Formation of NiCrAlY/NiAl multi-layered coating by low pressure plasma spraying
Takizawa Hidekazu; Yonehama Keisuke; Sugimoto Koh-ichi; Kobayashi Mitsuyuki
Abstract:NiCrAlY/NiAl multi-layered coating was produced on SUS310S steel by means of mutual low pressure plasma spraying of NiCrAlY and Al powders which was accompanied with self-propagating high-temperature synthesis (SHS) reaction of metal deposits. The NiAl layer contained Ni3Al particles and Cr2Al phase along the fine grain boundary. Also, Ni3Al was detected in the NiCrAlY layer with a small amount of NiAl particles. As the result, high hardness was obtained in both the layers, i.e., 650 HV in NiAl layer and 450 HV in NiCrAlY one at 673 K. The structure of the multi-layered coating changed hardly during annealing lower than 973 K because enriched Cr at NiCrAlY/NiAl interface suppressed NiAl plus Ni3Al yields Ni5Al3 peritectoid reaction. The SHS reaction time of an compressed Al droplet in diameter of 50 mm was calculated as 4.17x10-3 second. Key Words:intermetallic compound, low pressure plasma spraying, self-propagation high temperature synthesis reaction, b-NiAl, g'Ni3Al