The Hardness of Additively Manufactured Alloys

Abstract

The rapidly evolving field of additive manufacturing requires a periodic assessment of the progress made in understanding the properties of metallic components. Although extensive research has been undertaken by many investigators, the data on properties such as hardness from individual publications are often fragmented. When these published data are critically reviewed, several important insights that cannot be obtained from individual papers become apparent. We examine the role of cooling rate, microstructure, alloy composition and post process heat treatment on the hardness of additively manufactured aluminum, nickel, titanium and iron base components. Hardness data for steels and aluminum alloys processed by additive manufacturing and welding are compared to understand the relative roles of manufacturing processes. Furthermore, the findings are useful to determine if a target hardness is easily attainable either by adjusting AM process variables or through appropriate alloy selection.

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

“…AM terminologies and general principles are standardized by the ISO/ASTM 52900 (2015) international standard. Dissimilar from other manufacturing technologies, AM produces parts by a layer-by-layer stacking approach [1][2][3][4][5]. The process starts from a three-dimensional (3D) computer-aided design (CAD) model of the part to be built, which is sliced in several thin layers by a appropriate software [6].…”

“…Laser Powder Bed Fusion (PBF-LB) is also known as er Melting (SLM), Direct Metal Laser Sintering (DMLS), and Laser Cusing [7,8,11], ostly on the AM systems supplier. on PBF-LB, a micro-size powder is spread in thin layers of 20 and 50 µm [3], and then uided by a galvanometric mirror selectively melts the deposited material according to el. The parts are built progressively from bottom to top, also known as the building tical) [7,11].…”

“…Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part's core.Diverse metals AM techniques exist, and the most adopted in the industry are Powder Bed Fusion (PBF) and Directed Energy Deposition (DED), as for the classification by the ISO/ASTM 52900 (2015) international standard. These two techniques use a laser or an electron beam as a high energy density source to selectively melt the material and build the parts [3][4][5][6][7]. Actually, different nomenclatures are used for the same process.…”

“…[12,16,17].The microstructure is extremely dependent on the chemical composition and thermal history. IN718 is a complex material to be processed with AM processes, as it has a wide number of alloying elements (UNS N07718) [3]. IN718 is a precipitation strengthening alloy.…”

“…Its microstructure consists of a EVIEW 2 of 16 d products in the aerospace, automotive, biomedical/medical, and energy techniques exist, and the most adopted in the industry are Powder Bed ted Energy Deposition (DED), as for the classification by the ISO/ASTM 52900 ndard. These two techniques use a laser or an electron beam as a high energy ctively melt the material and build the parts [3][4][5][6][7]. Actually, different for the same process.…”