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Bond Coat (bond + coat)
Selected AbstractsCrystalline , -Alumina Deposited in an Industrial Coating Unit for Demanding Turning Operations,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2010Kirsten Bobzin Crystalline PVD ,-Al2O3 - coatings offer great potential for their use in high-speed cutting operations. They promise high hot hardness and high oxidation resistance at elevated temperatures. This is important for coatings that are used for machining of materials with low thermal conductivity such as stainless steel or Inconel 718 because heat generated during cutting can barely be dissipated by the chip. Because of the prevailing bonding forces of alumina, adhesion-related sticking can be reduced even for dry cutting. Furthermore, the high formation enthalpy of alumina prevents chemical reactions with frictional partners. The present work gives an overview of the deposition of ,-Al2O3 thin films on WC/Co-cutting inserts by using pulsed MSIP (magnetron sputter ion plating) PVD technology. To improve adhesion, a (Ti,Al)N bond coat was employed. The samples were analyzed using common thin film test equipment. Cutting tests and pin-on-disk examinations were carried out to test the coating's performance. For turning operations, the difficult-to-machine austenitic steel 1.4301 (X5CrNi18-10) was used. In comparison to a state-of-the-art (Ti,Al)N coating, (Ti,Al)N/,-Al2O3 showed a longer tool life. [source] Hollow Cathode Gas Flow Sputtering of NixAly Coatings on Ti-6Al-2Sn-4Zr-6Mo: Mechanical Properties and Microstructures,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2009Andreas Kohns A W-TiB2 -multilayer erosion resistant coating with a NixAly bond coat deposited by hollow cathode gas flow sputtering is under development for Ti6246 aero engine compressor blades. Blade vibrations in service can produce cracks in the coating propagating into the substrate and reducing the high-cycle fatigue strength of the component. It is assumed, that this effect can be diminished by adapting the mechanical and morphological properties of the NixAly bond coat. In this context, process parameter variations are performed and discussed. [source] The role that bond coat depletion of aluminum has on the lifetime of APS-TBC under oxidizing conditionsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 7 2008D. Renusch Abstract Bond coat oxidation as well as bond coat depletion of Al are still believed to be a major degradation mechanism with respect to the lifetime of thermal barrier coating (TBC) systems. In this study the top coat lifetime is described as being limited by both bond coat depletion of Al and mechanical failure of the top coat. The empirical results are introduced by considering three spallation cases, namely, Al depletion failure, thermal fatigue failure, and thermal aging failure. Al depletion failure occurs when the Al content within the bond coat reaches a critical value. In this paper bond coat depletion of Al is modeled by considering the diffusion of Al into both the thermally grown oxide (TGO) and substrate. The diffusion model results are compared to Al concentration profiles measured with an electron beam microprobe. These measured results are from oxidized air plasma sprayed TBC systems (APS-TBC) with vacuum plasma sprayed (VPS) bond coats for exposures up to 5000 h in the temperature range of 950,1100,°C. This paper focuses on the Al depletion failure and how it relates to top coat spallation. [source] Modelling the influence of reactive elements on the work of adhesion between a thermally grown oxide and a bond coat alloyMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 3 2006I. J. Bennett Abstract The durability of thermal barrier coating systems is primarily determined by the degree of adhesion between the thermally grown oxide (TGO) and the bond coat. Failure of the TBC is often the result of delamination at this interface. Adhesion can be improved by the addition of reactive elements (RE) to the bond coat alloy. REs include oxide forming elements such as Y, Zr and Hf. The so-called reactive element effect has been attributed to a direct improvement of the bonding between the TGO and the bond coat. A macroscopic atom model has been developed to allow the work of adhesion between two compounds (e.g. an oxide and a metal compound) to be estimated. By calculating the work of adhesion across a number of different interfaces, the influence of reactive elements and impurities present in the substrate can be assessed. It has been found that the REs have a limited direct influence on the work of adhesion and can even result in a weaker interface. A large reduction in the work of adhesion is calculated when S and C are present at the interface. REs have a high affinity for both S and C. This indicates that the RE effect is primarily that of impurity scavenging, preventing diffusion of impurities to the interface. A number of experiments are reported, which demonstrate the RE effect and support the modelling results. [source] The role that bond coat depletion of aluminum has on the lifetime of APS-TBC under oxidizing conditionsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 7 2008D. Renusch Abstract Bond coat oxidation as well as bond coat depletion of Al are still believed to be a major degradation mechanism with respect to the lifetime of thermal barrier coating (TBC) systems. In this study the top coat lifetime is described as being limited by both bond coat depletion of Al and mechanical failure of the top coat. The empirical results are introduced by considering three spallation cases, namely, Al depletion failure, thermal fatigue failure, and thermal aging failure. Al depletion failure occurs when the Al content within the bond coat reaches a critical value. In this paper bond coat depletion of Al is modeled by considering the diffusion of Al into both the thermally grown oxide (TGO) and substrate. The diffusion model results are compared to Al concentration profiles measured with an electron beam microprobe. These measured results are from oxidized air plasma sprayed TBC systems (APS-TBC) with vacuum plasma sprayed (VPS) bond coats for exposures up to 5000 h in the temperature range of 950,1100,°C. This paper focuses on the Al depletion failure and how it relates to top coat spallation. [source] | ||||||||||