THE EFFECT OF LASER GLAZING PROCESS ON MICROSTRUCTURE OF PLASMA SPRAYED THERMAL BARRIER COATINGS

Abstract

Thermal barrier coatings (TBCs) are widely used by aero and land based gas turbines to protect hot section parts from oxidation and reducing component temperature thereby increase life. TBCs are generally a combination of multiple layers of coating (usually two) with each layer having a specific function [Aktaa et al., 2005]. In this study air plasma sprayed TBCs were deposited on 304 stainless steel substrates then ceramic surfaces were glazed using Nd-YAG laser. Both glazed and as-coated samples were subjected to metallographic examination to investigate microstructural changes in glazed ceramic layer. Laser glazing provides a remelting and subsequent solidification of the surface, resulting on new top layer microstructure.

Keywords

• Thermal barrier coatings, laser glazing, plasma spray

Uygulamalı Bilimler ve Mühendislik

Abstract

Termal bariyer kaplamalar (TBK), havacılık ve enerji üretiminde kullanılan gaz türbinlerinin sıcak kısım parçalarını oksidasyondan korumak, bu parçaların çalışma sıcaklığını düşürmek ve böylelikle ömürlerini uzatmak amacıyla yaygın bir şekilde kullanılmaktadır. TBK’lar genellikle, her biri özel bir fonksiyonu üstlenmiş birden fazla kaplama katmanının (genellikle iki) kombinasyonu şeklinde üretilirler [Aktaa ve ark., 2005]. Bu çalışmada, hava plazma sprey tekniğiyle TBK 304 paslanmaz çelik malzeme üzerine kaplanmış ve daha sonra kaplama seramik yüzeyi Nd-YAG lazer kullanılarak sırlanmıştır. Sırlama işlemi uygulanmış ve uygulanmamış numuneler, sırlanmış seramik yüzeydeki mikroyapısal değişikliklerin değerlendirilmesi için metalografik olarak incelenmiştir. Lazer sırlama, yüzeyin tekrar ergimesi ve katılaşmasına yol açarak yeni bir üst katman mikroyapısı oluşmasına yol açmıştır

Keywords

• Termal bariyer kaplamalar, Lazer sırlama, Plazma sprey

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