Control of fatigue failure mechanisms in multilayer coatings by varying
the architectural parameters of an intermetallic interlayer
Abstract
A multilayer overlay coating system containing an intermediate
intermetallic layer (designated 2IML) is an architecture expected to
show good fatigue resistance. Experimental characterisation and
modelling simulations were carried out to classify the different crack
initiation mechanisms occurring during fatigue of this coating system
and to reveal how changes in the layer architecture lead to fatigue
improvement. Fatigue improvement is achieved by decreasing the IML-Top
layer thickness due to the increased surface crack initiation
resistance. However subsurface initiation mechanisms inhibit the
improvement (dominated by surface initiation mechanism) achieved by
locating the IML-Top layer closer to the top surface.