The Difference of Parts Properties Depending on Inert Gas
3D Printing Direct Metal Printing
17-4PH (equivalent to SUS630) is precipitation-hardened stainless steel, which can be hardened by aging treatment.
α-martensite hardens 17-4PH but γ-austenite does not contribute to the hardness of the product. The most primarily austenitic product, the hardness does not change even if the aging treatment is applied. It has been reported that the percentage of γ-austenite depends on atomize gas, Ar or N2. N2-atomized powder contains a lot of γ-austenite (Fig.1).
When the parts are produced using this N2-atomized powder, the properties of parts build under Ar gas becomes mostly α-martensite and parts build under N2 gas becomes γ-austenite (Fig.2) .
The parts build under N2 gas need solution treatment for transforming γ-austenite to α-martensite before aging treatment. On the other hand, the parts build under Ar gas do not need solution treatment before aging treatment.
 Lawrence E. Murr, Edwin Martinez, Jennifer Hernandez, Shane Collins, Krista N. Amato, Sara M. Gaytan, Patrick W. Shindo,