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Authors
Abstract(s)
O uso de revestimentos de barreiras térmicas (TBC’s) em componentes da área aeronáutica e aeroespacial é fundamental para a proteção dos materiais em condições de serviço severas. Estes TBC’s protegem os componentes das elevadas temperaturas e minimizam o seu desgaste e corrosão. Na área aeronáutica a temperatura de serviço está limitada usualmente a 1200ºC, enquanto que na área aeroespacial, em especial no caso de aeronaves tripuladas, o escudo térmico também necessita de ser melhorado (mais leve e reutilizável). Neste contexto, é necessário o desenvolvimento de novos materiais.
Diversos estudos apontam o compósito cerâmico baseado em zirconato de cálcio como uma alternativa viável para ambientes hostis (elevada temperatura, corrosão, desgaste e erosão). A adição de óxido de magnésio, através de uma solução sólida, permite obter um compósito cerâmico CaZrO3 – MgO (CZ-M) com melhores propriedades. Assim, foram desenvolvidas, fabricadas e caracterizadas amostras com diferentes composições (1:3, 1:1 e 2:3 de CZ-M). Além destas, fabricaram-se materiais com variação da sua composição lamelar (FGM).
Obteve-se materiais densos, de microestrutura homogénea e com tamanho reduzido de grão. Os materiais monolíticos apresentam uma dureza de 9,8 a 10,1 GPa, uma tenacidade à fratura de 1,6 MPa.m1/2 a 2,1 MPa.m1/2, uma condutividade térmica de 0,59 W/mK a 0,79 W/mK e uma energia de superfície de 43,27 mN/m a 51,39 mN/m. Estes resultados estão de acordo com a literatura e com os valores obtidos na composição lamelar. Assim, conclui-se que este compósito cerâmico de gradiente funcional é um bom candidato para revestimentos de barreiras térmicas.
The use of thermal barrier coatings (TBC’s) in components of aeronautical and aerospace industry is critical to the protection of materials under severe service conditions. These TBC’s protect components from high temperatures and minimize wear and corrosion. In the aeronautical area, the service temperature is limited to 1200ºC, while the aerospace area, especially in the case of human spaceflight, the thermal shield is also necessary (lighter and reusable). In this context, the development of new materials is required. Several studies point to the ceramic composite based on calcium zirconate as a viable alternative to hostile environments (high temperature, corrosion, wear, and erosion). The addition of magnesium oxide, through a solid solution, allows obtaining a CaZrO3 - MgO (CZ-M) ceramic composite with better properties. Thus, samples with different compositions (1: 3, 1: 1 and 2: 3 of CZ-M) were developed, produced and characterized. In addition, materials having a varying lamellar composition (FGM) were made. It was possible to obtain dense materials, with homogenous microstructure and reduced grain size. The monolithic materials have a hardness of 9.8 to 10.1 GPa, a fracture toughness of 1.6 MPa.m-1/2 at 2.1 MPa.m-1/2, a conductivity of 0.59 W/mK to 0,79 W/mK and a surface energy of 43.27 mN/m to 51.39 mN/m. These results are in agreement with the literature and with the values obtained in the lamellar composition. Thus, it is concluded that this functional gradient ceramic composite is a good candidate for thermal barrier coatings.
The use of thermal barrier coatings (TBC’s) in components of aeronautical and aerospace industry is critical to the protection of materials under severe service conditions. These TBC’s protect components from high temperatures and minimize wear and corrosion. In the aeronautical area, the service temperature is limited to 1200ºC, while the aerospace area, especially in the case of human spaceflight, the thermal shield is also necessary (lighter and reusable). In this context, the development of new materials is required. Several studies point to the ceramic composite based on calcium zirconate as a viable alternative to hostile environments (high temperature, corrosion, wear, and erosion). The addition of magnesium oxide, through a solid solution, allows obtaining a CaZrO3 - MgO (CZ-M) ceramic composite with better properties. Thus, samples with different compositions (1: 3, 1: 1 and 2: 3 of CZ-M) were developed, produced and characterized. In addition, materials having a varying lamellar composition (FGM) were made. It was possible to obtain dense materials, with homogenous microstructure and reduced grain size. The monolithic materials have a hardness of 9.8 to 10.1 GPa, a fracture toughness of 1.6 MPa.m-1/2 at 2.1 MPa.m-1/2, a conductivity of 0.59 W/mK to 0,79 W/mK and a surface energy of 43.27 mN/m to 51.39 mN/m. These results are in agreement with the literature and with the values obtained in the lamellar composition. Thus, it is concluded that this functional gradient ceramic composite is a good candidate for thermal barrier coatings.
Description
Keywords
Cazro3:mgo Cerâmica Avançada Condutividade Térmica Dureza de Vickers Energia de Superfície Material de Gradiente Funcional Tbc'S Tenacidade à Fratura