The role of parameters on the hardness of HVOF sprayed bond coats in thermal barrier coatings

摘要

Using thermal barrier coatings on metallic gas turbine or diesel engine components is widely preferred to enable increased operation temperature with reduced component temperature. A standard thermal barrier coating is applied on a metallic substrate and has two layers. Namely, a metallic bond coat for resisting oxidation and bonding top coat to substrate and a ceramic top coat for thermal insulation. Mechanical properties are important for thermal barrier coatings due to their effects on coatings' life and quality. Density and cohesive strength are the indispensable characteristics of coatings, which can be observed by improved hardness. In this paper three parameters, substrate temperature, substrate roughness and spray distance are selected and experiments are designed using Taguchi methods. Each parameter has three levels and a total of nine experiments are performed according to Taguchi's L9 design. A bond coat is sprayed on a stainless steel substrate using HVOF thermal spray system. Particle temperature and velocity are monitored during the experiments. A series of micro hardness characterizations are made for each coating.