197,555 research outputs found
La prospettiva antropologica
No full textLinee guida per insegnanti: l'approccio antropologico per una scuola inclusiva in contesti con forte presenza di migranti; il 'finto' problema linguistico, le relazioni familiari e il rischio di facili categorizzazioni non inclusive
Mechanical and metallurgical properties of AlTiN-coated HSS materials
No full textPurpose - The purpose of this paper is to examine mechanical and metallurgical properties of AlTiN coating HSS materials in detail. Design/methodology/approach - In this study, high-speed steel (HSS) parts were processed by the way of machining and were coated with AlTiN on physical vapour deposition (PVD) workbench at approximately 650 degrees C for 4 h. Tensile strength, fatigue strength and hardness tests for AlTiN coated HSS samples were performed. Samples were also analyzed by energy dispersive X-ray analysis (EDS), X-ray diffraction (XRD) and scanning electron microscope (SEM). The results were compared with uncoated HSS components. Findings - It was found that an amorphous aluminium-oxide layer emerges on surface of parts by AlTiN coating. This layer prevents further oxide formations. The coating thickness of AlTiN-coated sample is between 1,530 and 1,558 mu m. Compared to uncoated HSS, AlTiN coated HSS gives higher performance. Research limitations/implications It would be interesting to search different coatings for cutting tools. It could be the good idea for future work concentrated wear properties on tool materials using different coatings. Originality/value - This paper provides information on mechanical and metallurgical behaviour of AlTiN coated HSS materials and offers practical help for the researchers and scientists working in the coating area
Nitriding Effect on the Tribological Performance of CrN-, AlTiN-, and CrN/AlTiN-Coated DIN 1.2367 Hot Work Tool Steel
No full textIn this study, heat-treated and multisurface engineered DIN 1.2367 tool steel was subjected to room and elevated temperature wear tests, and the effect of nitriding on its tribological behavior was investigated. CrN, AlTiN, and CrN/AlTiN coatings with a total thickness of 2 µm were obtained by arc cathodic physical vapor deposition on conventional heat-treated and gas-nitrided steels. The white layer formed during nitriding was removed, and a diffusion layer (100 µm) was achieved in the cross section of the steel having a tempered martensitic matrix. The highest surface hardness was attained with an integral coating (CrN/AlTiN), and surface hardness increased even more after nitriding due to the formation of a multicomponent ceramic layer on top of the diffusion layer. The room temperature wear tests performed against an alumina counterpart revealed that (i) CrN/AlTiN-coated steel had the highest friction coefficient of 0.26, which further increased to 0.33 by nitriding due to the increase in shear strength, and that (ii) with increasing surface hardness, the specific wear rates (W) of the heat-treated and coated steels could be ranked as follows: WCrN/AlTiN < WAlTiN < WCrN. The wear rates decreased when nitriding was carried out prior to coating. In order to simulate the aluminum extrusion conditions, hot wear behavior of the surfaces against AA6080 alloy at 450 °C was investigated. The hot wear tests revealed that (i) high friction coefficients were reached due to the adhesive characteristic of aluminum to the surfaces, (ii) the nitrided and CrN/AlTiN-coated sample exhibited the lowest wear rate among all studied surfaces, and (iii) the film damage on the worn surfaces mostly occurred in the form of droplet delamination
Characteristic properties of AlTiN and TiN coated HSS materials
No full textPurpose - The purpose of this paper is to examine mechanical and metallurgical properties of AlTiN- and TiN-coates high-speed steel (HSS) materials in detail. Design/methodology/approach - In this study, HSS steel parts have been processed through machining and have been coated with AlTiN and TiN on physical vapour deposition workbench at approximately 6,500 degrees C for 4 hours. Tensile strength, fatigue strength, hardness tests for AlTiN- and TiN-coated HSS samples have been performed; moreover, energy dispersive X-ray spectroscopy and X-ray diffraction analysis and microstructure analysis have been made by scanning electron microscopy. The obtained results have been compared with uncoated HSS components. Findings - It was found that tensile strength of TiAlN- and TiN-coated HSS parts is higher than that of uncoated HSS parts. Highest tensile strength has been obtained from TiN-coated HSS parts. Number of cycles for failure of TiAlN- and TiN-coated HSS parts is higher than that for HSS parts. Particularly TiN-coated HSS parts have the most valuable fatigue results. However, surface roughness of fatigue samples may cause notch effect. For this reason, surface roughness of coated HSS parts is compared with that of uncoated ones. While the average surface roughness (Ra) of the uncoated samples was in the range of 0.40 mu m, that of the AlTiN- and TiN-coated samples was in the range of 0.60 and 0.80 mu m respectively. Research limitations/implications - It would be interesting to search different coatings for cutting tools. It could be the good idea for future work to concentrate on wear properties of tool materials. Practical implications - The detailed mechanical and metallurgical results can be used to assess the AlTiN and TiN coating applications in HSS materials. Originality/value - This paper provides information on mechanical and metallurgical behaviour of AlTiN- and TiN-coated HSS materials and offers practical help for researchers and scientists working in the coating area
Influence of Molybdenum Addition on the Structure, Mechanical Properties, and Cutting Performance of AlTiN Coatings
No full textThough AlTiN coating has been intensively studied, there is still a need to develop AlTiN coating to meet the growing demand of industrial machining. One effective way to improve the performance of AlTiN coating is by adding alloying elements. In this study, AlTiN and AlTiMo coatings were deposited using multi-arc ion plating to investigate the influence of molybdenum addition on the structure, mechanical properties, and cutting performance of AlTiN coatings. Spherical droplets formed on the surfaces of both coatings, with the AlTiMoN coating exhibiting more surface defects than the AlTiN coating. The grazing incidence X-ray diffraction results revealed the formation of an (Al,Ti)N phase formed in the AlTiN and AlTiMoN coatings. Molybdenum doping in the AlTiMoN coating slightly reduced the grain size. Both coatings exhibited excellent adhesion to the substrate. The hardness (H), elastic moduli (E), H/E, and H3/E2 ratios of the AlTiMoN coating were higher than those of the AlTiN coating. The improvement in the mechanical properties was attributed to grain refinement and solution strengthening. Molybdenum doping improved the tribological properties and cutting performance of the AlTiN coatings, which was ascribed to the formation of MoO3 as a solid lubricant. These results show a path to increase the performance of AlTiN coating through molybdenum addition and provide ideas for the application of AlTiMoN coatings for cutting tools
Kaplamasız, PVD tekniği ile TiN ve altin kaplanmış DIN 1.2379 soğuk iş takım çeliğinin aşınma davranışlarının incelenmesi
No full textBu çalışmada, kalıp sektöründe kullanılan DIN 1.2379 soğuk iş takım çeliğinin kaplamasız, PVD tekniği ile TiN ve AlTiN kaplamalı olanlarıyla karşılaştırılıp, aşınma davranışları incelenmesi hedeflenmiştir. Deney numuneleri 40Øx5 mm ebatlarında özdeş olarak hazırlanmıştır. Hazırlanan deney numuneleri ısıl işleme tabi tutulduktan sonra, PVD yöntemiyle TiN ve AlTiN kaplama işlemi uygulanmıştır. Aşınma testleri ileri geri aşınma tipi cihazda 0,5 m/s kayma hızında, 5N, 10N ve 15N yükler altında ve 120m kayma mesafesinde gerçekleştirilmiştir. Deneylerde aşındırıcı olarak 6 mm çapında alümüna top kullanılmıştır. Numunelerin mikro sertlik gibi mekanik özellikleri ile SEM ve EDS gibi metalografik incelemeleri yapılmıştır. Yapılan deneylerde malzemeye uygulanan kuvvet ve çevrim arttıkça aşınmanın arttığı gözlemlenmiştir. Kaplamasız numuneler, AlTiN kaplamalı numunelerden yaklaşık 2 kat fazla, TiN kaplamalı numunelerden de 1 kat daha fazla aşınmıştır. TiN kaplamalı numunelerin de AlTiN kaplamalı numunelerden 1 kat daha fazla aşındığı gözlemlenmiştir. Bu sonuç ile, kaplamalı numunelerin aşınma dirençlerinin daha fazla olduğu görülmüştür. Alınan SEM görüntülerinde ve yapılan EDS analizlerinde kaplamanın malzemeye homojen olarak nüfuz ettiği gözlemlenmiştir. Deney numunelerinin inceleme sonucunda AlTiN kaplamalı numunelerin TiN kaplamalı ve kaplamasız numunelere göre daha az aşındığı, TiN kaplamalı numunelerinde kaplamasız numunelere göre daha az aşındığı gözlemlenmiştir.In this study, TiN and AlTiN coated with PVD technique and uncoated of DIN 1.2379 cold work tool steel used in the mold industry have been compared each other and the wear behaviors of the materials have been investigated. The experimental specimens were prepared identically in the Ø40x5 mm dimensions. The experimental specimens have been heat-treated and then TiN and AlTiN PVD coating process is applied to them. The wear tests were performed 0,5 m/s sliding speed, 5, 10 and 15 N loads and 120m sliding distance using reciprocating abrasion device. 6 mm diameter alumina balls were used as abrasive in the experiments. The mechanical properties such as micro hardness and metallographic tests such as SEM and EDS of the samples were performed. In the experiments, it was observed that as the force applied to the material and the cycle increased, the wear also increased. It was observed that the uncoated specimens approximately two times more than AlTiN coated and one time more than AlTiN coated. TiN coated specimens wore approximately one time more than AlTiN coated. With this result, the wear resistant of coating specimens were much higher than other samples. In the SEM images and EDS analysis, It was observed that the coating was spread uniformly in the materials. As a result of the review of the test samples, It was observed that the AlTiN coated samples wore less than TiN coated and uncoated samples and the TiN coated samples wore less than the uncoated samples
Fatigue properties of ALTiN and TiN-coated high speed steels (HSS) steels
No full textWear of equipments limits usage life of machine parts. For this reason, coating technologies obtained from vapour phase occupy an important place in industrial applications. Coating obtained in this way has a wide usage area because it is not related directly to property of main materials to be covered. In physical vapour deposition (PVD) method, coating material is transmitted to surface in atomic, molecular or ionic form obtained not chemically but physically from solid, liquid and gas source. This work presents the fatigue properties of AlTiN and TiN-coated (high speed steels) HSS. In present study, TiN and AlTiN coatings were deposited onto HSS steel substrates by 'physical vapour deposition' technique at approximately 650°C for 4 h. Fatigue test for AlTiN and TiN-coated HSS steel samples were performed. The obtained results were compared with uncoated HSS components. It was observed that number of cycle for failure of AlTiN and TiN-coated HSS parts is longer than uncoated HSS steels. Particularly TiN-coated HSS parts have the most valuable fatigue results. © 2011 Academic Journals
Thermal Fatigue Resistance Studies of Multilayer CrN and AlTiN Coatings Deposited on Plasma Nitrided H-13 Hot Work Steel
No full textH-13 steel surface was duplex-treated using Plasma Nitriding (PN) and PVD coatings to solve the thermal fatigue problem faced in die-casting applications. Chromium-based multilayer CrN/Cr (m-CrN) coatings and multi-component aluminium–titanium-based AlTiN (m-AlTiN) coatings were deposited using a cathodic arc deposition technique after plasma nitriding the H-13 steel surface with different case-depths of 50 µm and 200 µm. The structural, tribological, corrosion, and mechanical properties of the duplex-treated samples were studied. The thermal fatigue (TF) test was conducted by heating the sample to 600 °C and rapidly cooling it to room temperature, simulating the die-casting process conditions. After multiple cycles, it was observed that the oxide layer thickness formed was lower on duplex-treated samples compared to that on the uncoated plasma nitride sample. In addition, the mechanical properties were improved with the increase in PN diffusion depth. The duplex-treated samples showed better mechanical and thermal fatigue properties compared to untreated and only coated samples. The sample with m-AlTiN deposited on plasma nitrided H-13 with 200 µm case depth displays better thermal fatigue properties compared to the other samples
Experimental investigation of the wear behaviour of DIN 1.2379 cold work tool steel uncoated, TİN and altin coated with PVD technic
No full textBu çalışmada, kalıp sektöründe kullanılan DIN 1.2379 soğuk iş takım çeliğinin kaplamasız, PVD tekniği ile TiN ve AlTiN kaplamalı olanlarıyla karşılaştırılıp, aşınma davranışları incelenmesi hedeflenmiştir. Deney numuneleri 40Øx5 mm ebatlarında özdeş olarak hazırlanmıştır. Hazırlanan deney numuneleri ısıl işleme tabi tutulduktan sonra, PVD yöntemiyle TiN ve AlTiN kaplama işlemi uygulanmıştır. Aşınma testleri ileri geri aşınma tipi cihazda 0,5 m/s kayma hızında, 5N, 10N ve 15N yükler altında ve 120m kayma mesafesinde gerçekleştirilmiştir. Deneylerde aşındırıcı olarak 6 mm çapında alümüna top kullanılmıştır. Numunelerin mikro sertlik gibi mekanik özellikleri ile SEM ve EDS gibi metalografik incelemeleri yapılmıştır. Yapılan deneylerde malzemeye uygulanan kuvvet ve çevrim arttıkça aşınmanın arttığı gözlemlenmiştir. Kaplamasız numuneler, AlTiN kaplamalı numunelerden yaklaşık 2 kat fazla, TiN kaplamalı numunelerden de 1 kat daha fazla aşınmıştır. TiN kaplamalı numunelerin de AlTiN kaplamalı numunelerden 1 kat daha fazla aşındığı gözlemlenmiştir. Bu sonuç ile, kaplamalı numunelerin aşınma dirençlerinin daha fazla olduğu görülmüştür. Alınan SEM görüntülerinde ve yapılan EDS analizlerinde kaplamanın malzemeye homojen olarak nüfuz ettiği gözlemlenmiştir. Deney numunelerinin inceleme sonucunda AlTiN kaplamalı numunelerin TiN kaplamalı ve kaplamasız numunelere göre daha az aşındığı, TiN kaplamalı numunelerinde kaplamasız numunelere göre daha az aşındığı gözlemlenmiştir.In this study, TiN and AlTiN coated with PVD technique and uncoated of DIN 1.2379 cold work tool steel used in the mold industry have been compared each other and the wear behaviors of the materials have been investigated. The experimental specimens were prepared identically in the Ø40x5 mm dimensions. The experimental specimens have been heat-treated and then TiN and AlTiN PVD coating process is applied to them. The wear tests were performed 0,5 m/s sliding speed, 5, 10 and 15 N loads and 120m sliding distance using reciprocating abrasion device. 6 mm diameter alumina balls were used as abrasive in the experiments. The mechanical properties such as micro hardness and metallographic tests such as SEM and EDS of the samples were performed. In the experiments, it was observed that as the force applied to the material and the cycle increased, the wear also increased. It was observed that the uncoated specimens approximately two times more than AlTiN coated and one time more than AlTiN coated. TiN coated specimens wore approximately one time more than AlTiN coated. With this result, the wear resistant of coating specimens were much higher than other samples. In the SEM images and EDS analysis, It was observed that the coating was spread uniformly in the materials. As a result of the review of the test samples, It was observed that the AlTiN coated samples wore less than TiN coated and uncoated samples and the TiN coated samples wore less than the uncoated samples
- …
