MCrAlY İçerikli Bağ Kaplamaya Sahip Termal Bariyer Kaplamaların (TBCs) Mikroyapısal Özelliklerinin ve İzotermal Oksidasyon Davranışının İncelenmesi

Termal bariyer kaplamalar (TBCs), havacılık ve endüstriyel gaz türbin motorlarının sabit ve hareketli parçalarını çevresel olumsuz etkilerden korumak amacıyla kullanılan yüksek sıcaklıkta çalışan koruyucu kaplamalardır. TBC sisteminde, servis süresince oluşabilecek oksidasyon ve korozyon gibi ana hasar oluşum mekanizmalarına karşı koruma sağlaması amacıyla kullanılan altlık malzeme, metalik bağ ve seramik üst kaplama malzemeleri kullanım koşulları altında TBC sisteminin ömrünü belirleyen ana unsurlardır. Bu çalışmada, NiCrAlY içerikli metalik bağ kaplama ve yitriya ile stabilize edilmiş zirkonya (YSZ) içeriğine sahip kaplamalar atmosferik plazma sprey (APS) kaplama yöntemi kullanılarak üretilmiştir. Üretilen TBC sistemi 1150 °C sıcaklık ve 5, 25 ve 50 saatlik zaman süreçlerinde izotermal oksidasyon testlerine maruz bırakılmıştır. Mikroyapısal değişimlerin belirlenebilmesi amacıyla yüksek sıcaklık fırın testleri öncesi ve sonrasında taramalı elektron mikroskopu (SEM) analizi gerçekleştirilmiştir. Metalik bağ ve seramik üst kaplama arayüzey yapısında oluşan oksit yapılarının karakteristik özellikleri yüksek sıcaklık sürecinde zamana bağlı değişimleri ayrıntılı olarak incelenmiş ve değerlendirilmiştir. Oksidasyon sürecine bağlı olarak metalik bağ ve seramik üst kaplama arayüzeyinde ısıl olarak büyüyen oksit tabakası (TGO) yapısının oluşum gösterdiği ve artan oksidasyon sürecine bağlı olan bu tabakanın parabolik olarak büyüme gösterdiği görülmüştür. TGO tabakasının içeriğinin ve büyüme davranışının yüzeyden arayüzeye difüze olan oksijen dışında bağ kaplamada yer alan alaşım elementlerine bağlı değişim gösterdiği tespit edilmiştir.

Anahtar Kelimeler:

Izotermal oksidasyon, atmosferik plazma sprey (APS), NiCrAlY, yitriya ile stabilize edilmiş zirkonya (YSZ), termal bariyer kaplama (TBC)

Investigation of Microstructural Properties and Isothermal Oxidation Behavior of Thermal Barrier Coatings (TBCs) with MCrAlY Bond Coat

Thermal barrier coatings (TBCs) are advanced protective coatings operating at elevated temperatures used to protect the fixed and movable parts of aero-engines and industrial gas turbine engines from environmental adverse effects. In the TBC system, the substrate material, metallic bonding and ceramic top coat materials used to protect against the major damage formation mechanisms such as oxidation and corrosion that may occur during service are the main elements that determine the life of the TBC system under usage conditions. In this study, NiCrAlY containing a metallic bonding coat and yttria stabilized zirconia (YSZ) coating were produced using atmospheric plasma spray (APS) coating method. The TBC system produced was subjected to isothermal oxidation tests at 1150 °C and at 5, 25 and 50 hours of time period. Scanning electron microscope (SEM) analysis was conducted before and after high temperature furnace tests in order to determine microstructural changes. The changes in the characteristics of the oxide structures formed in the metallic bonding and ceramic top coat interface structure based on time during the high temperature process have been studied and evaluated in detail. It has been observed that depending on the oxidation process, thermally grown oxide layer (TGO) structure is formed at the interface of the metallic bonding and ceramic top coat, and this layer, dependent on the increasing oxidation process, grows parabolically. It has been determined that the content and growth behavior of the TGO layer varies depending on the alloying elements in the bonding coat, except oxygen diffused from the surface to the interface.

Keywords:

Isothermal oxidation, atmospheric plasma spraying (APS), NiCrAlY, yttria stabilized zirconia (YSZ), thermal barrier coating (TBC),

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