Environmental Engineering Reference
In-Depth Information
Figure 6.48
Schematic diagram of aluminum concentration profile during pack alumi-
nizing.
In the low-activity pack process, direct formation of NiAl compound takes
place in a single thermal cycle during the coating operation, involving preferential
outward diffusion of nickel in the temperature range 1273-1373 K. The structural
development of NiAl-type coating on a nickel-based superalloy in a low-activity
process is illustrated schematically in Fig. 6.49. In the high-activity process,
Figure 6.49
Schematic illustration of an NiAl type of coating structure on a nickel-
based superalloy in a low-activity process [70].
