Laser powder bed fusion of 30CrNiMo8 steel for quenching and tempering: examination of the processability and mechanical properties

Abstract

The layer-by-layer principle of additive manufacturing technology laser powder bed fusion (LPBF) opens up completely new possibilities in the design and manufacturing of lightweight and efficient gear components. For example, integration of contour conform cooling and lubrication channels into gear components can increase their service life and reduce lubricant consumption. Steels for quenching and tempering and case hardening steels are commonly used materials for gear components. However, the availability of these alloys for LPBF processing is still limited. In particular, the 30CrNiMo8 steel for quenching and tempering is frequently used for gear wheels. This specific alloy is largely unknown regarding LPBF processing and remains challenging, because of its susceptibility to cracking and the high temperature gradients that occur during the LPBF process. Therefore, this study focuses on the LPBF processing of 30CrNiMo8 powder material including process parameter evaluation and material characterization. Additionally, effects of the heat treatment on the resulting microstructure and mechanical properties were investigated. Within this study the 30CrNiMo8 has been processed successfully with a density of well above 99.5% leading to promising mechanical properties. A more homogenous microstructure has been achieved with quenching and tempering, compared to the as-build state.

Increasing the safety against scuffing of additive manufactured gear wheels by internal cooling channels

“…Additionally, the elongation at break of 14.2-16.9% (quenched and tempered) is in line with values presented in the relevant literature [25,26]. The notch impact tests revealed remarkably high impact energies of 99-109 J for the LPBF-processed 30CrNiMo8 in the quenched and tempered states compared to the bulk material [25], indicating high ductility.…”

“…A previous study revealed promising mechanical properties of the 30CrNiMo8 and a high relative when processed with LPBF [25]. The yield strength and tensile strength of the quenched and tempered specimens were 1009-1016 MPa and 1094-1098 MPa [25], respectively, which are comparable with the bulk material with a similar heat treatment [25,26]. Additionally, the elongation at break of 14.2-16.9% (quenched and tempered) is in line with values presented in the relevant literature [25,26].…”

“…The yield strength and tensile strength of the quenched and tempered specimens were 1009-1016 MPa and 1094-1098 MPa [25], respectively, which are comparable with the bulk material with a similar heat treatment [25,26]. Additionally, the elongation at break of 14.2-16.9% (quenched and tempered) is in line with values presented in the relevant literature [25,26]. The notch impact tests revealed remarkably high impact energies of 99-109 J for the LPBF-processed 30CrNiMo8 in the quenched and tempered states compared to the bulk material [25], indicating high ductility.…”

“…The strongest anisotropy is observed in the mechanical properties such as the tensile strength and yield strength [29]. However, since all wheels are quenched and tempered, hardly any differences in strength are visible [25].…”

Dynamic conformal cooling improves injection molding

“…The point distance corresponds to the distance between each of the laser's exposure points, whereas the exposure time defines the duration of the laser exposure. The input volume energy density E V (2) is a function of the laser power P L , scan velocity v s , layer thickness l z , and hatch spacing h s [3].…”