Papers by Keyword: Diffusion Layer

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Authors: Myrna Ariati Mochtar, Rizki Aldila
Abstract: In metal forming process by die casting method, nitriding plays an important role in increasing the surface hardness. The influence of shot peening and shot blasting to the modified. H13 tool steel before nitriding process has been studied. Nitriding has been done in a gas vacuum furnace, at temperature of 510°C for 5 hours. Shot peening was conducted by using steel balls with a pressure of 461 kPa. Shot blasting has been done after shot peening using SiC particles. Characterization of the sample surface before and after the variation process is focused on changing the microstructure, micro hardness distribution, depth and composition nitriding layer. It has been found that shot peening prior to nitriding increase the maximum surface hardness to 1196 HV and effective depth of diffusion layer to 72 μm. Meanwhile, the nitriding without any prior surface treatment produces a maximum hardness of HV 1101.4 with effective depth of diffusion layer of 54 μm. Shot peening prior to nitriding produces white layer thickness of 4.1 μm thicker compared to white layer developed in nitriding without shot peening which produces 3.7 μm. While on nitrided material without any preceded surface treatment did not reveal any white surface layer.
Authors: Xue Jun Zhang, Ya Dong Li, Yan Hong Tian, Su Qing Wang, Li Zhang
Abstract: This paper has developed one way to produce flexible carbon cloth from artificial cotton cloth carbonized at 1000°C with using (NH4)2HPO4 as impregnation agent and phenolic resin as modification agent. The effects of (NH4)2HPO4 and phenolic resin on bulk resistivity, tensile strength, density, thickness and microstructure of the resultant carbon cloth were investigated. The results show that (NH4)2HPO4 impregnation is helpful to increase the carbon yield of artificial cotton cloth and decrease the bulk resistivity. The fibers in the carbon cloth are bond by carbonized phenolic resin, leading to higher tensile strength and lower bulk resistivity. When mass content of (NH4)2HPO4 was 5% and phenolic resin 54%, flexible and porous carbon cloth was prepared with thickness of 0.27mm, density of 0.34g/cm3, bulk resistivity of 0.06Ω·cm and tensile strength of 2.33MPa, which is promising materials for diffusion layer in fuel cell.
Authors: N. Grittner, B. Striewe, A. von Hehl, D. Bormann, M. Hunkel, H.W. Zoch, F.W. Bach
Abstract: The combination of different metallic materials enables the design of lightweight structures with tailor-made properties at global as well local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. Whereas titanium alloys show particular high mechanical strength and good corrosion resistance, aluminium alloys provide a considerable lower density and consequently higher potential for weight savings. However, after conventional fusion joining, e.g. after laser beam welding, heat affected zones, porosity or grain growth may occur and impair the local properties [1, 2]. In contrast, by solid-state joining techniques like co-extrusion these disadvantages can be avoided. Therefore co-extrusion exhibits an attractive solution for long products combining aluminium and titanium based alloys. Current investigations have been focused on the co-extrusion of aluminium and titanium, where titanium is the reinforcing element that is inserted in aluminium profiles. Two different billet variants were examined in the investigations, a titanium-core integrally moulded in the aluminium-billet and titanium-core inserted in a hollow drilled aluminium-billet. Experiments were made with different material combinations, Al99.5 with titanium grade 2 and AlSi1MgMn with Ti6Al4V. Beside mechanical properties of compound the formation of bonding zone are presented.
Authors: Yutaka Kameyama, A. Niwa, Jun Komotori
Abstract: To improve adhesion of DLC coatings, Fine Particle Bombardment (FPB) treatment using Cr based shot particles was performed. After the FPB treatment, DLC coating process was generated on the Chromium-molybdenum steel. The FPB treatment distributes diffused Cr elements onto the treated surface, creating a Cr-rich layer. The FPB treatment increases the surface hardness and roughness which also affect the adhesion of DLC coatings. Wear test was conducted to compare the tribological properties of the DLC coated FPB treated steels and that of the DLC coated non FPB treated ones. The DLC coated surface, after FPB treatment, kept low friction coefficient, while the DLC coated non FPB treated ones showed a sudden increase due to the delamination of DLC layer. These results imply that delamination of the DLC coating was suppressed by the Cr-rich surface layer created by the previous FPB treatment. Consequently, the applied method was effective to improve the adhesion of DLC coatings.
Authors: Kazumasa Sakoshi, Chuji Kagaya, Eiji Kagaya
Abstract: In recent years, global warming and resource exhaustion problems require the manufacturers to minimize substances of environmental concern and industrial wastes and adopt measures for expedited recycling. As a result, making effective use of wastes to try for further energy conservation and high quality products is an important assignment in the heat treatment and surface hardening treatment fields as well. This study has investigated the effectiveness of waste melamine resin in solid nitriding of JIS SUS304 austenitic stainless steel plate. After heating the stainless plate in waste melamine resin fragments and cooling in air, the surface was analyzed. It was found that a nitrided layer had formed on the surface of the plate, and the nitriding potential of waste melamine was shown to be high. It is therefore likely that this method can be effectively applied to the development of economically advantageous high-performance materials and value-added products.
Authors: Myrna Ariati Mochtar, Dwi Marta Nurjaya, Rizki Aldila
Abstract: Die soldering occurs when molten aluminum sticks to the surface of a die material and remains there after the ejection of the part. This resulted in low productivity and economic value in the foundry industry. Nitriding surface treatment is considered as an effective way in enhancing the service life of AISI H13 steel dies and to prevent soldering effect. The focus of this paper is to investigate the influence of three different surface conditions in terms of roughness, gas nitriding and pretreatment prior to gas nitriding on the soldering effect. Three kind of samples made of AISI H13 steel were pretreated (quenched and tempered) and followed by : shot peened, gas nitrided and shot peening followed by gas nitriding, were immersed in liquid melted ADC 12 Aluminium alloy at 30 seconds, 30 minutes, 2 hours and 5 hours, at a constant temperature of 680oC in a holding furnace. Characterizations on the surface of the steel were focused on the optical microstructure, microhardness profile, FE SEM observation and enegy dispersive spectrometry mapping. It was found that shot peening prior to nitriding gives a higher surface hardness and depth of nitride layer of H13 tool steel, 1140 HV (>70 HRC) and 120.5 μm, than the nitriding only process, 1033 HV (68 HRC) and 105 μm. The higher the hardness and depth of nitride layer expected would reduce the die soldering effect at the surface of the H13 tool steel dies. It was also found that the only shot peening treatment resulted in a tendency of soldering accompanied by the formation of intermetallic layers ; while soldering is not found on the nitrided and shot peened-nitrided samples.
Authors: Yan Ping Liu, Jin Xiang Xue, Pei De Han
Abstract: A new process technique that TiN permeation layer consisted of diffusion and deposition layer was synthesized on the surface of mild carbon steel has been firstly introduced, mainly according to plasma point discharge, hollow cathode effect and reactive vapor deposition technique. The surface appearance of this layer formed was uniform, compact and fine TiN cellular structure, a diffusion transitional region existing between the deposition layer and substrate. The surface texture was TiN deposition layer + TiN + Ti solid solution diffusion layer. From surface to inner Ti and N elements appeared graded distribution. This paper also mainly investigated the electrochemical corrosion behaviors of this multilayer. The polarization curves of specimens in 10% H2SO4 corrosive media were measured. The eroded surface morphologies were also surveyed by SEM. The results indicated that the erosion resistance of multi-permeation layer was increased many times than PVDTiN and a mild steel substrate, and almost equaled to that of compound process TiN layers.
Authors: Nijaz Delalić, Ejub Džaferović, Ejub Ganić
Abstract: Increase of the emission of CO2, which is mostly the result of the combusted fossil fuels into the atmosphere, exponentially increases. Through increased energy efficiency there is lower CO2 emission. There is a tendency to reduce exhaust gases temperatures down from their original value referred to as “acid dew point”, 115-160°C. A result is vapor condensation of wet flue in chimney. Condensation occurs when the surface temperature is below the dew point of the vapor-gas mixture. Therefore, Vapor-Liquid Equilibrium models are required in order to determine the dew point of the mixture. Wet flue gas is simulated with vapor-air mixture. A numerical model was presented to calculate the velocity and thermal field of turbulent vapor-air mixture flow trough a chimney. The momentum and temperature field were calculated via a finite-volume CFD code, using the k – e turbulence model. The validation of this calculation was conducted employing an experimental set for heat and mass transfer in vertical upward vapor-air mixture. Measurements were done using a stainless steel tube of 13.2 mm I.D. (internal diameter) and 70 I.D. lengths. Flow rates of steam and air were varied as the experimental parameters. The experiment involves two-phase, two-component, heat and mass transfer. Comparisons of wall temperature and condensate rate were made and the model was shown to give an acceptable results.
Authors: S. Mridha
Abstract: In gas nitriding the thickness of the case depth is reported to increase parabolically with processing time and ammonia content in the NH3/H2 gas mixture which consequently increases the thickness of undesirable surface iron-nitride (white layer). In this investigation two commercial grade low alloy steels were nitrided in gas atmospheres containing 10 to 80% ammonia at 4700, 5200 and 5700C for 6 to 96 h. A metallographic technique was used to reveal different zones of the nitrided surface and the thickness of the diffusion zone was recorded using microscope. The growth kinetics of the diffusion layer of these two steels were analyzed and compared with that of 3% chromium (En40B) steel from literature. The results of the investigation conclusively suggest that the growth rate of the nitrided layer for both steels reached to a maximum with the increase of ammonia content in the gas mixture up to an optimum level where the thickness of the white layer is a minimum. However, the growth rates of the nitrided case are different for different steels.
Authors: Simona Hutařová, Tomás Vlasák, Tomáš Podrábský, Jan Hakl, Martin Juliš
Abstract: High-temperature constructional parts of aircraft engines and energy units are exposed to high dynamic stress (fatigue processes and creep) and various temperatures in dioxide-corrosion condition (hot corrosion, oxidation and erosion). The improvement of aero-engine and turbine efficiency is possible through the increase of temperature in front of turbine. This requires the use of heat-resistant and creep-resistant materials, especially nickel-base superalloys which resist mentioned effects for a limited period of time. A deposition of protective layers should improve hot corrosion resistance. This paper is focused on microstructure of protective layers created by codeposition of Al and Si on nickel-base superalloys INCO 713 LC and INCO 738 LC after thermal and thermal-stress exposition and on microstructure of basic materials (substrates). The contribution also shows creep tests results for both superalloys with and without a protective layer.
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