Bangaru and Krutenat [13] recently characterized
and evaluated aluminum diffusion coatings on 316, 310
and Incoloy 800H stainless steel substrates. Each coating
was observed to consist of two distinct layers: an outer
layer composed of a continuous beta NiAl intermetallic
phase and an underlying layer, termed the interdiffusion
zone, which contained a chromium-rich alpha ferrite
matrix with both NiAl and Ni3Al precipitates distributed
throughout.
Fig. 1 shows microstructural features