A new method is described for the evaluation of the creep properties of as-
deposited overlay coatings. The method uses a composite tensile specimen co
nsisting of a core alloy of well-characterised creep properties onto which
the overlay coating is deposited. The overall strain/time response of this
specimen, tested under constant stress conditions, can then be deconvoluted
to obtain the creep characteristics of the coating. The method has the adv
antage that the coatings are evaluated for the same microstructural conditi
ons as they will be used under, i.e. having the same porosity levels and mi
crostructure. A limited demonstration of the method has been made for an ai
r plasma-sprayed Ni25Cr6AlY coating deposited onto an austenitic steel core
and creep tested at 900 degrees C. The creep strength of this coating was
surmised to be higher than that of equivalent monolithic samples produced b
y low pressure plasma spraying. (C) 2000 Elsevier Science S.A. All rights r
eserved.