Muhammet KARABAŞ, Emre BAL

3820

Yeni Nesil Termal Bariyer Kaplama Malzemeleri

Termal bariyer kaplamalar (TBK), enerji ve uçak-uzay sanayisine ait gaz türbinlerinde yapısal bileşenlerin yüksek sıcaklığa karşı korunmasında çok geniş uygulama alanına sahiptir. Bununla birlikte, güç üretici motorların yüksek verimliliğe sahip olması operasyon sıcaklığının artması olarak düşünülebilir. Termal bariyer kaplama kavramı; soğutulan metalik malzeme ile sıcak gaz katmanı arasına, iş parçasına ısı transferini engelleyecek\yavaşlatacak termal yalıtım yeteneği yüksek malzeme katmanını içermektedir. Günümüzde geliştirmiş en iyi ve yaygın Termal Bariyer Kaplama örneği %8 İtriyum ile stabilize edilmiş zirkonyum (YSZ) dur. TBK, seramik bir kaplama olup, oda sıcaklığından 1200 °C’ye kadar kullanılabilir, düşük termal iletkenliğe, yüksek termal şok dayanımına sahiptir. Zirkonya oda sıcaklığından 1170 °C’ye kadar monoklinik kristal yapıdadır ve artan sıcaklıklarda tetragonal (1170-2370°C) yapıdan kübik kristal yapıya (>2700°C ) allotropik dönüşümler gösterir. Bu dönüşümler % 3-5’lik hacim değişimini de beraberinde getirdiğinden kaplamaların bütünlüğü ve servis ömrü kısalır. Kullanımda olan mevcut kaplama malzemeleri yerine termal, mekanik ve kimyasal özellikleri daha üstün malzemeler; türbinlerin daha güvenli şekilde çalışmasını, türbin veriminin artmasını, türbin bakım aralıklarının uzamasını ve son derece pahalı olan sıcak kısım parçalarının ömürlerinin artmasını sağlayacaktır. Bu çalışmada potensiyel özellikleri ile YSZ yerine alternatif olabilecek malzemeler incelenmiş ve tartışılmıştır.

New Generation Thermal Barrier Coating Materials

Thermal Barrier Coatings (TBC) find a large application as a protection shield against high temperature for the structural components in stationary and aerospace gas turbines. The Thermal Barrier Coating (TBC) concept involves placing a thermally insulating layer between a cooled metallic component and the hot working gas to reduce heat transfer to the component. However, to achieve higher efficiencies in power engines, increasing the operation temperature is envisaged State of the art TBC´s based on yttria stabilized zirconia (YSZ) may be used at temperatures up to 1200°C, have the ability of low thermal conductivity and high thermal shock resistance. Pure zirconia exists in three crystal phases at different temperatures. At very high temperatures (> 2370°C) the material has a cubic structure. At intermediate temperatures (1170 to 2370°C) it has a tetragonal structure. At low temperatures (below 1170°C) the material transforms to the monoclinic structure. The tetragonal-to-monoclinic phase transformation is martensitic and can be observed in heating and cooling periods. The transformation occurs while cooling zirconia from high temperatures and involves a 3-5% volume increase. The volume change induces a significant shear strain in the structure, affecting the integrity and the service life of the coating. Improvements on new thermal barrier coating materials instead of presently used coatings ,better mechanical and chemical features will allow the turbines work more reliably, increase the turbine efficiency, extend the turbine maintenance periods and increase the lives of hot section parts that are of high cost. In this study, new generation ceramic thermal barrier coating materials which are used instead of YSZ have been discussed.
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Makine Teknolojileri Elektronik Dergisi (elektronik)-Cover
  • ISSN: 1304-4141
  • Yayın Aralığı: Yılda 5 Sayı
  • Başlangıç: 2004
  • Yayıncı: -
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