Formation of surface coating on milling balls during milling of Cr powders

1　ＩＮＴＲＯＤＵＣＴＩＯＮＮｅｗｍａｔｅｒｉａｌｓ ,ｓｕｃｈａｓｄｉｓｐｅｒｓｉｏｎｓｔｒｅｎｇｔｈｅｎｅｄａｌｌｏｙ ,ａｍｏｒｐｈｏｕｓａｎｄｉｎｔｅｒｍｅｔａｌｌｉｃｓ ,ｃａｎｂｅｏｂｔａｉｎｅｄｂｙｍｅｃｈａｎｉｃａｌａｌｌｏｙｉｎｇｗｈｉｃｈｓｈ

Formation of surface coating on milling balls during milling of Cr powders

The formation regularity of surface coating on milling balls during milling of Cr powders was investigated, revealing that the plastic deformation of the balls surface plays an important role in the formation of coating and that the stronger affinity between the powders and the balls is a necessary pre condition for the coating. The size of Cr powders, the coating thickness and the microhardness vary consistently with milling time during milling. At initial milling stage, the powder size decreases, while the coating thickness and the microhardness increase, however, after milling for 24?h, they all change slightly with prolonged milling, indicating a dynamic equilibrium between the powders cold welding and crashing, i.e. an almost equal rate for the powders attaching to and breaking off the milling balls.