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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Influence Of Malonic Acid On The Corrosion And SCC Behaviour Of Anodic Coated 1050 Al-Alloys

    Panayotis SpathisEfthimios PapastergiadisGeorgios StalidisGeorgios Papanastasiou...
    P.155-162页
    查看更多>>摘要：Aim of the present work is the study of corrosion and stress corrosion cracking behaviour of 1050 Al-Alloy anodised in a 3M H_2SO_4 anodising bath with the presence in it of malonic acid, in various concentrations and anodising current densities. The investigation was carried out by SCC (Stress Corrosion Cracking) tests and electrochemical measurements. The influence of applied potential on SCC behaviour was also examined.The corrosion and SCC behaviour of anodised 1050 Al-Alloy was found to vary with malonic acid concentration, anodising conditions, applied potential and stress level. In SCC conditions all prepared coatings protected the bare alloy, with better protective properties in the case of 0.015M concentration of malonic acid prepared with a 6 A.dm~(-2) anodising current density. The coating prepared in these conditions had better mechanical properties as indicated from the increased protection at a high stress level and also the better behaviour in corrosion, without stress, conditions of coatings prepared in different conditions of malonic acid concentration and anodising current density. For the interpretation of the results, properties of the anodic coatings as thickness, packing density, coating ratio, roughness, were also studied. The anodic coating formed in a electrolytic bath of 0.015M concentration of malonic acid and a 6 A.dm~(-2) anodising current density was found to be less porous, more compact and rough, with better oxide structure. Prepared coatings were found to increase protective properties in an area of applied potentials slightly more anodic than the free corrosion potential values.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Self-supporting nanocrystalline diamond foils - a new concept for crystalline diamond on any technical surface

    Matthias A. LodesStefan M. RosiwalRobert F. Singer
    P.163-169页
    查看更多>>摘要：The manufacturing and application of self-supporting nanocrystalline diamond foils is introduced. The high temperature manufacturing of nanocrystalline diamond foils by hot-filament chemical vapour deposition (HFCVD) is separated from the low temperature application, allowing the coating of temperature sensitive materials, which cannot be coated by HFCVD conventionally. By coating appropriate template materials and stripping-off after the CVD-process, self-supporting, flexible nanocrystalline diamond foils with high hardness (> 70 GPa) and very low thermal conductivity (< 1 W/mK.) with thicknesses of up to 100 μm can be produced. Lasercutting is an appropriate method for machining any desired geometry. Thus the possibility to use the extreme properties of diamond for protection against friction and wear on new substrate materials, e.g. steels, light metals and polymers, is generated.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Simulation of dynamic lubricant effects in sheet metal forming processes

    Manuel LudwigCecile MuellerPeter Groche
    P.171-178页
    查看更多>>摘要：Tribology plays an important role in sheet metal forming processes relating to near net shape production processes and achievable surface qualities. Nearly every process is realized by using characteristic lubricants affecting the tribological system to achieve the desired results. Deterministic structures on sheet surfaces can result in less friction and higher drawing ratios. This is caused by hydrostatic pressures build up in closed lubricant areas and hydrodynamic pressures due to the lubricant motion especially in thin fluid films [1,2, 3]. Friction mechanisms in the mixed lubrication regime are not fully understood till today. The numerical simulation of flows in lubricant pockets and their influence on surface evolution are promising ways to gain more knowledge of the lubricant behavior in tribological systems. Therefore, this paper shows results of combined numerical and experimental approaches. The described simulations of closed lubricant pockets on surfaces identify influencing parameters. Strip drawing experiments are done to verify the simulations. The influence and the importance of local pressures due to viscous effects in the lubricant are considered as well as the necessity to use fluid-structure-interactions to simulate the behavior of lubricants in the tribological system.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Tribological characterization of PVD-coatings

    Tobias SchraderUlf EngelMarion Merklein
    P.179-186页
    查看更多>>摘要：In cold forging processes the high tribological and mechanical loads often lead to early tool failure. If the cause of failure is wear, an extension of tool life could be achieved by the application of PVD coatings. In industrial tools there is a great variety of load cases that causes wear. Therefore a lot of coatings with different properties are necessary, which need to be adjusted to the various applications. In order to adapt the coatings appropriately to the different processes, a sufficient characterization of the coatings is required. In this paper three new types of PVD coatings based on TiC, AlCrN and TiAIN and two reference PVD coatings based on TiN and TiAlCN are investigated. Since friction plays an important role for the tribological conditions between workpiece and tool, the friction factor m of the coatings is determined for different lubricants in the so called Double Cup Extrusion (DCE) test. A major influence of the lubricants and a minor influence of the coatings can be seen in the conducted tests. Furthermore wear behavior of the coatings is investigated with a so called combined Punching-Forward Extrusion (CPFE) test. In this test it is possible to test simultaneously coated dies and punches under realistic conditions. For the new coating (TiAIN), characterized by monolayer structure, there is wear debris visible in some regions of the die shoulder. The early occurrence of wear might be caused by the ductility of the coating or adherence problems. The other new coatings (TiC and AlCrN), which have a multilayer structure, are revealing excellent wear behavior. The high wear resistance of these two coatings can be explained with their high hardness in combination with a special layer composition.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Evaluation of PVD Coated Tools' Life in Milling Ti6AI4V, based on Impact Tests at Ambient and Elevated Temperatures

    Nikolaos MICHAILIDISKonstantinos BOUZAKISFritz KLOCKEMartin WITTY...
    P.187-194页
    查看更多>>摘要：A methodology based on FEM-calculations and experimental tests for predicting coated tool efficiency in milling Ti6A14V by coated cemented carbide inserts is introduced. The used coatings were: (Ti,Al,Si)N and (Ti,Al)N films. The stress-strain curves and the fatigue critical loads of the coatings were determined by nanoindentations and impact tests respectively at various temperatures, employing FEM-supported procedures developed for results evaluation.The milling investigations were conducted at various cutting speeds. The stress and temperature fields in the cutting edge region were obtained by FEM calculations of the milling process. These results facilitated the explanation of the coated inserts' cutting performance versus the cutting speed.The cutting tests at various cutting speeds and the impact tests at ambient and elevated temperatures revealed that the tool life and the film impact resistance versus the temperature are not linear. Moreover, a sufficient correlation of the coatings' impact resistance at various temperatures with their cutting performance at corresponding cutting speeds was revealed. In this way, an adaption of the cutting conditions to the films' temperature-dependent strength can lead to a considerable cutting performance improvement.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Modified DLC-Coated Guide Pads for BTA Deep Hole Drilling Tools

    Dirk BiermannNadine KesslerThorsten UpmeierThomas Stucky...
    P.195-202页
    查看更多>>摘要：The BTA (Boring and Trepanning Association) deep hole drilling process is commonly used to machine boreholes with a large drilling depth-to-diameter ratio (I/D) and outstanding workpiece quality. The asymmetric tool design leads to a nonzero radial component of the cutting force and the passive force, which are conducted to the borehole wall by so-called guide pads. These guide pads smooth the borehole wall by a forming process and improve the surface quality. Processes, that machine materials with a high adhesion tendency, such as high alloy stainless steel, suffer from poor surface quality in the borehole and the adhesion from the workpiece material on the guide pads. In this paper modified Diamond-Like-Carbon (DLC) coated guide pads for BTA deep hole drilling tools are investigated. The scope of the experiments was the reduction of the adhesion by reducing the friction coefficient of the guide pads, as well as the improvement of the quality of the borehole wall.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Performance of Y-AI_2O_3-based Coatings and Environmentally Friendly Lubricants in Cutting Operations of Difficult-to-machine Materials

    Fritz KlockeSusanne Eva CordesKlaus Gerschwiler
    P.203-209页
    查看更多>>摘要：The machining of difficult-to-cut materials such as nickel-based alloys and austenitic steels are focus in a lot of investigations for a long time. When machining these materials, different effects are overlapping. Approaches to overcome the several problems when machining these materials can be an appropriate coating system for the cutting tool as well as innovative lubricants. Coatings are one of the most common possibilities to improve the cutting performance of tools, notably the tool life as well as the material removal rate. Aluminium oxide coatings made by Physical Vapour Deposition (PVD) technology is a promising coating material for cutting operations. Due to its outstanding characteristics, such as high hardness, high thermal stability and low tendency to adhesion aluminium oxide is a predestined material for the machining of difficult-to-cut materials. In combination with innovative environmental friendly lubricants, the performance of cutting tools is increasing significantly. The objective of this work is to study the wear mechanisms and the cutting performance of aluminium oxide based coated tools in turning, drilling and milling operations.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Influence of substrate nitriding on adhesion, friction and wear resistance of DLC (diamond-like carbon)-coatings

    Wolfgang TillmannEvelina VogliFabian HoffmannPatrick Kemdem...
    P.211-218页
    查看更多>>摘要：Since diamond like carbon layers feature excellent mechanical and tribological behavior under defined environmental circumstances, they are well established in a wide field of industrial and automotive applications in the last decade. However, the pretreatment of the substrate plays also an important role in supporting and enforcing the excellent properties of the coatings. This work analyses the effect of the plasma nitrided cold working steel substrate (80CrV2) on the adhesion, friction and wear resistance of DLC-coatings and compares it to the performance of DLC-coatings applied on a non-hardened substrate material. Therefore the grinded and polished specimens were nitrogen-hardened in an Arc-PVD (Physical Vapor Deposition)-device before the DLC-coating was applied in a Magnetron Sputter-PVD-process. In order to measure the hardness of the thin film coating, a nanoindenter was used. The adhesion was tested with a scratch tester and the wear resistance was measured by using a Ball-on-disc-tester. A 3D-profilometer and a SEM (Scanning Electron Microscope) were utilized to analyze the scratches and wear tracks on the samples. With these results correlations between the substrate nitriding and the mechanical and tribological performance of the DLC-coating were made.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd