Laser powder-bed fusion of CuCr1Zr: parameter study, properties and microstructure

Abstract In this work, the alloy CuCr1Zr is examined for additive manufacturing using the laser powder-bed fusion PBF-LB/M process for manufacturing of rocket engine components. CuCr1Zr has gained significant attention for PBF-LB/M over the last few years, and several studies have focused on its processability. However, inconsistencies between different studies with respect to suitable parameters and effects of parameters on microstructural defects require a detailed investigation of processing parameters. It is a common opinion that low-alloyed copper alloys need to be processed with high energy density, however, this leads to poor surface quality, high stresses and distortion. This work focuses on a detailed parameter study to find suitable parameters with less energy input. It employs Taguchi’s design of experiments methodology to explore the interactions of laser power, scan speed, hatch distance, and layer thickness on the porosity, microstructural defects, and mechanical properties of additively manufactured CuCr1Zr alloys. From these investigations, a range of optimal processing parameters is identified. On samples produced with optimal parameters, tensile-tests and measurements of thermal conductivity were performed, and the microstructure in the as-printed state as well as after aging heat treatment is investigated by means of scanning electron microscopy, scanning transmission-electron microscopy, energy dispersive X-ray analysis, and electron backscatter diffraction. It was found that the alloy consists of a huge amount of small zirconium oxide particles that presumably contribute to particle strengthening even in the as-printed state. After aging, nanoscale chromium precipitates form in the microstructure leading to a strength increase of more than 100 %.