Influence of Grinding Media Size and Sintering Time in the Processing of AISI D2 Tool Steel by High-Energy Milling

Abstract

Tool steels are fundamental in the current production processes, as they are used in dies and molds, essential for the transformation of raw materials into the final product. The tool steels for cold work have a low hot hardness, so their use is limited to temperatures below 200° C. The D-X series of tool steels, high carbon and high chromium, have a high wear resistance and is much used in the manufacture of dies and molds. Despite the high hardness, these steels have a microstructure with coarse carbides, which affects the hardness of the material. An alternative to the processing tool steels is the high-energy milling and subsequent powder metallurgy, in order to refine the microstructure of the material. This work aimed to study the influence of the size of the grinding media in the refining of the microstructure of AISI D2 by high-energy milling and the microstructural changes with the increase in sintering temperature. The results indicated that grinding media of smaller diameters had higher efficiency in high-energy milling due to smaller mean particle size obtained by grinding and subsequent final reduction in the average size of carbides. The sintering time had a direct influence on the microstructure of the material, higher sintering times led to formation of lower bainite, after cooling from sintering temperature.