Analysis of shape changes of steel powder compacts during sintering

In this paper an extension of the sintering method at atmospheric pressure, yet performed for tool steels, is proposed for prealloyed duplex stainless steels powders. A wide temperature range is tested and the efficacy of boron as activator of the process is investigated. In all the samples, no evidence of liquid phase is observed; the sintering process allows full density in the case of no boron addition and it occurs by solid phase diffusion, enhanced by the presence of two phases, austenite and ferrite : this makes needless to add boron as activator. We obtain density and hardness values comparable with the "as-cast" ones, isotropic phases structure and gamma/delta ratio of about 50/50 for the best sintering temperature (1,150degreesC).