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Inwook Park - One of the best experts on this subject based on the ideXlab platform.
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microstructures mechanical properties and tribological behaviors of cr al n cr si n and cr al si n Coatings by a hybrid Coating System
Surface & Coatings Technology, 2007Co-Authors: Inwook Park, Dong Shik Kang, John J Moore, Sik Chol KwonAbstract:Abstract Cr–Al–N, Cr–Si–N, Cr–Al–Si–N Coatings were successfully deposited on WC–Co substrates by a hybrid Coating System combining an arc ion plating technique using Cr target, and a magnetron sputtering method using Al and Si targets under N 2 /Ar atmosphere. XRD, HRTEM, and XPS analyses revealed that the synthesized Cr–Al–N Coatings consisted of solid-solution (Cr,Al)N crystallites, and the Cr–Si–N and Cr–Al–Si–N Coatings with Si content of ∼ 9 at.% were fine composites consisting of (Cr,Si)N and (Cr,Al,Si)N crystallites, respectively, embedded in an amorphous Si 3 N 4 /SiO 2 matrix. The hardness values of the Cr–Si–N (∼ 35 GPa) and the Cr–Al–Si–N (∼ 55 GPa) Coatings were significantly increased compared with those of CrN (∼ 23 GPa) and Cr–Al–N (∼ 25 GPa) Coatings. Besides, the average friction coefficients of the Cr–Si–N (∼ 0.30) and the Cr–Al–Si–N (∼ 0.57) Coatings with Si content of about 9 at.% were largely decreased compared with those of CrN (∼ 0.50) and Cr–Al–N (∼ 0.84) Coatings. A comparative study on microstructural characteristics among Cr–Al–N, Cr–Si–N, and Cr–Al–Si–N Coatings is reported in this paper.
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deposition and mechanical evaluation of superhard ti al si n nanocomposite films by a hybrid Coating System
Thin Solid Films, 2004Co-Authors: Inwook Park, Sung Ryong Choi, Chan Gyung ParkAbstract:New superhard TiAlSiN films, characterized by a nanocomposite comprising nano-sized (Ti,Al,Si)N crystallites embedded in amorphous Si3N4 matrix, could be successfully synthesized on WCCo substrates by a hybrid Coating System of arc ion plating (AIP) and sputtering method. The hardness and Young's modulus value of the TiAlSiN film increased with incorporation of Si, and had the maximum value of ∼55 GPa and ∼650 GPa at the Si content of 9 at.%, respectively. The average friction coefficient of the TiAlSiN films largely decreased with an increase of the Si content. This behavior would be attributed to the tribo-chemical reaction between Si and ambient humidity, which enabled to form SiO2 or Si(OH)2 tribo-layer playing a role as self-lubricant. The harder TiAlSiN film was found to be more wear-resistant against steel. A Systematic work on the microstructure and mechanical properties of TiAlSiN films is reported in this paper.
Gholam Hossein Farrahi - One of the best experts on this subject based on the ideXlab platform.
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stress analysis of thermal barrier Coating System subjected to out of phase thermo mechanical loadings considering roughness and porosity effect
Surface & Coatings Technology, 2015Co-Authors: Gholam Hossein Farrahi, Mohammad Azadi, Mohamad GhodratiAbstract:Abstract This paper presents the out-of-phase thermo-mechanical stress analysis of thermal barrier Coating (TBC) System in real working conditions used as thermal barrier in diesel engine cylinder heads. The Coating System in this research comprises 350 μm zirconium oxide top coat (TC) and 150 μm metallic bond coat (BC). These layers were deposited on the substrate, aluminum A356 alloy, by the aid of air plasma spray (APS) method. Afterwards, the specimen was subjected to thermo-mechanical fatigue (TMF) loadings. Based on the experimental conditions, FE simulations were performed by both time-independent and time-dependent substrate material properties in ABAQUS software. Simulation results related to heat transfer analysis demonstrate only about 10.5% comparative error compared to experimental results. Moreover, defining time-dependent properties, which were obtained from two-layer visco-plastic model, yields results with 15% less comparative error in comparison to the results based on time-independent material properties. In addition, the effects of roughness and porosity in Coating layers and substrate were studied on three different models by the aid of a scanning electron microscopy image. Obtained results based on real geometry illustrate that consideration of porosity in TC layer has an effective role in the stress distribution of this layer. However, BC layer stress distribution is much more dependent on interface morphology.
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thermo mechanical stress analysis of thermal barrier Coating System considering thickness and roughness effects
Surface & Coatings Technology, 2014Co-Authors: Arefe Moridi, Mohammad Azadi, Gholam Hossein FarrahiAbstract:Abstract Cast aluminium–silicon alloy, A356.0, is widely used in automotive and aerospace industries because of its outstanding mechanical, physical, and casting properties. Thermal barrier Coatings can be applied to combustion chamber to reduce fuel consumption and pollutions and also improve fatigue life of components. The purpose of the present work is to simulate stress distribution of A356.0 under thermo-mechanical cyclic loadings, using a two-layer elastic-visco-plastic model of ABAQUS. The results of stress–strain hysteresis loop are validated by an out of phase thermo-mechanical fatigue test. Different thicknesses from 300 to 800 μm of top coat and also roughness of the interfaces are simulated to get best stress gradient. Results show that increasing top coat thickness causes stress increase. The realistic interface model is useful for identifying critical areas in stress development. Two important factors having considerable effect on development of high stress in TBC, are the severity of undulations relating to amplitude and wavelength of interface waves; and the thickness of BC layer relating to mutual positioning of either interfaces. However the realistic model has some limitations including long calculation time and difficulties of generating a suitable mesh. To diminish these limitations, after recognizing critical area, in second stage of the study, a periodic unit cell is used instead . Eight models considering different mutual positioning of interfacial asperities along with different penetration in adjoining layers are simulated and compared. Results show that detachment of the thermal barrier Coating System from substrate is more probable Results show that IP positioning of mutual waves produce more severe stress but contour pattern is less likely to promote crack propagation.
Yan Song - One of the best experts on this subject based on the ideXlab platform.
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a theoretical model for predicting residual stress generation in fabrication process of double ceramic layer thermal barrier Coating System
PLOS ONE, 2017Co-Authors: Yan Song, Weijie Wu, Tiejun WangAbstract:Residual stress arisen in fabrication process of Double-Ceramic-Layer Thermal Barrier Coating System (DCL-TBCs) has a significant effect on its quality and reliability. In this work, based on the practical fabrication process of DCL-TBCs and the force and moment equilibrium, a theoretical model was proposed at first to predict residual stress generation in its fabrication process, in which the temperature dependent material properties of DCL-TBCs were incorporated. Then, a Finite Element method (FEM) has been carried out to verify our theoretical model. Afterwards, some important geometric parameters for DCL-TBCs, such as the thickness ratio of stabilized Zirconia (YSZ, ZrO2-8%Y2O3) layer to Lanthanum Zirconate (LZ, La2Zr2O7) layer, which is adjustable in a wide range in the fabrication process, have a remarkable effect on its performance, therefore, the effect of this thickness ratio on residual stress generation in the fabrication process of DCL-TBCs has been Systematically studied. In addition, some thermal spray treatment, such as the pre-heating treatment, its effect on residual stress generation has also been studied in this work. It is found that, the final residual stress mainly comes from the cooling down process in the fabrication of DCL-TBCs. Increasing the pre-heating temperature can obviously decrease the magnitude of residual stresses in LZ layer, YSZ layer and substrate. With the increase of the thickness ratio of YSZ layer to LZ layer, magnitudes of residual stresses arisen in LZ layer and YSZ layer will increase while residual stress in substrate will decrease.
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effects of Coating spray speed and convective heat transfer on transient thermal stress in thermal barrier Coating System during the cooling process of fabrication
Applied Surface Science, 2015Co-Authors: Yan Song, Zhichao Lv, Xin Zhuan, T J WangAbstract:Abstract The Coating spray speed and the convective heat transfer have significant effects on transient thermal stress in TBCs (Thermal Barrier Coating System) during the cooling process of fabrication. In this work, a simplified analytical model is developed firstly, to predict the transient thermal stress in YSZ (ZrO2–8%Y2O3) Coating and shear stress at the Coating-substrate interface during the cooling process of fabrication. Then, based on this simplified model, the effects of Coating spray speed which determines the initial temperature field of YSZ Coating, and the convective heat transfer coefficient between YSZ Coating and the environment on transient thermal stress in TBCs during the cooling process have been studied. The results indicate that the YSZ Coating spray speed has a significant effect on the transient thermal stress in YSZ Coating and the shear stress near the edge of YSZ–substrate interface; effect of convective heat transfer on the thermal stress is more significant when convective heat transfer coefficient is bigger enough, and for a given convective heat transfer the effect becomes smaller as the cooling down process going on.
Yichun Zhou - One of the best experts on this subject based on the ideXlab platform.
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evaluation of microhardness fracture toughness and residual stress in a thermal barrier Coating System a modified vickers indentation technique
Surface & Coatings Technology, 2012Co-Authors: J Ding, Y Zhang, Yichun Zhou, Chunsheng LuAbstract:Abstract The evolution of microhardness, fracture toughness and residual stress of an air plasma-sprayed thermal barrier Coating System under thermal cycles was investigated by a modified Vickers indentation instrument coupled with three kinds of indentation models. The results show that fracture toughness on the top Coating surface after thermal cycles changes from 0.64 to 3.67 MPa m 1/2 , and the corresponding residual stress near the indented region varies from − 36.8 to − 243 MPa. For the interface region of Coating and bond coat, fracture toughness in the Coating close to interface ranges from 0.11 to 0.81 MPa m 1/2 , and residual stress varies from − 5 to − 30 MPa, which are consistent with available data. For the lateral region of Coating, fracture toughness and residual stress display strong gradient characteristics along the thickness direction due to the special layered structure.
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coupled effects of temperature gradient and oxidation on thermal stress in thermal barrier Coating System
International Journal of Solids and Structures, 2001Co-Authors: Yichun Zhou, Toshiyuki HashidaAbstract:Abstract The thermal stress fields in thermal barrier Coating (TBC) System are studied in the present paper. The thermal stress fields are induced by the non-linear coupled effect of temperature gradient, oxidation, thermal fatigue, creep, morphology of TBC System as well as cooling rate. TBC System is assumed to be partially stabilized ZrO 2 by 8 wt.% Y 2 O 3 (PSZ) or mullite over a NiCrAlY bond coat sprayed on nickel superalloy or steel substrate. The TBC System is a composite medium with four layers in cylindrical coordinate System. The temperature fields for the non-homogeneous problem with energy generation in medium are analytical solved by using Taylor transformation and Green’s function approach. The analytical solutions for thermal stress fields in composite medium are obtained when eigenstrain rate is taken into consideration. The constitutive equations, such as the creep of ceramic Coating (PSZ and mullite) and substrate (Ni-superalloy), plasticity of bond coat are given by a general formula. Thermal growth oxidation (TGO) and the temperature dependence of thermal–mechanical parameters are taken into consideration. The calculated results of temperature fields and thermal stresses fields are given and the related results are discussed. TGO does not affect the temperature fields in PSZ Coating Systems. But it has influence on temperature fields in mullite Coating Systems. The residual stress with TGO considered is larger than that with TGO non-considered. It is very interesting to have the conclusion that TGO may make the residual tangent stress from tensile to compressive. The characterization of thermal stresses in PSZ Coating System is very different from that in mullite Coating System. It may be due to the difference of mechanical behavior such as creep, thermal mismatch as well as mechanical mismatch which is reflected by Dundurs' parameters α and β . The geometrical radius not only affects the quantum of thermal stress but also affects the characterization of thermal stress. The effect of cooling rate on residual stress is due to the high creep rate of ceramic Coating operating at high temperature. The effect of cooling rate on residual stress is not large for System operating at relative low temperature.
Myungchang Kang - One of the best experts on this subject based on the ideXlab platform.
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cutting performance of crn and cr si n coated end mill deposited by hybrid Coating System for ultra high speed micro machining
Surface & Coatings Technology, 2008Co-Authors: Sungchan Shin, Myungchang Kang, Donghee KwonAbstract:Abstract In this paper, comparative studies on the properties and cutting performance between CrN and Cr–Si–N coated micro end-mill for ultra-high speed machining applications were conducted. Ternary Cr–Si–N Coatings, in which Si was incorporated into CrN, were synthesized onto WC–Co substrates using a hybrid System of arc ion plating and sputtering techniques. In the hybrid Coating System for Cr–Si–N Coatings, the CrN Coating process was performed substantially by a cathodic AIP technique using Cr target, and Si could be added by sputtering Si target during CrN deposition. The high hardness of Cr–Si–N Coatings was related to the composite microstructure consisting of fine CrN crystallites and amorphous Si3N4. The average friction coefficient of Cr–Si–N Coatings gradually decreased with increase of Si content in CrN Coatings. Good oxidation resistance of the CrN film was further improved by the incorporation of Si into the CrN films. Cutting tests were carried out to evaluate the characteristics of micro tool in vertical machining center using ultrahigh-speed air turbine spindle. Especially, the reliable evaluation System of coated tools for micro machining, where the cutting force and tool wear were simultaneously measured, was introduced
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Microstructure and Mechanical Properties of Cr-C-N, Cr-Si-N and Cr-Si-C-N Coatings by a Hybrid Coating System
Key Engineering Materials, 2007Co-Authors: Chul Sik Jang, Myungchang Kang, Won Sub ChungAbstract:CrN-based multi-component Coatings were deposited by a hybrid Coating System combining the arc ion plating (AIP) and sputtering technique. In this work, comparative studies on microstructure and mechanical properties of microhardness and wear behaviors among Cr-C-N, Cr-Si-N, and Cr-Si-C-N Coatings were Systematically conducted. Adding carbon and silicon atoms into CrN Coatings had large effects on microstructural change and mechanical properties of CrN Coatings. The hardness value of Cr-Si-C-N Coatings showed about 44 GPa, while those of Cr-Si-N and Cr-C-N Coatings were 34 and 23 GPa, respectively. The average friction coefficient of CrN-based Coatings decreased from 0.65 to 0.4 with the incorporation of silicon and carbon content.
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Cutting performance of Ti–Al–Si–N-coated tool by a hybrid-Coating System for high-hardened materials
Surface & Coatings Technology, 2005Co-Authors: Myungchang KangAbstract:Abstract Hard Coatings are known to improve the performance of cutting tools in aggressive machining applications, such as high-speed machining. Unfortunately, the development of cutting tool for high-speed machining is not enough in machining of difficult-to-cut material. New superhard Ti–Al–Si–N films, characterized as a nanocomposite nano-sized (Ti,Al,Si)N crystallites embedded in amorphous Si 3 N 4 matrix, was successfully synthesized on WC-Co substrates by a hybrid-Coating System of arc ion plating (AIP) and sputtering method. The hardness of Ti–Al–Si–N film increased with incorporation of Si, and had the maximum value ∼50 GPa at the Si content of 9 at.%, respectively. In this study, Ti–Al–Si–N Coatings were applied to end-mills made of WC-Co material by a hybrid-Coating System. The tool performances for the high-hardened material were studied under high-speed cutting conditions. Additionally, the relationship between the machining characteristics and the Si contents were investigated under various high-spindle speeds. It showed the tool life was improved up to 50% at the Si content of 9 at.%.