It was found that the mismatch strain between the zirconia ceramic and SS during cosintering is significant, which leads to bond cracking and joint failure. Nevertheless, interlayer diffusion of Zr, Fe, and Cr and the formation of a reaction zone, particularly during vacuum...