Initial stage sintering model of 316L stainless steel with application to three dimensionally printed (3DP(TM)) components

The design phase of manufacturing has become increasingly dependent upon computers for geometric and functional analysis of design concepts [1]. The ability to manufacture final components directly from computer images has been made possible by recent developments in rapid prototyping technologies and improvements in material processing, namely rapid manufacturing. Three Dimensional Printing (3DP(TM)) is a powder metallurgical rapid pro-totyping technique that incorporates initial stage sintering within the rapid manufacturing process. Initial stage sintering is characterized by neck growth between powder particles resulting in a light cohesive strengthening bond while preserving dimensionality. This study involved a detailed look into the theoretical mechanisms that produce material transport via diffusion methods to produce a quantitative dimensional sintering strain model.; Here, we modify the accepted isothermal theoretical model describing initial stage sintering presented by German [2] and Ashby [3] to support a non-isothermal load history. Isothermal theoretical models have defined sintering in terms of surface and bulk mechanisms, where literature assumes that surface mechanisms do not produce interparticle approach for the ideal two-particle geometry. An expansion of the two-particle neck geometry from isothermal sintering theory to non-isothermal is performed by defining both the neck geometry and sintering mechanisms in terms of three geometric parameters. A quantitative sintering model is developed by introducing a volume constraint on the geometry and enforcing the assumption that surface sintering mechanisms do not produce inter-particle approach (no sintering strain). The sintering model produces quantitative strain results which are accurate to within 20% experimentally obtained final sintering strains. A qualitative strength model based on empirical data is also developed based on the amount of the final sintering strain.; Modeling efforts were supported by several sets of experimentation. Initial experimental results indicate that the anisotropic manufacturing of 3DP(TM) components result with orthotropic sintering strain development. Particle diameter experimentation revealed that components comprised of small particles (20mum) experienced more strain than components comprised of large particles (200mum). Strength experimentation showed two different types of mechanical responses from load-deflection measurements, where specimens with less sintering strain exhibited a brittle response and specimens with more sintering strain experienced plastic deformation.