An integrated approach to the characterization of powder metallurgy components performance during green machining

Abstract

Green machining of powder metallurgy (P/M) components appears as an interesting procedure to solve the eternal problems associated with the poor machining behaviour of porous metallic samples. With the increasing usage of sinter-hardenable powders for high performance applications, green machining is an attractive method to lower production costs and compete against other shaping processes. Green machining is not a straightforward procedure. There is quite more to control in green machining than the cutting parameters. Several variables must be optimized to obtain adequate results in terms of surface finish, geometrical conformance and productivity. Other considerations such as density gradients in green compacts also influence the final outcome of this process. This study presents a new technique, based on cutting force measurements during green turning, to quickly and precisely characterize density gradients in powder metallurgy components. This new technique also allows the characterization of green machinability. Moreover, this study shows that timing sprockets can be produced by green machining of gear blanks. Timing sprockets produced by this process show a surface finish comparable to that of powder metallurgy components machined after sintering.