The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Liang Wang - One of the best experts on this subject based on the ideXlab platform.
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low temperature anodic Nitriding of aisi 304 austenitic stainless steel
Materials Letters, 2014Co-Authors: Yang Li, Huizhong Xu, Liang WangAbstract:Abstract In conventional plasma Nitriding process, the treated components were submitted to high cathodic potentials. In this present work, AISI 304 austenitic stainless steels were nitrided at anodic potential in plasma atmosphere. Nitriding experiments were carried out at low temperature 430 °C for 3 h, 6 h, and 9 h. The specimen was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and a microhardness tester. The results showed that the nitrogen expanded austenite layer was formed on the surface during the low temperature anodic Nitriding. The surface microhardness and the thickness of the hardened layers increased as the Nitriding Time increased. It suggested that nitrogen was present as a solid solution in the nitrided layer.
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effect of Nitriding Time on the nitrided layer of aisi 304 austenitic stainless steel
Surface & Coatings Technology, 2006Co-Authors: Liang Wang, Shijun JiAbstract:The effect of plasma Nitriding Time on the microstructure and phase composition of nitrided layers on AISI 304 stainless steel was investigated. The phase composition and structure of the nitrided layer have been studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis of samples treated at 420 °C showed the presence of γN phase in the nitrided layers for all Nitriding Times involved in this study. The lattice parameters calculated based on γN(111) and γN(200) were different and became larger with Time for up to 5 h of Nitriding treatment. The surface hardness of nitrided layer was also increased with Nitriding Time. The maximum thickness of the nitrided layer reached 27 μm after 44 h of treatment in this study.
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structural characteristics of low temperature plasma nitrided layers on aisi 304 stainless steel with an α martensite layer
Surface & Coatings Technology, 2002Co-Authors: Liang Wang, Jianbing Qiang, Zukun HeiAbstract:The characteristics of the structure formation of a low-temperature plasma-nitrided layer on AISI 304 austenitic stainless steel with a pre-existing α′-martensitic deformation layer were studied in detail by glancing-angle X-ray diffraction (XRD). The results show a two-step formation process for the plasma-nitrided layer. The α′-martensitic layer gradually reverts to the original γ-austenite structure at first, followed by the transformation of γ→γN as the nitrogen content increases with treatment Time. Within the same Nitriding Time, the sample with an α′ layer shows much less lattice expansion than the sample without an α′ layer. The volume fractions of α′ and γ phases transformed during the plasma-Nitriding process were calculated by quantitative XRD. The transformation of α′→γ is dependent on the nitrogen content dissolved in α′, apart from that resulting from heating at the Nitriding temperature.
Dong Cherng Wen - One of the best experts on this subject based on the ideXlab platform.
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influence of layer microstructure on the corrosion behavior of plasma nitrided cold work tool steel
Journal of Materials Science, 2010Co-Authors: Dong Cherng WenAbstract:The influence of layer microstructure on the corrosion behavior of plasma nitrided cold work tool steel, of commercial name “DC53”, in 3.5% NaCl solution is reported. The specimens were nitrided at 520 °C for different treatment Times using a constant [N2 + H2] gaseous mixture by a DC-pulsed plasma system. The microstructure of the nitrided layers was investigated by optical microscopy and X-ray diffraction. The corrosion behavior was evaluated by potentiodynamic polarization experiments. The plasma Nitriding process considerably improves the corrosion resistance of material in NaCl environment as compared to the unnitrided DC53 steel. The modified surface layer consisting mainly of e-nitride (Fe2–3N) and a small amount of γ′-nitride (Fe4N) confers this outstanding behavior. The corrosion resistance dependence on specific Nitriding processes is reported and the role of the e-nitride is discussed. In particular, the correlation of pitting current density, density of pits, and volume fraction of e-nitride with Nitriding Time is analyzed. The results denote that the most important parameter for controlling the corrosion resistance of the material is the volume fraction of e-nitride and the nitrided layer thickness. It is expected that a nitrided layer would be thicker and rich in e-nitride phase to achieve a high corrosion resistance.
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Microstructure and corrosion resistance of the layers formed on the surface of precipitation hardenable plastic mold steel by plasma-Nitriding
Applied Surface Science, 2009Co-Authors: Dong Cherng WenAbstract:Abstract Plasma-Nitriding is used to improve the wear resistance and corrosion resistance of plastic mold steels by modifying the surface layers of these steels. In this study, a precipitation hardenable plastic mold steel (NAK80) was plasma-nitrided at 470, 500, and 530 °C for 4, 8, and 12 h under 25% N2 + 75% H2 atmosphere in an industrial Nitriding facility. The microstructures of the base material and nitrided layers as well as the core hardness were examined, and various phases present were determined by X-ray diffraction. The corrosion behaviors were evaluated using anodic polarization tests and salt fog spray tests in 3.5% NaCl solution. The results had shown that plasma-Nitriding does not cause the core to soften by overaging. Nitriding and aging could be achieved simultaneously in the same treatment cycle. Plasma-Nitriding of NAK80 mold steel produced a nitrided layer composed of an outer compound layer constituting a mixture of ɛ-nitride and γ′-nitride and an adjacent nitrogen diffusion layer on the steel surface. The amount of ɛ-nitride and total nitrides increased with an increase in Nitriding temperature and Nitriding Time. Corrosion study revealed that plasma-Nitriding significantly improved the corrosion resistance in terms of corrosion potential, corrosion and pitting current density, and corrosion rate. This improvement was found to be directly related to the increase in the amount of ɛ-nitride at the surface, indicating the amount of ɛ-nitride controlling the corrosion resistance.
Zukun Hei - One of the best experts on this subject based on the ideXlab platform.
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structural characteristics of low temperature plasma nitrided layers on aisi 304 stainless steel with an α martensite layer
Surface & Coatings Technology, 2002Co-Authors: Liang Wang, Jianbing Qiang, Zukun HeiAbstract:The characteristics of the structure formation of a low-temperature plasma-nitrided layer on AISI 304 austenitic stainless steel with a pre-existing α′-martensitic deformation layer were studied in detail by glancing-angle X-ray diffraction (XRD). The results show a two-step formation process for the plasma-nitrided layer. The α′-martensitic layer gradually reverts to the original γ-austenite structure at first, followed by the transformation of γ→γN as the nitrogen content increases with treatment Time. Within the same Nitriding Time, the sample with an α′ layer shows much less lattice expansion than the sample without an α′ layer. The volume fractions of α′ and γ phases transformed during the plasma-Nitriding process were calculated by quantitative XRD. The transformation of α′→γ is dependent on the nitrogen content dissolved in α′, apart from that resulting from heating at the Nitriding temperature.
E. J. Mittemeijer - One of the best experts on this subject based on the ideXlab platform.
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the microstructure of the diffusion zone of a gaseously nitrided fe 1 5 wt cr 1 5 wt al alloy
Materials Science and Technology, 2010Co-Authors: A. R. Clauss, R E Schacherl, Ewald Bischoff, E. J. MittemeijerAbstract:AbstractGaseous Nitriding experiments of an Fe–1·5 wt-%Cr–1·5 wt-%Al (i.e. Fe–1·6 at.-%Cr–3·1 at.-%Al) alloy were carried out as a function of Time at 853 K. The microstructure of the diffusion zone was characterised by microhardness, electron probe microanalysis (EPMA), X-ray diffraction analysis (XRD), scanning transmission electron microscopy (STEM) in combination with energy dispersive X-ray spectroscopy (EDX) and Auger electron spectroscopy (AES). Chromium and aluminium precipitate together as a mixed Cr1−xAlxN phase in the diffusion zone. The size of the (semi)coherent precipitates and the amount of excess nitrogen have a strong influence on the microstructure of the diffusion zone. Crack formation occurs after a certain Nitriding Time starting from the specimen surface and propagating along grain boundaries more or less perpendicularly to the surface towards larger depth. The grain boundary brittleness could be ascribed to the precipitation of excess nitrogen as nitrogen gas at the grain boundaries...
Hesam Pouraliakbar - One of the best experts on this subject based on the ideXlab platform.
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duplex ceramic coating produced by low temperature thermo reactive deposition and diffusion on the cold work tool steel substrate thermodynamics kinetics and modeling
Ceramics International, 2015Co-Authors: Hesam Pouraliakbar, Gholamreza Khalaj, Lidija Gomidželovic, Mohamadjavad Khalaj, Mohsen NazerfakhariAbstract:Abstract Specimens of DIN 100MnCrW4 steel (type O1 tool steel) have been cut and prepared for performing a duplex surface treatment involving Nitriding and low temperature vanadium thermo-reactive deposition and diffusion (TRD) technique. The TRD process was performed in a molten salt bath at different temperatures of 575, 650 and 725 °C for 1–30 h. The treatment formed a vanadium carbonitride coating with the thickness up to 10.5 μm on a hardened diffusion zone. Characterizations by means of an optical microscope (OM), scanning electron microscope equipped with energy dispersive X-ray spectrometer (SEM–EDS) and X-ray diffraction analysis (XRD) indicated that the compact and dense coating mainly consisted of V(C,N) and V2(C,N) phases. All the growth processes of the formed vanadium carbonitride layer obtained by TRD followed a parabolic kinetics while the calculated activation energy (Q) for the treatment was 181.1 kJ/mol. An artificial neural network (ANN) based model for predicting the layer thickness of ceramic coatings was presented. Constructing the model, training, validating and testing of experimental results from 72 different specimens were conducted. The data used as inputs in the proposed model were arranged in a format of five parameters that comprised of “pre-Nitriding Time”, “ferro-vanadium particle size”, “ferro-vanadium weight percent”, “salt bath temperature” and “coating Time”. Accordingly, the thickness of duplex coating in each specimen was estimated accurately. Finally, the proposed ANN-based model showed a strong potential for predicting the layer thickness of duplex ceramic coating performed by the TRD technique on the substrate of cold work tool steel.
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chromium carbonitride coating produced on din 1 2210 steel by thermo reactive deposition technique thermodynamics kinetics and modeling
Surface & Coatings Technology, 2013Co-Authors: Gholamreza Khalaj, Ali Nazari, Seyyed Mohammad Mousavi Khoie, Mohammad Javad Khalaj, Hesam PouraliakbarAbstract:Abstract A duplex surface treatment on DIN 1.2210 steel has been developed involving Nitriding and followed by chromium thermo-reactive deposition (TRD) techniques. The TRD process was performed in molten salt bath at 550, 625 and 700 °C for 1–14 h. The process formed a thickness up to 9.5 μm of chromium carbonitride coatings on a hardened diffusion zone. Characterization of the coatings by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) indicates that the compact and dense coatings mainly consist of Cr(C,N) and Cr 2 (C,N) phase. All the growth processes of the chromium carbonitride obtained by TRD technique followed a parabolic kinetics. Activation energy (Q) for the process was estimated to be 185.6 kJ/mol of chromium carbonitride coating. A model based on genetic programming for predicting the layer thickness of duplex coating of the specimens has been presented. To construct the model, training and testing was conducted by using experimental results from 82 specimens. The data used as inputs in genetic programming models were five independent parameters consisting of the pre-Nitriding Time, ferro-chromium particle size, ferro-chromium weight percent, salt bath temperature and coating Time. The training and testing results in genetic programming models illustrated a strong capability for predicting the layer thickness of duplex coating.