PARTICOAT. Collaborative Project Large-scale integrating project

Transcription

1 PARTICOAT THEME 4 Nanoscience,, nanotechnologies, materials new production technologies (NMP) Collaborative Project Large-scale integrating project Proposal full title: New multipurpose coating systems based on novel particle technology for extreme environments at high temperatures Grant agreement no.: CP-IP Consortium Beneficiary no Beneficiary name Fraunhofer ICT (co( co-ordinator) DECHEMA SVÚM TECNATOM PyroGenesis WIP Prague Sibthermochim Universidad Carlos III Madrid Université de La Rochelle Turbocoating Acciona Infraestructuras Siemens Power Generation Steinbeis R-Tech LARCO Business Research Research Research Industry SME Industry SME University University SME Industry Industry SME Industry Country D D CZ E GR CZ RU E F I E D D GR

2 The Idea The idea: oxidation of nano- and micro-sized Al particles Aluminium: 0,3 0,7 μm Aluminium: 2-3 μm Intensität Intensität 1 0,9 Al 1 0,9 Al 0,8 α-al2o3 0,8 α-al2o3 0,7 0,7 IZ [norm.] 0,6 0,5 0,4 Θ-Al2O3 IZ [norm.] 0,6 0,5 0,4 0,3 0,3 0,2 γ-al2o3 0,1 Al μm T [ C] 0,2 0,1 ab 675 C Schmelze Al μm T [ C] Oxidation on heating from room temperature to 1100 C (Microscopy of Oxidation, Birmingham 2005)

3 Metal Oxide Metal Cations Oxygen Anions Electrons Oxide Thickness x Oxygen Containing Environment Schematic view of of the the Transport Processes During Oxide Scale Growth x Parabolic Oxidation dx k p = x² = 2k p t dt x t Bulk diffusion coefficients

4 Conversion of Metallic Aluminum Nano/Micro Powder Particles Into Hollow Aluminum Oxide Spheres Aluminum Oxide Al-diffusion Aluminum Oxide Al-diffusion Aluminum Aluminum Aluminum Nano/micro size = low amount of grain boundaries Aluminum = very creep ductile, i. e. adherence to oxide maintained during conversion Potential of Nano- and Micro-Scale Metal Powders Scanning Electron Microscopy / EDX Al spherical,, 2-32 µm 10 μm 10 μm - Homogeneous distribution, no agglomerates - Spherical particles - Particle size 2-5 μm

5 Potential of Nano- and Micro-Scale Metal Powders Al 31% 0-50 µm, 69% µm 1,0 0,9 0,8 Al and α-al 2 O 3 portionintensity as a function of temperature Intensity curves iz(t) Al (cubic) α-al2o3 0,7 IZ [norm.] 0,6 0,5 0,4 0,3 0,2 0,1 0, T [ C] WORK FLOW CHART Base powder: Al Suspension Binder: PVA Al/Binder Dispersant Rheology GREEN COATING Ni-Base René alloys H SS steels MCrAlY-2231 TT1-SINTERING Binder evaporation Al sintering CHARACTERIZATION THERMAL TREATMENTS TT2-ASSEMBLING Al 2 O 3 formation Al diffusion Thermal stability Diffusion 100, 300, 1000 h HT-XRD, metallography

6 DEPOSITION PROCEDURE Production of source metal particles by PSP and EEC Spherical metal particles with defined size Deposition by brushing, spraying, rolling, sol-gel raw coating Heat treatment ev. pre-treatment oxidation sintering diffusion coating with quasi-foam top coat and diffusion layer THERMAL TREATMENT Dip-coating T/ C Assembling Binder evaporation Sintering 1 1 time 10

7 Examples of Coatings Produced So Far Binder #1 400 C 500:1 5000:1 Vaporization of the organic binder and beginning of Al particle sintering

8 Binder #1 650 C 500:1 Densification of the metallic green coating Binder #1 650 C 3000:1 Densified aluminum green coating

9 Binder #1 900 C 500:1 3000:1 Broken up cross-section of the ceramic alumina foam Binder #1 900 C 2000:1 3000:1 Substrate/foam interface

10 Binder #2 900 C 100:1 Opened-up surface of the ceramic alumina foam Binder #3 650 C 1000:1 5000:1 Hollow ceramic alumina spheres

11 Binder #3 900 C 1000:1 5000:1 Influence of binder: Example of reduced sintering activity and appearance of meta-stable alumina phases Binder #3 900 C 100:1 500:1 Possibility to influence the coating/substrate interface (wavy interface = keying effect)

12 Summary PARTICOAT is developing an innovative concept for thermal barrier coatings where in one single thermal treatment step a combined bondcoat/topcoat topcoat system is being formed This is achieved by the use of spherical nano-/micro micro-scale metal particles.. These serve as a reservoir for the formation of the Al rich bond coat and are converted into hollow alumina spheres by oxidation The top coat,, in the form of the sintered hollow alumina spheres, provides a thermal barrier Initial results demonstrate the viability of the concept Properties Easy to apply Low cost Low application temperatures Possibility to form dense layers with increased mechanical compliance Alumina is no oxygen conductor and provides a very good barrier effect against ingress of corrosive species Significant potential for electrical and thermal insulation Al subsurface reservoir for protective alumina scale formation

13 Application areas Gas turbines in electric power generation and aero-engines engines Abradable coatings Steam turbines in electric power generation Combustion chambers, boilers Steam Steam generators, superheaters Waste Waste incineration Fire Fire protection of composite materials in construction Reformers and reactors in chemical and petrochemical industry Electrical insulation in arc melting furnaces