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 (similar to Alodine) that is used for steel and stainless steel. It is used mainly for appearance and for mild corrosion resistance. Black oxide impregnated with oil can provide the highest amount of corrosion resistance. Black oxide is formed in a process similar to anodizing, where the parts are dipped into various hot baths of chemicals that convert the surface of the material into magnetite, which creates the black color. Black oxide does not have a significant dimensional impact, therefore masking parts is not necessary. This process can take a longer time due to the manual labor required and the time it takes for the baths to come to the correct temperature.
