Abstract:

Experimental results show that, after being diffusion annealed, each layer in the Ti N/CoCrAlTaY/Al multi layer composite coating is firmly bonded with the neighboring ones, the microstructure of Ti N film is stable, and that Al has completely diffused into the CoCrAlTaY, giving rise to the formation β CoAl compound. It was discovered that after being aged at 1000℃, the CoCrAlTaY layer will self divided into 7 sub layers (not including the outer oxide film and Ti N layer), 3 of which are enriched with Ta, 2 of which contain more Al, and 2 of which are normal CoCrAlTaY sub layers. With the prolonging of aging time, the boundaries between different sub layers tend to be more straight, continuous, and integral. Kirkendall vacancies were observed on the inner side of some sub layer, indicating the diffusion of atoms towards the outer side. The formation mechanism of Ta enriched sub layer and the diffusion zone between GH220/Ti N have been interpreted.

Key words: MCrAlX cladding coating, composite coating, Kir kendall vacancies, selfscaling