Graded plasma spraying of premixed metalceramic powders on metallic substrates

Abstract

The mismatch between the thermal expansion coefficients of ceramics and metals and the differential stresses it causes at the interface create problems in metal to ceramic joining. Research has been conducted to solve this problem in thermal barrier coating technology. Previous studies have considered metal-ceramic multilayers or graded-coatings, which include a metallic bond coat. In this study, a graded plasma-sprayed metal-ceramic coating is developed using the deposition of premixed metal and ceramic powders without the conventional metallic bond coat. Influences of thickness variations, number, and composition of the layers are investigated. Coatings are prepared by atmospheric plasma-spraying on Incone1718 superalloy substrates. Ni-Cr-AI and ZrO2 -8 % Y203 powders are used for plasma spraying. Adhesive and cohesive strength of the coatings are determined. The concentration profile of the elements is determined by x-ray energy-dispersive analysis. The microstructure and morphology of the coatings are investigated by optical and scanning electron microscopy (SEM). Results show that the mixed metal-ceramic coating obtained with the deposition of premixed powders is homogeneous. The morphology and microstrncture of the coatings are considered satisfactory. l

On resultant properties of atmospheric plasma sprayed yttria stabilised zirconia coating deposits: Designed experimental and characterisation analysis

“…It is believed that adhesion is substantially dependent on the microstructure aspects generated under process conditions. 43 Higher bond strength can be seen for a coating sprayed under optimum spray condition due to its minimum porosity ( Fig. 4e and f).…”

Evaluation and Characterization of Plasma Sprayed Cu Slag-Al Composite Coatings on Metal Substrates

“…Ceramic coatings on relatively ductile metal-alloy substrates behave in a complex way under static mechanical loads and/or thermal cycling conditions and hence result in poor interfacial mechanical properties. Recent studies have shown improvement of coating properties with premixed metalceramic powders [14][15][16]. In the view of this, the present study explores the coating potential of Cu Slag-Al composite for different engineering and structural applications.…”

Revestimentos para barreira térmica: evolução e perspectivas

“…As trincas são devidas às tensões residuais provocadas pela oxidação da camada de ligação metálica em altas temperaturas (formação e crescimento da TGO), devido à permeabilidade da camada cerâmica porosa, e às diferenças de expansão térmica cíclica (fadiga térmica no aquecimento e resfriamento dos componentes, durante o serviço), resultantes da diferença de cerca de 30 % no coeficiente de expansão térmica entre a zircônia parcialmente estabilizada e a camada de ligação metálica [2,3,4]. Diversas pesquisas têm sido realizadas na busca de solucionar estes problemas, envolvendo, inclusive, o conceito de revestimentos graduados [19,20], pré ou pós-tratamentos dos revestimentos [21,22,23] e adição de dopantes [24,25].…”

“…Lima e Trevisan [20] estudaram um revestimento para barreira térmica com graduação dos pós metálico e cerâmico, sem utilização de bond-coat metálico convencional, eliminando a interface abrupta metal-cerâmica entre a camada de ligação metálica e a camada externa cerâmica, típica dos sistemas duplex. Como resultado, o sistema com graduação de mistura 25% metal -75% cerâmica na interface com o substrato metálico apresentou resultados bem próximos ao sistema convencional duplex, quando avaliado pela resistência adesiva, dureza, microestrutura e estabilidade de fases, em espessuras de até 300 µm.…”