Formation of cellular structures in carburized high-speed steels

Conclusions

In alloy steels of the ferrite-carbide type it is possible for precipitation to occur by a discontinous-α¹→α+M²C- which occurs at high temperatures (> 1000°); at lower temperatures discontinuous decomposition is suppressed by the competing continous process. Cobalt favors discontinous decomposition, since, as is known [11], it inhibits growth ofuniversal precipitates. The initial stage of discontinuous decomposition (nucleation of a cell) is characterized by general morphological signs of structure descrtibed previously in studies of different alloys [3–9]. Examination in a scanning electron microscope and successive grinding showed that development of the cell is accompanied by intensive branching of the carbide frame with formation of numerous featherlike branches. This causes doubts about existing concepts of cell development [7], where the main attention was given not to branching but to individual nucleation at the growth front.