High speed steels (often abbreviated HSS) are ferrous based alloys of the Fe–C–X multicomponent system where X represents a group of alloying elements comprising mainly Cr, W or Mo, V, and Co. These steels are mainly used for cutting tools, since they are characterized by their capacity to retain a high level of hardness while cutting metals at high speed. Generally, the X component is present in excess of 7%, along with more than 0.60% carbon.
Black oxide is a conversion coating used on iron, zinc, steel, stainless steel, and copper. It results in a black, smooth surface finish
