Nature of Angular Carbides in Damascus Steel

Abstract

It is detected that in some specimens of Damascus steel part of the excess cementite is of unusual origin, in contrast to excess phases of secondary cementite, ledeburite cementite, and primary cementite in ironcarbon alloys. It is revealed that a morphological feature of separate particles of cementite in Damascus steel includes anomalously large excess carbides in the form of irregular octahedral and prisms. It is shown that angular carbides form within the original metastable ledeburite colonies, and therefore they are called “eutectic.” It is established that unalloyed materials of the carbide class acquire Damascus properties steel properties during isothermal exposure on annealing, which leads to thermal separation of colonies of metastable ledeburite, to limitation of newly formed eutectic carbides, and to their subsequent coalescence. It is revealed that some sorts of Damascus steel, being within the field of white cast iron with respect to carbon content, do not contain broken ledeburite within their structure. It is shown that the pattern of carbide inhomogeneity entirely consists of eutectic of angular carbides of non-etching triangular-prismatic morphology.