Abstract
EQ coating, which is a new and stable bond coat system, suppresses the diffusion of alloying elements between the substrate and coating and the formation of secondary reaction zone (SRZ). In this study, high velocity frame sprayed (HVOF) EQ coatings designed for 2nd generation Ni-base superalloy were deposited on 4th and 5th generation Ni-base superalloys. The stability of microstructure at the interface and creep property of the coating system were investigated. Less than 50 μm-thick of the interdiffusion zone and no SRZ were observed in EQ coating system after 300 h heat treatment at 1100°C, in contrast to beyond 90 μm-thick of diffusion zone and 140 μm-thick of SRZ in the conventional CoNiCrAlY coating system. Creep strength of Al-diffusion and CoNiCrAlY coated 4th generation superalloys showed decrease in thin creep specimens, but EQ coated 4th generation superalloy showed equivalent creep strength for bare material.
