Pure molybdenum manufactured by Laser Powder Bed Fusion: thermal and mechanical characterization at room and high temperature

As a refractory material, molybdenum is regarded with high interest for high-temperature applications. The concurrent use of powder bed Additive Manufacturing (AM) technology can provide significant design and production advantages. In this work, the Laser Powder Bed Fusion (LPBF) process parameters tuning lead to produce almost fully-dense AM Mo blocks (density of 99.5±0.5%). Fine-tuning of the parameters, also involved the Single Scan Tracks analysis, are aiming at the continuous and homogeneous melt-pools production. High-density Mo specimens have been characterized at room- and high-temperature in terms of thermal and mechanical properties, then compared with conventionally manufactured Mo samples. The thermal diffusivity measurement at room temperature allowed to verify that the thermal conductivity value of AM Mo is approximately half of standard Mo. Stress relieving heat treatment improves the thermal conductivity approximately by 13%. The estimation of emissivity and thermal conductivity carried out in the 600÷1600 °C temperature range led to a similar result. The Vickers microhardness measured on fully dense specimens (212 ± 18 HV0.15) is similar to commercially available Mo. Tensile tests have been performed at both room temperature and 600°C. The effect of building direction and post-processing machining of AM specimens have been also investigated for tests at room temperature. Although the AM samples exhibited a very similar density to standard Mo, the AM Mo mechanical properties resulted generally lower.