CAD System brings a new dimension to high temperature corrosion research and development studies

In studying the degradation experienced by alloys during their exposure to aggressive high temperature gaseous environments, thermodynamic considerations can give a good insight into which corrosion products may form as a result of the various gas/metal reactions. Although these considerations cannot be used as a predictive tool to forecast with certainty which products will actually form, they are nevertheless useful to the corrosion scientist. In the case of relatively simple environments, binary phase‐stability diagrams have been constructed and used for many years. In more complex situations, however, where the corrosive atmosphere contains several reactants, e.g. sulphur, oxygen, carbon, etc., the construction of three‐dimensional diagrams or models has been found necessary. The building of models is both time‐consuming and expensive whilst 3‐D diagrams suffer from a number of draw‐backs, not least of which is the difficulty experienced in fully comprehending the complex situations depicted by such diagrams. The purpose of this paper is to illustrate how an interdisciplinary approach, involving both the research scientist and the design engineer, has been successfully applied to this topic. A “Medusa” computer aided design (CAD) system has been used initially to construct the simpler binary phase stability diagrams direct from thermodynamic data much more quickly and efficiently than could be achieved by hand‐drawing. Of much greater significance, however, has been the evolution from these 2‐D line drawings to 3‐D perspective diagrams and finally to the superimposition of rotated images thereby enabling stereographic projections to be made. These latter projections markedly improve the user's visualisation of spatial relationships which was previously extremely difficult or impossible.