Microstructural evolution an dmechanical properties of Rapidsteel 2.0

Abstract

At present, the research on rapid tooling by the selective laser sintering (SLS) method is mainly focused on the production of parts with high accuracy and definition. Very little effort has been devoted to the microstructural evolution and mechanical properties of this material. This paper gives detailed information about microstructural development and mechanical behaviour of Rapidsteel material after subsequent heat treatment cycles for binder removal, partial sintering, and liquid phase infiltration.

The microstructure of SLS samples heated to 1120°C for 3 h in 30H₂-70N₂ atmosphere at 2 K min^-1 consisted of a mixture of austenite, M₂₃C₆, and Cr₂N phases. Subsequent infiltration of the above sample with bronze at 1050°C for 2 h in 30H₂-70N₂ atmosphere at 2 K min^-1 produced similar phases together with an additional α(Cu-Sn) phase. The mechanical tensile fracture strength of the partially sintered part increased ten times after infiltration with bronze. However, the fracture behaviour is found to be different between the samples subjected to various heat treatment cycles. The sample heated after the first cycle showed fracture along the necks between stainless steel particles, whereas the infiltrated sample showed fracture along the bronze infiltrant.