FEM-Supported Development of a Radial Forging Process for Surface Densification of P/M Gears

Because of its capability for net- or near-net shape production, P/M technology is well suited for the production of complex shapes such as gears. Nevertheless, the usage of P/M parts has been limited for a long time on low to moderate stress applications due to their porosity. To improve the mechanical properties of P/M gears, the high stressed regions have to be densified. As the highest service stresses for gears occur in a thin layer below the surface, it’s sufficient to densify just the cogs surface and keep porosity with its positive influence on weight and noise damping over the rest of the gear. Due to new surface treatment processes, which provide a local densification of high stressed areas up to full density, P/M components are now successfully used in high performance applications. One new idea for surface densification of P/M gears is the use of a specific radial forging process. To prove the applicability and to generate specific knowledge about the new process, FEM studies have been done before running pilot trials. The main purpose of the FEM studies is the investigation of the influence of preform and die design on surface densification and the expectable dimensional accuracy. Therefore different ways of forging the cogs have been investigated. The deduced basic coherences and process characteristics enable a demonstration of advantages and disadvantages of the planned process. Hence, basic conditions for an application of the radial forging process for gear productions are deduced.