Investigation on the Case-Hardening Behavior of Additively Manufactured 16MnCr5

Abstract

Additive manufacturing (AM) technologies, such as laser-based powder bed fusion of metals (PBF-LB/M), allow for the fabrication of complex parts due to their high freedom of design. PBF-LB/M is already used in several different industrial application fields, especially the automotive and aerospace industries. Nevertheless, the amount of materials being processed using AM technologies is relatively small compared to conventional manufacturing. Due to this, an extension of the material portfolio is necessary for fulfilling the demands of these industries. In this work, the AM of case-hardening steel 16MnCr5 using PBF-LB/M is investigated. In this context, the influences of different processing strategies on the final hardness of the material are studied. This includes, e.g., stress relief heat treatment and microstructure modification to increase the resulting grain size, thus ideally simplifying the carbon diffusion during case hardening. Furthermore, different heat treatment strategies (stress relief heat treatment and grain coarsening annealing) were applied to the as-built samples for modifying the microstructure and the effect on the final hardness of case-hardened specimens. The additively manufactured specimens are compared to conventionally fabricated samples after case hardening. Thus, an increase in both case-hardening depth and maximum hardness is observed for additively manufactured specimens, leading to superior mechanical properties.

In situ modification of case-hardening steel 16MnCr5 by C and WC addition by means of powder bed fusion with laser beam of metals (PBF-LB/M)

“…Based on determined relative part density, the process window for further experiments with CB-addition is constricted to laser powers between 250 and 300 W as well as scanning speeds in the range of 600 to 900 mm/s. These best results are also similar to Kamps [5], Schmitt et al [8], and Bartels et al [7], who all have found a relative part density above 99.9%.…”

“…Furthermore, the researchers presented results on the overhanging angles and the influence of contour scans on the corresponding roughness values. Within their work, Bartels et al [7] studied the carburizing and hardening of additively manufactured 16MnCr5 specimens. They found that an increased hardness and case-hardening depth can be observed for additively manufactured specimens from case-hardening steels.…”

Influence of laser powder bed fusion process conditions and resulting microstructures on the electromagnetic properties of a 16MnCr5 steel

“…Bartels [19] also manufactured 16MnCr5 steel with L-PBF with the samples "F") and some tilted at 25 • with respect to the (x,y) plane (tilted samples "T") to check the effect of the grain growth direction on the material properties. Bars (5 × 3 × 30 mm 3 ) for electrical conductivity measurements were also built in two directions, parallel to the (x,y) plane (samples H) and vertically, along the z axis (samples V), as depicted in Fig.…”

“…the SF sample built with high VED. In [18,19] the stress relief heat treatment for 16MnCr5 has been performed at 650 • C for 6 h. However, these studies also reported recrystallization and grain refinement after the heat treatment. In the present work, to avoid potential recrystallization that would also have an effect, in addition to the already mentioned stress relief effect, on the magnetic properties, we chose a lower temperature for the heat treatment.…”

PBF-LB/M of Low-Alloyed Steels: Bainite-like Microstructures despite High Cooling Rates

“…First studies on the processing of this group of steels by means of PBF-LB/M have already been performed. Independent researchers, e.g., Kamps [ 14 ], Schmitt et al [ 15 ], and Bartels et al [ 16 ], show that defect-free parts from 16MnCr5 can be manufactured additively. Schmitt et al [ 17 ] also state in another work that a predominant bainitic microstructure with shares of martensite is formed when processing the low-alloyed steel 16MnCr5 by means of PBF-LB/M.…”