Design of a Nickel-Based Bond-Coat Alloy for Thermal Barrier Coatings on Copper Substrates

Abstract

To increase the lifetime of rocket combustion chambers, thermal barrier coatings (TBC) may be applied on the copper chamber wall. Since standard TBC systems used in gas turbines are not suitable for rocket-engine application and fail at the interface between the substrate and bond coat, a new bond-coat material has to be designed. This bond-coat material has to be chemically compatible to the copper substrate to improve the adhesion and needs a coefficient of thermal expansion close to that of copper to reduce thermal stresses. One approach to achieve this is to modify the standard NiCrAlY alloy used in gas turbines by adding copper. In this work, the influence of copper on the microstructure of NiCrAlY-alloys is investigated with thermodynamical calculations, optical microscopy, SEM, EDX and calorimetry. Adding copper leads to the formation of a significant amount of β-NiAl and α-Cr. Reducing the aluminum and chromium content leads furthermore to a two-phase fcc microstructure.

Mechanical Integrity of Thermal Barrier Coatings: Coating Development and Micromechanics

“…The materials for the HVOF process were fed in powder form. The bond coat material is a newly developed NiCuCrAl alloy [15], the top-coat material is a Ni- based superalloy Rene80 [27]. The compositions and the sizes of the powder are shown in Table 1.…”

“…In a second step, an improved thermal-barrier coating system was developed, consisting of a NiCuCrAl bond-coat and a Ni-based superalloy top-coat [11,12,15,16].…”

Modelling Thermal Barrier Coatings and Their Influence on the Lifetime of Rocket Engine Nozzle Structures

“…This seems to be a reasonable idea since the damage and failure behaviour of the copper alloy/copper substrate is highly temperature dependent. Special thermal barrier coating (TBC) systems for the application on copper alloys have been developed by the Institute for Materials at TU Braunschweig in order to protect the copper alloy from extremely high temperatures [3,4,5,6,7,8,9]. A thermal barrier coating typically consists of two layers: a bond coat and a top coat.…”

Stress evolution in thermal barrier coatings for rocket engine applications

“…Recently, a suitable bond coat material, a modified NiCrAl alloy with added copper, has been developed (Fiedler et al 2014). One promising coating system thus consists of this material (Ni 30Cu 6Al 5Cr) as a bond coat and a standard NiCrAlY (Ni 22Cr 10Al 1Y) as a top coat material.…”