INVESTIGATION OF NONMETALLIC IMPURITIES IN HIGH-SPEED STEEL USING SIMS IMAGING AND SCANNING TECHNIQUES

Non-metallic impurities or phases are often unintentional but importan t constituents in steel - they primarily influence the properties and behavior of the material by forming crystallization nuclei during the solidification process of the molten material. The kind, formation and spatial distribution of these inclusions has been investigated in thi s work by 2D SIMS, depth profiling and scanning SIMS. These non-metall ic phases can be divided into oxides, nitrides, carbides, sulfides and gas bubbles. Probably the most important phase, the oxy genic, result s from reactions of the molten bath with the ambient air and from the admixture of de-oxidation components. The investigated HSS specimen ex hibits two different classes of inclusions. The first class mainly con tains sulfide precipitates and differs widely from the second. The lat ter exhibits a spherical structure with the outer sphere combining the oxygenic precipitation and the core containing nitrides and sulfides. Due to the small size of the inclusions, they have been investigated by high resolution scanning SIMS to separate the different phases.