Roughened bond coats for a thermal barrier coating system and method for producing

#The invention relates to bond coats. In particular, the invention relates to roughened bond coats for thermal barrier coating systems.

#Thermal barrier coating systems are used in hot-section components in turbines, for example jet engine and gas turbines. The thermal barrier coating system insulates the turbines from high temperatures during thermal cycling. Thermal barrier coating systems include a thermal barrier coating (TBC) disposed on a bond coat, which in turn is disposed on a substrate. The thermal barrier coating normally comprises zirconia, such as example at least one of a stabilized zirconia and a partially-stabilized zirconia (PSZ). The bond coat typically comprises an oxidation-resistant metallic layer disposed between the TBC and substrate turbine component. The TBC is adhered to the bond coat typically by mechanical interlocking, so the bond coat provides oxidation resistant to the substrate and a relatively rough surface. The bond coat surface generally has Ra (Arithmetic Average Roughness (Ra) as determined from ANSI/ASME Standard B461-1985) values over about 350 mainly by mechanical interlocking. So the function of the bond coat is to provide oxidation resistant to the substrate and a relatively rough surface, preferably with Ra values over about 350 microinches, for the TBC to adhere to the substrate. Thus, the TBC is disposed over the turbine component can provide thermal insulation.

#FIG. 1 is a schematic representation of a known thermal barrier coating system 1. A substrate 10 comprises an underlying part of a component, for example a turbine component. A bond coat 12 is disposed on the substrate 10. The bond coat is disposed on the substrate 10 by any appropriate method, for example, but not limited to, thermal spray processes, such as vacuum plasma spray (VPS), air plasma spray (APS) and hyper-velocity oxy-fuel (HVOF) spray processes.

#FIG. 1 is a schematic representation of a known thermal barrier coating system;

#FIG. 2 is a schematic representation of a thermal barrier coating system including a roughened bond coat;

#FIG. 3 is a plan illustration of a screen for use in a roughened bond coat;

#Roughened bond coats enhance adhesion between a thermal barrier coating (TBC) and a bond coat in a thermal barrier coating system. Roughened bond coats prevent de-bonding and separation between the TBC and bond coat of the thermal barrier coating system. A roughened bond coat increases interfacial mating surface areas of adhered elements, enhances mechanical interlocking between the bond coat and TBC, and provides for accommodation of thermal mismatches between the TBC and bond coat. Accordingly, expansion of elements in a thermal barrier coating system with a roughened bond coat does not lend to separation and de-bonding therebetween. An effect of the roughened bond coat includes an enhanced life of the TBC in the thermal barrier coating system.

#In the following description, material compositions of mixtures are provided in approximate weight percent unless otherwise expressed. Further, individual compositions are provided in weight percent, unless otherwise provided. For example, if a mixture comprises about 70% of Constituent A and about 30% of constituent B, the percents are in weight percents. Nomenclature used for compositions is as follows. If Composition A comprises Ni-23Cr-6Al-0.4Y, yttrium is provided at 0.4 weight percent, aluminum is provided at 6 weight percent, chromium is provided at 23 weight percent, and nickel is provided as the balance weight percent.

#A thermal barrier coating system 100 including a roughened bond coat, as embodied by the invention, is schematically illustrated in FIG. 2. The thermal barrier coating system 100 comprises a substrate 10, a roughened bond coat 22 and a TBC 14. An interfacial surface area 28 is located at adjacent, adjoining surfaces 21 and 15 of the roughened bond coat 22 and the TBC 14, respectively. The roughened bond coat 22 is attached to the substrate 10, by at least one connection 110. The connection 110 comprises a physical attachment, for example a weld, such as at least one of a tack weld, laser weld, and ultrasonic weld. The number of connections varies dependent on factors such as, but not limited to, a screen's wire and mesh opening sizes.