Formation of Pt-Modified γ'-Ni_3Al and Re-Based o-Alloy Coating System and Cyclic Oxidation Behavior of Coated Superalloy

摘要

A duplex layer, outer Pt-modified γ'-Ni_3Al + γ-Ni and inner multi-barrier σ-Re(Cr,Ni,W), coating system was formed on a Ni-based single crystal 4th generation superalloy. Oxidation behavior of the coated alloy was investigated under thermo-cycling conditions, and analyzed by EPMA and XRD. During cyclic oxidation 1hr at 1100°C and 20 min at room temperature, a slow growing α-Al_2O_3 formed for up to 400 cycles and its spallation was rare. The parabolic rate constant of mass change was 6.3×10~(-16) kg~2m~(-4)s~(-1). The Pt-modified γ'-Ni_3Al + γ-Ni contained 19Al, 12Pt, 4Cr, and 3Co in at%, and their concentration profiles were almost flat across the outer layer. The multi-barrier, σ-Re(Cr,Ni,W) contained 40Re, 23Cr, 17Ni, 7Al, 4W, 3.5Mo, and 3Co in at%. Furthermore, the γ'-Ni_3Al containing Pt was newly formed between the multi-barrier and bulk alloy substrate. It was concluded that the σ-Re(Cr,Ni,W) is compatible with the Pt-modified γ'-Ni_3Al in the multi-diffusion barrier coating on Ni-based single crystal, 4th generation superalloy at high temperatures.