Influence of surface topography on the wear of hot forging dies

Abstract

Forging processes are widely employed in the manufacture of consumer goods. The forging dies have machined cavities which usually are produced by high speed milling (HSM) with ball nose tools and, consequently, their final surfaces have a characteristic topography generated by the cutting conditions. The purpose of this study was to gain a better understanding of the correlation between the surface topography of a milled die and its wear during the hot forging process. To this end, dies were produced by milling process with four different types of topography, using distinct cutting conditions, and were tested by forging typical workpieces. The best tribological performance was achieved with the topography composed of micro cavities generated by high values of feed per tooth (fz) and radial depth of cut (ae) in the milling process, because it enabled the retention of a larger amount of lubricant, thus minimizing the adhesion of workpiece material on the die. Moreover, the use of high values of fz and ae reduced the production time of a die. Low values of fz and ae produced the opposite results, i.e., the worst tribological performance and the longest production time, indicating that their use should be avoided.