Scanning Electron Microscopy of Graphite Growth in Iron and Nickel Alloys

Principles of the scanning electron microscope are outlined, and a description is given of an instrument and techniques which have been employed for high-resolution microscopy of graphite crystals. Growth processes of graphite in iron—carbon and nickel—carbon alloys have been studied, with observations of crystals at magnifications of up to ×20 000. The paper presents an initial summary of some of the observations which have been made. It is shown that an element in solution of the type which spheroidizes graphite adsorbs on the crystal surface and blocks growth. For a limited adsorption of impurity, holes are formed in the crystal surface. The blockage of growth increases in extent as the melt concentration of impurity increases, eventually suppressing normal flake development. Branched crystals are associated with the initial stage of impurity adsorption, and spherulitic crystals with a later stage corresponding to total surface coverage.