Phase transformations during composite-chromization of steel 20

作者：Wu CL^*; Luo CP; Zou GF

来源：Acta Metallurgica Sinica, 2004, 40(10): 1074-1078.

• steel 20
• composite-chromization
• phase transformation
• chromized layer
• nitrided layer

The morphology and formation mechanism of the microstructure of the composite ion-nitrided plus chromized layers obtained at various chromization temperatures in a plain low-carbon steel (steel 20) were investigated using metallography, X-ray diffraction and microanalysis. It was found that the surface zone of the composite-chromized layers obtained at various temperatures was composed of the phases CrN (fcc), beta-Cr2N (hcp) and alpha-(Cr, Fe) (bcc), in which the fraction of a-(Cr, Fe) decreased with increasing the chromization temperature. During chromization of the nitrided layer, the diffusion-controlled reaction transformation occurred within the white (compound) layer of the former nitrided layer, forming a white composite-chromized layer. Meanwhile, the precipitation/eutectoid reaction took place in the transition (diffusion) zone of the nitrided layer during air cooling from a chromization temperature at or above 580 V, resulting in the formation of a gamma' nitride precipitate zone and/or an (alpha+gamma') eutectoid zone similar to the pearlitic structure.

• 出版日期2004-10-11
• 单位华南理工大学