Effects of Powder Atomization Route and Post‐Processing Thermal Treatments on the Mechanical Properties and Fatigue Resistance of Additively Manufactured 18Ni300 Maraging Steel

Abstract

In this work the effect of microstructural homogenization and solution annealing prior to ageing on mechanical properties and fatigue resistance of 18Ni300 maraging steel parts processed by laser powder bed fusion (L‐PBF), using two different feedstock powders with different N and O contents is investigated. The static mechanical properties are not significantly affected by the selection of the different feedstock powders. This is ascribed to the extremely fine size of the nonmetallic inclusions, characteristic of L‐PBF process, even by using feedstock powders containing higher O and N contents. The tensile properties in both “directly aged,” and “homogenized, solution annealed and aged” samples are comparable. The tensile strength and ductility are slightly improved compared with the vacuum melted wrought counterparts. The dynamic mechanical properties are affected by the O and N contents of the powders. Heat treatment schedule imposed a significant effect on the fatigue properties. The obtained fatigue strength in directly aged samples is already comparable to the wrought counterparts. Fatigue resistance is improved by using feedstock powders with lower oxygen and nitrogen levels. Proper homogenization heat treatments prior to ageing led to a further improvement of fatigue strength because of the elimination of intercellular microsegregation.

Microstructural and mechanical characterization of additively manufactured parts of maraging 18Ni300M steel with water and gas atomized powders feedstock

“…2 (e) and (f), the GA batch has a normal particle size distribution between 20 and 40 μm (normal distribution). This range is commonly used for LPBF processing of 18Ni300M steel powders [7][8][9]18]. On the other hand, the WA batch has a bimodal particle size distribution, with two predominant ranges: between 20 and 40 μm and between 60 and 100 μm.…”

“…Deirmina et al [18] investigated the mechanical properties of 18Ni300M additive manufactured parts processed from steel powders with different contents of N and O. The authors verified that the monotonic properties of the specimens were not significantly affected by the raw material.…”

“…The authors verified that the monotonic properties of the specimens were not significantly affected by the raw material. However, the fatigue strength of the samples processed with the powder containing lower oxygen content was approximately 20% higher [18]. Another attempt to compare WA and GA powder has been reported in 4130 steel [19], where the components processed with WA feedstock showed a loss of ductility.…”

Microhardness and Microstructure Analysis of the LPBF Additively Manufactured 18Ni300

“…Precisely, it displays a fully martensitic microstructure in the solution-annealed state. If 18Ni300 is directly aged after LPBF, it contains more austenite than its solutionannealed and aged counterpart (RA+ reverted austenite during ageing) [31].…”

Effects of Heat Treatment on Fatigue Properties of Double Vacuum Smelting High‐Carbon Chromium‐Bearing Steel

“…[ 11 ] Accordingly, the fatigue strength of high‐strength steels significantly decreases with the increase in inclusion content or inclusion size. [ 12,13 ] Murakami [ 14 ] proposed a quantitative relationship indicating that the smaller the inclusion size is, the better the fatigue performance. Since the middle and late 1990s, the smelting process of bearing steel includes electric furnace + external refining (ER), electroslag remelting (ESR), and vacuum induction melting (VIM) + vacuum arc remelting (VAR).…”