Another important factor has been working hard cutting surface quality is the formation of a white layer. White layer is accompanied by an organizational form of hard cutting process is formed, it has a unique wear characteristics: one high hardness, good corrosion resistance; the other hand, showed high brittleness, can lead to early spalling failure. Thin white layer size, it is difficult to accurately analyze its organizational characteristics, its formation mechanism are still controversial. One view is that the white layer is the result of a phase change, is a fine grain structure of fine martensite the material is rapidly heated and cooled suddenly in the cutting process and the formation of the composition. Another view is that the formation of a white layer just below the deformation mechanism, but obtained by the plastic deformation unconventional type martensite. The white layer is currently regarded as martensite view has been unanimously approved, the main controversy lies in the fine structure of the white layer.