THE ADHESION OF GROWING OXIDE SCALES TO THE SUBSTRATE

There is only limited new understanding of the structure of the evolvi ng dynamic metal/oxide interface itself but there is valuable circumst antial evidence from cooled specimens and from other interfaces. Ident ification of flaws for crack initiation, definition of a composite def ect and elaboration of delamination models, involving a plastically-re laxed crack tip region, have been undertaken. Loss of adhesion has rec eived more attention, by the alternatives of film buckling or crack pr opagation along the metal/oxide interface by wedging, including cases where stress relief occurs by creep. Mapping of scale failure modes ha s progressed. Computation and modelling using electronic and atomistic models are useful, but ''clean'' metal/oxide and contaminated interfa ces require in-depth work. Stress development and relaxation are compl ex. Models involve dislocation climb and the role of vacancy transport and cavity development. Sweeping of various particles by moving bound aries is receiving renewed analysis. The role of convoluted metal/oxid e interfaces in promoting or diminishing adhesion has been analysed qu antitatively. Explanation of reactive element effects by the embedded atom method is instructive, as are the relative roles of S and P in we akening interfacial adhesion.