Investigation on mm-wave sintering of metal powder compacts using in-situ dilatometry and electrical resistivity measurements

Sintering of metal powders is a well-established industrial process for specific applications, which allow a cheap series production of metal parts even with complex shape. The residual porosity, always present in sintered power compacts, limits their mechanical strength. On the other hand, for several products such porosity is needed. Products of that kind are for example: metal filters showing a porosity of about 50%, or self-lubricating plain bearings with a value between 5% and 30%, depending on the technological working conditions. In the case of self-lubricating plain bearings made of sintered iron or sintered brass, the open pores are filled with lubricants. Pore-free sinter metals are obtained by hot pressing or impregnation with a low-melting metal The use of microwave technology for metal powder sintering had been reported by many researchers, demonstrating improvements in the materials properties and/or in the overall process. Although microwave are not able to penetrate into bull metals, significant penetration depth in metal power compacts has been reported by theoretical as well as experimental investigations [1, 2]. Here, the progress of microwave sintering of metal power compacts with focus on copper powders was investigated by systematic variation of process parameters. Those investigations were supported by both in-situ electrical resistivity and dilatometry measurements that give important information about the sintering progress and microstructural changes.