Characteristics of Surface Profile of Cemented Tungsten Carbide Dies after Shot Peening and Their Lubrication Performance in Cold Ring Compression

Abstract

The characteristics of the surface profile of cemented tungsten carbide dies after either shot peening (SP) or conventional mechanical polishing (MP) surfaces were investigated with a surface roughness tester. The relationship between arithmetic and ten-point mean roughness was almost the same in the MP and SP dies. The mean period of the surface roughness profile of the SP die was approximately 1/3 times shorter that of the MP die. The distribution of the peaks and valleys of the surface profile was symmetric in the SP die, whereas it was skewed toward the peaks in the MP die. The lubrication performance of the MP and SP dies in cold forging of a titanium workpiece was measured by the ring compression test. The SP die with a mirror surface reduced the friction at a high reduction in height range because the die holds liquid lubricant in the micro valleys on its surface during the ring compression test.