Additive manufacturing and mechanical properties of martensite/austenite functionally graded materials by laser engineered net shaping

Abstract

Laser engineered net shaping (LENS) is an advanced additive manufacturing technology combining rapid prototyping and synchronization technology. Its multi-powder feeder delivery system enables multi-materials building in single deposition, which is appropriate for additive manufacturing of functionally graded materials (FGMs). In this study, martensitic-stainless steel (MSS)/austenitic stainless steel (ASS) FGMs with composition transitioning from 100% MSS incrementally graded to 100% ASS by 25% composition gradients are fabricated by LENS. The Vickers hardness of MSS/ASS FGMs ranges from 358 to 170 HV. The decrease of hardness is found to relate to the grain-growth region with the increase of austenite. The obtained specimens of MSS/ASS FGMs show a tensile strength of 669 MPa and an elongation of 19%. In addition, the fracture location of MSS/ASS FGMs in tensile test is in the region of 100% ASS, which is dominated by austenite structure. Finally, the Scheil–Gulliver model is introduced to validate the phase formation of MSS/ASS FGMs’ failure region. Experimental and modeling results indicate that precipitation of α-ferrite in the austenite structure leads to reduced ductility of MSS/ASS FGMs.