Different metal powders have different properties, and even those designated to be “the same” in terms of size and chemistry can behave very differently under varying process parameters. LPW Technology recently conducted a study to demonstrate how stainless steel 316L reacted to changes in processing conditions.
Four batches of SS 316L were tested. According to LPW, SS 316L is an austenitic stainless steel, which is not age or precipitation hardenable. It also possesses high corrosion resistance and toughness; good all-around mechanical properties ranging to 300°C; and is highly machinable.
The materials were produced using different atomization processes including melting conditions and atomization gasses, and with a variation of particle size distribution. Then, a series of builds was completed with each powder, systematically varying the energy density delivered by the laser. The resulting microstructure density of the part was then measured after sectioning and polishing samples. For this study, a target density greater than 99.5 percent was desirable, as this represents the point at which good properties can be predicted, LPW says.
In all four batches, at least some acceptable parts were produced, but density varied in response to build parameters of the starting material. According to the researchers, using a well-characterized powder with a wide processing window enables the material to tolerate a range of build variables, resulting in increased success in AM builds.