This paper investigates the characteristics and the formation of white layers and dark layers induced by hard turning of through-hardened AISI 52,100 steel. The investigation showed that different types of white layers exist e.g., formed predominantly through excessive thermal or mechanical energy loading. The thermally induced white layer is formed when the cutting temperature is above the critical austenitisation temperature for the material. The nano-sized microstructure is initiated through dynamic recovery, which transitions to dynamic recrystallisation when the temperature rises above the onset temperature for dynamic recrystallisation. The corresponding white layer is characterised by a higher retained austenite content compared to the unaffected material, and the presence of a dark layer beneath the white layer. The white layer and the adjacent dark layer are found to be ∼12% harder and 14% softer, respectively, compared to the unaffected material. On the other hand, the mechanically induced white layer is formed through severe plastic deformation, where the formation is controlled by dynamic recovery and results in an elongated and broken-down substructure. Neither austenite nor an adjacent dark layer could be found for such white layers. The mechanically induced white layer is ∼26% harder than the unaffected material. For both types of white layer, (Fe, Cr)₃C carbides are found in the microstructure. The investigation shows that the heating rate, cooling rate, pressure, and duration of contact between the cutting tool and workpiece surface should also be considered to understand the underlying formation mechanisms. The characteristics of the examined white layers and the cutting conditions are summarised in a descriptive phenomenological model in order to create a systematic approach for the definition of the different types of white layers.

本文研究了通过硬化AISI 52,100钢的硬车削引起的白层和黑层的特征和形成。研究表明存在不同类型的白色层，例如主要通过过度的热能或机械能负荷形成。当切削温度高于材料的临界奥氏体化温度时，就会形成热致白层。纳米级的微观结构是通过动态恢复而启动的，当温度升高到高于动态重新结晶的起始温度时，该微观结构将转变为动态重结晶。相对应的白色层的特征在于，与未受影响的材料相比，残余奥氏体含量更高，并且在白色层下方存在暗层。与未受影响的材料相比，发现白色层和相邻的深色层分别硬约12％和软14％。另一方面，机械诱导的白色层是通过剧烈的塑性变形而形成的，在这种情况下，其形成受到动态恢复的控制，并导致伸长和破裂的子结构。对于这样的白色层，既没有发现奥氏体也没有发现相邻的暗层。机械诱导的白色层比未受影响的材料坚硬约26％。对于两种类型的白色层，（Fe，Cr）地层是由动态恢复控制的，并导致子结构拉长和破裂。对于这样的白色层，既没有发现奥氏体也没有发现相邻的暗层。机械诱导的白色层比未受影响的材料坚硬约26％。对于两种类型的白色层，（Fe，Cr）地层是由动态恢复控制的，并导致子结构拉长和破裂。对于这样的白色层，既没有发现奥氏体也没有发现相邻的暗层。机械诱导的白色层比未受影响的材料坚硬约26％。对于两种类型的白色层，（Fe，Cr）在微观结构中发现了₃ C碳化物。研究表明，还应考虑加热速率，冷却速率，压力以及切削刀具与工件表面之间的接触持续时间，以了解潜在的形成机理。在描述性现象学模型中总结了所检查的白色层的特征和切削条件，以便为定义不同类型的白色层创建一种系统的方法。