Laser assisted powder bed fusion of refractory metals using ultra short laser pulses

Refractory metals are used in applications requiring extreme high temperature-resistance, e.g. jet propulsion systems in aerospace applications or for controlling nuclear reactions. However, the traditional manufacturing of these metals is demanding and expensive, especially if fine structures are required. Here, we report on the laser assisted powder bed fusion of pure Molybdenum. The high melting point and thermal conductivity together with a high susceptibility to solidification fractures make it difficult to identify a suitable parameter window for the laser-based melting process using standard continuous wave laser systems. Thus, we apply an ultra-short pulse laser system operating at a center-wavelength of 1030nm and a repetition rate of 32,5MHz with a pulse width of around 260fs for the additive processing. Using the additional parameter field provided by the pulsed laser source, we are able to fabricate thin-walled structures well below 70µm as well as volumetric parts with a relative density close to 100%.