# Studies of the Thermophysical Properties of 42CrMo4 Steel Manufactured Conventionally and via Laser Powder Bed Fusion (L-PBF)

## TL;DR

This study compares the thermophysical properties of 42CrMo4 steel made using traditional methods and laser powder bed fusion from room temperature to 1000°C.

## Contribution

The study provides a direct comparison of thermophysical properties between conventionally and additively manufactured 42CrMo4 steel.

## Key findings

- No significant differences were found in thermophysical properties between L-PBF samples in different build orientations.
- Thermophysical properties of conventionally and L-PBF manufactured 42CrMo4 steel were largely similar.
- Standard heat treatment and stress-relief annealing did not cause major differences in material behavior.

## Abstract

In this work, measurements of thermal diffusivity, heat capacity and thermal expansion of 40HM (42CrMo4, 1.7225, AISI 4140) steel manufactured conventionally and via Laser Powder Bed Fusion (L-PBF) were carried out in the temperature range from room temperature (RT) to 1000 °C. Thermophysical properties were tested using specialized test stands from NETZSCH. Thermal diffusivity was studied using both the LFA 427 laser flash apparatus and the LFA 467 xenon flash apparatus. Specific heat capacity was investigated using DSC 404 F1 Pegasus differential scanning calorimeter, and thermal expansion was investigated using the DIL 402 C. Inconel 600 and A310 steel were selected as the reference materials during the thermal diffusivity test using LFA467 in the RT÷500 °C range. The conventionally manufactured 40HM steel, in the form of hot-rolled bar stock, was subjected to standard heat treatment for this steel grade—quenching followed by high-temperature tempering. The additively manufactured 40HM steel was subjected to stress-relief annealing. The results revealed no significant differences between the thermophysical properties of the L-PBF-produced samples in the out-of-plane and in-plane build orientations. Furthermore, no substantial differences were observed between the thermophysical properties of the conventionally produced material and the material manufactured using the L-PBF technique.