Influence of initial defect density on mechanical properties of AISI H13 hot-work tool steel produced by laser powder bed fusion and hot isostatic pressing

Abstract

In this study, the microstructure and mechanical properties of martensitic hot-work tool steel AISI H13 produced by laser powder bed fusion (LPBF) under argon atmosphere in different LPBF process times were analysed in the as-built, hardened and tempered (HT) and hot isostatic pressed, hardened and tempered (HIP+HT) condition and compared to conventionally manufactured reference material. Three parameter sets were selected to adjust an initial defect density of 0.6%, 0.9% and 2.2% and thus process time reductions of 17% and 29%. We observed a change in the defect type from almost argon-free microcracks to argon-filled pores with higher scan velocities. Argon embrittlement was evident also in the results of tensile, notched impact toughness and fatigue tests. After HIP+HT a fatigue strength of 972 MPa was obtained for the set with 0.6% microcracks, but only 775 MPa and 718 MPa were obtained for samples with argon porosity.

Influence of the L-PBF Process Atmosphere on the Microstructure and Tensile Properties of AISI 318LN Duplex Stainless Steel

“…The powder was gas-atomized under a nitrogen atmosphere and was free of argon before processing; therefore, the L-PBF process was the only plausible source of argon through which pick-up might have occurred. This phenomenon is well established, and argon contents of over 0.50 ppm can lead to a significant decrease in the toughness of DSS [40][41][42]. However, these results also indicate the difficulties in measuring very small amounts of argon just above the lower limit of detection of 0.049 ppm.…”

A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading

“…Recently, the material X38CrMoV5-3 for which the viscoplasticity model was developed is manufactured also by additive manufacturing such as laser melting. Current works investigate the material behavior which differs from conventional manufactured tools, e.g., [57][58][59][60][61]. In future investigations, thus, an additive-manufactured specimen could be tested and compared with results computed with the viscoplasticity model.…”

Improving the Fatigue Strength of Laser Powder Bed‐Fused AISI M3:2 by Hot Isostatic Pressing

“…As a result, the specimens produced by LPBF show a lower fatigue strength than conventionally produced material, which is a well-known phenomenon in many studies. [5,7,11,13,27] Eliminating the porous defects in the material is crucial to improve the fatigue strength of the components produced by LPBF. HIP with integrated heat treatment can modify the microstructure and densify the material simultaneously.…”

“…[3] Today, the most prominent tool steel for LPBF is the hot work steel H13 because of its relatively good processability. [4,5] The processability and microstructure of high-speed steels M2 and M50 produced by LPBF have been also investigated. [6,7] With preheated powder bed, tools with even higher carbon content can be processed.…”

“…[12] Hot isostatic pressing (HIP) is applied to densify the material at high temperature and high pressure to improve the fatigue strength of these parts. [5,7,13,14] An HIP device with an integrated quenching facility can even combine the heat treatment and HIP densification into one step, which is a promising post-treatment method for AM parts. [15] AISI M3:2 is a highly alloyed high-speed steel (HSS) with good wear resistance and high hardness.…”