Wire electrical discharge machining (WEDM) cuts material using the principles of electroerosion, which conclusively defines the resulting morphology of the machined surface. During the erosion process, removal of tiny particles of material (tiny globules) is achieved using a stream of dielectric. On certain surfaces, these tiny globules get stuck during the thermaltreatment and remain on the machined surface. This thesis studies these globules of debris on foursamples of two metallic materials with various heat treatment using electron microscopy. Furthermore, a part of the globule was removed using a focused iont beam, which allowed for studying its inside and analyzing the chemical composition in its individual parts.