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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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    Physico-chemical aspects of surface activation during fluxless brazing in shielding-gas furnaces

    Friedrich-Wilhelm BachKai MoehwaldUlrich Hollaender
    P.73-80页
    查看更多>>摘要：Continuous process brazing in shielding-gas furnaces is tailor-made for manufacturing mass production components by means of brazing technology. Which brazing tasks can actually be carried out by a shielding-gas furnace, depend on many ancillary conditions. In particular these are, besides the component size and joint geometry, the base materials and brazing filler metals as well as the material specific process parameters which are to be maintained in a continuous furnace in order that a process assured brazing can be guaranteed. In this context, the activation of the component's surfaces play a central role for wetting with the braze melt. Within the scope of this contribution, the variables and ancillary conditions concerning this matter are presented and discussed using the brazing process on stainless steels as an example.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Characterization of Heat Transfer Coefficients of Tool Materials and Tool Coatings for Hot Stamping of Boron-Manganese Steels

    Michael WielandMarion Merklein
    P.81-88页
    查看更多>>摘要：One characteristic of hot stamping of ultra high strength steels is the high wear rate of the used tools which leads to shorter tool life. Coatings improving wear resistance can increase the lifetime of the used tools but process relevant data such as the heat transfer capability of coated tool steels are missing. Within this paper the heat transfer capabilities of coated tool steels for the hot stamping processes are determined. Therefore different coating systems based on AlCrN are applied on the tool steels and the pressure dependent heat transfer coefficient is determined using process relevant conditions. As semi-finished blank the hot stamping steel 22MnB5 with an aluminum-silicon pre-coating is used. With respect to a finite element analysis of the forming operation of the hot stamping process the heat transfer coefficient represents an important input data for the process layout.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Determination of mechanical and corrosion properties of boride coating on P91 steel

    Haidar OMARNikolaos MICHAILIDISStefanos SKOLIANOSAzarias MAVROPOULOS...
    P.89-96页
    查看更多>>摘要：In many applications, even high-performance alloys have to be covered with protective coatings, providing higher corrosion and oxidation resistance, as compared to the alloy itself. This study investigates the feasibility to apply boron coatings on P91 steel by pack cementation process, to increase the steel durability in oxidative and corrosive environments, as well as its mechanical strength.Micro-indentation and the coating impact test were used to characterize the hardness and fatigue properties of the film respectively. The coating corrosion resistance versus the one of the uncoated P91 steel was tested in a salt spray chamber. The coating performance was characterized by optical and scanning electron microscopy to check the consistency of the coated and uncoated surfaces and the oxidation extend. The results show an increased film strength, good fatigue performance and adequate corrosion resistance.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Interlaboratory Comparison of Friction Conditions in Hot Stamping Operations

    F. BorsettoA. GhiottiS. BruschiT. Stoehr...
    P.97-105页
    查看更多>>摘要：The paper presents results obtained at two labs, on in Germany and one in Italy, in terms of friction coefficient as function of hot stamping process parameters. Even if the testing procedures and analysis tools to evaluate tribological conditions are different for the two labs, both the approaches show a similar trend as regards the friction coefficient dependence from the process parameters.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    New Methods for Characterizing Coating Properties at Ambient and Elevated Temperatures

    K.-D. BouzakisM. BatsiolasG. MalliarisM. Pappa...
    P.107-114页
    查看更多>>摘要：In the paper, innovative methods for characterizing coatings' properties at ambient and elevated temperatures are introduced based on various experimental procedures. Nanoindentation results, which were obtained at elevated temperatures, are evaluated by FEM algorithms, rendering possible the determination of temperature dependent coating mechanical properties. Impact tests conducted on coated specimens revealed a non-linear film impact resistance versus the temperature. The latter results were evaluated by appropriate FEM supported procedures, to predict the coating fatigue endurance stress versus the temperature. In these investigations, the impact load was induced electromagnetically for a duration of ca. 1ms, depending on the force amplitude. To change the impact load characteristics, such as frequency, impact duration etc., a new test device has been developed, employing a piezoelectric actuator. This device enables the investigation of the impact time effect on the dynamic response of coated surfaces and on the coating fatigue endurance stress. Finally, diffusion phenomena in coatings were examined by a developed convenient experimental setup. A specimen is pressed onto a coated surface at adjustable high temperature and pressure in an inert atmosphere. After this test, the diffusion of characteristic elements into the coating and vice versa is detected by EDX-microanalyses. These results contribute, among others, to the description of diffusion phenomena between coatings and various materials.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Grinding of Arc-Sprayed Tungsten Carbide Coatings on Machining Centers - Process Configuration and Simulation

    D. BiermannT. MohnH. BlumH. Kleemann...
    P.115-122页
    查看更多>>摘要：This paper describes the special demands placed on the grinding of arc-sprayed WC-Fe coatings on a conventional machining center. Basic process configuration, experimental results, measurement methods and an approach for a hybrid simulation system are presented.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Non-contact geometry inspection of workpieces with optically non-cooperative surfaces

    Friedrich-Wilhelm BachKai MoehwaldMartin NicolausEduard Reithmeier...
    P.123-129页
    查看更多>>摘要：In order to produce optically cooperative surfaces to use triangulation measuring systems, the methods of surface and thin-coating technology are resorted to. Among these number physical methods such as PVD technology, (electro-)chemical treatment as, for example, electrochemical etching and electroless coatings as well as mechanical treatments of the components by means of glass-bead and corundum blasting. The processes mentioned are suitable for producing optically cooperative surfaces since, owing to the corresponding test parameters, a change of the component's surface occurs at the sub-micrometer scale. Currently, no indication in the literature is provided that such processes are employed for manufacturing optically cooperative surfaces vis-a-vis triangulation methods.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Determination of the Effective Film Mechanical Properties in the Impact Test Imprint of Coated Specimens

    K.-D. BouzakisG. SkordarisE. BouzakisE. Lili...
    P.131-138页
    查看更多>>摘要：If the film of a coated component deforms plastically because of operational loads, residual stresses are developed in the coating material after the load removal. In this way, material mechanical properties changes occur due to endogenous reasons i.e. induced by the coating crystalline structure plastic deformation. In this case, the determination of the effective film mechanical properties has been introduced in a recent publication [1]. Moreover, if the loading conditions lead only to a substrate plastic deformation, the coating remains elastically deformed during the relaxation, due to the substrate residual stresses. Thus, the associated material mechanical properties changes are caused by exogenous parameters related to the permanent substrate deformation. In the present paper, a novel experimental-analytical method based on FEM calculations is introduced to determine the effective film mechanical properties when the coating is stressed elastically due to a plastic substrate deformation. The perpendicular impact test is a convenient experimental procedure to investigate such an effect because under appropriate loading conditions, the substrate deforms plastically and the coating elastically. The pristine constitutive law of the applied PVD film was determined by nanoindentation and FEM supported results evaluation. Impact tests were conducted at various loads and loading cycles. The impact test was simulated by a two dimensional FEM model. Additionally, the developed elastic residual stress fields in the coating and the plastic ones of the substrate in the imprint were determined. In these calculations, a rate-independent anisotropic plasticity with kinematic hardening material law was considered and the film as an anisotropic material with variable mechanical properties in three main directions. Finally, by a FEM supported simulation of the nanoindention, the coating's load-displacement behaviour in various areas of the impact imprint were predicted and the effective coating mechanical properties as well.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Suspension Plasma Spraying of triboactive coatings for high temperature applications

    Martin ErneDaniel KolarKai MoehwaldFriedrich-Wilhelm Bach...
    P.139-146页
    查看更多>>摘要：In recent years, suspension plasma spraying (SPS) was investigated regarding the spraying of functional coatings with deterministic abilities. In this contribution the possibilities are discussed to achieve oxide ceramic coatings based on titania by SPS, which show a reduction of their coefficient of friction under dry sliding conditions. Besides the possibility to mix different feedstock suspensions in the process, the achievable low thickness and homogenous microstructure of suspension-sprayed coatings shall allow an operation in fields, where high demands towards the adhesion, cohesion and near net shape are made.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Surface zone modification by atmospheric plasma-nitriding (APN) with the aid of the transmitted plasma-arc

    Thomas HasselChristoph BirrFriedrich-Wilhelm Bach
    P.147-154页
    查看更多>>摘要：Current research activities at the Institute of Materials Science of the LeibnizUniversitat Hannover are engaged with the development of a new nitriding-process. This process has the convenience that a nitridation of surfaces is possible under atmospheric conditions so that the device treatment may be performed fractional. With the aid of the transmitted plasma-arc, diffusion able nitrogen is applied at the workpiece surface. This atomic nitrogen diffuses into the device and constitutes special- and iron-nitrides which raises the abrasion- and corrosion resistance.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd